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THE BIO-ARTIFICIAL PANCREAS

There are over 400 million diabetics in the world today. Diabetes mellitus is a disease in which high levels of sugar occur in the blood and urine. The cause of the raised sugar levels is insufficient secretion of the hormone insulin by the pancreas. In the absence of this hormone, the body's cells are not able to absorb sugar from the blood stream in normal fashion, and the excess sugar is excreted in the urine. While medications such as injectable insulin and oral hypoglycemics allow diabetics to live longer, diabetes remains the third major killer, after heart disease and cancer. Diabetes is also a very disabling disease, because medications do not control blood sugar levels well enough to prevent swinging between high and low blood sugar levels, with resulting damage to the kidneys, eyes, and blood vessels.

In recent years, many scientists have sought to solve the problem of varying blood sugar levels by developing an implantable pump that would deliver insulin more consistently than manual injections. In some designs, the insulin is slowly, continuously infused; the disadvantage of these is that they cannot respond to fluctuation caused by variations in diet and activity. In others, the amount of insulin to be infused is controlled by an electrode that senses the level of sugar in the blood. The difficulty of these designs has been in making an electrode that would function reliably for many months. Deterioration of the electrode could be disastrous; too large or too small a dosage of insulin could be fatal.

Doctor Kenneth Matsumura has developed a novel approach to this problem by making an "artificial" pancreas that is powered by live, insulin-secreting pancreatic cells obtained from animals. Called the bio-artificial pancreas, the short cylindrical device is connected to a blood vessel in a limb, and assumes the normal functions of a natural endocrine pancreas.

The device is a hollow tube made of a synthetic semi-permeable membrane with pancreatic islet cells attached to its outer surface. As the blood flows through the device, any sugar present in the blood diffuses across the membrane of the tube and triggers the secretion of insulin by the islet cells. The amount of insulin secretion would be precisely controlled by the cells, depending on the amount of sugar present in the blood stream. If blood sugar rises, insulin secretion rises proportionately, so that the patient's blood sugar would be kept at a normal level. Unlike the artificial electrode that can fail, the living cell would be more reliable and safe. The cells survive indefinitely because nutrients and oxygen are supplied by the blood.

For one version of the bio-artificial pancreas, a component was produced on the Space Shuttle in the zero gravity environment of outer space. The final prototype is expected to begin clinical trials soon. Dr. Matsumura's concepts are now being copied by many laboratories, whose work are often described in the popular press, unfortunately without due credit to the original inventor.

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