New Microscope Enables Real-Time 3-D Movies of Developing Embryos [Slide Show]
A European lab combines "light sheet" microscopy with an illumination process that subtracts the static caused by scattered photons to devise a way to clearly observe the inner workings of cells over a period of days
Image Courtesy of Philipp Keller
Fly-by-Light The early development of the fruit fly is shown at 3.2, 4.85, 8.15, and 11 hours after fertilization. The light sheet microscope technology has been licensed to optics company Carl Zeiss, but until a commercial version hits the market, biologists looking to try the technique will have to build the scopes themselves.
See-Through Flies The latest breakthrough, published in
Nature Methods, is the addition of structured illumination to light sheet microscopy. This allows biologists to subtract out static from scattered photons and get clear pictures of samples that are largely opaque, like the highly opaque fruit fly embryo shown here at 3.2 and 4.85 hours after fertilization. Some biologists are even planning to use it on chick and mouse embryos, whose large, dense yolks have traditionally made them challenging specimens. Philipp Keller
The raw data used to build the digital model [
right hemisphere] are matched up with the model [ left hemisphere] at about five, six, 10 and 14 hours after fertilization. Because the images from light sheet microscopy are so much clearer than those from other forms of fluorescence microscopy, biologists can use computer algorithms to analyze the images and build detailed digital reconstructions. Philipp Keller
Dividing to Multiply
The nuclei in these images are color-coded according the direction they are traveling. After a cell divides the daughter cells go in separate directions, appearing as streaks of different colors moving away from one another. In the very early stages of development [
top] the zebra fish embryo is sparsely populated and cells are dividing quickly; each two-tone stripe is a pair of daughters. Just a short while later [ middle and bottom] the cells are more crowded, but they keep dividing at a breakneck pace. Philipp Keller Advertisement
Twelve hours after fertilization the cells have arranged themselves in a pattern that is just beginning to resemble the body they will become. The empty space just below the center of the embryo is the closing blastopore, where the fish's tail will form. Before light sheet microscopy became available such large, live samples could not be imaged for more than a few hours; the European Molecular Biology Laboratory team that developed the technique has made movies lasting up to 58 hours.
Using a fluorescent microscopy technique that allows long viewing times and exceptionally clear images, scientists can now track each cell in a growing embryo, creating a digital model of development. Here, thousands of cell nuclei in an eight-hour-old embryonic zebra fish are color coded according to speed: cyan nuclei are stationary, whereas orange nuclei are moving more than a micrometer per minute. The technique, called digital light sheet microscopy, debuted in 2008, but recent advances have made it even more powerful.
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