Which stain provides a purple to dark blue color for Nissl granules?

The correct choice is based on the specific characteristics of Cresyl fast violet, which is a histological stain used primarily to visualize Nissl granules in neuronal tissue. Nissl granules are essentially rough endoplasmic reticulum and ribosomes in neurons involved in protein synthesis, and when treated with Cresyl fast violet stain, they exhibit a distinctive purple to dark blue coloration.

This staining is particularly useful in neurological studies and can help identify changes in neuronal populations and is valuable in diagnosing various neurological conditions. The specificity of Cresyl fast violet for RNA makes it an ideal choice for highlighting cell bodies of neurons, allowing pathologists and researchers to examine the morphology and distribution of neurons effectively.

In contrast, other stains listed have different properties and applications. For example, Lendrum's Phloxine is not primarily used for staining Nissl granules; instead, it is associated with different cellular components. Luxol fast blue with PAS (Periodic Acid-Schiff) is commonly used to stain myelin but does not target Nissl granules. Wright-Giemsa stain is typically used for blood cells and may highlight certain structures in tissues but is not specific for Nissl granules and does not produce the same color outcomes.