“Combining these imaging modalities could improve our understanding of the brain’s structure and behavior in specific conditions such as after treatment with a targeted drug,” said research team leader Emmanuel Bossy from the CNRS/ Université Grenobe Alpes Laboratoire Interdisciplinaire de Physique. “The endoscope’s small size helps minimize damage to tissue when inserting it into the brains of small animals for imaging.”

In The Optical Society (OSA) journal Biomedical Optics Express, Bossy’s research team, in collaboration with Paul C. Beard’s team from University College London, describe their new multi-modality endoscope and show that it can acquire photoacoustic and fluorescent images of red blood cells and fluorescent beads.

Two images are better than one

Acquiring fluorescence and photoacoustic images with the same device provides automatically co-registered images with complementary information. Fluorescent signals, which are created when a fluorescent marker absorbs light and re-emits it with a different wavelength, are most useful for labeling specific regions of tissue. On the other hand, photoacoustic images, which capture an acoustic wave generated after the absorption of light, do not require labels and thus can be used to image blood dynamics, for example.

The new endoscope uses a technique called optical wavefront shaping to create a focused spot of light at the imaging tip of a very small multi-mode optical fiber. “Light propagating into a multi-mode fiber is scrambled, making it impossible to see through the fiber,” said Bossy. “However, this type of fiber is advantageous for endoscopy because it is extremely small compared to the bundles of imaging fibers used for many medical endoscopic devices.”

To see through the multi-mode optical fiber, the researchers used the spatial light modulator to send specific light patterns through the fiber and create a focus spot at the imaging end. When the focus spot hits the sample, it creates a signal that can be used to build up an image point by point by raster scanning the spot over the sample. Although other researchers have used multimode fibers for fluorescence endoscopy, the new work represents the first time that photoacoustic imaging has been incorporated into this type of endoscope design.

Adding sound sensitivity

The researchers added photoacoustic imaging by incorporating an additional, very thin optical fiber with a special sensor tip that is sensitive to sound. Because commercially available fiber optic acoustic sensors are not sensitive or small enough for this application, the researchers used a very sensitive fiber optic sensor recently developed by Beard’s research team.

“The focused spot of light allows us to build the image pixel by pixel while also increasing the strength of fluorescence and photoacoustic signals because it concentrates the light at the focal spot,” explained Bossy. “This concentrated light combined with a sensitive detector made it possible to obtain images using only one laser pulse per pixel, whereas commercial fiber optic acoustic sensors would have required many laser pulses.”

The researchers fabricated a prototype microendoscope that measured just 250 by 125 microns squared and used it to image fluorescent beads and blood cells using both imaging modalities. They successfully detected multiple 1-micron fluorescent beads and individual 6-micron red blood cells.

Because fluorescence endoscopy in rodent’s brain has been performed by other scientists, the researchers are confident that their dual modality device will work in similar conditions. They are now continuing work to increase the device’s acquisition speed, with a goal of acquiring a few images per second.

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Materials provided by The Optical Society. Note: Content may be edited for style and length.

In an era of rising sea level, beaches need to migrate landward, otherwise they drown. Beach migration, also known as shoreline retreat, causes coastal erosion of private and public beachfront property. Shoreline hardening, the construction of seawalls or revetments, interrupts natural beach migration — causing waves to erode the sand, accelerating coastal erosion on neighboring properties, and dooming a beach to drown in place as the ocean continues to rise.

The team of scientists, led by graduate researcher in the SOEST Department of Earth Sciences Kammie Tavares, assessed the shoreline around O?ahu that would be most vulnerable to erosion under three scenarios of sea level rise — all estimated to occur before, and shortly after mid-century.

They identified the location and severity of risk of shoreline hardening and beach loss, and a potential timeline for the increase in erosion hazards. The most threatened properties fall into an “administrative erosion hazard zone,” an area likely to experience erosion hazards and qualify for the emergency permitting process to harden the shoreline.

“By assessing computer models of the beach migration caused by 9.8 inches (0.25 meters) of sea level rise, an amount with a high probability of occurring before mid-century, we found that emergency permit applications for shoreline hardening to protect beachfront property will substantially increase,” said Tavares.

According to co-author Dr. Tiffany Anderson, Assistant Researcher in the Department of Earth Sciences, “We determined that almost 30 percent of all present-day sandy shoreline on O’ahu is already hardened, with another 3.5 percent found to be so threatened that those areas qualify for an emergency permit today. Our modeling indicates that, as sea level rises about 10 inches (0.25 meters) by mid-century, an additional nearly eight percent of sandy shoreline will be at risk of hardening — meaning at that point, nearly 40% of Oahu’s sandy beaches could be lost in favor of hardened shorelines.”

“In another study published in 2018, we showed that accelerated erosion on neighboring properties, called flanking, usually leads to additional shoreline hardening, and condemnes entire beaches,” said co-author Dr. Chip Fletcher, Associate Dean and Professor in SOEST. “It is clear that management decisions made today, and during the careers of most of today’s natural resource managers, will be critical in determining if future generations will inherent a healthy shoreline, or one that has been ruined by seawalls, and other types of shoreline hardening.”

Coastal erosion is inevitable when sea level is rising and global mean sea level has been rising for decades and is accelerating. The Intergovernmental Panel on Climate Change has projected continued sea level rise for many centuries, even if greenhouse gas emissions are reduced or stopped altogether. However, economists are projecting that greenhouse gas emissions will likely continue into mid-century and we will see more years like 2019 when the use of fossil fuels rose faster than the use of renewable forms of energy.

“Despite these facts, we continue to see shoreline hardening as the preferred policy choice, largely because management agencies have failed to develop assisted transition plans for beachfront landowners who are caught in a tightening vice because of accelerating sea level rise,” said Fletcher. “In fact, directly to the contrary, beachfront lands continue to be sold to unwitting buyers with no appreciation for the expensive and frustrating situation they are entering into.”

“Because coastal zone management laws continue to allow hardship variances in this era of rising sea level, despite widespread knowledge that seawalls kill beaches under these conditions, the same legal system designed to protect public trust lands, is responsible for destroying them,” according to Fletcher. “Government agencies must develop creative and socially equitable programs to rescue beachfront owners and free the sandy ecosystem so that it can migrate landward as it must in an era of rising seas. It is urgent that options are developed soon for beachfront landowners and resource managers to avoid further destructive management decisions.”

“Beaches are critical ecosystems to native plants and animals, offer protection from storms, are an essential cultural setting, and attract tourists, who are important for Hawai’i’s current economy,” added Tavares. “This research shows that conversations on the future of our beaches and how we will care for them must happen now rather than later, if we are to protect our sandy beaches.”

The method is described in a paper, “Small subunits can determine enzyme kinetics of tobacco Rubisco expressed in Escherichia coli,” published in the journal Nature Plants.

Scientists have known that crop yields would increase if they could accelerate the photosynthesis process, where plants convert carbon dioxide (CO₂), water and light into oxygen and eventually into sucrose, a sugar used for energy and for building new plant tissue.

Researchers have focused on Rubisco, a slow enzyme that pulls (or fixes) carbon from carbon dioxide to create sucrose. Along with CO₂, Rubisco sometimes catalyzes a reaction with oxygen from the air, and when it does, it creates a toxic byproduct and wastes energy, thereby making photosynthesis inefficient.

“You would like Rubisco to not interact with oxygen and to also work faster,” said Maureen Hanson, professor of plant molecular biology at Cornell.

In an effort to achieve that, the researchers took Rubisco from tobacco plants and engineered it into E. coli. Tobacco serves as a common model plant in research. “We can now make mutations to try to improve the enzyme and then test it in E. coli,” Hanson said.

The advantage is that since bacteria reproduce so rapidly, researchers may test an altered Rubisco in E. coli and get results the next day. “If you introduce a new Rubisco into a plant, you have to wait a few months” to get results, she said.

Initial work by another group that engineered tobacco Rubisco into E. coli led to very weak expression of the enzyme. In plants, Rubisco is composed of eight large and eight small subunits. A single gene encodes each large subunit, but many genes encode each small subunit. The complex process of enzyme assembly and the presence of multiple versions of the enzyme in plants has made it very hard to experiment with Rubisco.

Led by Myat Lin, a postdoctoral research associate in Hanson’s lab and the paper’s first author, the researchers were able to break down the process and express a single type of large subunit and a single type of small subunit together in E. coli, to understand the enzyme’s properties. By doing this, they attained expression of the enzyme in E. coli that matched what was found in plants.

They also discovered that a Rubisco subunit found in trichomes (tiny hairs on plant leaves) worked faster than any of the subunits found in leaf cells.

“We now have the ability to engineer new versions of plant Rubisco in E. coli and find out whether the properties of an enzyme are better,” Hanson said. “Then, we can take the enzyme that’s improved and put that into a crop plant.”

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Materials provided by Cornell University. Original written by Krishna Ramanujan. Note: Content may be edited for style and length.