Animal study suggests deep space travel may significantly damage GI function in astronauts

October 1, 2018, Georgetown University Medical Center
Credit: CC0 Public Domain

Simulations with animal models meant to mirror galactic cosmic radiation exposure to astronauts are raising red flags for investigators at Georgetown University Medical Center (GUMC) about the health of astronauts during long voyages, such as to Mars.

Their most recent study, published in the Proceedings of the National Academy of Sciences (PNAS), suggests that bombardment by galactic cosmic radiation (GCR) could significantly damage gastrointestinal (GI) tissue leading to long-term functional alterations. The study also raises concern about high risk of tumor development in the stomach and colon.

Their previous work has highlighted potential impairment to brain tissue as well as accelerated aging on long space trips due to the effect of energetic , which don't affect Earthlings due to the protective global magnetosphere.

"Heavy ions such as iron and silicon are damaging because of their greater mass compared to no-mass photons such as x-rays and gamma (γ)-rays prevalent on earth as well as low mass protons in outer space," says the study's senior investigator, Kamal Datta, MD, an associate professor in the Department of Biochemistry and a project leader of the NASA Specialized Center of Research (NSCOR) at GUMC.

"With the current shielding technology, it is difficult to protect astronauts from the adverse effects of heavy ion radiation. Although there may be a way to use medicines to counter these effects, no such agent has been developed yet," says Datta, also a member of Georgetown Lombardi Comprehensive Cancer Center. "While short trips, like the times astronauts traveled to the Moon, may not expose them to this level of damage, the real concern is lasting injury from a long trip such as a Mars or other which would be much longer" he says.

The GI tract is a self-renewing tissue with continuous cell division/proliferation, the researchers say. The mucosal (top) layer of is replaced every three to five days through coordinated migration of new cells from the bottom of a flask shaped structure called crypt towards the lumen of the gut. "Any disturbance of this replacement mechanism leads to malfunctioning of physiologic processes such as nutrient absorption and starts pathologic processes such as cancer," says co-author Georgetown's Albert Fornace Jr., MD, director of the NSCOR.

To investigate the effect of heavy ions on the GI tract, the scientists used mouse small intestine as a model system. Mice were exposed to a low dose of iron radiation at the NASA Space Radiation Laboratory (NSRL) in Brookhaven National Laboratory on Long Island, New York, and the animals were then examined at Georgetown.

Researchers compared the group of mice that received heavy ions to mice exposed to gamma rays, which are comparable to X-rays, and to a third, unexposed control group. The scientists found that intestinal cells in the heavy ion group did not adequately absorb nutrients and that they formed cancerous polyps.

Additionally, there was evidence that iron radiation induced DNA damage that increased the number of senescent cells. Senescent cells are incapable of normal cell division but they are not "quiet," says Datta.

"They generate oxidative stress and inflammatory molecules that induce more damage. This greatly affected migration of cells that are needed to replace the intestinal lining which slowed down GI functioning," he says.

Even though a very low dose was delivered over the equivalent of months-long period in deep space, the effects of heavy ion radiation appeared to be permanent, says Fornace.

"We have documented the effects of deep space on some vital organs, but we believe that similar damage responses may occur in many organs," says Datta. "It is important to understand these effects in advance so we can do everything we can to protect our future travelers."

Explore further: Exposure to space radiation reduces ability of intestinal cells to destroy oncoprotein

More information: Santosh Kumar el al., "Space radiation triggers persistent stress response, increases senescent signaling, and decreases cell migration in mouse intestine," PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1807522115

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rrwillsj
1 / 5 (4) Oct 01, 2018
Gosh, but, butt, Butterrible! This can't possibly be true!
None of the comicbook and cgi-f/x cartoon spacemen ever got stuck on the toilet! Or had to rake a enormous supply of adult diapers with them as they voyaged across the cosmos.

As for those who bellyache about $18,000 toilet seats? Hah! The designers got the last laugh. Try taking a shit flying upside down, accelerating backwards. Simultaneous with pitch, roll and yaw!

Good thing Dr, Denton invented the power flap. He should be immortalized with all the other pioneers of space technology.
Thorium Boy
2.6 / 5 (5) Oct 01, 2018
Project Orion ship could get to Mars in 3 weeks, carry 10,000 TONS of supplies, set-up a colony base and 3 weeks back, if needed. Get RID of ridiculous chemical rockets for manned spaceflight.
envy887
3 / 5 (2) Oct 01, 2018
The dose rate isn't given in this study, but in a previous study (Exposure to heavy ion radiation induces persistent oxidative stress in mouse intestine) by Datta and Suman et. al, they delivered the entire 1,000 day mission radiation dose in 30 seconds! And they delivered that mission dose entirely as heavy ions, when the vast majority (some 98%) of it will be less damaging protons and alpha particles (helium nuclei).

Since the effect of ionizing radiation is highly dependent on dose rate and particle type, this study does not at all reflect the real effect of GCR on Mars-bound astronauts. They are likely overestimating the effect by 100 times or more.
danR
not rated yet Oct 01, 2018
envy887
https://journals.....0042224
"Exposure to heavy ion radiation induces persistent oxidative stress in mouse intestine"

I'm not finding 30 seconds or 1000 day mission anywhere in that article.
thingumbobesquire
1 / 5 (1) Oct 02, 2018
Project Orion ship could get to Mars in 3 weeks, carry 10,000 TONS of supplies, set-up a colony base and 3 weeks back, if needed. Get RID of ridiculous chemical rockets for manned spaceflight.

Correct. Acceleration/deceleration for inertial/gravity and development of radiation shielding are obvious necessary goals for space colonization. http://thingumbob...ive.html
envy887
5 / 5 (2) Oct 02, 2018
danR: read the study in the article above: "Since the estimated radiation dose for a 1,000-d Mars mission is about 0.42 Gy, with an estimate of an 860-d Mars mission dose equivalent of 1.01 Sv so doses of 0.5 Gy or less are more relevant, we have used 0.5 Gy to study IEC migration"

So the authors assume 0.5 Gy of heavy ions is relevant to a deep space mission on the order of 1000 days (which it isn't, because GCR is 98% protons and alpha).

In the other study the same authors write:

"Mice were placed in rectangular clear lucite boxes (3″×1.5″×1.5″) with multiple holes for respiration and exposed to 56Fe (energy: 1000 MeV/nucleon; LET: 148 keV/µm), and γ radiation at a dose rate of 1 Gy/min"

The "1 Gy/min" is 0.5 Gy in 30 seconds, while an astronaut would need many years in space to absorb 0.5 Gy. It's about as representative of the deep space radiation dose as hitting that same mouse with a hammer.
antialias_physorg
not rated yet Oct 02, 2018
Project Orion ship could get to Mars in 3 weeks, carry 10,000 TONS of supplies

And then what? Mars also doesn't have a magnetosphere.

Shielding is essential

So they assume 0.5 Gy of heavy ions is representative of a deep space mission

Gy (absorbed dose) isn't the figure of merit. Biological effective dose (Sv) is.
The unit is the same (both are units of absorbed energy per mass), but heavy ions are a lot more biologically effective. 1Gy of alpha nuclei is on the order of 20 Sv.
ShotmanMaslo
not rated yet Oct 02, 2018
And then what? Mars also doesn't have a magnetosphere.


Mars does have plentiful soil to use as shielding. Also, atmosphere is what mainly protects us against cosmic rays, not magnetosphere. Sadly, this error is mentioned even in the article. Astronauts on the ISS get hit by heavy ions, too, just less so than in deep space because third of the sky is blocked by Earth.

Mars mission radiation dose is <1 Sv, assuming fast trajectory of 3-6 months one way. Cosmic rays will not stop a Mars mission, period. They are a grave concern for future missions spending longer than a year in deep space, tough. Very heavy shielding (multiple tons per square meter, emulating our atmosphere) would be required for such missions.
Mark Thomas
not rated yet Oct 02, 2018
None of the comicbook and cgi-f/x cartoon spacemen ever got stuck . . .


rrwillsj, that is a great idea! NCC-1701 Enterprise used strong active shielding to cut down on radiation, so we should do the same. A bimodal (electricity and propulsion) nuclear rocket engine would give us the megawatts we need to generate a strong em field to defect the heavy ions. A bimodal nuclear rocket engine would be a win-win for space travel by enabling us to drastically reduce charged ion radiation and decrease interplanetary travel times. Although we don't know exactly how the shields on Enterprise work, we could use electrostatic or magnetic fields, possibly with plasma. Maybe you should watch all the old episodes and see if you can get any hints as to how they did it.

rrwillsj, I have to admit you were right this time. We should always look to Star Trek for inspiration. :-)

http://large.stan.../clark1/
rrwillsj
1 / 5 (2) Oct 02, 2018
Sorry Mark but if you consider FICTION such as Star Dreck or Star Boors as inspiration? I am very happy that you are not my travel agent!
Orion Rocket? Screw you! Not in my backyard.

Physical shielding is primitive level stupid. But until some smart-ass kid invents invents some form of energy field mechanism that can capture and re-direct space radiation?

We will have to copy the Hermit Crab. Inner shell / outer shell. During the outbound voyage, the outer shell collects damaging cascades of radiation. Get to Mars, hastily abandon the outer shell. Voyage back to Earth with inner shell. To be abandoned in turn upon arrival.

Outrageously expensive in terms of quantity of reaction mass needed. But at least it's a method within rationally foreseeable technology. Not vaporware or unobtanium.
danR
not rated yet Oct 02, 2018
envy887
I'm simply going by the study indicated by the article title you exactly provided. It took some doing to locate a (non-paywalled [no longer in university, I regret the loss of transparent access to such things] ) copy, to which I had linked. For the rest of it, there seems to be some conflation of several studies. Based on my guesstimate the lowest total Fe ion dose-time was ~90 seconds, but I don't know how that relates to the 1000 days not mentioned in the article whose title you provided.

Be that as it may, I'll take it for granted that:
a. The authors of the current study are thoroughly familiar with previous work, and
b. What you have provided may be orthogonal, in the long run, to the outcomes of humans, inasmuch as rodent guts in general can differ from ours (always a problem in medical experiment comparisons), and are generally more robust to abuse.
HealingMindN
not rated yet Oct 02, 2018
We should always look to Star Trek for inspiration. :-)

http://large.stan.../clark1/


It's a wonder how the Enterprise Crew survived the away missions to all those "M" class planets.
envy887
5 / 5 (2) Oct 02, 2018
So they assume 0.5 Gy of heavy ions is representative of a deep space mission

Gy (absorbed dose) isn't the figure of merit. Biological effective dose (Sv) is.
The unit is the same (both are units of absorbed energy per mass), but heavy ions are a lot more biologically effective. 1Gy of alpha nuclei is on the order of 20 Sv.


This is exactly why 0.5 Gy of heavy ions is not representative of deep space radiation measured by Mars probes inclusing MSL. 0.5 Gy of heavy ions is 10 Sv of equivalent dose (the weighting factor is 20), which is more than 11x NASA's estimate of 0.9 Sv for a 860 day Mars mission.

The actual heavy ion dose during a 860 day Mars mission with appropriate shielding would be on the order of 0.010 Gy (10 milliGray), and this would accumulate over a much longer time span. This only contributes about 0.2 Sv of the total dose, the remainder is mostly from protons.
envy887
not rated yet Oct 02, 2018
What you have provided may be orthogonal, in the long run, to the outcomes of humans, inasmuch as rodent guts in general can differ from ours (always a problem in medical experiment comparisons), and are generally more robust to abuse.


Seeing as the same authors wrote the previous study, I'm sure they are familiar with it. No doubt they are experts in the effects of radiation. However, they appear to have difficulty estimating a radiation dose that's actually consistent with measured deep space radiation.
Mark Thomas
5 / 5 (1) Oct 03, 2018
Star Dreck or Star Boors as inspiration? I am very happy that you are not my travel agent!
Orion Rocket? Screw you! Not in my backyard.


rrwillsj, your comment casts you in an unfavorable light. As Luke Skywalker would say, "That's amazing, everything in that statement was wrong."

Bimodal nuclear thermal rocket (NTR) engines do NOT explode nuclear material like Orion would. NTRs are nuclear reactors that work at higher temperatures to heat and expel a propellant, often hydrogen, with high thrust AND high specific impulse (efficiency). Real, working NTRs go back to the Werner Von Braun era, but were never deployed in space by the U.S.

Try reading and thinking more carefully before commenting next time, for example, start here:

https://en.wikipe...l_rocket

Mark Thomas
not rated yet Oct 03, 2018
rrwillsj, one more thing. Star Trek has a long history of predictions that have come true. Simply labeling it as FICTION and implying it is impossible is wrong. I would say it is aspirational, and there is a HUGE practical difference. Your "fictional" means it is not even worth trying, my "aspirational" means we should do everything we can to meet and exceed that future. Your approach concedes failure, mine strives for success.
rrwillsj
not rated yet Oct 04, 2018
I suppose I should attempt some sort of apology to you Mark. If you so desperately need your belief in fairytales to get yourself through the day?

The problem I have? Is that I am a sadist and enjoy tormenting all the masochists who hang out around here.

We all, myself included, have our fragile egos to prop up. Whatever keeps us from crashing despondent.

As I have speculated before? I think the phys.org site is a goldmine for grad students in the Social Sciences and Psych Health fields.

Hey, Dr. Lechter. Would you care to comment?
Mark Thomas
5 / 5 (1) Oct 04, 2018
rrwillsj, everyone has their reasons for commenting. I usually hope to correct a misconception or shed a little light on topics I am familiar with such as space exploration. No S&M required or wanted. After all, this is a science website.

No offense, but your tormenting looks more like confusion and is coming off more as a minor nuisance at most. The path forward has always been littered with naysayers who argue it can't be done. "If God wanted man to fly he would have given him wings." "Going to the moon is a fantasy." "Electric cars will never be practical." "We can't reach Mars (for one reason or another)." All those people were wrong.

idjyit
not rated yet Oct 04, 2018
" Star Trek has a long history of predictions that have come true."

I've heard this before, but I'm at a loss as to what "Prediction" actually came true.

Anyone care to elaborate ?
Mark Thomas
not rated yet Oct 04, 2018
idjyit, you really need to google this. Cut and paste the quote into google or your favorite browser. Google has about 10,300,000 hits.

https://www.googl...dg8eykGc

Star Trek has been right so often one has to wonder how much is a self-fulfilling prophecy. Meaning, people watch the show and are inspired to try to build it.
rrwillsj
not rated yet Oct 05, 2018
id, any day now the trekies cult will think of something physical they can point to.

Meanwhile, here on Earth. You need to buff up and get sirius about combat training. Gotta step lively for when the klingons and cardassians get a hankering for the sweet taste of barbecued human.

Or perhaps the vulcans and romulans could logically argue over which of them gets stuck with the tedious duty of attempting to "civilize" the primitive savages of Earth.

Sorry id, I realize that sort of nonsense is not really what you want to read about. But many of the commentators cannot discuss a real-world issue, existing technology or empirical evidence without releasing their inner ape. To drag in cgi-f/x imagery as a diversion from real scientific achievements.

Mark Thomas
not rated yet Oct 05, 2018
any day now the trekies cult will think of something physical they can point to


Doors that open when you approach them, computer tablets, communicators in the form of mobile phones, hands-free phones, computers with speech recognition, translating computers, tricorder-like devices, huge flat television screens, transparent aluminum, intelligent personal assistants, replicators (3D printers), augmented reality, virtual reality, video calls, tractor beams (for tiny objects), laser weapons, artificial eyes, personal computers.

Roddenberry guessed it would take us 300 years to reach the Star Trek level of technology and only 50 years have elapsed. What do you say we stick around for another 250 years and see how it all turns out? We might even get our warp drive by then, who knows?

https://qz.com/76...hnology/
Mark Thomas
not rated yet Oct 05, 2018
You don't like Star Trek, fine, your loss. The active shielding link I posted above is from Stanford University, not a television show. As you probably don't know, Stanford has gained some prominence for their engineering program over the years. Look them up. You claim you focus on reality, then you proceed to ignore it. Again, you appear more confused than anything.

http://large.stan.../clark1/
idjyit
5 / 5 (1) Oct 05, 2018
So what does everyone think of Star Trek Discovery then ?

I personally think it is an awesome progression , and breaking the Canon was long overdue.
Mark Thomas
5 / 5 (1) Oct 05, 2018
From my admittedly biased perspective, it is great. I liked all the characters except I wasn't thrilled with Captain Lorca. I was afraid that it was sloppiness on the part of the writers, so when I learned there was very good reason he was a little off, I thought that was awesome.

If you want a complaint, I would have liked the second season to have started by now. At the very end of the first season, the instant they started showing part of good ol' NCC-1701's call sign, I knew that Enterprise was near. It will be interesting to see what the writers do with that.

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