Her triumph came in 1986, when she shared the Nobel Prize in physiology or medicine with her student, the biochemist Stanley Cohen, for their contributions to the understanding of growth factors in human development.

By the 1950s, the pattern of cell growth and differentiation had long been established, and scientists knew that the addition of blood or organ extracts to cells in culture resulted in their successful growth. They did not know, however, the identity of the active substances, just as cancer researchers understood little of the unregulated growth of tumour cells.

In 1952, Rita Levi-Montalcini found that when tumours from mice were transplanted to chick embryos, they induced potent growth of the chick embryo nervous system . She concluded that the tumour released a nerve growth-promoting factor (NGF) which had a selective action on certain types of nerve cells.

Following this discovery, she began to measure the effect of NGF on cells in culture, and discovered that a sensory or sympathetic nerve cell reacted within 30 seconds of the addition of minute quantities of NGF. Just one billionth part of a gram of NGF per millilitre of culture medium exerted a potent growth-promoting effect.

In 1953 the biochemist Stanley Cohen joined her research group at Washington University, St Louis, and together they purified a nerve growth-promoting extract. Rita Levi-Montalcini’s discovery improved scientific understanding of the processes involved in certain physical malformations and diseases. It has led to improved therapeutic agents and could be central to eventual treatments for diseases such as multiple sclerosis or Alzheimer’s as well as psychiatric disorders such as depression or anorexia.

Rita Levi-Montalcini was born, with her twin sister Paola, in Turin on April 22 1909, the youngest of four children. Her father, Adamo Levi, was an electrical engineer and mathematician, and her mother, Adele Montalcini, a talented painter. Their elder brother, Gino, would become a prominent Italian architect and professor at the University of Turin.

Though the family was cultured, Rita’s father took a traditional view of a woman’s place and decided that his three daughters should not go to university. But Rita was convinced she could not be content with a merely domestic role and, at the age of 20, begged her father to be allowed to try for university. Eventually he relented and within eight months she had rectified her deficiencies in Latin, Greek and Mathematics, graduated from high school, and enrolled at the medical school in Turin, where she studied under the histologist Giuseppe Levi.

In 1936 she graduated with a summa cum laude degree in Medicine and Surgery, and began postgraduate work in neurology and psychiatry. But that year, Mussolini issued the Manifesto per la Difesa della Razza, signed by 10 Italian scientists, which called for laws barring academic and professional careers to non-Aryan citizens. She therefore left Italy for Belgium, where she worked as a guest of a neurological institute in Brussels. In 1940, on the eve of the German invasion of Belgium, she returned to the relative safety of Turin.

Realising it would not be possible to pursue her scientific interests openly, Rita Levi-Montalcini built a small research unit in her bedroom. By this time, inspired by a 1934 article by Viktor Hamburger reporting on the effects of limb amputation in chick embryos, she had become interested in the mechanisms controlling the development of the vertebrate nervous system. She had barely begun work when her former teacher, Giuseppe Levi, who had also escaped from Belgium, returned to Turin and joined her in her work.

Forced to leave Turin by the heavy Allied bombing of the city in 1941, she moved her laboratory to a cotta