Immunization against Viral Diseases

Insulin Found to Treat Diabetes

Vitamins

In the field of nutrition the outstanding advance of the 20^th century was the discovery and the appreciation of the importance to health of the ‘‘accessory food factors”, or vitamins. Various workers had shown that animals did not thrive on a synthetic diet containing all the correct amounts of protein, fat, and carbohydrate; they even suggested that there must be some unknown ingredients in natural food that were essential for growth and the maintenance of health. But little progress was made in this field until the classical experiments of the English biologist F. Jowland Hopkins were published in 1912. The name “vitamine” was suggested for these substances by the biochemist Casimir Funk.

In 1921, at the University of Toronto, Frederic Grant Banting and Charles H. Best conducted experiments that successfully isolated the hormone insulin. This hormone id used to control the disease diabetes. The name of the hormone is derived from the Latin word for island, insula, because the hormone is produced in the part of the pancreas called the Islets of Langerhans.

Although it had been known for some time that the pancreas made the enzymes responsible for digesting proteins, it had not been possible to isolate insulin.

Insulin is a protein and id digested by the enzymes. Ban ting and best used animal experiments to extract insulin and demonstrated that it stopped symptoms of diabetes. Commercial production of insulin uses pigs, oxen, and sheep as sources for the hormone.

With the exception of smallpox, it was not until well into the 20^th century that efficient viral vaccines became available. In fact, it was not until 1930s that much began to be known about viruses. The two developments that contributed most to the rapid growth in knowledge after that time were the introduction of the electron microscope and the introduction of tissue culture as a means of growing viruses in the lab.

Once the virus could be cultivated with comparative ease in the laboratory, the research worker could study it with care and evolve methods for producing one of the two requirements for a safe and effective vaccine: either a virus that was so attenuated, or weakened, that it could not produce the disease for which it was responsible in its normally virulent form: or a killed virus that retained the faculty of inducing a protective antibody response in the vaccinated individual.

The first of the viral vaccines to result from these advances was for yellow fever, developed by the microbiologist Max Thieler in the 1930s. About 1945 the first relatively effective vaccine was produced for influenza; in 1945 the American physician Jonas E. Salk introduced a vaccine poliomyelitis and in 1960 an oral poliomyelitis vaccine, developed by the virologist Albert B. Sabin, came into wide use.

These vaccines went far toward bringing under control thee of the major diseases of the time, although in the case of influenza a major complication id the disturbing proclivity of the virus to change its character from one epidemic to another. Even so, sufficient progress has been made to ensure that a pandemic like the one that swept the world in 1918-1919, killing more than 15,000,000 people, is unlikely to occur again.

Дата добавления: 2014-12-29