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SPERM USE HEAT SENSORS TO FIND THE EGG

Rehovot, Israel - Much like guided missiles that sense the heat of a plane's engine, sperm are guided to the fertilization site by temperature, reports a Weizmann Institute study published in the current issue of Nature Medicine.

The site where the egg lies is slightly warmer than the place where the sperm make a pause in their journey through the female genital tract. Sperm cells are apparently guided by this temperature difference in their navigation. Such a temperature driven mechanism was previously known to exist in microorganisms and worms, but the Weizmann study for the first time has provided evidence for its existence in mammals.

According to team leader Prof. Michael Eisenbach of the Institute's Biological Chemistry Department, the study contributes to the understanding of fertilization in humans and other mammals. In the future, it may be possible to make use of temperature guidance to improve in vitro fertilization. The research was performed by Ph.D. student Anat Bahat, along with Anna Gakamsky, also a student in Eisenbach's team, Dr. Ilan Tur-Kaspa from the Barzilai Medical Center in Ashkelon and visiting scientist from Argentina Dr. Laura C. Giojalas.

After passing the uterus, sperm cells enter the fallopian tubes. Once inside a tube, they attach themselves to the tube's wall and pause for "storage," during which they go through a maturation process that prepares them for penetrating the egg. A sperm cell that has completed this maturation process detaches itself from the wall and leaves the storage site. If ovulation had taken place in the preceding 24 hours, releasing an egg ready to be fertilized, the mature sperm would embark on a long, complicated journey through the tube to the site of potential fertilization.


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