SCIENCE, MEDICINE, AND ANIMALS
Several months before his thirtieth birthday, Greg Maas discovered a lump in his abdomen that would not go away.1 He went to his doctor for tests, and then to a specialist for a biopsy, and 2 weeks before his birthday he was told that he had non-Hodgkin 's lymphoma, a cancer of the lymph nodes that was once invariably fatal. An initial round of chemotherapy controlled the cancer for 3 years, during which time Maas and his wife had their second child. When the cancer reappeared, Maas underwent a more aggressive round of chemotherapy, followed by a bone marrow transplant to repair the damage done to his immune system by the chemotherapy. Today, several years after the treatment, the cancer appears to have been eliminated.
The drugs used to kill the cancer cells in Greg Maas's body have been screened and tested over the past several decades in inbred strains of mice susceptible to leukemia. These mice are genetically identical, making it possible to compare chemotherapeutic compounds and develop treatment regimes that minimize the compounds ' side-effects. More recently, inbred mice have been developed that contract a disease virtually identical to non-Hodgkin's lymphoma, offering both the possibility of more specific chemotherapies and basic information about the biological causes of the disease.2
Mice and other laboratory animals have also been instrumental in the development of organ transplantation. By studying inbred mice with slightly different immune systems, researchers discovered that transplanted organs are rejected because of immunological reactions in the host. This work led to tissue typing techniques that make it possible to identify the best donor for an organ transplant. At the same time, studies of mice, rats, dogs, and other animals led to drugs that suppress the immune reaction to a transplanted organ, greatly increasing the transplant's survival. Today, many thousands of people are alive because of transplanted kidneys, hearts, lungs, livers, bone marrow, and other organs and tissues.3
In 1976, at the age of 52, Gloria Barry sank into a depression worse than any she had ever experienced. Her family doctor referred her to a psychiatrist, who at first treated her with standard antidepressants. But the antidepressants tended to make Barry slightly manic, leading her doctor to conclude that she actually suffered from manic-depressive illness, which affects as many as 1 in 200 adults. He therefore decided to treat her with lithium, a drug that had been used for several decades to treat manic-depression. The result was what Barry calls a “miracle”: her depression quickly disappeared and in the years since then has never returned.
The psychiatric effects of lithium were discovered in 1949 by an Australian psychiatrist who was trying to find a toxic substance responsible for mania. In the course of his research, he observed that one compound—lithium urate—had a calming effect on guinea pigs. He then tested lithium in humans and obtained dramatic results: patients who had been manic for years showed greatly relieved symptoms. However, lithium was denied immediate acceptance, because in the 1940s it had been used in very high doses as a substitute for sodium in low-sodium diets, and severe intoxication and several deaths had resulted. It took another two decades of research with animals, and subsequently humans, before lithium gained acceptance as a safe and effective treatment for manic–depressive illness.4
When Charlotte Evert was 8 weeks old, she contracted pneumonia, which was successfully treated using antibiotics. During follow-up studies, she was found to have hypoplastic pulmonary artery syndrome, a potentially fatal narrowing of the arteries leading from the heart to the lungs. At 12 months, she became one of the 600,000 people to undergo open-heart surgery in the United States each year. However, by the age of 3, her heart was again failing because of the excessive pressures required to pump blood to her lungs. Doctors considered a heart–lung transplant, but such procedures are still experimental and are rarely used in children. So Charlotte instead underwent an experimental procedure known as balloon angioplasty to widen the arteries to her lungs and improve blood flow. The procedure was totally successful: it has given Charlotte a normal life, and it is unlikely that she will ever need a heart–lung transplant.
Balloon angioplasty for the treatment of cardiovascular disease was developed by a Swiss physician in the 1970s using dogs and cadavers. The technique involves passing a very narrow catheter through an artery to the blood vessels very near the heart. When the catheter encounters a narrowing of the arteries, whether congenital or caused by the buildup of cholesterol, a balloon surrounding the catheter is inflated, widening the vessel. Today, more than 200,000 people in the United States receive balloon angioplasty each year for the treatment of heart disease, and various catheterization techniques are saving the lives of an increasing number of children with congenital heart defects.
People who recover from previously incurable diseases are the most obvious beneficiaries of research involving animals. But in fact we all benefit from animal research. The vaccines against diphtheria, whooping cough, tetanus, and polio that we received as children were developed and are still tested in animals. New antibiotics used to treat everything from minor infections to severe illnesses are continually being discovered and then tested in animals to make sure that they do not cause unexpected side effects. We are much more confident about the safety of food, water, pharmaceuticals, and household products that we use than we would be without animal research.5
This white paper contains a number of examples, set off from the main text, of diseases that have been controlled through animal research and of diseases that will be cured only through continued animal research. These examples can be multiplied many times over. Nearly half of the biomedical investigations carried out in the United States would not have been possible without laboratory animals. More than two-thirds of the research projects that have led to the Nobel Prize in physiology or medicine directly involved animal experiments.6 Laboratory animals are an indispensable part of biomedical research, and their contributions to health, well-being, and increased understanding are unassailable.
Research using laboratory animals has also had a less direct but ultimately even more important benefit. It has taught us more about the world we live in and about the living things that inhabit that world. This process of discovery is a profound intellectual adventure in its own right. But it is also true that without this fundamental knowledge, most of the clinical advances described in these pages would not have occurred. This connection between scientific understanding and clinical applications will become even stronger as biomedical research reveals more of the basic principles of biological systems.