Images reveal cell organization, behavior and more
BOSTON – Scientists from various disciplines came together to discuss the latest imaging techniques and innovations at the recent American Association for the Advancement of Science (AAAS) annual meeting.
Interdisciplinary collaboration is vital to biophotonics, especially in the area of imaging. A special symposium called “Innovations in Imaging: Seeing is Believing” brought physicists and cell biologists together to discuss collaboration and innovation in microscopic imaging.
“All of the recent advances in imaging have required interdisciplinary collaborations between biologists, who bring the motivating questions, and physicists and computational biologists, who supply the microscopy innovations and/or computational tools needed to address the hypothesis-driven questions of experimentalists,” said session organizer Amy S. Gladfelter of Dartmouth College in Hanover, N.H., and the Marine Biological Laboratory (MBL) in Woods Hole, Mass.
Cellular structures are seen by Bessel beam plane illumination microscopy. Clockwise from upper left: membrane ruffles in a monkey kidney cell; chromosomes (green) and golgi (magenta) in a dividing pig kidney cell; mitochondria in a living pig kidney cell; and microtubules (green) and nuclei (magenta) in a pair of human osteosarcoma cells. Courtesy of Eric Betzig/HHMI.
The panel featured three physicists and three biologists, several of whom are affiliated with MBL, a leading center for innovation in biophysics and biological imaging. “Imaging is an interdisciplinary endeavor that marries expertise and innovation in physics, computer science and applied mathematics with challenging questions in cell and organism assembly,” Gladfelter said.
“We are beginning to understand the basis for cell organization at unprecedented spatial and temporal resolution through the creative application of fundamental physics to microscopy,” she added.
The symposium was designed to “help motivate the next phase of interdisciplinary approaches to advance the visualization of life, from the scale of a single molecule to the whole organism.”
Fluorescence image of a living cell (MDCK: Madin-Darby canine kidney) expressing septin molecules linked to green fluorescent protein. The image was recorded with the Fluorescence LC-PolScope and shows fluorescent septin fibers in color, indicating that the fluorescence is polarized and the septin molecules are aligned in the fibers. Courtesy of Amy Gladfelter/Dartmouth College and Rudolf Oldenbourg/MBL.
The session included discussions on capturing 3-D dynamics in cells and embryos, and single-molecule imaging and analysis. “All of the talks addressed ways that barriers in time and space are being dismantled to enable the detection of events in the cell that are smaller and/or happening on a faster timescale than ever before seen,” Gladfelter said.
The data can be used for diagnosis and development of pharmaceuticals as well as fundamental understanding of biology, she added. “Images also bring us to a beautiful world beyond the grasp of our normal senses. In this way, microscopes give us beauty and application, often in the same image.
“The interdisciplinary nature of the imaging field, combined with the far-reaching implications of advances in imaging, makes this topic a natural mix of application and beauty.”
Optical microscopy has traditionally been limited by low resolution; electron microscopy must be performed in a vacuum, and even then it has poor penetration. X-ray microscopy could bridge the resolution gap between the two, combining the best of both to hit a sweet spot for chemical and elemental imaging, according to a presentation at a separate session during the AAAS meeting.
“Advances in x-ray sources, detectors, instrumentation and computing power are transforming x-ray microscopy from a scientific curiosity practiced by a few specialists to a widely available form of high-resolution imaging,” said Janos Kirz, a scientific adviser at Lawrence Berkeley National Laboratory’s Advanced Light Source in California and a distinguished professor emeritus at Stony Brook University in New York.
These spermatocytes are from the crane fly Nephrotoma suturalis. This color-enhanced image was generated using a Nikon microscope equipped with liquid crystal components for polarized light imaging, an LC-PolScope that reveals the birefringence of meiotic spindles with striking contrast, regardless of specimen orientation. Thus, the spindle fibers – actually bundles of microtubules – are clearly imaged as bright structures on the nonbirefringent (or weakly birefringent) background cytoplasm. Courtesy of James LaFountain/University at Buffalo and Rudolf Oldenbourg/MBL.
Kirz pioneered the development of soft x-ray microscopy and spectromicroscopy, and he described 2-D and 3-D x-ray chemical imaging of biological systems at the meeting. His presentation, titled “Chemical and Elemental Imaging with X-Ray Microscopy,” was part of the panel session “Visualizing Chemistry: Seeing Another Dimension of Plants and Animals.”
The advantages of x-ray microscopy, Kirz said, are its short wavelength and depth of penetration; with this technique, the absorption edges provide contrast, he pointed out, and fluorescence enables elemental identification.
“State-of-the-art x-ray microscopes can be used to create three-dimensional images with elemental and/or chemical sensitivity,” Kirz said. “Some instruments are also capable of creating movies, or providing stop-motion or flash images of cells and proteins in their natural hydrated state.”
Imaging is not limited to two dimensions, or even three; four are possible, although radiation damage with 4-D imaging must be minimized with cryocooling. X-ray microscopes are “sprouting” at all synchrotron sources, Kirz added.
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