From scopes that help premature babies breathe to techniques for imaging live
neurons and beating hearts as they develop, the latest optical and laser technology
being deployed in medicine and the biosciences will be on display at the Optical
Society's (OSA) Annual Meeting, Frontiers in Optics (FiO), which takes place
Oct. 11-15 at the Fairmont San Jose Hotel and the Sainte Claire Hotel in San
Jose, Calif.
Peripheral nerves are the organic wires that connect the command centers in
the brain to the muscles and other tissues they control. Understanding how these
nerves function is of critical importance because of their central role in many
human diseases. Now a group of researchers at Stanford University has designed
a way to observe one critical aspect of peripheral nerve function -- the transport
of essential proteins and other materials from one end of a nerve fiber to another.
Because they can snake several feet from the spinal cord to the extremities,
peripheral nerves are often quite long -- sometimes 100,000 times longer than
other cells in the body. The transportation of materials along this entire length
is an extremely long and complicated process that can take days or even weeks.
Studying this process has always been a complicated proposition, but Bianxiao
Cui and her Stanford colleagues have demonstrated a new way of observing this
transport by tagging single molecules, called nerve growth factors, with "quantum
dots" that can be followed with a powerful microscope as they move along
live neurons.
The researchers' technique is analogous to looking at a dark highway from the
window of an airplane. The dark, invisible lanes of roads are microtubules,
the skeleton of the cell. The nerve growth factor molecules ride in the cars
that are illuminated by their quantum dot headlights. One thing Cui and her
colleagues have observed, which has never been seen before, is that packages
in transport can jump from one microtubule to another as they move along --
like cars switching lanes as they roll down the highway. They also discovered
that the majority of those cars are single passenger; they only contain a single
nerve growth factor molecule.
Scientists have known for a long time that these proteins are essential, since
they help the nerve cells survive by regulating gene expression. But Cui and
her colleagues showed that even a single molecule of nerve growth factor is
enough to trigger the transport process and sustain signaling during axonal
transport to the cell body. (Paper LSThB3, "Single Molecule Imaging of
Axonal Transport in Live Neurons" is at 9 a.m. Thursday, Oct. 15).
Posted September 29th, 2009
