Types of Slides in Biology

Introductory Biology classes are when you begin working with slides of biological samples for the first time. Slides allow us to examine biological samples under a microscope in a greater level of detail than we possibly could with the naked eye. While you will most likely start off with unstained slides of living samples, it is helpful to understand all of the types of slides that may be used.

Fresh Mounts

Fresh mounts are useful when you wish to view living samples under a microscope. These simply magnify the samples in question, with no additives or stains. When a sample of living cells need to be examined under magnification, the cells are pipetted onto a microscope slide, with a coverslip then placed over the sample, before being placed under a light microscope. Under the appropriate magnification, this allows you to view cell organelles, or the miniature organs within cells, at a substantial amount of detail.

Stained Fresh Mounts

Stained fresh mounts are useful when you need to learn a specific detail about the cells that you are viewing. For instance, to count which cells in your sample are living and which ones are dead, mix a small solution of your cells with a small amount of dye that stains the cell membranes of dead cells. You may then pipette your solution onto the slide. When you view your cells under the microscope, the parts of cells in question, such as the cell membranes of dead cells, will be dyed a certain color.

Prepared Mounts

If you pursue biology for a career, you will encounter prepared slides. Prepared slides allow you to view a cross-section of a dead organism under a microscope, and are obtained by freezing the organism part, then cutting it on a cryostat into micrometer-thick sections, then mounting one or more of the sections on a microscope slide. For example, in biomedical research studying the effect of certain drug-loaded particles on the brain, prepared slides will likely be used to study samples of the brain of a lab animal.

Stained Prepared Mounts

Stained prepared mounts, similar to stained fresh mounts, place emphasis on a particular part of the mount. For instance, in the case of rat brains injected with drug-loaded particles, a fluorescent dye may allow those particles to show up more clearly during examination of the slide under a microscope. This requires following a staining protocol that involves dipping the entire slide into a series of fluorescent stains, until an appropriate amount of staining has been obtained.

References

• An Introduction to the Laboratory: Microscope Slides