Tissue culture technique Unlike other parasites, parasitic protozoans are difficult to study due to their small size and association with blood cells. After the discoveries since late 19th century the nature of their infections and diseases they caused, no advancement was made in laboratory culture for half a century. The first successful culture of any protozoan parasite was achieved by Meyer and her colleague Felipe Nery Guimarães. Meyer and Guimarães worked on
Toxoplasma gondii, a protozoan that causes neurological disorders (toxoplasmosis) in a wide range of mammals including humans. After failing with several tissues for maintaining the parasites in culture plates, they used chicken embryos in a Maximow slide which proved to be a success. The procedure made way for further developments of culture methods using various mammalian tissues and cells. In 1942, Meyer with Cecilio Romaña From the basic method, Meyer was able to develop culture methods for other protozoans including
Trypanosoma cruzi (that causes
Chagas disease) and
Plasmodium gallinaceum (that causes bird
malaria).
Electron microscopy of parasites Meyer set up
Philips transmission electron microscopy obtained by Filho from the grants of the National Research Council, and with it she was one of the first scientists to effectively use electron microscopy for biological studies. They used the specimens directly from the culture media and treated them in
osmium tetroxide and
chromium. Only the outline images could be seen, and was anyhow published by them in the journal
Parasitology in 1954. Using the same Porter's method, she and a colleague, I. de Andrade Mendonça at the Biophysics Institute, reported the first image analysis of
T. gondii in
Parasitology in 1955. The method was clearly not applicable on protozoans, they realised, as the cells were too thick for the electrons to penetrate and give clear images. In 1953, Porter and J. Blum developed an
microtome (specifically ultramicrotome) that could cut tissues into extremely thin sections. Realising that it could be the key for the preparation of protozoans, Porter gave Meyer one of the prototypes. In it they gave the first description of what was later called
apicoplast, a cell organelle that distinguishes the phylum
Apicomplexa.
Discovery of nerve growth factor Meyer's friend at Turin, Levi-Montalcini was working as a research associate to
Viktor Hamburger, German embryologist at
Washington University in St. Louis, United States, and was investigating the development of peripheral nerves in chicken embryos. When she removed the growing limbs and transplanted the wing buds in place, she noticed that the degenerated nerves could grow back to normal. Using a tumour cells, mouse sarcoma 180, she induced the growth nerve cell but found that the tumour cells did not actually make any contact with the nerve fibres, indicating that they release some sort of signalling molecules. With Hamburger, she reported the findings in 1951 in
Journal of Experimental Zoology. After several failed attempts to identify the unknown agent, she realised that only sophisticated cell culture would reveal the mysterious molecule, and she did not have that facility. She knew Meyer's laboratory was the only place able to do the experiments. Her experiment with Meyer was a quick success, both tumour cells did produce growth-promoting molecules. Levi-Montalcini, Meyer and Hamburger published the discovery in 1954 in
Cancer Research, drawing the conclusion:It is concluded that the mouse sarcomas tested produce a diffusible agent which strongly promotes the nerve fiber outgrowth of ganglia. The results obtained
in vitro are compared to previous results obtained by intra-embryonic transplantation of the same sarcomas, and the conclusion is reached that the
in vitro and the
in vivo effects on the spinal and sympathetic ganglia are due to the same agent.In 1953, Levi-Montalcini returned to St. Louis and started working with a young biochemist
Stanley Cohen, recruited by Hamburger for chemical analysis. With Meyer's help, they were able to set up their own tissue culture equipment, with which they isolated the elusive molecule in a year. They reported the identification of the new molecule, giving it the obvious name nerve growth-stimulating factor (later shortened as
nerve growth factor) in 1954. For the discovery, Levi-Montalcini and Cohen received the 1986
Nobel Prize in Physiology or Medicine. Levi-Montalcini never forgot to credit the contributions of Meyer, and later lightheartedly recalled:The tumor had given a first hint of its existence in St. Louis but it was in Rio de Janeiro that it revealed itself, and it did so in a theatrical and grand way, as if spurred by the bright atmosphere of that explosive and exuberant manifestation of life that is the Carnival in Rio. == References ==