Sunday, July 28, 2019

Sperm selection

I've blogged before about selection of sperm donors, but here's a story from the NY Times about the selection of sperm itself:

Tinder for Sperm: Even in the Petri Dish, Looks and Athleticism Are Prized
What makes one sperm cell — a blob of DNA with a tail — stand out? The selection process is like a microscopic Mr. America contest.
By Randi Hutter Epstein

“Not that one with the droopy head,” Lo said, pointing to a sperm that looked like a deflated balloon sagging over its string. He rejected a sperm with a thickened midpiece that he described as a “turtleneck,” and said he also avoids sperm with curlicue tails or an extra tail. Slow pokes and non-swimmers are spurned as well.

"When a sperm cell reaches the egg, it releases hyaluronidase, an enzyme that dissolves the cumulus, a layer of cells surrounding the egg. Next, the acrosome, a vesicle inside the sperm cell’s head, fuses with the outer layer of the egg, igniting the release of enzymes that ease the route inside. The sperm’s vigorously waving tail provides an extra push to help it through. Once inside, proteins within the sperm cell’s head prompt the oocyte to finish maturing and to release chemicals that harden the outer shell of the egg, preventing other sperm from barging in.

"These days, many leading fertility centers use techniques that allow them to bypass all these steps. Instead, they pick a single sperm and inject it into the egg, a technique called intracytoplasmic sperm injection or ICSI (pronounced ICK-see). ICSI was designed to help men with few or defective sperm, but has become so common that it’s used in more than half* of all I.V.F. procedures.
"In addition to having a keen eye for promising sperm, an embryologist must have excellent hand-eye coordination. Even then, learning to identify and successfully catch a single sperm before it swims away can take months of practice, said Lo. “I told my parents those years of video game playing, they’ve really paid off.”

* From The Lancet: "Globally, between 2008 and 2010, more than 4·7 million treatment cycles of assisted reproduction techniques were performed, of which around half involved intracytoplasmic sperm injection (ICSI), leading to the birth of 1·14 million babies.

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