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Frontiers
Life Like You've Never Seen It Before
February 1996
Follow a white blood cell as it mobilizes to attack
a foreign invader. A drop of serum, triggering the same response that
would occur in an infection, causes the white cell to reorient itself
(in the middle frame, where nucleus and pseudopod, or leading edge, are
indicated), then elongate in a new direction. When the cell arrives at
the source of the stimulus, it will release the toxic eosinophilic granules
shown clustered here.
The images in the right column show the calcium ion level in the cell;
lighter areas indicate a higher concentration of calcium. Calcium increases
when the cell is stimulated and is always highest in the rear of the cell.
Scientists know that calcium is essential for the cell's movement in the
correct direction, but the method these calcium ions use to steer the
cells is still under investigation. The photographs vividly illustrate
the power of a new microscopic imaging technique developed with NSF funding.
Photographs on the cover and these two pages illustrate a new microscopic imaging
technique with nearly four times the resolution of previous microscopes. The
technique, developed by an NSF-funded team of researchers at the University of
Massachusetts Medical Center, combines conventional light microscopes, a sensitive
high speed camera and sophisticated computer programs. The technique makes it
possible to see details of cellular structures that were previously obscured
and to follow chemical events at higher speeds. Researchers can watch as these
structures go about their functions in living cells-as in the sequence on the
cover. Earlier microscopes show sub-cellular particles, but only at lower speed
and lower resolution and under such strong light that the cells are damaged or
destroyed.
The new technique uses a mathematical algorithm that reassigns unfocused light
to its point of origin, eliminating the blurring that occurs in many microscopes.
John Cross, NSF program director of biological instrumentation, describes the
procedure as similar to what was done to the Hubble Space Telescope to improve
its vision.
CENTROSOME
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Credit: Scanalytics and the University of Massachusetts Medical Center |
The centrosome is a sub-cellular organelle that is responsible for organizing
many of the proteins which enable cells to move and repoduce. This cage-like
structure, one micron (.000001 meters) in diameter, was identified using fluorescent
dye, which highlights one of the centrosome's critical proteins, pericentrin.
CELL MEMBRANE
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Credit: Scanalytics and the University of Massachusetts Medical Center |
When studying muscle cells in organs such as the heart, scientists need to know
the exact location of cell mebrane. A robotic vision system helps to define the
surface membrane of the cells that have been stained with a fluorescent dye.
NUCLEAR ENVELOPE
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Credit: Scanalytics and the University of Massachusetts Medical Center |
When cells replicate, they move genetic information in the form of messenger
ribonucleic acid (mRNA) to specialized sites where proteins are made from specific
genes. Researchers believe that the two large clusters within the dark circle
called the "nuclear envelope" are the spots in the cell nucleus where DNA is
transcribed from the gene into mRNA.
TRANSCRIPTION SITE
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Credit: Scanalytics and the University of Massachusetts Medical Center |
In this closeup of a transcription site, the bright spots show signals representing
mRNA.
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