Feulgen stain

Feulgen Stain is a histochemical staining technique used in cytogenetics and histology to identify deoxyribonucleic acid (DNA) in cellular preparations. Named after its inventor, Robert Feulgen, this method is specific for DNA, allowing researchers and medical professionals to visualize and quantify DNA in individual cells. The Feulgen stain reacts with the aldehyde groups produced by acid hydrolysis of DNA, resulting in a magenta coloration under the microscope. This specificity makes it a valuable tool in various fields such as pathology, forensics, and biology research.

Background

The Feulgen stain was developed in the early 20th century by Robert Feulgen and his colleague, H. Rossenbeck, in 1924. The technique is based on the Schiff reagent reacting with the aldehyde groups of DNA, which are exposed by hydrolyzing the DNA with hydrochloric acid (HCl). The reaction produces a magenta or purple color, allowing for the visualization of DNA within cells. This method has been instrumental in the study of cell cycle, chromosomal abnormalities, and the quantification of DNA in various cell types.

Procedure

The Feulgen staining process involves several steps:

1. Fixation: Cells or tissue samples are fixed, typically with formaldehyde, to preserve the cellular structure and prevent degradation of DNA.
2. Hydrolysis: The samples are treated with 1N hydrochloric acid at 60°C for about 10 minutes to hydrolyze the purine bases, leaving the aldehyde groups of the deoxyribose sugar exposed.
3. Staining: The hydrolyzed samples are then stained with Schiff reagent, which reacts with the aldehyde groups to produce a magenta color.
4. Washing: The samples are washed to remove excess stain and then mounted on slides for microscopic examination.

Applications

Feulgen stain is widely used in various scientific and medical fields:

• In cytogenetics, it helps in the identification of chromosomal abnormalities and in the study of the cell cycle.
• In pathology, it is used to quantify DNA in cancer cells, aiding in the diagnosis and research of cancer.
• In forensics, the technique can be used to identify cells in biological samples.
• In biology research, it facilitates the study of cell division, differentiation, and development.

Advantages and Limitations

Advantages:

• Specificity for DNA allows for accurate visualization and quantification.
• Can be used on fixed cells, making it compatible with various sample types.

Limitations:

• Requires precise control of hydrolysis time and temperature to ensure specificity.
• Quantification can be affected by the degree of chromatin condensation in different cell types.

Related Techniques

Other DNA-specific stains include Acridine Orange Stain, DAPI Stain, and Propidium Iodide Stain, each with its own advantages and applications. However, the Feulgen stain remains unique in its specificity for DNA and its utility in quantitative analysis.

See Also

• Cytogenetics
• Histology
• DNA
• Schiff reagent