One of the major impediments to understanding how brain cells die during a stroke and identifying new ways to protect them has been the long-standing inability to image strokes, or "ischemic events" in living tissue. Now researchers at Cornell University, led by Research Associate Nozomi Nishimura, have developed methods to induce strokes in animal models and image the events as they unfold.
"We can see the dynamics of interaction," Nishimura says, adding that some neurons most likely die due to interactions with many different types of cells, including immune system cells, vascular cells, astrocytes and glial cells. She and her colleagues visualize intercellular dynamics via two-photon excited fluorescence (2PEF) microscopy, which is able to image individual cells and capillaries. Employing relatively long wavelengths of light, Nishimura and her colleagues have succeeded in imaging at greater depths into tissue than has been possible to date.
Nishimura and her colleagues have also developed a method to induce localized lesions within rodent models. They adapted a technology, femtosecond laser ablation, typically used in micromachining of solid materials, for a novel biological use. This ability to induce specific small lesions is particularly important to creating viable models in which to study the progression typical of dementia. According to Nishimura, it is becoming clear that many elderly people suffering from dementia have experienced a series of microstrokes, triggering cumulative damage. "How is it that these small bleeds or blood clots affect neurons?" she asks, adding that the ability to introduce and then image microstrokes in a model system should shed light on how damage might best be mitigated.
The laser ablation system is also being explored for use in surgical manipulation and in examining tumor migration, specifically, how cells shed from tumors might also block blood vessels.
The presentation, "Nonlinear Optical Tools for Studying Small-Stroke at Microscopic Scales," takes place on Oct. 26 at the Frontiers in Optics (FiO) 2010/Laser Science XXVI -- the 94th annual meeting of the Optical Society (OSA), which is being held together with the annual meeting of the American Physical Society (APS) Division of Laser Science at the Rochester Riverside Convention Center in Rochester, N.Y., from Oct. 24-28.
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