Exercise 2.1 - Selective Staining: Prepared Slides

LEVEL I

Materials

• Prepared slides of:
  • DNA by Feulgen reaction
  • DNAase treated Feulgen reaction
  • RNA by methyl green -- pyronin
  • RNAase treated methyl green -- pyronin
  • PAS or Best carmine positive granules
  • Amylase treated PAS or Best carmine sections
  • Sudan black or osmium stained lipid
  • Lipase treated sudan black sections
• Microscope

Procedure

1. Obtain one of the prepared slides which has not been treated with an enzyme. Examine the slide carefully and draw a representative field of view.

2. Select a corresponding enzyme treated section and draw a representative field. Note any structures present in the untreated slide which are absent in the enzyme treated slide.

Figure 2.4a Feulgen stained, Phase contrast, liver cells

Notes

Each preparation in this exercise has a control (untreated) and enzyme treated slide. Each pair should be examined and compared. The pairs represent a view of similar cells which have had something removed by enzymatic digestion. You should determine which structures were removed by the enzyme treatment. Figure 2.4a presents an image of feulgen stained liver cells (left) and a similar section (right) stained identically, but pretreated with the enzyme DNAase. There are prominent nuclei present before DNAase treatment, but they are absent after treatment with the enzyme. Thus, the conclusion that nuclei contain significant amounts of DNA.

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