Question

There are a multitude of chemical stains used in microscopy to help visualize structures in cells. The types of stains available for prokaryotic vs eukaryotic cells will vary due to differences in chemical composition and compartmental organization of these cells.

For this discussion assignment, select a chemical stain of your choice and prepare an initial post describing the chemical composition of the stain and the cellular structures stained, the chemical reaction of the stain, the procedure for applying the stain to the specimen, whether the specimen needs to be alive or dead, and the visual changes seen by the stain.

Include a photomicrograph of a cell visualized with your stain. This can be found by googling images.

Please no handwritten or picture replies - only typed answers.

Answer 1

Stain: Hematoxylin

Explanation: Hematoxylin remains one of the most widely used stain for staining the cellular structures. This stain is primarily used to stain the membrane boundaries, especially the basophilic structures including the nucleic acids and plasma membrane. Hence, a tissue stained with hematoxylin gives blue to purple appearance of the plasma membrane/tissue boundaries as well as the nuclei.

Principle: The staning method is based upon the principle that the hematoxylin is a composed of some complex molecules called hemalum. These hemalums combine with the cations such as tri-positive iron, tri-positive aluminium or di-positive iron ions and form an insoluble complex structure called hematin. This hematin has a color ranging from deep blue to purple. This imparts color to the structure being stained.

Chemical reaction:

Hematoxylin + Tissue specimen + cations+ Oxidaton   $\rightarrow$ Hematin-cation complex (colored)

Procedure: Generally, tissues samples ranging from slice thickness 4-30 micron are used to be stained using hematoxylin. The target tissue is dipped briefly in hematoxylin solution and rinsed with water. Following it, alcohol wash is also given to lock the hematin complex formed in the tissues. The tissue picks up bluish color and then it can be counter-stained to visualize the whole tissue structure.