Semen Analysis · Pathology

In sperm vitality testing, why do dead sperm cells appear pink or red when using an Eosin-Nigrosin stain?

  1. Dead sperm have an acidic pH that reacts with the dye
  2. The stain only binds to DNA in non-viable cells
  3. The damaged plasma membrane of dead cells allows the dye to enter
  4. Live sperm actively pump the dye out via ATP-dependent transporters
Show answer and explanation

Correct answer: The damaged plasma membrane of dead cells allows the dye to enter

Eosin is a 'supravital' stain that is excluded by the intact membranes of living cells. Dead cells with compromised membranes take up the eosin and appear pink/red, while live cells remain white/clear against the dark nigrosin background.

Difficulty: Medium Question 6 of 20

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