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passage 3
P1
The survival of nerve cells, as well as their performance of some specialized functions, is regulated by chemicals known as neurotrophic factors, which are produced in the bodies of animals, including humans. ███
Context ·
Nerve cells are regulated by chemicals called neurotrophic factors
Spotlight ·
Levi-Montalcini's discovery of NGF was important development in biochemistry
NGF was the first known neurotrophic factor.
P2
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Levi-Montalcini's hypothesis ·
Many nerve cells are programmed to die
Experimentation ·
Discovered that nerve development could be stimulated in chick embryos by implanting tumors
Additional hypothesis ·
Chemical produced by tumors caused nerve growth
Experimentation ·
Tissue culture method confirmed hypothesis and identified the "nerve growth factor" (NGF)
P3
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Later research ·
NGF directs nerves toward appropriate connections, and is necessary for survival of nerve cells
Passage Style
Single position
Spotlight
19.
The passage describes a specific ██████████ ████ ██████ █████ ███ ██ ███ █████████ ███████████
a
A certain kind ██ █████ █████ ████████ █ ████████ ████ ██████████ ███ ██████ ██ █████ ██████
b
Developing embryos initially ████ ████ ████ █████ █████ ████ ████ ████ ██████████ ████████
c
In addition to ████ █████ ███ ███████ █████ █████████ ████████████ ███████ ██████████ ████ ████████ ███ █████████
d
Certain organs contain ███ ██ ██████████████ ████ ██████ ████ ██ ███ ███████████ ███████
e
Certain nerve cells ███ ████████ ████ ███ ██ ███ ██████ █████ ██ █████ ████ ███ ██████████