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10 May 2007

Microscope Centre


ROB MORRISON: Conventional microscopes look through slices of tissue far thinner than a piece of paper. Stained and mounted on slides, the images of cells are like tiny stained glass windows.

But the technology of the past few years has changed microscopes profoundly. Not only can they magnify to a much greater degree, they can dissect specimens with laser beams, chemically analyse them, and even build virtual models of living animals, producing images that are spectacular, revealing and often very beautiful.

At the University of Adelaide in South Australia Adelaide Microscopy has brought these technologies together in a unique resource for imaging things that can't be seen in any other way.

DR MEREDITH WALLWORK: The most exciting thing about this centre is that people come in here with problems and we can look at things under very high magnification or we can give them the option of looking at things in lower magnification in different ways. And it's very exciting when we can do that by combining these technologies which are really state of the art here.

ROB MORRISON: Ordinary lenses will get you only so far. Just as cameras can zoom in and magnify so can microscopes, but eventually the laws of light restrict you to magnification of about 1500 times.

Then you have to use beams of electrons, tiny charged particles that can magnify to about 10,000 times.

DR MEREDITH WALLWORK: For example, the scanning electron microscope will allow you to look at the surface, in very fine detail, of an object that you're able to prepare, the sorts of images that people will sometimes seen where they're shown spider legs and the detail of feathers and things like that, where they're things we can't see in any other way. And you do see nature at its most beautiful in some of those images because they're enormous blowups if you like, of things we would not otherwise see and you see the perfection of nature. It's wonderful.

ROB MORRISON: While those are impressive images they're only a surface view. Other microscopes take you inside a specimen. Some even take you there by laser. A light microscope at high magnification can reveal cells of interest but they're tiny and it's hard to locate them once you remove the slide.

The laser dissecting microscope chops them out while you watch with microscopic precision.

DR MEREDITH WALLWORK: So while you're looking at the tissue under the microscope you can control the laser to cut around the cells of interest, the cells you need to sample, and they will then be sampled into a tube you can take back to the laboratory.

ROB MORRISON: But once cells are cut up like this they can't be put back together which doesn't help when you want to see inside a specimen without destroying it. If you want to learn how parts of a brain fit together you can fix the brain in plastic then cut it into pieces like a jigsaw puzzle but a light microscope will need that brain cut into thousands of slices thin enough to see through.

You can project them onto plastic sheets, colour those in and put them together in a model, but it's only a model and the original has been destroyed.

A confocal microscope leaves the specimen intact but still provides a transparent virtual model in three dimensions, its various parts revealed in glowing colours.

DR MEREDITH WALLWORK: To do that we need to have a subject that actually glows, that fluoresces. We add stains that fluoresce and those stains will bind to those structures so that they will glow a particular colour. Some might glow green, others red and we can visualise those different colours in the confocal microscope.

And it actually produces slices, much like a CT scanner might slice through your brain but in this case what you're doing is producing fluorescent images through the sample. You're not actually cutting the sample but you're producing a series of images as you focus the microscope through it.

So that series of images can then be taken to another computer which reconstructs, in three dimensions, the original material. In that way you can then rotate it. You can have a look through that sample and you get a very clear picture of how things are placed in that material in three dimensions.

We can even image live animals. This same process can be done using a CT scanner. To do that the animals are sedated. They're put into the scanner. We monitor their health, their temperature, their breathing while they're being scanned and that uses x-rays and you can actually look at the structure of the bones and things like that, the hard tissue within these whole animals.

ROB MORRISON: These microscopes combine the latest technologies with some that are centuries old and as more technologies develop that trend will give us even more powerful ways of imaging the world we can't see.

DR MEREDITH WALLWORK: I think imaging is getting bigger and bigger in the sense that I think that scientists are very excited and become quite passionate about the possibility that they can answer questions by seeing things in real time. They can see things as they happen and it means that their science is so much more relevant, and I think to that it means they can answer questions they've never been able to think about answering before.