Q+A CENTER

Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico Image and Vision Laboratory (Morelos, Mexico)

The Imaging Challenge

Sperm motility has been widely studied in two dimensions by analyzing their bidimensional trajectories when swimming near a flat surface. Under real conditions, the spermatozoid swims in a three-dimensional space before finding its target, the egg.

The Solution

The system uses a piezo-electric device (PD) displacing a large focal-distance objective mounted on an inverted microscope (over its optical axis) to acquire 70 stacks of 60 images at a rate of 4,200 images of 512 x 512 pixels per second, over a depth of 100 µm. The PD was mounted between the long-distance objective of the microscope and the turret. It was excited with a 70 Hz ramp waveform via the PD’s high-current amplifier. The high speed video camera had an acquisition rate of 4,200 images per second.

The Tools

• Physik Instruments piezoelectric device
• Nikon Eclipse TE2000-U inverted microscope
• Hewlett Packard 3311A function generator
• Redlake Motion-Pro HS4 high-speed camera
• Image-Pro 6.0 imaging software from Media Cybernetics.

The Difference it Made

The implemented imaging solution for the first time permits 3D observation and quantification of microscopic dynamic phenomena of multi free-swimming sperm, which had been historically restricted to 2D. This method may have transcendent implications regarding the fertilization process.