How fucking long will it take before stroke leadership looks at this and says; 'Maybe we could repurpose this to identify stroke damage and processes that fix such stroke damage.' Like exactly how neuroplasticity and neurogenesis can be made repeatable on demand.
But nothing will occur since we have NO STROKE LEADERSHIP.
Summary
A powerful new technique combines expansion microscopy with
lattice light-sheet microscopy for nanoscale imaging of fly and mouse
neuronal circuits and their molecular constituents that’s roughly 1,000
times faster than other methods.
Scientists mapped the location of all synapses – over 40 million –
across an adult fruit fly brain. A half-million colored balls represent
synapses associated with dopaminergic neurons. Credit: Gao et al./ Science 2019
Eric Betzig didn’t expect the experiment to work.
Two scientists, Ruixuan Gao and Shoh Asano, wanted to use his team’s
microscope on brain samples expanded to four times their usual size –
blown up like balloons. The duo, part of
Ed Boyden’s
lab at the Massachusetts Institute of Technology (MIT), uses a chemical
technique to make small specimens bigger so scientists can more easily
see molecular details.
Their technique, called expansion microscopy, worked well on single
cells or thin tissue sections imaged in conventional light microscopes,
but Boyden’s team wanted to image vastly larger chunks of tissue. They
wanted to see complete neural circuits spanning millimeters or more. The
scientists needed a microscope that was high-speed, high resolution,
and relatively gentle – something that didn’t destroy a sample before
they could finish imaging it.
So, they turned to Betzig. His team at the Howard Hughes Medical
Institute’s Janelia Research Campus had used their lattice light-sheet
microscope to image the rapid subcellular dynamics of sensitive living
cells in 3-D. Combining the two microscopy techniques could potentially
offer rapid, detailed images of wide swaths of brain tissue.
“I thought they were full of it,” Betzig remembers. “The idea does
sound a bit crude,” Gao says. “We’re stretching tissues apart.” But
Betzig invited Gao and Asano to try the lattice scope out.
“I was going to show them,” Betzig laughs. Instead, he was blown
away. “I couldn’t believe the quality of the data I was seeing. You
could have knocked me over with a feather.”
A forest of dendritic spines protrudes from the branches of neurons in the mouse cortex. Credit: Gao et al./ Science 2019
Now,
he
and his Janelia colleagues have teamed up with Boyden’s group and
imaged the entire fruit fly brain and sections of mouse brain the
thickness of the cortex. Their combined method offers high
resolution with the ability to visualize any desired protein – and it’s
fast, too. Imaging the fly brain in multiple colors took just 62.5
hours, compared to the years it would take using an electron microscope,
Boyden, Betzig, and their colleagues report January 17, 2018, in the
journal,
Science.
“I can see us getting to the point of imaging at least 10 fly brains
per day,” says Betzig, now an HHMI investigator at the University of
California, Berkeley. Such speed and resolution will let scientists ask
new questions, he says, like how brains differ between males and
females, or how brain circuits vary between flies of the same type.
Boyden’s group dreams of making a map of the brain so detailed you
can simulate it in a computer. “We’ve crossed a threshold in imaging
performance,” says Boyden, who was selected as an HHMI investigator in
2018. “That’s why we’re so excited. We’re not just scanning
incrementally more brain tissue, we’re scanning entire brains.”
Expanding the brain
Making detailed maps of the brain requires charting its activity and
wiring – in humans, the thousands of connections made by each of more
than 80 billion neurons. Such maps could help scientists spot where
brain disease begins, build better artificial intelligence, or even
explain behavior. “That’s like the holy grail for neuroscience,” Boyden
says.
Years ago, his group had an idea to figure out how everything was
organized: What if they could actually make the brain bigger – big
enough to look inside? By infusing samples with swellable gels – like
the stuff in baby diapers – the team invented a way to expand tissues,
making the molecules inside less crowded and easier to see under a
microscope. Molecules lock into a gel scaffold, keeping the same
relative positions even after expansion.
After
expanding the fruit fly brain to four times its usual size, scientists
used lattice light-sheet microscopy to image all of the dopaminergic
neurons (green). Credit: Gao et al./ Science 2019
But it wasn’t easy to image large tissue volumes. The thicker a
specimen gets, the harder it is to illuminate only the parts you want to
see. Shining too much light on samples can photobleach them, burning
out the fluorescent “bulbs” scientists use to light up cells.
Expanding a sample just four-fold increases its volume 64-fold, so
imaging speed also becomes paramount, Gao says. “We needed something
that was fast and didn’t have much photobleaching, and we knew there was
a fantastic microscope at Janelia.”
The lattice light-sheet microscope
sweeps an ultrathin sheet of light through a specimen, illuminating
only that part in the microscope’s plane of focus. That helps
out-of-focus areas stay dark, keeping a specimen’s fluorescence from
being extinguished.
Inside the mouse cortex, myelin sheaths insulate nerve cells.
Scientists can measure how these sheaths vary along the length of a
nerve cell’s axon. Credit: Gao et al./ Science 2019
When Gao and Asano first tested their expanded mouse tissues on the
lattice scope, they saw a thicket of glowing nubs protruding from
neurons’ branches. These nubs, called dendritic spines, often look like
mushrooms, with bulbous heads on skinny necks that can be hard to
measure. But the scientists were able to see even “the smallest necks
possible,” Asano says, while simultaneously imaging synaptic proteins
nearby.
“It was incredibly impressive,” says Betzig. The team was convinced
that they should explore the combined technique further. “And that’s
what we’ve been doing ever since,” he says.
