The discovery of insulin
In May 1921, Banting and Best began to conduct experiments on dogs. They removed the pancreas of some dogs and tied off the pancreatic duct of others. The dogs whose pancreas had been removed altogether developed diabetes, as expected, while the dogs whose ducts had been tied did not. While the pancreatic cells that produced digestive secretions degenerated in the dogs whose pancreatic duct had been tied, the islets of Langerhans remained undamaged. Clearly, the islets of Langerhans produced the secretions that prevented diabetes occurring. Banting and Best wanted to extract and isolate
these secretions, but it was difficult to keep the dogs alive long enough to carry out tests.
After numerous setbacks, resulting in the deaths of several dogs, they succeeded in keeping a severely diabetic dog alive with injections of an extract made from the tied-off pancreas. They called this extract isletin. Their next challenge was to find a way of producing enough extract to make it a practicable treatment for diabetes.
Realizing that relying on a supply of dogs was going to hold back research, Banting and Bestmoved on to using the pancreas of cows, obtained from a local slaughterhouse. They managed to extract a substance that contained a greater amount of the active ingredient and injected it into one of the laboratory dogs that had had its pancreas removed. The dog’s blood sugar dropped significantly.
Human testing
At the end of 1921, Macleod invited James Collip, a skilled biochemist to help purify Banting and Best pancreatic extract for clinical testing in humans. On 11 January 1922, the extract was injected into 14-year-old Leonard Thompson a diabetic patient who was close to death, at the Toronto Gene Hospital. The first test proved disappointing, but it was repeated with a purer version of the extract around two weeks later, this time with much better results. Thompson’s blood sugar returned to normal levels and his other symptoms abated.
’In May 1922, Macleod delivered a paper, “The Effects Produced on Diabetes by Extracts of Pancreas”, on behalf of the team at the annual conference of the Association of American Physicians. He received a standing ovation. The paper used the word “insulin”for the first time.
The discovery of insulin
Pandemics are outbreaks of infectious disease spread over multiple countries. Some spread rapidly but are less damaging, such as the pandemic swine flu of 2009. Others spread slowly but are highly dangerous, such as Ebola. A few spread quickly and make many who catch it very ill. The COVID-19 outbreak that erupted in 2020 is one such pandemic. The Great Influenza was one of the most devastating pandemics in history, killing 50 million people in the wake of World War I. Like COVID-19, this was caused by a virus – now identified as a deadly strain of the H1N1 influenza virus. A major discovery in the century between these two outbreaks is that all it can take to trigger a pandemic is a tiny chance mutation in a virus, especially an influenza virus or a coronavirus such as the virus that causes COVID-19. That mutation conceals the virus’s identity, leaving the human body defenceless. The proximity of people and animals in the modern world makes such mutations highly likely. Pandemics are complex global threats that test to the limits how people and governments behave. Epidemiologists have made much progress in understanding how an epidemic spreads fromone area to multiple countries (at which point it becomes a pandemic), and experts provide detailed protocols for taking action. Yet vaccines remain the one proven weapon against such outbreaks. In 2005 – more than 80 years after the Great Influenza pandemic – American virologist Jeffery Taubenberger revealed the complete genetic structure of the 1918 H1N1 virus, enabling it to be reconstructed and analysed. This was a landmark achievement in increasing scientists’ ability to pin down the exact nature of a mutant virus and provide the necessary data to create a vaccine quickly.