Sometimes Sci has a wonderful week in which she is completely inundated with fabulous possibilities for Friday Weird Science. Such a week was this one. There is SO MUCH CRAZY SCIENCE OUT THERE YOU GUYS.
So first I was going to do one paper, and then another, and then a third, and finally Mary Roach got on Twitter and posted a link to this article, commenting on the lack of real paper citation to back it up. Sci never takes that sort of thing lying down, and so I began hunting for papers. And I found this one.
It’s got rats. Rats doing handstands. And sperm. Can it get any better?
Tash et al. “Long-term (6-wk) hindlimb suspension inhibits spermatogenesis in adult male rats” Journal of Applied Physiology, 2002.
Now, you might well ask “why the HECK would anyone want to make rats do handstands and look at their sperm?” The answer? To study MICROGRAVITY.
See, this paper was written back when the international space station was just being built, and they were concerned about what would happen to the people going up there. To ALL PARTS of the people going up there. Scientists studies psychological aspects, muscle, bone, digestion, etc, etc, and…sperm!
But the question is, how do you study the effects of microgravity on earth? Contrary to some popular beliefs (I really do know someone who believes this) there are no zero gravity chambers anywhere on the planet. If you want to simulate zero gravity, you often have to try things fully immersed in water, or in things like the vomit comet. But the vomit comet only gives you a few seconds of microgravity, and rats don’t really DO well immersed in water for long periods of time. So with rats (and humans) to stimulate microgravity…they keep your legs elevated. It’s no where near perfect, but it does allow for the bone and muscle loss and other physiological changes associated with microgravity in space.
So previous studies have done this with rats doing handstands. See below.
(Source)
You elevate the rat with a harness around the base of its tail so it’s rear paws are off the floor, in a procedure called Hind Limb Suspension. Notice that the harness is elastic and loose so the rat can propel itself around the cage with its frontpaws and do whatever else it has to do. In this way, the rats have it better than humans put in this scenario, the humans have to lie down with their heads angled toward the floor and just LIVE like that.
Now there’s one problem with this scenario that the scientists had to get around. You may notice from this photo that rats have HUGE balls.
(See? I wasn’t kidding. Source)
These balls are so big they drag the floor for many rats, but they are also RETRACTABLE. So if you hang a rat up so that his legs are off the floor, the balls will retract into his abdomen. It’s not a good thing if you’re trying to study fertility. Most people are aware that your balls hang low (and wobble to and fro under proper experimental conditions) to keep them at a cooler temperature than the rest of you. This temperature is necessary for the production of fully mature sperm.
And this makes it a problem if you’re trying to study the effects of microgravity on sperm in rats while the rats do handstands. If the balls retract into the abdomen, they’ll get too hot, and you’ll get no sperm. So these scientists actually had to get around that, and they did it…by sewing the testicles into the ball sack, so they couldn’t retract. Ow. I was hoping for some sort of cute little rat supportive spanx-like system or something…
(Like that! Source)
Oh well, it is was it is. Anyway, they had them with their feet off the floor for 6 weeks. The control rats had a tail cuff like the suspended rats, and had the same thing with the balls, but were allowed to move around like normal.
And then they took some measurements. What they found was that rats with hind limb suspension (mimicking microgravity) had major reductions in testicle weight compared to rats with their feet on the floor.
(Yeah, the data was ALL in tables. I graph because I love!)
They also found that the rats had significant decreases in sperm count.
But picture of a testicle is worth 1000 words…
The four panels on the left are the control rat group, while the four on the right are in hind limb suspension. You can see the panels on the right look far less populated, and in fact the two panels on the far right were rats with no sperm count at all. Pretty severe for six weeks of leg rest.
In this picture, the two shots on the left are supposed to be showing sperm tails visible, while the right shows no sperm tails. I will admit, however, that I wouldn’t know what a sperm tail in one of those photos looks like if it walked up and planted a kiss on me. Anyone see anything looking like sperm tails?
But the moral of the story, microgravity (or the mimic of it used here) produces SEVERE decreases in sperm count, and in fact produces decreases in the cells responsible for producing sperm.
But the question is, how does this happen? The authors hypothesize a mechanism, and it involves that increased temperature. Even though the testes were supposed to remain in the ballsack, the angle meant they spent a lot of time resting against the body. The temperature could therefore still be too high. This would also apply to men in space, as floating around ALSO means your testicles tend to stick closer to your body. This is supported by the finding that a lot of men with lower limb paralysis show decreased sperm counts, possibly as a result of high temperatures of the nuts from sitting all the time in a wheelchair (makes you wonder about the sedentary lifestyles of many of us…). So it could be that men in space could suffer decreased sperm count from having their balls hover. Of course, we don’t KNOW this yet, at least not until we can get some astronauts to give up the goods.
Tash JS, Johnson DC, & Enders GC (2002). Long-term (6-wk) hindlimb suspension inhibits spermatogenesis in adult male rats. Journal of applied physiology (Bethesda, Md. : 1985), 92 (3), 1191-8 PMID: 11842058
