Contents:
Introduction
Thanks to advances in biomedical research, the average age
of our population has been increasing. Today, the average human
life expectancy is 70 years. Unfortunately, increased life
expectancy has brought with it a number of diseases, particularly
neurological diseases, which strike mainly in the middle and later
years of life. Among these are Alzheimer's and Parkinson's diseases.
Alzheimer's Disease
One of the most debilitating of these neurological diseases
is Alzheimer's, discovered by Dr. Alois Alzheimer in Germany,
in 1906. Alzheimer's disease is a degenerative disease
that attacks the brain. Slowly, it kills the brain cells,
until the brain can no longer send messages properly to other
parts of the body, or to each other. The symptoms of Alzheimer's
are generally characterized by progressive loss of memory and language
skills, disorientation, personality change and dementia. Tragically,
the disease culminates in the childlike helplessness of its victims
and eventually causes their death. The progressive degradation of this
disease is endured not only by the patient, but also by his or her
family and, oftentimes, an entire community.
According to a recent study, an estimated 300,000 adults in Canada
and 4 million adults in the United States suffer from this disease,
which severely debilitates more than 125,000 of them each year.
Alzheimer's disease is the leading cause of hospitalization
of the elderly, afflicting 10% of people over the age of 65 and
almost 50% of those over 85. Alzheimer's disease often appears
in families, making a genetic cause for the disease suspect.
Studies of the human brain continue to give important information to
researchers on the total effect of the disease in its final stages. However,
this work can only be done after the patient is deceased. Alzheimer's
disease needs to be looked at during its development to find clues to its
origin and how it progresses. Such information is vital if physicians are
to improve diagnosis and treatment.
Researchers are now developing several diagnostic tests for Alzheimer's
disease. While still experimental, these tests hold much promise.
Aging monkeys and cats with some signs and symptoms of human senility
are being studied as partial models. More recently, a mouse strain has
been developed which serves as a model for studying Down's syndrome.
Down's syndrome sufferers almost always suffer from Alzheimer's
as they grow older. Because brain and behavioral studies of Down's
syndrome patients reveal conditions identical to those of Alzheimer's
patients, researchers believe this mouse may also be a good model for
studying Alzheimer's.
Using the rat as animal model, researchers are studying how the disease
may affect the brain in the early stages of the disease, before human
patients would even be diagnosed. The rat also permits researchers to
study how the disease progresses, as well as how safe and effective
various drug treatments are at different stages of the disease. Such
information can then be used to design safe treatments for Alzheimer's sufferers.
Parkinson's Disease
Another serious disease of the elderly is Parkinson's
disease, a degenerative disorder of the central nervous system.
This disease is characterized by increasing loss of muscle control,
causing tremors, stiffness, slowness of movements and difficulty in
balance. In advanced stages of the disease, sufferers lose the ability
to walk, speak or feed themselves, and they eventually die. More than
100,000 Canadians are now suffering from the disease.
Scientists are studying the effectiveness of transplanting
embryonic brain tissue (called brain grafts) to both monkeys
and rats which have Parkinsonism. This difficult surgical
technique has taken many years to perfect, and has required the
use of animal models in its development. Successful surgery
permits the brain graft to grow and secrete the chemicals, such
as dopamine, which the patient's brain cannot produce on its
own. In a 1984 study of Alzheimer's lesions in rats, for
example, 73% of the rats who received brain grafts showed better
memory skills than they had before the implant of the grafts.
Similar improvements have been seen following brain grafting in
monkeys with Alzheimer's lesions.
The nematode, an animal which has long been used by
developmental and molecular biologists, is also providing important
clues to researchers on the mechanisms that cause cell death,
information of vital significance to those studying
Alzheimer's, Parkinson's and other neurological diseases.
Since nerve cell death is the common characteristic of all of these
neurological diseases, researchers are using the nematode to
learn more about how cells die. Genes that cause nerve cell death
in the nematode have been isolated, opening the door to identifying
and understanding the biochemical events which underlie the cell
deaths. This basic biomedical research on one of the simplest of
animals is providing important clues to the mysteries of neurological disease.
Incidence of Leading Neurological Disorders
It is estimated that more than 5 million Canadians are
affected by DISORDERS OF THE BRAIN AND NERVOUS SYSTEM.
- Strokes occur In 1,200 Canadians each day. Cats are being used to
study recovery from strokes.
- Migraine headaches afflict over 24 million Canadians and Americans.
Following extensive research and testing with rodents, rabbits and dogs, a new drug is
now available to treat migraines.
- Alzheimer's and other dementias affect 1 of every 30 people. More than
200,000 Canadians suffer from Alzheimer's. Primate research has identified one of
the important features of Alzheimer's disease: an abundance of clusters of
fibrillary tangles in the brains of patients.
- Epilepsy affects more than 2,500,000 people across North America. Studying
seizures in mutant mice, researchers have discovered that petit mal epileptic
seizures in these mice are triggered by an over-abundance of GABAb receptors in the brain.
- Parkinson's disease currently affects 100,000 Canadians. Lobsters
are being used to study motor coordination in order to treat diseases like Parkinson's.
- Spinal cord injuries occur in 10,000 Canadians every year: Scientists have
stimulated growth of new nerve cells in rats. Injury to the head and/or spinal cord is
the leading cause of death and disability in Canada for people under 24 years of
age.
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