What is the stain used to measure or assess sperm viability?

What is the stain used to measure or assess sperm viability?

• A. Papanicolaou stain
• B. Giemsa stain
• C. Gram stain
• D. Eosin-nigrosin stain (Bloom's technique)

Answer: (D)

Assessing sperm viability relies on whether the sperm cell membrane is intact. A stain that exploits membrane permeability lets us tell live cells from dead ones. Eosin-nigrosin stain, used in Bloom’s technique, does this by allowing eosin dye to penetrate only cells with compromised membranes. Dead sperm take up the dye and appear pink or red, while live sperm exclude the dye and stay unstained or lightly colored. The nigrosin provides a dark background, creating strong contrast so you can easily count live versus dead cells under the microscope. Other stains shown are used primarily for different purposes—Papanicolaou and Giemsa are for cellular morphology in cytology and blood films, and Gram stain is for bacteria—so they don’t differentiate viability in sperm the way eosin-nigrosin does.

Assessing sperm viability relies on whether the sperm cell membrane is intact. A stain that exploits membrane permeability lets us tell live cells from dead ones. Eosin-nigrosin stain, used in Bloom’s technique, does this by allowing eosin dye to penetrate only cells with compromised membranes. Dead sperm take up the dye and appear pink or red, while live sperm exclude the dye and stay unstained or lightly colored. The nigrosin provides a dark background, creating strong contrast so you can easily count live versus dead cells under the microscope. Other stains shown are used primarily for different purposes—Papanicolaou and Giemsa are for cellular morphology in cytology and blood films, and Gram stain is for bacteria—so they don’t differentiate viability in sperm the way eosin-nigrosin does.