Under a microscope, human sperm float like a wig, grab the tail and blow as they seek an egg to fertilize.
But now, new 3D microscopy and high-speed video show that sperm do not swim in this simple, symmetric motion. Instead, they move with a rolling spin that compensates for the fact that their tails actually beat on one side only.
“It’s almost the same if you’re a swimmer, but you can only put your foot aside,” said the study’s author, Hermes Gadalha, a mathematician at the University of Bristol in the UK “if you’ve done it in the swimming pool and You only did this for one side, you will always swim in circles. Nature understood this [up] Very complicated, simple way to go further. ”
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The first person to observe human sperm closely, Antony van Leeuwenhoek, was a Dutch scientist known as the father of microbiology. In 1677, van Leeuwenhoek developed his new The microscope Towards her own semen, seeing for the first time that the fluid was filled with small, attractive cells.
Under a 2D microscope, it was clear that the sperm was induced by the tail, which tended to rotate side-to-side as the sperm’s head rotated. For the next 343 years, it was understood how human sperm moved.
“[M]Any scientist has posted that there is likely to be a very important 3D element in how the sperm tail moves, but to date we do not have the technology to make such measurements reliably, “Alan Said Paci, a university professor and astrologer in England at Sheffield, who was not involved in research.
The new research is thus “an important step,” Passy wrote in an email to Live Science.
Gadleha and his colleagues began research on “blue-sky exploration” at Universidad National Autónoma de Mexico, Gadleha said. Using microscopy techniques that allow imaging in three dimensions and a high-speed camera that can capture 55,000 frames per second, they recorded human sperm swimming on a microscope slide.
Gadleha told Live Science, “What we found was something surprising, because it was completely broken by our belief system.”
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Sperm were not fighting the tail, whip-like, side-to-side. Instead, they could only beat in one direction. To prevent further movement from this asymmetric tail movement, the head of the sperm was rotated at the same time with a jerking motion, causing the tail to rotate. The head rotation and tail are actually two different movements controlled by two different cellular mechanisms, Gadalha said. But when they combine, the result is like a spinning otter or rotating drill bit. During a 360-degree rotation, the tail movement of one side exits, which adds up to forward propulsion.
“The sperm isn’t even swimming, the sperm is drilling in fluid,” Gadalha said.
The researchers published their findings in the journal today (31 July) Science advance.
Asymmetry and fertility
In technical terms, how a sperm moves is called, which means that it rotates around an axis, but the axis of rotation is changing. Planets do this in their rotational travel around the Sun, but a more familiar example might be a spinning top, which stumbles and dances about the floor as it rotates at its tip.
“It is important to note that on their journey to the egg that sperm will swim in a much more complex environment than the drop of fluid in which they were seen for this study,” Pacey said. “In the woman’s body, they will have to swim in narrow channels of very viscous fluid in the cervix, the walls of the cells in the fallopian tubes, as well as the muscle contractions and fluid they face (along with the wafting tops ) Cells called celia) in the opposite direction to where they want to go. However, if they are actually able to move their way, I can now see in much better clarity that sperm reaching the egg with this attack How to cope. And be able to go inside it, “said Pacey
Gadaleha said that sperm motility, or the ability to move, is one of the major matrix fertility when males assess fertility. Rolling of the sperm head is not currently considered in any of these matrices, but it is possible that further studies may detect some defects that inhibit this rotation, and thereby inhibit the movement of the sperm. gives.
Fesi said that fertility clinics use 2D microscopy, and more work needs to be done to find out if 3D microscopy can benefit their analysis.
“Certainly, any 3D approach would have to be quick, inexpensive and automated for any diagnostic value,” he said. “But regardless, this paper is definitely a step in the right direction.”
Originally published in Live Science.