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Sperm cells’ swimming secrets revealed

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sperm swim molecular channelThe predictable swimming sperm featured in health class videos are rather uncharacteristic portraits of the life of these sex cells.

Spermatozoa actually spend most of their time resting up in the male reproductive tract so they can make a dash to the egg once the opportunity arises. It has long been known that the little swimmers get their cue to start moving from a big change in pH levels, but a new study explains just how that shift occurs: a specific molecule in the sperm cells’ tails releases protons when the time is right.

"The concentration of protons is extremely high at all times while the sperm are in the male reproductive tract, which makes the intracellular sperm environment acidic and inhibits the activity of the sperm cell," Yuriy Kirichok, of the University of California, San Francisco, said in a prepared statement. So releasing many of those protons from inside of the sperm cells lowers the internal acidity, a cue to the sperm cells to start flipping their flagella.

But how does that proton release happen? Previously, researchers had been unsure because they were not able to measure the membrane conductance on human sperm. But by using a whole-cell patch-clamp method to measure electrophysiological changes, Kirichok and his team were able to pinpoint the specific molecule—called Hv1—that opens up proton channels on the sperm cell membranes to release the extra protons. "The Hv1 channel, when opened, can allow protons to exit, and activates a cascade of biochemical reactions that cause the spermatozoa to move, mature and prepare to fertilize the egg," said Kirichok. This channel is signaled by increased pH and decreased zinc—both relative characteristics of the female reproductive tract compared to that of the male.

Another change in the environment that seems to spur on the sperm is an endocannabinoid that is common in both male and female reproductive tracts. The role of the endocannabinoid system also raises questions about the reported link between marijuana, which activates cannabinoid receptors, and male infertility. "Marijuana likely activates sperm prematurely, leaving them burnt out in a matter of hours," said Kirichok, who is a co-author of the new study, published online February 4 in the journal Cell.

A better understanding of sperm cells’ swimming tactics might open the door to different methods of contraception. "You can imagine now that we know the molecule responsible we could block it to prevent activation and fertilization," Kirichok noted. Conversely, those spermatozoa needing a boost might some day get a little help with their Hv1 channels.

Image courtesy of iStockphoto/wdi2007





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  1. 1. jtdwyer 4:05 pm 02/4/2010

    Perhaps the compassionate solution to decreasing population would be to simply encourage marijuana use… I’m sure the pharmaceutical industry can come up with a more politically correct means.

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  2. 2. robert schmidt 7:06 pm 02/4/2010

    I don’t understand how cells would have free protons. Are we talking about ionized hydrogen atoms free floating in the intracellular milieu? Or are we talking about some other ion such as sodium or potassium? How is it that they can remain free? How does the cell create them? Sorry, chemistry is not my subject.

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  3. 3. ScottC 12:04 am 02/5/2010

    Hydrogen ions are also protons… Hydrogen has only one electron to lose, so when it is ionised and that electron is lost, there’s nothing left but a proton.

    Link to this
  4. 4. Catbiscuit 2:34 am 02/5/2010

    I wonder if it is a simular process that makes plant sperm swim (given things like cycads have mobile sperm) or if there was a different trigger in that circumstance. Totally off topic but I find it facinating that animals have evolved with mobile sperm, and whilst early plants also had sperm the flora kingdom is now dominated by flowers (which use pollen and not little tadpoles). Is it a bit of a stretch to presume acidity would have been at different levels in prehistoric times; or is it more likely that like the kreb cycle the process has been simular for eons.

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  5. 5. Memegene 12:33 pm 02/5/2010

    That’s odd. I recall that semen is highly basic to counter the relative acidity of the vaginal environment. Does this mean that when sperm are ejaculated, they’re mixed at the last second with the components of semen that make it basic, and this triggers the reaction?

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  6. 6. Ralf123 1:01 pm 02/5/2010

    Protons (hydrogen ions) are a normal component of water. pH is the negative log of the proton concentration. Neutral water has a pH of 7, i.e. 10^-7 of the water molecules are dissociated into H+ and OH- ions. The more protons, the more acidic a solution gets.

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  7. 7. theaterlon 12:59 am 02/6/2010

    In fact, the spermatozoa is mixed with seminal fluid, produced by the prostate gland at the time of ejaculation.

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  8. 8. Memegene 1:29 pm 02/6/2010

    It’s not adding up that the article claims that the vaginal environment is the high pH trigger – the vagina has relatively low pH as it is slightly acidic. It is plausible that the seminal fluid is the factor, but the article should revisit this inconsistency.

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  9. 9. Seagu11 4:57 pm 02/10/2010

    From the review of P. Karkhumaa (http://herkules.oulu.fi/isbn9514266641/html/x548.html):
    The pH of the human vagina is acidic throughout the menstrual cycle. {} However, during coitus, seminal plasma increases vaginal pH rapidly from 4.3 to 7.2 due to its high bicarbonate concentration. In human cervical mucus, pH varies during the menstrual cycle, the highest values being found at the time of ovulation {}. The pH of human uterine fluid appears to vary around 7.0, depending on the stage of the cycle (pH 6.6-7.6) and the pH of human follicular fluid has been estimated to vary between 7 and 8.

    Link to this
  10. 10. eddierleram 1:01 am 02/12/2010

    I’ve done the comment entering bit twice. The response was, your comment will show up on the site momentarily, but, that does not occur. Why not?

    Link to this
  11. 11. eddierleram 1:08 am 02/12/2010

    Even with all of the info in the above article, and in an article by T. J. and H. M. Mitchison in the journal Nature of 21 January, 2010; the exact method of how the sperm, or cilia cell, swimming is done, nor from where in the internals the energy to drive the system comes from; seems to be known by the crews of scientists who work on the subject. That is a universal problem, which should be addressed by those with interests in the advancements to science.

    The cut view of the cilia’s tail in the journal, the waggle part, actually shows the system that controls the portions of the swimming mechanisms, and that even though the producers of the image do not understand what they have in that little image.

    Their problem is that they stand too close to the trees in the forest and cannot tell what the leaves are doing, while someone like some of us in the working class may not be specialists, but we have a broader range of trades and information on subjects that are interconnected, such that to know one subject is to be well on the way to knowing other subjects.

    It’s too bad that science does not have an access point in which information can enter the scientist’s mind from unknowns, as opposed to the one way street with them providing us with bits of information wrapped up in questions they would dearly love to know the answers to: Especially when the answers are so easy to explain, C/W two of science’s created images as proofs, in this instance.

    It’s really quite ludicrous that organizations will spend millions; and billions in some cases, when simple yells for help would answer, not all, but so very many of their questions; and that covers more subjects than animal biology.

    Eddie R.

    Link to this
  12. 12. eddierleram 1:10 am 02/12/2010

    Even with all of the info in the above article, and in an article by T. J. and H. M. Mitchison in the journal Nature of 21 January, 2010; the exact method of how the sperm, or cilia cell, swimming is done, nor from where in the internals the energy to drive the system comes from; seems to be known by the crews of scientists who work on the subject. That is a universal problem, which should be addressed by those with interests in the advancements to science.

    The cut view of the cilia’s tail in the journal, the waggle part, actually shows the system that controls the portions of the swimming mechanisms, and that even though the producers of the image do not understand what they have in that little image.

    Their problem is that they stand too close to the trees in the forest and cannot tell what the leaves are doing, while someone like some of us in the working class may not be specialists, but we have a broader range of trades and information on subjects that are interconnected, such that to know one subject is to be well on the way to knowing other subjects.

    It’s too bad that science does not have an access point in which information can enter the scientist’s mind from unknowns, as opposed to the one way street with them providing us with bits of information wrapped up in questions they would dearly love to know the answers to: Especially when the answers are so easy to explain, C/W two of science’s created images as proofs, in this instance.

    It’s really quite ludicrous that organizations will spend millions; and billions in some cases, when simple yells for help would answer, not all, but so very many of their questions; and that covers more subjects than animal biology.

    Eddie R.

    Link to this
  13. 13. eddierleram 1:19 am 02/12/2010

    Even with all of the info in the above article, and in an article by T. J. and H. M. Mitchison in the journal Nature of 21 January, 2010; the exact method of how the sperm, or cilia cell, swimming is done, nor from where in the internals the energy to drive the system comes from; seems to be not known by the crews of scientists who work on the subject. That is a universal problem, which should be addressed by those with interests in the advancements to science.

    The cut view of the cilia’s tail in the journal, the waggle part, actually shows the system that controls the portions of the swimming mechanisms, and that even though the producers of the image do not understand what they have in that little image.

    Their problem is that they stand too close to the trees in the forest and cannot tell what the leaves are doing, while someone like some of us in the working class may not be specialists, but we have a broader range of trades and information on subjects that are interconnected, such that to know one subject is to be well on the way to knowing other subjects.

    It’s too bad that science does not have an access point in which information can enter the scientist’s mind from unknowns, as opposed to the one way street with them providing us with bits of information wrapped up in questions they would dearly love to know the answers to: Especially when the answers are so easy to explain, C/W two of science’s created images as proofs, in this instance.

    It’s really quite ludicrous that organizations will spend millions; and billions in some cases, when simple yells for help would answer, not all, but so very many of their questions; and that covers more subjects than animal biology.

    Eddie R.

    Link to this

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