DIRECT MEASUREMENT OF THE TAIL BEAT FREQUENCY OF HUMAN SPERM BY FLASHLIGHT SYNCHRONIZATION

Based on the synchronization between a periodic vibration and flashing light, we designed a device to determine the flagellar beating freque ncy of human sperm. The head of a spermatozoon was either held by the tip of a micropipette operated with a micromanipulator or adhered by i tself on the surface of a glass slide when the sperm swam out of the m icropipette into the fresh Ham's F-10 medium. The beat frequency of th e flagellum was measured by synchronization of the frequency-adjustabl e flash light built on an inverted microscope. The light frequency syn chronizer included a controller, a pulse generator, a signal counter, and a flash illuminator. During each measurement, the spermatozoon was transferred to the center of the observing field and the frequency ge nerator created a series of signals which developed flashing signals o nto the sample plane. When the vibration of the flagellum was observed as a constant two-step-like movement after frequency adjustment, the beating frequency was read from the signal counter and the count was t wice that of the beat frequency of the sperm tail. As the flash signal was decreased to half of this frequency, an apparently immobilized sp erm flagellum was observed and the exact beating frequency could then be determined. This device was then used to measure the effect of pent oxifylline on sperm motility. The results showed that the increase of tail beat frequency as measured by this device is well correlated with the increase of beat cross frequency as detected by a computer-assist ed semen analyzer. These findings suggest that this flash light synchr onization device is a reliable and useful system for the assessment of sperm motility.