Developments in Imaging Technology and Staining Techniques. Unit C: Section 1.3 Science 10. Light Microscopes. Light microscopes magnify cells through the use of one or more curved lenses and a light source. Two important aspects of microscopy are contrast and resolution.
Unit C: Section 1.3
Which dot grabs your attention?
The dark one due to the sharpcontrast against the white background. In this example, the contrast even overrides the size of the larger circle in its ability to focus the user’s visual awareness.
Contrast (pg 253 – 254)
- With Brightfield microscopy, most of the cells are
colorless because light passes directly through them.
Contrast Enhancing Techniques & Fluorescence Microscopy
(pg 256 – 257)
Techniques were developed to improve images by altering the light path through the specimen.
These systems of illumination include darkfield, phase contrast, and differential interference contrast illumination (see page 256 for examples).
Shown here are optical slices through a pollen grain as viewed by a CLSM. The last image was created by stacking the optical slices.
Fluorescence Microscopy – was also developed to improve images but also gave information about the molecules on a cell’s surface
Mice with the GFP gene inserted
DyesDifferent dyes will glow different colours
An example would be using different dyes to highlight the various stages of cell division.
It depends on a beam of electrons passed through a very thin section of fixed and stained tissue embedded in plastic.
- The material has to be dead.
The electrons pass through the specimen, through a tube and then fall on a fluorescent screen or on photographic film (producing black-and-white photographs).
- The air inside the tube must be particle free and dry.
One of the drawbacks of the TEM is the difficulty of building up a three-dimensional picture of the cell from very thin sections and make any sense out of it.
You have all seen these things many times!
All belong to animals!
Mite on a human hair
Head of a Tapeworm
Do Check & Reflect P. 260 # 1 - 6