Veterinary Physiology-III

HISTORICAL BACKGROUND

• How did scientists first find out what endocrine glands do?
  • Scientists first removed the gland and monitored the organism for changes (like in hormone deficiency).
  • Then scientists replaced the gland or gave an extract of the gland to see if the abnormalities disappeared (like in replacement therapy).
  • Then scientists implanted the gland or gave extract to a normal individual to see the symptoms (like in hormone excess).
  • Once a gland was identified as a source of hormones, extracts from the gland were purified and a test was designed to calibrate the activity of the hormone in another organism (known as a bioassay).
• The writings of Hippocratus and Aristotle as early as BC 460 to 322 contain some information that their might be internal control over body functions
• First recorded endocrine experiment was published by Berthhold (1849). He discovered castrated cockerels failed to develop their combs and wattles and also failed to exhibit male behaviour. Replacement of one or both testes back into abdominal cavity restored the lost function.
• In 1889, von Mering and Minkowski demonstrated that surgical removal of pancreas from dog produced a disease later to be known as diabetes mellitus. This led to the recognition of insulin in the control of diabetes mellitus in man and dogs.
• In 1902, Canadian physiologists Bayliss and Starling discovered that a substance liberated by small intestinal mucosa stimulate the pancreatic juice flow. The active substance was named as secretin. They coined the word “hormone” (from the Greek "I arouse to activity" or "I excite") to this newly discovered substance.
• Banting and Best (1921) isolated the potent pancreatic extract containing insulin
• In 1949, Hench and co workers isolated a hormone from adrenal cortex- cortisone or compound E that relieved some of the symptoms of rheumatoid arthritis.
• In 1953, Simpson and Tait found that unidentified steroid present in adrenal gland was aldosterone. In the same year, Sanger established the amino acid sequence for insulin for which he bagged the Nobel Prize.
• In 1953, Du Vigneaud and his co-workers determined the structure of oxytocin and vasopressin.
• In 1955, Harris provided the data suggesting that the release of pituitary hormones was controlled by humoral factors of hypothalamic origin.
• In 1962, Earl Sutherland described the presence of cyclic AMP in biological materials.
• In 1978, insulin was synthesized by a strain of genetically engineered E.coli.
• For the development of RIA for hormone analysis, Rosalyn Yalow received the Nobel prize in 1978.