As I’m sure many attendees of the ACS national meeting this week noticed, the shuttle pick-up times were rather, um, sparse. This threw a wrench into the works for those who like to hop back and forth between sessions. As a result, many of us had to commit to certain symposia and listen to talks that we might otherwise have skipped out on.
And there are always one or two talks in a session that don’t entirely fit in with the theme running through the others. But sticking around for those talks doesn’t necessarily turn out to be such a bad thing.
I attended a session hosted by the Division of Analytical Chemistry on Wednesday that might loosely be described as “imaging biological systems with nonlinear optical techniques.” Most of the talks described results obtained from in vivo imaging of biological matter (human hair, cancer cells, etc.) via second or higher harmonic generation microscopies.
Chris B. Schaffer of Cornell University, however, presented fascinating results his group has obtained using nonlinear techniques to cause localized damage to cells, rather than just to image them. Schaffer’s group is studying small-scale strokes in the brain; these tiny clots or leakages in small blood vessels are implicated in dementia and Alzheimer’s disease. Normally, larger scale strokes are studied in animal models by tying off blood vessels to initiate a stroke, Schaffer said, but in small strokes, this isn’t really possible.
Image of blood vessels on the surface of a live rat's brain. Courtesy of the Schaffer Group
So his group uses nonlinear laser ablation to “produce an occlusion in a targeted way,” he said. After a specific blood vessel has been damaged, the natural clotting cascade is triggered, producing what looks like a small stroke. At this point, the researchers are able to study the changes in blood flow in the network around the damage with two-photon excited fluorescence microscopy.
Schaffer’s group has found that if an artery on the surface of the brain is damaged, blood flow is not impacted much, presumably because of the connectivity of all the blood vessels in that network. However, if an artery that penetrates down into the brain is damaged, blood flow in the system is severely affected. In addition, when the team created an occlusion in the brain of a rat with Alzheimer’s disease, new amyloid plaques formed around the damaged area relatively quickly, indicating what might be a “positive feedback cascade for treating” the disease, Schaffer said.
Anyone else out there stick with a session that forced you to learn something new and exciting?