Paul Turek
speaker
358 appearances
1 recordings
1 series
first heard Jun 2025
last heard Jun 2025
Paul Turek’s voice in public audio — every appearance, attributed to the second.
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It's just wildly compact, 10 times more compact than any other cell in the body. From a mitochondrial density standpoint? From a cytoplasmic standpoint and nuclear standpoint, it goes from histones, the protamines, the DNA is condensed a lot more because it's got to go on the road.
So it's got to be packaged really well to survive outside the body and be in good shape because it's transgenerational. So a lot of energy in that. And then during the epididymis, which is a collecting duct.
So that's going to bring the physics in. So then there's a two-week period where it stays in the epididymis, which is a 35-foot tubule with estrogen, and there's a lot of post-modification of the sperm.
Epididymis has been relatively understudied, but it has actually become very important. Epididymisomes, and there's a lot of modifications we don't really understand. I wrote the chapter for our textbook on reproductive physiology, and it really is a lot of work in the 50s and 60s, but now we're beginning to understand epididymis.
DNA fragmentation and the quality of sperm is driven by the epididymis. A lot of the quality of sperm, not the shape and stuff like that. Meaning based on its residence time within the epididymis? And what other environmental influences that occur there? Because the epididymis is not as walled off from the body as the testis is. immunologically and otherwise.
It's more susceptible to drugs, exposures, heat, et cetera. Testis is very walled off. Very little happens in the testis because the sertolo cells that line the tubules have a blood-brain barrier, a blood-testis barrier. Same as the brain, it's highly protective. It's as protective? Yes.
Harvey Cushing at Yale did that in the late 18th century, took brain-dead patients, injected them with dye, methylene blue, I think, The blood-brain barrier came about when nothing went into the brain and nothing went into the testicle. Two areas of the body that were completely immune from normal transport processes. Wow. Blood-testis barrier.
So the two things that we know happen in the epididymis after production of sperm are motility improves. So sperm begin to learn progressive motility. So they start moving forward as opposed to not moving or moving in circles, which is important. And the most curious thing is they learn how to smell.
So they actually detect follicular fluid. So if you take testicular sperm and inseminate it into a uterus with insemination technology, it'll just be killed. If you take an epididymal sperm and you do that from the top of the epididymis, it'll maybe run in circles and it'll be killed by the immune system of the female. It has to go through that whole epididymal cycle.
Once it's at the end of the epididymis where it's stored. And that's how many weeks? Two, 10 to 14 days. 600 million sperm live in a bucket, a pot of soup to call it epididymis. And you ejaculate from that pot, which tells you a lot about sperm quality because it can get old.
But that sperm, if you put in it, will know exactly where to go and it'll move forward because it's like a shark sensing blood in the water. One part per billion of follicular fluid can be sensed by a sperm. That's incredible. It's literally an olfactory sense. It's a smell sense that sperm have for particular food.
It was published in Nature recently and stuff like that. So it's really interesting. It's an olfactory type receptor.
Is there any smell, Peter?
And I'd also say that if you block a sensory bank of the five, others increase remarkably like braille. I'm a microsurgeon. This stuff matters a lot, but I can't do braille or hearing. I think you can crank it up if you lose a sense and you see that with people who are deaf. Your ability to see and I don't think seeing better is really the issue, but hearing and smell, I think it can crank up.
So that's a great extrapolation of the pot of soup idea. And so on that note, I would say... Typically, we recommend two days of abstinence, sex every other day.
But not for the semen analysis. That's for conception. Depends how old you are in your biology, but most men need a day or two to recharge completely, a day or two. That's why we recommend that. That's sort of a generalization. Some men are fine every day. I had a guy once who had to bank sperm for hepatitis treatment. And he was like Mickey Rourke, and he had a wooden leg, and he was about 50.
And I said, you're going to need to abstain for a couple, three days to do this semen analysis so we get a good sample. I want it to be an optimized one. And he looked at his partner, and she looked at me, and she grabs him and says... he can't do that. He's every day. He can't do that. I'm always going to do. So he's like, he was panicking that he had to hold off for a day.
I said, how often do you have sex? He said, twice a day, every day. I'm like, okay, that was great. Then I had one man, wonderful orthopedic surgeon at Stanford. And I asked him on my questionnaire, I said, how often do you have sex? And he wrote 0.00001356. I was like, He divided once a year. 0.00 weekly, 0.00155, Avogadro's number, right? Which meant he was so frustrated.
A beautiful way to say that was the 0.001355. So anyway, for a semen analysis for diagnostics for infertility, when you abstain longer, your sperm count will rise.
When you're not going to gain that much, you're not going to lose that much motility after that. So there's biological variability, which we try to minimize when we do the semen analysis. So two to four days of abstinence. That's a different period than what we're recommending for sex, which is every other day.
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