Imaging


By Laurel Hamers

One of the brain’s amazing abilities is self-repair: Although injury or illness may disrupt neural circuits, many connections will reform over time.

Artur Llobet, an MBL Research Awardee from the University of Barcelona, is spending his second consecutive summer in the Whitman Center for Visiting Research investigating olfactory neuron repair in Xenopus laevis, the African clawed frog.

Calcium labeling of olfactory sensory neurons' presynaptic terminals in a Xenopus laevis tadpole. Photo credit: Artur Llobet

Labelling of presynaptic terminals of olfactory sensory neurons in a Xenopus laevis tadpole using calcium green dextran. Image is pseudocolored so that yellow represents higher and blue lower calcium concentration.
Photo and caption: Artur Llobet

“One of the advantages of working with frogs is that they have fantastic regenerative capabilities,” says Llobet. Tadpoles are able to repair damaged neural circuits in a few days, making them ideal test subjects.

Llobet is working with a transgenic line of Xenopus tadpoles that express green fluorescent protein (GFP) in their neurons, allowing him to easily see the neural connections. Last year, he studied the timeframe of Xenopus neural repair by measuring how long snipped olfactory nerves took to regrow. Now, he is trying to understand in greater detail the mechanisms behind the repair process.

Neurons pass electrochemical messages between each other at junctions called synapses; when a neuron fires, the voltage change propagates along the nerve fiber (axon) and calcium increases at the presynaptic terminal, which releases neurotransmitters. By labeling the tadpoles’ synaptic terminals with calcium indicators, Llobet can visualize the functionality of the re-grown connections and determine when during the repair process the new synapses start signaling.

“In a GFP animal, we can see that the nerve has re-grown, but we don’t know if that nerve is actually working or not,” says Llobet. “So we look at the synapses and see whether the calcium concentration increases when we stimulate olfactory sensory neurons.” This calcium accumulation indicates that the new nerve is not just present, but also functional.

By examining neural repair in frogs, scientists hope to gain insight into this process in more complex systems such as the human brain.

Llobet’s research is taking place through the National Xenopus Resource (NXR) at the MBL, a center that maintains breeding stocks of frogs and provides training on advanced imaging and experimental technologies. According to Llobet, the specialized resources offered by the NXR make this research project possible. He is one of six MBL Research Awardees in 2014 to be using the animals and research services of the NXR, which is one of 28 National Institutes of Health-funded Animal Resource Centers nationwide and a cornerstone facility of the MBL’s Bell Center for Regenerative Biology and Tissue Engineering.

A whimsical, enlightening video about cuttlefish camouflage by Jacob Gindi, a senior and biology major at Brown University, appeared in The New York Times last week. Gindi had encountered live cuttlefish when he visited the MBL’s Marine Resources Center as a student in The Art and Science of Visual Perception, a Brown course co-taught by Roger Hanlon of the MBL and Mark Milloff of Rhode Island School of Design. Gindi then had a chance to make a CreatureCast video in Casey Dunn’s Invertebrate Zoology class at Brown. Inspired by Hanlon’s research, Gindi’s artful video about the cuttlefish’s amazingly adaptive skin can be enjoyed by marine biology-lovers of all ages.

“It is so gratifying to see science and art promoted at this national/international scale,” says Hanlon, an MBL senior scientist and professor in Brown’s Ecology and Evolutionary Biology Department through the Brown-MBL Partnership and Graduate Program.

CreatureCast, a collaborative blog produced by members of the Dunn Lab, is supported by a National Science Foundation grant.

 

 

Pedestrians in Edinburgh, Scotland, have been treated to a springtime display of giant photos of “glowing” or bioluminescent animals, including images of the jellyfish Aequorea aequorea captured by MBL Distinguished Scientist and 2008 Nobel Laureate Osamu Shimomura (panel behind girl on bike).

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The display, called “Living Lights,” was part of the 2014 Edinburgh International Science Festival and this week is moving to another venue in Edinburgh, Our Dynamic Earth, where it will remain through October.

Shimomura took these photos of Aequorea in 1961, when he was a young chemist at Princeton University asking, “What makes the jellyfish glow?” He captured thousands of jellyfish from the waters off Friday Harbor, Washington, and painstakingly searched for their bioluminescence molecule. The two photos on top (below) and at the one at bottom left he took in daylight, shooting directly into the clear Friday Harbor water, using a Nikon F camera and 50 mm lens. Shimomura brought one jellyfish into a darkroom and exposed it to fresh water to trigger its luminescence, allowing him to capture the phenomena on camera (bottom right).

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Shimomura did find and isolate the jellyfish’s bioluminescence protein—which he called “aequorin” –that year, and in the process he also discovered a fluorescent jellyfish protein that he called “green protein.”

Years later, in 1994, Martin Chalfie of Columbia University discovered that the jellyfish’s green fluorescent protein (GFP) could be an extremely useful tool for lighting up microscopic cells and their parts for study. GFP and other fluorescent proteins are now used in biomedical research worldwide, and they have been crucial in illuminating many processes that were previously invisible, such as the development of nerve cells or the spread of cancer. Shimomura, Chalfie, and Roger Tsien of University of California, San Diego, were awarded the 2008 Nobel Prize in Chemistry for their contributions to GFP’s discovery and applications.

The "Living Lights" photo exhibit of bioluminescent organisms in front of the Scottish National Gallery, Edinburgh.

The “Living Lights” photo exhibit of bioluminescent organisms in front of the Scottish National Gallery, Edinburgh, Spring 2014.

 

MBL Distinguished Scientist Osamu Shimomura at Friday Harbor, Washington, in 2003. Photo by Martin Chalfie

MBL Distinguished Scientist Osamu Shimomura at Friday Harbor, Washington, in 2003. Photo by Martin Chalfie

 

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One barometer of the weather is a plant’s seasonal cycles, such as the date when its leaves sprout in spring or drop off in fall. What these cyclic events, called plant phenology, might reveal about climate change is the focus of a long-term Brown-MBL study in a Martha’s Vineyard, Mass., forest.

An automated camera on a tower can record seasonal changes in overall leaf color, but photos might not always correspond to seasonal biochemical changes within leaves themselves. Credit: Marc Mayes/Brown University

An automated camera on a tower records seasonal changes in leaf color in a Martha’s Vineyard forest. Credit: Marc Mayes/Brown University

“Our overall goal is to understand the phenology of trees in a temperate, deciduous forest, and how it responds to climate change,” says MBL Ecosystems Center scientist Jianwu (Jim) Tang.

Tang and his collaborators have placed digital cameras on meteorological towers in the Vineyard’s Manuel F. Correllus State Forest, at the Nature Conservancy Hoft Farm Preserve, and in a private forest, and have been continuously capturing images of the trees and leaves since 2000.

They discovered recently that forest “greenness,” as captured by the digital images, does not necessarily correspond to direct measures of peak chlorophyll content in the leaves, which is an indicator of photosynthesis. (Photosynthesis levels, in turn, indicate rates of carbon absorption by the leaves, which is important information for modeling the impacts of climate change.) Their results are published online in the Journal of Geophysical Research: Biogeosciences.

“While color of leaves is important information, we found it is not sufficient to derive the real phenology change,” says Tang. They needed to supplement the imaging data by collecting leaves on a weekly basis and measuring chlorophyll levels in the lab. “This is a warning for future study,” says Xi Yang, a graduate student in the Brown-MBL Partnership and Graduate Program and lead author on the new paper. Yi’s advisors are Tang and John F. Mustard, professor of geological sciences at Brown University.

For more information, please see this press release issued by Brown University.

Citation:

Yang X, Tang J, Mustard J (2014) Beyond leaf color: comparing camera-based phenological metrics with leaf biochemical, biophysical and spectral properties throughout the growing season of a temperate deciduous forest. J. Geophys. Res. DOI: 10.1002/2013JG002460

 

 

The MBL hosted the annual Brown-MBL Partnership retreat, November 8-9 in Woods Hole. Thirty-six Brown undergraduate students visited MBL laboratories, the Marine Resources Center, the Semester in Environmental Science, and the Waquoit Bay National Estuarine Research Reserve to investigate research and internship opportunities at MBL.

The retreat featured a symposium, “Imaging Across Biology,” and a display organized by MBL Senior Scientist Rudolf Oldenbourg with contributions from Shinya Inoué (MBL), Louie Kerr (MBL), Mai Tran (MBL), and Jim McIlvain (Zeiss Inc.) and others that traced the history of microscopy at the MBL.

Rudolf Oldenbourg explains the principles of polarized light to Brown students visiting for the Brown-MBL Partnership retreat.

 

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