The Relationship between Stained Specimens and Bright Field Microscopy

Using stained specimens with bright field microscopy is necessary so that proper viewing of samples is attained. The relationship between these two concepts is discussed below.

Bright field microscopes are the ones referred to as classical microscopes. Generally, these are the same ones you get to use at school. Bright field microscopes are called as such because when they are used, the specimen under observation is subject to illumination from its back. The image produced on the device then, is formed because the properties of the imaged sample is absorbed and reflected towards the eyepiece.

Just as a piece of trivia though, bright field microscopes are widely used in research facilities, schools, and laboratories, over the last 300 years. The bright field microscopy technique is the perfect technique used for viewing stained specimens or any other samples that can naturally absorb the right amount of light in order to make it visible through the microscopes eyepieces.

There are certain specimens that are colorless in nature. This means that it is impossible to see them through one’s naked eye - not because they are already small, but because light passes right through them. With these types of organisms, using bright field microscopes simply won’t work. The concept of lighting employed by the bright field microscope is not effective with transparent specimens.

This is why staining the specimens is required. Adding viewable colors to naturally colorless specimens are necessary so that they become visible through the lenses of a bright field microscope. A bright field microscope also has plain white background. So if the sample you are viewing matches that color, you are not likely to see you specimen fairly well either.

Staining specimens to be used with a bright field microscope is a very essential step. The stains used work because it fixes itself to the different structures of the cell that is to be observed. Their structure can easily be determined with the use of the right staining method.

Stains come in different colors and compositions. Stains are chemical formulations that can be added to the specimen. There are stains that can bring out the protein, starch, and nucleic acids content of the viewed specimens. Using a combination of one or two stains at a time is also possible, so that better information can be obtained by the user.

There are certain types of stains that are used for insects too. Small insects, if they are supposed to be viewed under the microscope, have to be preserved nicely. This step is essential if they are to be viewed countless of times as well. Preservation is necessary so that the insect will not decompose naturally. Insects to be viewed under a bright field microscope have their bones and essential body parts stained. Their bodies however, are made transparent. These are all done for ease of viewing, and teaching, even.

Examples of commonly used laboratory stains are the Eosin Y stain, Gram stain, and methylene blue. The Eosin stain is best used with viewing a cell’s cytoplasm. The cytoplasm is the fluid that surrounds the nucleus of the cell. Eosin is a 1% aqueous solution. It works to provide a stronger color to the cytoplasm than the cell nucleus. This stain is pink in color.

Gram stain is actually a stain set. It is the staining system developed by Hans Christian Gram in order to differentiate the pneumococci bacteria from the Klebsiella pneumonia. Normally, a Gram stain contains four solutions. Solution 1 is a combination of crystal violet, ethanol, and ammonium oxalate. Solution 2 is iodine and its derivatives. Solution 3 is acetone and ethanol. Solution 4 is safranin.

Methylene blue, just like Eosin Y, is a 1% aqueous solution. It works much like Eosin. The only difference is that this one stains blue instead of pink. Methylene blue also has the ability to stain bacteria.

These stains are available locally or through laboratory suppliers. These stains are dispensed in 15 ml bottles or even larger. Usually, they are priced less than $5. For sets like the Gram stain, it is a little pricier at more than $20.

Staining specimens are not mandatory for every sample viewed under a bright field microscope. But as stated earlier, staining becomes compulsory will be if the specimen to be viewed is on the colorless side. Without properly staining them, they cannot be observed even with the most complex bright field microscope available in the market today.