Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UCSD Laser Technique Sheds Light on Strokes

05.01.2006


Images showing direction of blood flow (white and red arrows) before, during and after clot formation (red X) Credit: Chris Schaffer, Nozomi Nishimura and David Kleinfeld, UCSD, PLOS Biology


A technique developed at the University of California, San Diego that precisely creates and images blood clots in the brain in real time could make it possible to understand the small strokes implicated in many forms of dementia, including Alzheimer’s disease.

The study, published this week in the early on-line edition of the journal Public Library of Science Biology, represents a collaboration between the research groups of David Kleinfeld, professor of physics at UCSD, and Patrick Lyden, professor of neurosciences at UCSD’s School of Medicine. The paper will appear in the print edition of the journal in February.

Using a laser to trigger the formation of individual blood clots in tiny arteries of the brains of anesthetized rats, the researchers were able to monitor the resulting changes in blood flow. They say that their study provides a way to understand small strokes common in elderly humans. These strokes often cause no immediate symptoms, but they are thought to contribute to dementia and may ultimately cause larger strokes.



“Our technique makes it possible, for the first time, to precisely target individual blood vessels to create a blood clot while causing very little collateral damage,” explained Kleinfeld. “We can then follow, in real time, the changes in blood flow in surrounding vessels that occur as a result of the formation of a clot in one small artery of the brain.”

“We know from MRI scans that small strokes are very common in the brains of elderly patients,” added Lyden. “Such small strokes have been linked with dementia, and may also put patients at risk for a major stroke. The power of the technique we describe in the paper is that it allows us to study the response of the brain to stroke in a controlled way. By understanding what happens, we hope to learn how to prevent the major damage associated with stroke.”

In the study, the team members used tightly focused laser light to excite a dye that they had injected into the bloodstream. The excited dye reacted with oxygen to form a free radical, which “nicked” the cells lining the blood vessel at the target location, and triggered the natural blood clotting cascade.

Using two-photon fluorescence microscopy—a powerful imaging tool that uses brief (less than one-trillionth of a second) laser pulses to peer below the surface of the brain, the researchers snapped frames every second before and after the formation of the blood clot. They also measured blood flow in the arteries upstream and downstream of the clot. Remarkably, immediately following the formation of the clot, blood flow downstream of the clot reversed itself.

“People tend to think of blood flow like a river,” said Chris Schaffer, the lead author on the paper, who was an assistant project scientist working with Kleinfeld in physics at the time of the discovery. “If you dam one tributary, then everything downstream from there would be cut off. However, we’ve found that the more complicated topology of the blood vessels leads to the counterintuitive result that blood flow in some downstream vessels reverses direction to compensate for the blockage.”

In the paper, the researchers discuss how this result can explain the observation, by clinicians, that certain regions of the brain seem to be protected from stroke. These protected regions of the brain have networks of vessels with extensive redundant connections. In the case of a blockage, these redundant connections permit blood to flow through alternate loops and be pushed in the opposite direction below the clot, as observed in this study. The reversal prevents downstream regions of the brain from being starved of oxygen.

In addition to what the researchers could observe in real time, the technique facilitates follow-up because the fluorescent molecules used to visualize blood flow bind to injured places in the artery.

“Rather than having to tediously search for the targeted vessels using brain sections, the fluorescence provides a kind of footprint that can be followed,” said Beth Friedman, an associate project scientist working with Lyden in neurosciences and a contributing author on the paper. “Then you can look to see if there have been biochemical changes in the region of the clot, or changes in what genes are expressed, which is especially important to determine if an intervention protects against damage from stroke.”

Kleinfeld and Lyden attributed the advance to collaboration across traditional disciplinary boundaries.

“Pat and I are coming from different worlds, but we had the same question at the back of our minds,” said Kleinfeld.

“Joining forces allowed us to crack a puzzle that either one of us couldn’t crack alone,” added Lyden

Other contributors to the study were Nozomi Nishimura, Lee Schroeder and Philbert Tsai at UCSD and Ford Ebner at Vanderbilt University, Nashville. The research was supported by the David and Lucille Packard Foundation, the Veteran’s Affairs Medical Research Department, the National Institutes of Health, the Burroughs Wellcome Fund and the National Science Foundation.

Media Contact: Sherry Seethaler, (858) 534-4656.

Comment: David Kleinfeld, (858) 822-0342.

Sherry Seethaler | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Life Sciences:

nachricht Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View
22.06.2018 | University of Sussex

nachricht New cellular pathway helps explain how inflammation leads to artery disease
22.06.2018 | Cedars-Sinai Medical Center

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>