Sperm may follow rising temperature to egg. (Heat-seeking missiles).As a blast of Arctic air chills much of the United States this winter, many people travel long distances seeking warmth. Much like sperm, apparently.
A new study suggests that rabbit sperm find their way toward an unfertilized Adj. 1. unfertilized - not having been fertilized; "an unfertilized egg"
infertile, sterile, unfertile - incapable of reproducing; "an infertile couple" egg by heading toward higher temperatures within the animal's fallopian tubes Fallopian tubes
The narrow ducts leading from a woman's ovaries to the uterus. After an egg is released from the ovary during ovulation, fertilization (the union of sperm and egg) normally occurs in the fallopian tubes. . The egg rests at a spot slightly warmer than the site where sperm begin the final leg of their journey, and sperm can sense that temperature difference, report Michael Eisenbach of the Weizmann Institute of Science The Weizmann Institute of Science (מכון ויצמן למדע) is a world-renowned institute of higher learning and research in Rehovot, Israel. in Rehovot, Israel, and his colleagues in the February Nature Medicine.
About a decade ago, Eisenbach's team found that mammalian sperm cells can move toward chemicals secreted by unfertilized eggs, a phenomenon called chemotaxis chemotaxis: see taxis. . That led the investigators to argue that mammalian eggs lure sperm by using attractants. The finding challenged the dogma that the egg is a passive partner in the fertilization process.
Yet Eisenbach wasn't convinced that sperm chemotaxis could occur over the full 2 to 3 centimeters of the mammalian fallopian tube fallopian tube (fəlō`pēən), either of a pair of tubes extending from the uterus to the paired ovaries in the human female, also called oviducts, technically known as the uterine tube. . The tube's natural pulsing prevents a gradient of the attractant attractant
a material used to attract animals for capture purposes. from being stable except near the egg, he says.
Recently, Eisenbach read about experiments performed more than a decade ago that showed temperatures varying within female mammals' genital tracts. In one example, English reproductive biologist Ronald Hunter had found that during ovulation ovulation /ovu·la·tion/ (ov?u-la´shun) the discharge of a secondary oocyte from a graafian follicle.ov´ulatory
The discharge of an ovum from the ovary. , the isthmus--a site in the fallopian tube where sperm rest and mature before moving on--is slightly cooler than the site where fertilization occurs. Hunter had even raised the notion that sperm perceive this temperature difference.
Intrigued, Eisenbach and his colleagues designed a chamber mimicking a fallopian tube. It contains two liquid-filled wells, one held at 39[degrees]C--about the body temperature of rabbits--and one at 37[degrees]C. After videotaping the swimming of rabbit sperm placed in this chamber, Eisenbach's team concluded that a small share of rabbit sperm, 7 to 17 percent, exhibit a clear preference for moving toward the warmer well, a process called thermotaxis thermotaxis /ther·mo·tax·is/ (-tak´sis)
1. normal adjustment of bodily temperature.
2. movement of an organism in response to an increase in temperature. .
The researchers obtained similar results when the wells had only a half-degree temperature difference between them. They also found evidence of thermotaxis with human sperm. Eisenbach and his team determined that the isthmus isthmus (ĭs`məs), narrow neck of land connecting two larger land areas. Since it commands the only land route between two large areas and is on two seas, an isthmus has great strategical and commercial importance and is a favorable situation of live rabbits is nearly 2[degrees]C cooler than the fertilization site--a result similar to Hunter's.
"The evidence for thermotaxis is, in my opinion, as good as the evidence for chemotaxis," says Eisenbach. His group's experiments indicate that only the small percentage of sperm that are fully mature can sense the temperature gradient and chemical cues needed to reach an egg.
While finding the new work "intriguing," sperm researcher Susan Suarez of Cornell University calls for more studies. "I would stop short of concluding that the data provide strong proof for the existence of thermotaxis in rabbit sperm," she says. "The problem with [the] studies is that so few sperm appear to respond."
Assuming that human sperm navigate by temperature, Eisenbach envisions physicians' using a thermotaxis assay to evaluate the fitness of a man's sperm. An unusually large number of sperm unresponsive to temperature differences might explain some cases of male infertility.
PARAG NANDI (Member): Sperm Thermotactic movement!! 11/6/2009 12:41 PM
We have found also that if we place semen in a macler chamber under microscope for 10 to 15 mins then sper generally gets acumulated the place where microscope light is there....initially we thought that it may be due to light, but we understood the phenomena is thermotactics as the microscope slide base has not got any warmer and gets cool down, and sperm follows the warmer place under light of microscope!!