What is the purpose of re-staining with eosin when specimens are prolonged in alcohol?

Re-staining with eosin after specimens have been prolonged in alcohol is primarily aimed at achieving better color differentiation in the tissue sections. When specimens are dehydrated in alcohol, the cellular components can lose their staining affinity, particularly for hematoxylin and eosin (H&E), which are the most common stains used in histopathology.

Eosin, being an acidic dye, stains proteins and cytoplasmic elements in tissues, providing an important contrast to the hematoxylin stain, which binds to nucleic acids and gives a blue color to nuclei. If specimens are left in alcohol for extended periods, the eosin may not adhere as effectively, causing poor visualization of various cellular components. Hence, re-staining allows for restoration of optimal color differentiation between the cell types and structures, improving the overall histological interpretation.

The other responses, while related to staining or specimen handling, do not accurately capture the primary reason for re-staining in the given context. The focus is on improving the contrast and detail in the stained sections, which is crucial for accurate diagnosis and analysis in histopathology.