Nerves of steel

Working quietly in her bedroom, Rita Levi-Montalcini used a scalpel fashioned out of a sewing needle and a watchmaker's tweezers to cut a tiny hole in the shell of a fertilised chicken egg, and nip out a budding tissue that would have grown into a wing. She then stained and fixed the embryo in melted wax, mounted it on a glass slide, and examined it under a microscope to see how growing nerve cells would respond to the missing wing. When an air raid siren sounded outside, she had to stop her experiment and hurry down to the basement with her family to escape to a bomb shelter, microscope and slides tucked under her arm.

Levi-Montalcini was living in Turin, Italy, in the 1940s, when nighttime bombings by Allied Forces were routine. Growing up with a strict father, she bucked tradition to study medicine after her governess died from cancer. She then veered towards research on the nervous system, inspired by anatomist Giuseppe Levi, who later became her collaborator. In 1938, she lost her academic job when dictator Benito Mussolini passed laws banning Jews from professional careers. Undeterred, she converted her bedroom into a lab and continued her research.

In 1940, she was struck by an article by American scientist Viktor Hamburger, who suggested that developing tissues attracted nerve fibres to grow towards them. Keen to test his idea, she bicycled to nearby farms — her family had by then moved to the countryside to escape the bombings — to buy fertilised eggs under the pretext of feeding her family, and continued her experiments in her bedroom (bit.ly/Nobel-Laureate). Unlike Hamburger, who had focused only on the early days of embryo development, Levi-Montalcini checked the embryos each day throughout their development. Using tissue stains, she and Levi noticed that nerve cells grew until they reached the missing wing, but then just gave up and died. They realised that the wing must be releasing some chemical which neurons needed to survive and reach their target organ.

Impressed with her work, Hamburger invited Levi-Montalcini to the U.S., where she spent the next 30 years. Working with him and biochemist Stanley Cohen, she found that grafting a tumour slice onto the nerve tissue helped neurons grow profusely — "like rivulets flowing over a bed of stones" (bit.ly/Tumour-Grafting) — confirming that the tumour also released the chemical. She even managed to smuggle tumour-riddled mice to a collaborator's lab in Rio de Janeiro so she could capture vivid images of growing nerve fibres stretching towards the tumour tissue. Cohen also discovered that snake venom surprisingly contained large amounts of the same chemical. It turned out to be a peptide that they extracted and named nerve growth factor (NGF). For their work, Levi-Montalcini and Cohen jointly won the Nobel Prize in Physiology or Medicine in 1986.

In later years, Levi-Montalcini became a revered figure in Italy, where she was appointed Senator for Life — among the country's highest honours. She lived to the ripe age of 103, becoming the longest-living Nobel Laureate in history.

Ranjini Raghunath is a Bengaluru-based science writer and editor.