Physical characteristics of mouse sperm nuclei

Area of Science:

• Sperm biology
• Cellular and molecular biology
• Biophysics

Background:

• Sperm nuclei from different inbred mouse strains (C57BL/6J and CBA/J) retain distinct head shape characteristics after isolation.
• Understanding these physical differences is crucial for sperm research and potential applications.

Purpose of the Study:

• To compare the physical characteristics of isolated sperm nuclei from C57BL/6J and CBA/J mice.
• To investigate the relationship between nuclear properties and sedimentation velocity.
• To evaluate the potential for physical separation of sperm based on these characteristics.

Main Methods:

• Isolation of epididymal sperm nuclei using resistance to trypsin digestion.
• Measurement of projected dimensions (length, width, area) of nuclei.
• Reconstruction of nuclear volumes from serial electron micrographs.
• Determination of buoyant density using density gradients (CsCl, Renografin-76).
• Measurement of sedimentation velocities at unit gravity.

Main Results:

• CBA/J nuclei are longer and have greater projected area but smaller volumes than C57BL/6J nuclei.
• Buoyant densities are similar, but CBA/J nuclei have less mass due to smaller volume.
• CBA/J nuclei exhibit slower sedimentation velocities than C57BL/6J nuclei.
• Sedimentation velocity differences are primarily attributed to nuclear volume variations, not shape factors.

Conclusions:

• Nuclear volume is the key determinant of sedimentation velocity differences between C57BL/6J and CBA/J sperm nuclei.
• The distinct physical properties offer possibilities for developing physical sperm separation techniques.