cc >> Tom Zinnen: Welcome everybody
to Wednesday Nite at the Lab. I'm Tom Zinnen and welcome
to the Biotechnology Center here at UW-Madison.
On behalf of our partners, the Wisconsin Alumni Association,
Wisconsin Public Television, and the Science Alliance,
thanks for coming here. We do this every Wednesday
night, 50 times a year. Tonight I'm delighted to have
Steve Paddock give a talk on "A Brief History of Time Lapse:
Picture the World Through Kaleidoscope Dyes."
Which I think is from "Lucy in the Sky with Diamonds."
I get to date myself tonight. Sean, excuse me, Steve works in
Sean Carroll's lab here on campus and is employed by the
Howard Hughes Medical Institute. He got his PhD at the University
of Bristol in the UK and then did a post doc on Northwestern
University studying cell behavior.
He came to the University of Wisconsin Madison about 20 years
ago to work in the microscopy facility and starting about 15
years ago, started working in the Carroll lab.
I'm looking forward to this presentation very much, and
please join me in welcoming Steven Paddock to Wednesday Nite
at the Lab. [APPLAUSE]
Steve Paddock: Thanks, Tom.
Thank you, everybody, for coming out this evening.
The title is actually a little strange in that it is the title
of two talks. I gave the first title, "A Brief
History of Time Lapse," and then I switched to "Picture the
World with Kaleidoscope Dyes." So when I saw it advertised on
the website I threw a few time lapse images in.
If you're for a Brief History of Time Lapse, the history is going
to be incredibly brief. [LAUGHTER]
So the whole talk is based around "Picture the World
with Kaleidoscope Dyes." As Tom said, it's from
"Lucy in the Sky with Diamonds." And I guess Paul McCartney
insisted that "Lucy in the Sky with Diamonds" came from his
daughter, Lucy, or his daughter came to him with a picture,
a painting that she made. And he said, what's that?
And she said, "That's Lucy in the sky with diamonds."
So that was the story behind the song.
Not LSD. [LAUGHTER]
But I guess maybe. I don't know.
So I'm just showing you a slide show right now up here.
I don't know if any of you passed through the Dane County
Regional Airport last year. I had the good fortune of
helping with an exhibit entitled "Tiny: Art from Microscopes
at UW-Madison." And it was up longer than we
expected it to be, and it got a lot of interest from people
going back and forth to the airport.
And we got many great comments, one or two negative comments
but not many. And what I thought I'd like to
do this evening would be to try and explain to you how these
images are produced, some of the history behind the scientific
imaging that's led to these images and how we use some of
these images in our work. Most of the images in the Tiny
exhibit were actually produced using a relatively modern
technique called laser scanning confocal microscopy.
And we're lucky enough to have an instrument in the lab in
molecular biology. So I'm going to stop the DVD and
go to my PowerPoint show. And so here's just a collection
of images. These are not all of my images.
These are images produced by people on campus here that were
part of this show. And kind of in an abstract way
the bright colors, they do have kind of an artistic side to
them, but they do also have scientific meaning.
And several of the labs that I have been trained in most of the
people that I have worked with have stressed the value of
trying to make an image aesthetically appealing as well
as scientifically kind of relevant.
And I should probably stress from the outset that it's easy
to view these images kind of as if they are pieces are artwork,
but they're actually the result of many long hours of
painstaking experiments, not always by me but by other people
in the lab. And these are just kind of the
tip of the iceberg. So it's easy just to see them
and think oh, this is great, but they are the results of a lot of
hard work and research. So, as Tom said, I work in Sean
Carroll's lab, and over the years we work on developmental
biology and evolution. So we're trying to figure out
the actual mechanism of how evolution works at the molecular
level. And the key to studying
evolution is to study developmental biology.
And it's a relatively new field, and Sean is kind of one of the
leaders in this new field of evolutionary developmental
biology or Evo Devo for short. And my nickname is actually
Stevo Devo. [LAUGHTER]
And it takes in from molecular biology through embryology
to developmental biology, from comparative anatomy
all the way out to paleontology. So we're used to studying genes
that are millions of years old. And we talk about deep
evolutionary time of 200 million years.
A model organism that we use is mainly the fruit fly.
I meant to bring some, I forgot to bring them, sorry.
So but what I'd like to do is tell you a few stories about how
this imaging developed. And what I'd like to start off
with is kind of deep technological time.
So I'm going to go way back in deep technological time to 1985.
[LAUGHTER] My first story starts with
two Englishmen sitting in a Bedouin tent in the dark.
And I'm not talking about the Sahara or the Arctic or the
Antarctic. I'm talking about this place,
which is Cambridge in England. And you can tell it's Cambridge
because this is the King College's chapel, the famous
chapel at King's College. This is the River Cam.
And one other clue to it being Cambridge rather than Oxford is
that the people in the boat, which is called a punt, in
Cambridge when you're punting you stand on the deck, which is
the sensible way of doing it, but in Oxford they stand
actually inside the boat on the other end.
So there's a great kind of rivalry between the two towns in
cricket and rugby and there's a boat race in London and they put
their milk in their tea in different ways.
So anyway, it goes back hundreds of years, thousands.
But anyway, getting back to the two English scientists sitting
in a Bedouin tent. They were actually developing a
microscope in the MRC labs in Cambridge.
And the two scientists were John White and Brad Amos.
And John White just retired as the chair of our department
here. And John had a biological
problem to solve. In growing up in England,
English science, a lot of the problems you solve you have to
start off with paper and string and try and build the equipment
yourself. And so John was a great
equipment builder. And, oops, oh, I see.
So John was a great tinkerer and an equipment builder.
The biological problem he was trying to solve was back in 1985
many people were looking at cells and embryos using a
technique called immunofluorescence microscopy.
So they were using the power of immunology to label specific
structures within cells so that people were able to raise
specific antibodies to purified proteins and then tag a
fluorescent dye to the antibody which was binding to the protein
in the cell. This is an image that I took way
back then of some cells growing in tissue culture.
And here's my first reference to time lapse microscopy.
A and B is two frames from a time lapse movie that I was
making. So what I was doing I was
filming some cells in tissue culture, and what actually is
happening is I was filming the nucleus rotating.
Sometimes the nucleus will actually up and rotate.
And then I was trying to figure out what the cytoskeleton was
doing during nuclear rotation. So I would film it and then fix
it, kill it and then label it with a fluorescently labeled
antibody. And then I would look at the
distribution of the cytoskeleton within the cells and try and
figure out how the cytoskeleton was related to the nuclear
rotations. So with cells growing in tissue
culture they're kind of very flat.
So you can actually resolve structures in the fluorescent
structures in cells growing in tissue culture.
This is a schematic of the microscope that you'd use, a
fluorescence microscope. It would have a very bright
lamp, the HBO lamp house, which would supply a bright light.
And it would go through an excitation filter which would
filter out all of the wave lengths that you don't need.
So a common dye that we would use would be something called
fluorescein, which is excited at 480 nanometers.
So that excitation filter would take everything else out except
for 480, and then the light would bounce off of the dichroic
beam splitter, go through the objective lens which would focus
it on the specimen. Any labeled structures within
the cell would fluoresce because they would be excited by the
light. And then a longer wavelength
light of less energy would be emitted.
And then that would come back up along the green path.
And the dichroic beam splitter would let that longer wavelength
light through. And then the barrier filter
would kind of clean up the signal so you'd only just get
what wavelength that was coming off the fluorescein.
And then you could see it by eye and that would take the
photograph of it. Okay, so it worked well for
cells growing in tissue culture, flattened cells.
There's a fluorescence microscope.
There's the light source at the back, and then you look at it by
eye on the stage and everything. In such a microscope, the
specimen is actually flooded with light.
You can see there that the light is kind of shining off the
specimen. So the specimen with significant
3-D structure, this is a HeLa cell.
I don't know if you've read, many cancer cells, not all of
them, but many cancer cells have a significant 3-D structure.
That's one of their properties, they tend to round up in
culture. This is a HeLa cell labeled with
anti-tubulin, fluorescently labeled.
You could actually focus it up and down.
Looking by eye, you could see microtubules but taking a
photograph was impossible. And then with an embryo, this
was a nematode embryo and this was John White's specific
problem. He was trying to follow the cell
divisions within a nematode embryo.
And the first 24 hours or so of embryogenesis there's many,
many, many cell divisions. And so the cells kind of don't
increase in size. They get smaller and smaller,
but the structures get brighter and brighter because there's
more cells. And you just can't see any
structure. By the way, John had just spent
the previous 14 years trying to figure out the neuro-connections
of the 302 nerve cells in the nematode using electron
microscopy. So John kind of knew about this
technique called confocal microscopy.
This is a pattern from 1957 from Marvin Minsky.
And so rather than kind of flooding the whole specimen with
light, the idea of confocal microscopy is to scan the
specimen with a discrete beam of light.
And in Minsky's microscopy apparatus, his aim was to look
at cells in living brains, living nerve cells in brains.
But the idea, all of the confocal microscopes of today
are based on this basic design. But his idea was way before its
time. The technology wasn't really
available to him. So the technique is the light
path, this would be a transmitted light microscope.
The light source, a very bright light source on this side, the
light passes through a pin hole, number 14, it's focused by a
lens into the specimen, and then any light going through the
specimen is again focused by another lens on a second pin
hole, number 24, and then that is some kind of a detector that
detects the point of light. So in that kind of setup we
would just get a point of light. So in Minsky's apparatus the
actual specimen moved. It was called a stage scanning
mechanism. And he used a primitive tuning
fork device. It worked but his visual display
was in a telescope so the images were not very kind of
impressive, especially to biologists who were using
microscopes with stained specimens and could get really
good images. In his pattern there is also an
epifluorescent, a reflected light version which is
incredibly similar to the first diagram I showed you of the
fluorescence microscope. And in this is setup, the lens,
you only use one lens, number 11, which got rid of a lot of
alignment problems which you had with the transmitted system.
So John knew about the stage scanning systems but they were
kind of not good for biology because biological specimens
tend to be wet and wobbly. So any wobble in stuff you just
lose your resolution. If you move your camera taking a
picture, then goodbye clarity. So what John and Brad would do
is they were trying to figure out how they could actually scan
the beam itself. And they, after a lot of kind of
time in the Bedouin tent and the workshop and coming out and
making kind of modifications to that apparatus, they hit upon a
two-galvanometer scanning scanner.
I'm not going to go into the details of it because I don't
really understand them, but basically they were able to
figure out a way of scanning the beam in a pretty efficient way.
And it was about this time I moved to Madison to the
microscopy facility, and we actually took delivery of one of
the first four prototype microscopes.
They hooked up with Bio-Rad. And this was the actual
instrument. You can see the fluorescence
microscope on the bottom here, the regular epifluorescence
microscope. And then this was their scan
head which produced a scanned beamed of the specimen.
The detectors were photomultiplier detectors and
the output was sent into a computer frame store, which at
that time computer frame stores were kind of new too.
So not only did they have to solve the problem of scanning
the beam, but they also had to tame a computer programmer to
write them the program and get the computer hooked up with a
scanning beam. So you could imagine that the
mirrors have to, the computer has to keep track of where the
mirrors are in order to build the image on the screen.
So as the beam is scanning across the specimen then the
computer kind of puts the image onto the screen.
And this system would produce an image of a fluorescent specimen
in about one second. And I'd never heard of confocal
microscopy when this thing came but everybody really wanted to
use it. It was really amazing and fun
technique to use. So John and Brad and Mike
Fordham, who I guess was a computer programmer, published a
paper in the Journal of Cell Biology which is an evaluation
of confocal versus conventional imaging of biological structures
by fluorescence microscopy. And this paper literally took
the cell biological community by storm because what they did is
they just went around and collected specimens and took a
picture in the regular fluorescence microscope and then
took a picture in the confocal microscope.
So here's or HeLa cell which is how it looked in the regular
microscope. You could actually see
structures by eye because your eye has a better dynamic range
than anything else. But looking in the confocal mode
you start to see spindle microtubules.
And if you move the fine focus just a little tad, you've got a
different view. So the actual out-of-focus
fluorescence was just gone. So these images were actually
called optical sections because you were actually sectioned the
structure by light rather than a physical means.
So the paper really was just amazing because people just saw
a real proof of the art. Here's John's nematode embryo in
the regular epifluorescence microscope, and suddenly you're
seeing structures. This is a sea urchin embryo.
Again, what people used to see, and then what they say with the
confocal microscope. One of the things they started
to worry about was that the microtubules looked kind of
wiggly and wavy in the confocal. And it turned out that their
specimen preparation was not up to scratch.
Once they kind of figured that out, the microtubules looked
more normal. And so even just cells growing
in tissue cultures the images were improved.
You could start to see microtubules kind of going about
the nucleus. I probably would have benefited
from that with my nuclear rotation studies, my time lapse.
So you could optically section, because as long as the specimen
stayed still, it didn't move, you could take an image, the
computer would move the stage by a certain set amount and then
take another image, and so you could take a Z series section
through something like a mitotic spindle and then send the images
into another program to make a 3-D reconstruction.
And a lot of these programs already existed for MRI and
other data. So it's kind of like an MRI at
the microscopic level. One of the advantages, I mean
I'm just telling the story as if John White and Brad Amos were
the only people doing this, but there were other confocal
microscopes coming out. There was another, Brakenhoff in
the Netherlands had one. Once the companies saw that
these microscopes were so popular then Zeiss and Olympus
and all the different companies got on board.
But the great advantage of the White and Amos microscope,
because of the way they were scanning the beam, was that you
could adjust the pin hole in front of the detector so you
could increase or decrease the optical section and thickness
that you were taking. You could also, so this is a
tissue taken at 4X where you can take kind of a map view of it.
And this is taken at 40X where you can actually see cellular
structures. But then you can decrease the
area of specimen that you scan and increase magnifications but
not changing the actual lens. So you can impart different
magnifications to the same lens. And this is a little schematic
that I kind of drew. A human egg is at 130
micrometers. Using a 4X with a pin hole open
you can get the whole egg. With the pin hole kind of closed
down you get a smaller optical section.
So these are the kinds of structures that you can kind of
visualize using the confocal system.
The other thing you could do was you could label with two
different immunofluorescent dyes.
So the green one would be fluorescein and the red one
would be rhodamine. And as long as the specimen
stayed steady and your dichroic mirror angle was consistent and
you used a lens which was corrected for chromatic
aberration, then you could look at two different proteins in the
same cell and then color them green and red.
Another thing you could do would be to take an optical section,
this is a nuclei in an epithelium and then there's
another layer of nuclei at a different level and colorize
them. So that's kind of the basic kind
of story behind the development of the MRC microscope.
And when I moved up to Sean Carroll's lab, I was hit with
some more kind of interesting kind of problems.
At that time we were working exclusively on fruit fly
development. And this is a fruit fly embryo.
And he were interested in the genes that control the setting
up of the different segments of the body early on in
embryogenesis. And I was working with a
graduate student then, Jim Langeland, and he was working on
the gene Harry which is expressed in seven stripes in
the early embryo. And he was wanting to look at
different genes that related to Harry at the same time.
And at the time we could do double labeling so we could look
at Harry and Kruppel, or Giant and Harry.
And Jim said to me, well, Steve, do you think we could do three
at the same time? And we had a krypton/argon laser
on our microscope at the time which had three lines in it,
568, 488, remember that was the fluorescein line, and 647.
And there was a knew dye that had just come out called
cyanine 5, and Jim figured out the immunological staining
protocol of staining three different immunofluorescently
labeled proteins in one cell. And at that time it was really
hard to get an image from a PC to a Mac.
So we had to get another computer guy trained up and he
wrote this program called RGB Merge where we took the three
images and then it clunked through combining them and then
it turned it into a TIF file. Most of the microscope companies
have their own propriety formats too which then they didn't used
to give out the code for that. And then we put it all together
in Photoshop. And at that time it came up with
this triple-labeled embryo. And we presented this at a fruit
fly meeting, I don't know, 15 years ago, and it was really
kind of quite well received. And one of the things that you
can immediately see is the little round circles are
actually nuclei and where the same gene is being expressed in
a nucleus then you get an additive color.
So where the green and the red gene are being expressed then
you get yellow. So you get these kind of rainbow
effects. And it also has biological
meaning. And then a couple of years later
Bio-Rad came out with this system that had three detectors
on a light path whereby you could actually excite three
fluorochromes at the same time simultaneously.
And then on the screen you'd get the red, the green, and the blue
image and the merged image at the touch of a button within a
second. Whereas RGB Merge took about an
hour to figure out one image but technology moves on.
So the idea is that we can look at development in a series of
fixed and stained cells and figure out which genes are being
turned on. This is an early embryo where
you kind of get a few domains coming up and then the seven
stripes of Harry and then gastrulation occurs and then
engrailed comes on and you get 14 stripes and these cells are
starting to know where they're going to be in the embryo and
they're getting their fates kind of worked out and some are dying
because they're not in the right place.
So people work on this kind of thing to figure out how a single
cell develops into a multi, and we're using microscopy to figure
these things out. So with fruit flies, the
appendages develop in the, for want of a better word, in the
larva, in the maggot, from these structures called imaginal
discs, which are really great for confocal imaging.
They're relatively flat sheets of cells.
And this one here is going to be the wing.
This is a wing imaginal disc. You can dissect them out and
then stain them, fix and stain them, and then look at them in
the microscope. This is the wing.
This is the haltere. Fruit flies just have one pair
of wings and then they have these reduced wings called
halteres which are balance organs that flap along behind
the wings. And then this is the antenna,
antenna imaginal disc. So the study of this is called
pattern formation where you could look at the gene
expression patterns and figure out what's going on in
development. There's an awful lot of genes
turned on at the same time. And these are wing haltere
imaginal discs. And Scott Weatherbee in the lab
many years ago came up with these beautiful images of
different genes being expressed all at the same time.
And these are all fixed and stained different discs.
So with the multiple labeling you can get an idea of how these
fields of cells are being set up.
So some of the biology here. This is called the wing pouch,
this whole area. And the red gene is called
vestigial, and that labels all of the cells that are going to
form the wing. And then the blue gene, which
kind of looks purple here, overlapping the red, is called
apterous, and those are going to be the cells on the underside of
the wing. And later on in development this
whole structure is going to fold along this boundary here.
And then the green gene is something called CI, and that's
actually not a nuclear, one that's outside of the cell.
You can see it's around all the little circles.
All the circles nucleus. Many of these control genes are
what are called transcription factors, but CI is on the
outside. And again here's another wing
imaginal disc. There apterous in green, and
then these yellow dots here are going to form the sensory
bristles. These cells are being told by
a gene that they're going to be the sensory bristles.
So then you can play around with the colors for kind of
presentation purposes too, which is a lot of fun within
Photoshop. And this purple/green image is
generally recommended because a lot of people with red/green
color blindness have trouble with these red and green ones.
So if you're giving a presentation you want everybody
to see it. And the purple/green ones are
the best ones to use. Okay, so Sean gives a lot of
talks, he gives a lot more talk now than he did, but he was at
the University of North Carolina giving a talk, and he had just
given his talk and he was being walked across campus by this
really great biologist, Fred Nijhout, who is kind of the
world's expert in butterfly biology.
And he said, gee, Sean do you think all this fruit fly stuff,
what do you think happens with butterflies?
And to cut a long story short we started up a whole big project
with butterfly development. Butterflies have a lot more
colorful patterns on their wings than fruit flies.
And this is a butterfly embryo. And just to pick a gene, this
gene is called distalis in red. And it stains the distal
portions, it tells the cells in the distal portions of the
developing limbs that they're going to be the ends of limbs.
And distalis is expressed in distal portions of fruit fly
appendages too. Distalis is also expressed in
centipede limbs and something very basic to the insects
called -- limbs. So this kind of gives you a
flavor of how we study evolution at the molecular level.
We kind of look at the comparative gene expression
patterns and find them. Evolution doesn't use different
genes for different animals, it uses the same genes in different
ways. So it's not the gene itself,
it's what regulates the gene that we're finding at least for
limb development. And then one of the great
surprises is when we looked at imaginal discs.
These butterfly imaginal discs, you dissect them out of a
caterpillar. They have five instars.
This is the fifth instar and you can actually see the shape of
the wing starting to develop within this beautiful wing disc.
The peripheral tissue actually dies off in the end.
So it's kind of like a cookie cutter.
The shape kind of comes out with a cookie cutter, and the cutter
part just dies away. But you can see the venation
developing here, and then the engrailed, the genes that set up
the territories in the fruit fly wing imaginal disc are exactly
the same as the ones that set up territories in butterfly
imaginal discs. One of the great surprises was
that when we looked at distalis in imaginal discs, it was
actually setting up the positions of where the eye spot
field is. So another theme of this Evo
Devo is that genes actually recycle during development.
They're used for different things, for controlling
different things. Distalis was used back in the
embryo for setting up the limb fields and now it's setting up
the eye spot fields. And you can see it a little more
clearly here. This is a 4X confocal image that
I showed you before and. Then if I go to 60X, you can
actually see the cells within a single eye spot field.
And it's probably kind of a gradient of gene expression
that's set up. And when Julie Gates in the lab
looked at different wing discs from different species, only the
ones with eye spots had the hot spots of distalis where the eye
spot fields were. And if we looked at mutant cells
this kind of finding held up. And then Craig Brunetti in the
lab looked at some other genes, and then the actual color seemed
to be related to other gene expression.
So engrailed is in purple with distalis in, again engrailed is
being recycled. So that kind of gives you a
flavor of this is all fixed and stained tissues.
There's another engrailed. So around 1990 or so people
started to figure out that the green fluorescent, has anybody
heard of green fluorescent protein?
So many jellyfish have this protein that fluoresces.
It happens to fluoresce, excited by the same wavelength as
fluorescein at 488. And it's turned out, to cut a
long story short and one Nobel Prize later, that figuring out
the gene sequence to green fluorescent protein you can
actually genetically engineer animals so that they, you can
tag the gene for GFP to a gene of interest.
So where the gene of interest is being expressed in a cell then
the GFP will also be expressed. So if you shine a 488 nanometer
light on a transgenic animal that has GFP, then anywhere
that's green will be where that protein is being expressed.
So here's John White's nematode embryo circa 2009.
This is taken by Kevin O'Connell.
And it's a transgenic nematode. This is GFP, a nuclear GFP,
I think, or maybe it's a microtubule one, but anyway what
Kevin is able to do is follow the cell divisions in exquisite
detail. His microscope is fast enough to
take Z series over time of the GFP being expressed within the
mitotic spindles. This is called multi-dimensional
imaging. So you can actually look at gene
expression in living cells using GFP.
Here's a fruit fly labeled with engrailed GFP.
If you shine a 488 nanometer light on it, anywhere the
engrailed gene is being expressed fluoresces green.
And there's been much work in kind of engineering GFP, genetic
mutants of GFP. So now there are many, many
color variants available of these called fluorescent
reporter proteins. In the Tsien lab in California
what they did was streak a bacterial plate with different
GFPs, different colored GFPs and came up with a nice little
California scene. And Roger Tsien just recently
won a Nobel Prize for his work with GFP, along with Marty
Chalfie and a Japanese worker whose name I don't remember.
So the modern confocal microscopes from the days of
White and Amos, technology has moved on and the companies have
incorporated, lasers have become a lot cheaper to put in.
So rather than one laser, we have many different smaller,
kind of diode lasers. But one of the great advances is
what's called an AOTF which is an acousto optical filter, which
allows you to kind of, rather than using a glass filter, you
use an electronic filter that filters the light really, really
fast, kind of really high rates of speed.
So you can kind of collect images a lot more quickly.
You can filter the light a lot more quickly.
And this is kind of the light path within the system that we
have in the lab. What I'm leading up to is kind
of a neat new technique that I think is so cool in that now you
can genetically engineer three different colors of reporter
proteins into a single mouse. And so the cells in the mouse
will randomly incorporate the three different reporters.
So if one cell has three copies of CFP, it will fluoresce blue,
in two CFPs one YFP will be fluoresced light blue and so on
and so on. You can't control where the
reporters are going to be expressed.
But using the new kind of microscopes with the AOTFs and
filter switching and kind of very sensitive detectors,
scientists in Jeff Lichtman's lab have been able to delineate
up to 99 different colors. So this is how the brain looks
in such a mouse, which is called a brain-bow mouse.
So rather than two or three you can look at 99 different.
So this is really kind of incredibly artistically
beautiful. But it's also used for kind of
mapping, it's much easier to map a whole bunch of different
colored cables than all gray cables.
So people are using it to map out kind of neuro-networks.
One thing Jeff Lichtman is finding out is it's incredibly
hard to do this, but also that young animals start off
complicated and the nerve becomes simpler as you get older
rather than the other way around.
But even using this beautiful brain-bow technique, they're
calling these things connectomes.
And they're actually having to go back to electron microscopy
to actually figure out the whole, oh yeah, I did put the
gray one in. So I've told you a little bit
about how the confocal microscope was developed.
How we're using it to study the mechanisms of evolution.
And some of the new kind of techniques of imaging living
cells. Microscopy is an incredibly fast
moving and exciting kind of field right now.
Not to short change you on the time lapse aspect of the thing,
I want to just show you just how complicated development actually
is. And there's a relatively new
microscope that's come out called a swept field microscope
where the field sweeps this way and that way.
And Ernst Stelzer in Germany has come up with some amazing images
of zebrafish development. These are GFP labeled zebrafish
embryos. And what he's done is he's
interested in where the cells actually go, and so he's able to
add color to the actual direction of where the cells are
going. So with that I'll just leave you
with this.
So it's a whole jumble of cell movements out of which comes
some order. >> Is that a single embryo
developing? >> This is a single zebrafish
embryo developing. That's time going by at the top
there. So this technique is incredibly
kind to cells. They don't die.
One of the problems with the early confocal microscopes was
that they were very hard on living cells.
And that's it.
Well thank you very much for coming out tonight.
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