giving small doses of steroids, some of these kidneys functioned for a surprisingly long time compared with the findings in animals in whom a rejection of kidneys occurs between seven and ten days. The longest function in this clinical series was five and a half months’.30 These clinical observations gave encouragement to develop the technique further.
Scientists hoped that the latest techniques of genetic engineering would enable them to create new animal models which more closely mimicked human disease. An example is cystic fibrosis where discovery of the faulty gene in human sufferers led animal researchers to disrupt a similar gene in mice. The resulting ‘cystic fibrosis mice’ quickly develop a fatal illness but there are differences from the disease in people:31 most importantly the animals’ lungs do not become infected or blocked with mucous as they do in human patients, although it is lung infections which kill 95% of people with cystic fibrosis.
Many other genetically engineered mouse models are proving unreliable. Retinoblastomas are tumours of the developing retina and occur exclusively in children. They arise when a cancer-suppressing gene is disabled in some way. However, when a similar gene is disrupted in mice, the animals do not develop retinal tumours.32 Robin Holliday of the CSIRO Laboratory for Molecular Biology in Australia points out that such differences should not be surprising since ‘….tumour-suppressor genes and onco-genes (cancer genes) behave very differently in mouse and man.’33
Attempts to develop transgenic mice with multiple sclerosis led to animals with severe neurological illness, referred to by the scientists as ‘wonky’ mice. But whereas multiple sclerosis is thought to be an auto-immune disease in people where the immune system attacks the body’s own tissues, this is not the case in the transgenic mouse model.34 And whilst a transgenic animal model of fatal familial insomnia produced progressive terminal illness in mice, a key protein which characterises the human disease could not be found in the animals.35
Preventive Medicine at Risk
It is a medical cliché that prevention is better than cure. However, before preventive health policies can be initiated the actual causes of disease must be discovered. This is the primary role of epidemiology, the study of disease in human populations. Unfortunately many scientists believe that epidemiological findings must be replicated in the laboratory before they can be accepted. The concept originated in the 19th century when microbiologist Robert Koch published a set of rules for proving that a specific germ caused the disease under investigation. When inoculated into animals, Koch argued, the microbe should produce the same condition seen in people. In 1928 Bridge and Henry set out similar rules for cancer-causing agents. These ideas have pervaded medical science and even now, failure to induce AIDS in animals has been used to support arguments against HIV as the cause.35 >>
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