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Endocrine System - Historical Background There are two major systems designed to maintain or reestablish homeostasis in the body. The first is the nervous system which carries out this function through nerve impulses. The second is the endocrine system. The endocrine system consists of a group of organs which produce chemical messengers called hormones. These chemicals are released into the blood and may have their effect on distant organs. This description was first stated in 1855 by the French biologist Claude Bernard. Western medicine owes a great deal to the work of Arab and Chinese physicians most of whom are unheralded and unknown. For example, by 700 AD, Chinese healers had associated the endocrine disease myxedema with inactivity of the thyroid gland. They treated their patients with extracts of thyroid glands. This method of treating myxedema was "rediscovered" by Edward Schaefer in the 1890's. Long before Western medicine was established as a science, Chinese physicians could diagnose diabetes mellitus by tasting the patient's urine. This practice was described by the English physician Thomas Willis in the mid 1660's: "Taste thy patients urine. If it be sweet like honey, he will waste away, grow weak, fall into sleep and die." 1775 - Matthew Dobson discovered elevated sugar levels in the blood, as well as, the urine of diabetics. He concluded that the disease was metabolic and not just a defect of the urinary system. 1855 - In France, Claude Bernard was studying the role of the liver in regulating blood sugar levels. He concluded that "the body maintains steady internal conditions through the release of internal secretions (hormones) from ductless (endocrine) glands". 1869 - Paul Langerhans, a young German scientist, discovered unique clusters of cells in pancreatic tissue. These clusters were named Islets of Langerhans in his honor. Langerhans found that the isles did not connect to the system of ducts leaving the pancreas. 1870 - In England, Richard Bright noticed that in patients who died of diabetes mellitus, the pancreas showed signs of degeneration. This condition was called Bright's disease. 1885 - The English physician Thomas Addison noticed that a catastrophic illness was always associated with degeneration of the cortex of the adrenal glands. Addison's disease, as it was called, was generally a product of chronic tuberculosis. 1889 - After removing the pancreas' from dogs, Von Mering and Minkowski noted that an abundance of flies and ants were attracted to their urine. They reasoned that this was due to the presence of sugar in the urine - a sign that the dogs had become diabetic. In another experiment, they tied off the pancreatic ducts of another group of dogs. This prevented the exocrine product of the pancreas from reaching the small intestine. This resulted in the atrophy of the exocrine tissue of the pancreas without the dogs becoming diabetic. Von Mering and Minkowski concluded that the basis of diabetes mellitus was endocrine. 1894 - Oliver and Schaefer isolated epinephrine from the adrenal glands of dogs. When this substance was injected into a healthy dog, it produced a profound hypertension and rapid heart beat. Later in 1901, Frederick Stolz synthesized epinephrine. 1895 - Edward Schaefer removed the pancreas from a group of dogs rendering them diabetic. He them surgically implanted a pancreas from another dog. This procedure eliminated the symptoms of diabetes mellitus almost immediately. 1901 - Eugene Opie of Johns Hopkins University found that in diabetic patients, the islets of Langerhans were degenerated. 1902 - William Bayliss and Ernest Starling suspected
that the entrance of acidic material into the duodenum from the stomach
triggered the release of pancreatic juice from the pancreas. They proved
their hypothesis by grinding up a piece of small intestine in hydrochloric acid.
They injected and extract from this mixture into a dog and observed pancreatic
juice being released from its pancreatic ducts. Bayliss and Starling
proposed that a chemical, secretin, was released from the intestinal lining into
the blood. This chemical messenger travels to the pancreas through the
blood and triggers the release pancreatic juice into the duodenum. 1914 - Edward Kendall purified the hormone thyroxine from the pig thyroid. He had to process over three tons of thyroids to prepare 1 oz of thyroxine crystals. In 1921, thyroxine was synthesized. 1921 - At the University of Toronto in Canada, Fredrick Bunting and Charles Best extracted insulin from the pancreas' of fetal pigs to produce the first preparation to treat humans suffering from diabetes mellitus.
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