What does the term “over staining” refer to in the context of regressive staining?

In the context of regressive staining, “over staining” specifically refers to the application of too much dye. This technique is used in histology to color and visualize tissue samples under a microscope. Regresive staining involves initially applying a dye that saturates the tissue, and then the excess dye is removed or decolorized to enhance contrast and detail in the staining.

When too much dye is applied, it can lead to a situation where the tissue becomes overly colored, obscuring or masking important structural details, which defeats the purpose of the staining process. This can result in a lack of distinction between different cellular components and hinder the accurate assessment of the sample. Therefore, applying too much dye directly impacts the quality and interpretability of the stained tissue sections in diagnostic and research settings.

The other options relate to different aspects of the staining process. Neglecting rinsing can lead to residual dye affecting the results, inappropriate staining times can affect the intensity of the color, and over-fixing impacts cellular morphology but is distinct from the concept of "over staining."