Too much space travel is hazardous for your eyeballs

Dec 1, 2016

By Sarah Kaplan

Something strange has been happening to people who stay too long in space: The backs of their eyeballs start to flatten. Spider-web-like marks called choroidal folds crisscross the thin layer of blood vessels and connective tissue that surround their retinas. Their vision goes blurry, their optic nerves become inflamed. The damage can last long after the astronauts return to Earth. And scientists haven’t been able to explain why.

“People initially didn’t know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to earth,” notes Noam Alperin, a professor of radiology and biomedical engineering at the University of Miami Miller School of Medicine.

Now Alperin may have found the source of this mysterious syndrome. In a study presented this week at the annual meeting of the Radiological Society of North America, he suggests that the problem might be caused by pressure from the fluid that cushions the brain.


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21 comments on “Too much space travel is hazardous for your eyeballs

  • This is pretty interesting and I will admit not readily intuitive for me. While it makes sense, the underlying cause “microgravity” is not where my thought process goes.

    As i read the article, I anticipated reading about take off and re-entry and their monstrous G-force causing the malady. I was “on” the wrong side of the spectrum. Very very cool… Homeostasis must be maintained on both sides of the “set point”. So, I was looking at increased forces during take off and re-entry, but in fact it is the flip side — decreased forces are the culprits.



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  • Crooked, forces by drag race drivers is much greater than the take off. But the damage is not there.
    Its apparently the duration of the force and in this case the deceased force for a extremely long duration in space.
    Am I close?



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  • crookedshoes #1
    Dec 1, 2016 at 8:00 pm

    Homeostasis must be maintained on both sides of the “set point”.

    I think that is the key issue.

    Quite a few problems with eyes can be caused by raised blood-pressure

    https://medlineplus.gov/ency/article/000999.htm

    High blood pressure can damage blood vessels in the retina. The higher the blood pressure and the longer it has been high, the more severe the damage is likely to be.

    You have a higher risk of damage and vision loss when you have diabetes, high cholesterol level, or you smoke.

    Rarely, blood pressure readings suddenly become very high, but when they do, it can cause severe changes in the eye.

    Other problems with the retina are also more likely, such as:

    Damage to the nerves in the eye (ischemic optic neuropathy), due to poor blood flow
    Blockage of the blood supply in the arteries to the retina (retinal artery occlusion)
    Blockage of the veins that carry blood away from the retina (retinal vein occlusion)




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  • Alf and Alan4,

    Alf, I should have looked up the forces of other activities compared to the forces experience in take off and re-entry. I fell victim to a combo of “lazy” and “hollywood stereotype” — I visualized the “movie version” of space exploration and didn’t think past it. There’s a lesson in there somewhere.

    Speaking of lessons, I find this super interesting. I would like to go biology teacher here and use this to demonstrate a key point in biology.

    Life evolved HERE on earth. As such, it is confined to the conditions that have been consistent through life’s development and history. I get sick to death of hearing about design and “disproof” and all the other hackneyed horseshit that gets thrown around, especially the trope regarding no way to demonstrate evolution. This clearly does. So while these astronauts are having “problems” after partial “lifetimes” in space, I’d like to extrapolate this damage out to full lifetimes and then to generations in space. What we see as “damage” upon return, would be “selection pressure” over lifetimes and generations. And, change would logically be in motion.

    When we look for another planet to hop to and slowly (or quickly) rip it to shreds for our own profit, we (of course) look for a planet with similar conditions to earth. And we focus (especially in hollywood) on BIG things like oxygen and water….. But, if these men and women are feeling selection short term, imagine what long term exposure would yield. Then, imagine the human who through DNA replication mistakes in Meiosis, has the fortune (or misfortune) of being sent to space and they have a random “workaround” to the accumulation of this damage. They reproduce and the workaround affords advantage…. Oh, there it is!!!! Evolution.

    What needs to be understood and underscored is that ANY deviation from earth has the potential to cause the population of inhabitants of the new planet to change, generation by generation (because of selection and mutation) until they were significantly different enough from humans here on earth that the two populations could no longer interbreed. Then we would have earth humans and “other” humans. So, if the force of gravity was not exactly the same on the new planet as on ole earth, we’d have the potential for change. The further this value is from earth’s, the faster this change may accrue. The closer it is to earth’s, the slower the change may accrue. You may not think that a flattened back of the eyeball could lead to speciation… But, look at the Grant’s work with Finches… Anyway, all that really has to occur are changes that cause sex to be unpalatable enough to be off the table (look at drosophila fed maltose vs glucose — they won’t have sex because they “smell funny” to each other) Also take into account that if eyeballs are being affected, it is likely many other things are too and this could include “preference of mates” and then we are talking sexual selection.

    Now, technically, the “other planet” humans would be a different species as soon as they established a population on the other planet, as we and they would be temporally and spatially separated and interbreeding would be prohibitive due to time and distance. (Look up 17 year cicadas and “brood X”…) But, certainly, when the two populations drifted far enough apart genetically, due to isolation and differences in environment — we’d have allopatric speciation– and clear proof of evolution (we can add it to the monster pile of evidence).

    Sorry this is long winded, but every time I went to post it, I had to add something. It is a spectacular thought experiment and rooted in real science. Can anyone say science fiction novel? It would be a good one.



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  • crookedshoes #4
    Dec 2, 2016 at 9:02 am

    There are two issues related to this article – gravity and air pressure. There are technical solutions to both of these in space-flight

    But, if these men and women are feeling selection short term,

    The short-term issues on the space station are because no provision to deal with weightlessness has been made.

    imagine what long term exposure would yield.

    On this related Stephen Hawking discussion, I provide the answers.

    https://www.richarddawkins.net/2016/11/stephen-hawking-just-gave-humanity-a-due-date-for-finding-another-planet/#li-comment-215132 – Zero G can easily be overcome by engineering a rotating wheel shaped craft or station, rotating a linear one end over end, or simply by operating a one G thrust rocket engine pushing the habitation unit.

    Then, imagine the human who through DNA replication mistakes in Meiosis, has the fortune (or misfortune) of being sent to space and they have a random “workaround” to the accumulation of this damage.

    Inter planetary and inter stellar craft would require radiation shielding around crew quarters, but things like stores and water tanks could be used for this purpose.

    They reproduce and the workaround affords advantage…. Oh, there it is!!!! Evolution.

    When it comes to living on another planet or moon, the gravity would be important and populations may well evolve to adapt to the new conditions in the longer term.



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  • Alan4,
    Imagine a “reunion” of “Romeo” whose ancestor’s jumped to Mars ten generations ago, and “Juliet” whose ancestors decided to stay on earth despite World dictator Trump’s reign of terror.

    Ten generations…. two hundred years, maybe two hundred and fifty. Can they still produce fertile offspring? Yes? Let’s go 50 generations…..

    Another thought experiment. Let’s invent a time machine and send a man back 3000 years. Let’s “check out the women”…. Would a man from today be willing to have sex with a woman from back then? Think hygiene, think teeth, hair, smells, cultural practices…. For the same reasons would the woman from then be willing to engage in sex with a man from today????

    (The entire thought experiment can have the genders reversed and a woman from today can go back and …. would she be ok with sex with a man from back then???)

    See, it’s more than simple machinery “fitting together” and the mechanical act of sex coupled with gametes that “can” form a zygote. Point being, there’s lots more to it… Even in drosophila and “lower” animals.
    So, do Romeo and Juliet succeed in procreating or not??? If not… We have speciation.



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  • crookedshoes #6
    Dec 3, 2016 at 12:21 pm

    Imagine a “reunion” of “Romeo” whose ancestor’s jumped to Mars ten generations ago, and “Juliet” whose ancestors decided to stay on earth despite World dictator Trump’s reign of terror.

    Unlike travel in a spacecraft where artificial gravity can be produced by rotation or acceleration, as @#5, living on Mars is living in reduced gravity.
    Gravity on Mars’ surface is much lower than it is here on Earth – 62% lower to be precise. At just 0.38 of the Earth standard.

    This means that there will be immediate phenotypic adaptations in astronauts and in their offspring. – As has been shown by health monitoring of astronauts on the space stations.

    https://www.wired.com/2014/02/happens-body-mars/

    Without the quadriceps, buttocks, calves, and erector spinae that surround the spinal column and keep it standing tall, the pull of gravity would collapse the human body into a fetal ball and leave it curled close to the floor. These muscle groups are sculpted by the force of gravity, in a state of constant exercise, perpetually loaded and unloaded as we go about our daily lives. That’s why the mass of flesh that constitutes the bulk of our thighs and works to extend and straighten the knee are the fastest-wasting group in the body.

    In experiments that charted the changes in the quadriceps of rats flown in space, more than a third of the total muscle bulk was lost within nine days.

    Our bones, too, are shaped by the force of gravity. We tend to think of our skeleton as pretty inert — little more than a scaffold on which to hang the flesh or a system of biological armor. But at the microscopic level, it is far more dynamic: constantly altering its structure to contend with the gravitational forces it experiences, weaving itself an architecture that best protects the bone from strain. Deprived of gravitational load, bones fall prey to a kind of space-flight-induced osteoporosis. And because 99 percent of our body’s calcium is stored in the skeleton, as it wastes away, that calcium finds its way into the bloodstream, causing yet more problems from constipation to renal stones to psychotic depression.

    The biological adaptations to gravity don’t stop there. When we’re standing up, our heart, itself a muscle pump, has to work against gravity, pushing blood vertically in the carotid arteries that lead away from our heart toward our brain. When deprived of the need to work against the force of gravity, the heart and its system of vessels become deconditioned — slowly taking athletes and turning them into couch potatoes.

    The system of accelerometers in our inner ear, the otoliths and semicircular canals, are engineered to provide the finest detail about movement, sharing their inputs and outputs with the eyes, the heart, the joints, and the muscles. These organs are not considered “vital” in the sense that they are not required to keep the human body alive. As a result, the essential role they play in delivering a finely calibrated sense of motion is often overlooked.

    Like all of the best things in life, you don’t really appreciate what you’ve got until you lose it. Imagine a gently oscillating, nausea-inducing scene from which there is no escape. That’s what it feels like when the organs of the inner ear malfunction. And that can be caused by disease, drugs, poisons, and — as it turns out — the absence of gravity.

    The impairments don’t stop there. There are other, less well-understood alterations. Red blood cell counts fall, inducing a sort of space anemia. Immunity suffers, wound healing slows, and sleep is chronically disturbed.

    Ten generations…. two hundred years, maybe two hundred and fifty. Can they still produce fertile offspring?

    I don’t think that is the issue. First of all the Mars dwellers would be fragile in comparison to their Earth bound counterparts, and secondly, these medical conditions would produce intense selection pressure.

    Yes? Let’s go 50 generations…..

    If the Mars colonists evolved quickly (as with the domestication of dogs or foxes), various organs would be recalibrated to become adapted to the low gravity conditions.
    This could well mean that any hybrid offspring were non-viable, or only weakly viable, in both sets of gravitational conditions.



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  • CrookedShoes, Maybe I should have looked them up. They aren’t that much different. The drag racers do this on a regular basis however and the effect should have been more intense?
    http://www.gforces.net/a-discussion-on-typical-examples.html
    • Bugatti Veyron from 0 to 100 km/h in 2.4 s, has g force = 1.18 g
    • High-g roller coasters have g forces ranging from 3.5–6.3 g
    • Top Fuel drag racing world record of 4.4 s over 1/4 mile, g force = 4.2 g
    • Space Shuttle, maximum during launch and reentry, g force =3 g



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  • @#7 – Gravity on Mars’ surface is much lower than it is here on Earth – 62% lower to be precise. At just 0.38 of the Earth standard.

    BTW; – Also – In regard to Moon-bases:-

    Gravity on the surface of the Moon is 1.62519 m/s2, about 16.6% that on Earth’s surface or 0.16 ɡ.



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  • Alf1200,
    I do feel better when there are actual facts, thanks for providing them!

    Alan4,
    Very interesting, the physiological effects seem like the tip of the iceberg when you consider that many of the events in fertilization and embryonic development could be significantly impacted (and even impeded) when gravity is decreased by this drastic amount. Head/tail axis determination comes to mind.

    About 15 years ago, I tried to transform the embryonic cells of pine trees with a plasmid carrying the GFP gene (green fluorescent protein)… I (selfishly) wanted to create glow in the dark Christmas trees and sincerely thought it was a million dollar idea. Well, it turns out that getting a plasmid into an embryo that is inside a seed is equivalent to throwing a paper airplane through a brick wall. I needed alternatives. So, i turned to tissue culture.

    I tried to coax pine tree embryos to grow outside of the seed (oversimplified explanation alert)… Anyway, that didn’t go too well and one experiment I did was to try to culture the embryos in an environment that spun slowly. It is not hard to culture developed plant parts, but I was trying to go from embryos (so that the plasmid would get into the max # of cells)… Anyway in the slowly spinning environment, all that developed was what they called calluses. A blob of disorganized plant cells — a mess. I think that this would be a real issue for gestation on Mars.



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  • Crooked

    Another thought experiment. Let’s invent a time machine and send a man back 3000 years. Let’s “check out the women”…. Would a man from today be willing to have sex with a woman from back then? Think hygiene, think teeth, hair, smells, cultural practices…. For the same reasons would the woman from then be willing to engage in sex with a man from today????

    First of all, 3000 years isn’t far enough back in time to make your thought experiment interesting. Why not push it back to 50,000 so we can imagine men as different as Neanderthals? The hygiene aspect is overrated. Americans are horrified by body odor but the rest of the world is more forgiving. Evidence: take a ride on the Paris metro at the end of August. Many locations in the third world have water shortages and wasting water on a daily shower is folly, if they even have a shower. Still, they manage to breed. Same thing with the teeth. Americans are horrified by less than perfect teeth. Rest of the world; not so much. Your high standards definitely do not translate over to our species.

    From a female perspective, male body hair is an indicator of adequate testosterone. Although at first glance, that much body hair can seem appalling, it does stick in the mind and force a second look…and some certain thoughts…Actually, the prospect of mating with a male alien with no body hair is much more repulsive (to me) than mating with a hirsute male of my own species. A male with no body hair…ugh…is this an adult or a very large boy? (Yuck factor).

    It’s interesting to learn about why humans lost most of their body hair but what is also interesting is why we kept it in the places we have it now.

    So Crooked, I’m saying that you are imposing your high standards of selection on the rest of our species. Males will mate with anybody or anything for a quickie (even out of species and even inanimate objects). Is there any sapiens female in the world right now who could not manage to become pregnant if they so desire it? Men are selective for a life partner though. Women now a days (because of contraception) are also not averse to slumming on occasion. Much more selective when considering paternity of future offspring.



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  • LaurieB,
    Points taken. I am often guilty of thinking very provincially. Coupled with the fact that I really have never travelled and have not ever spent any time in any foreign lands, I would always welcome the corrections of my errors. And, your points are true — I stand corrected.

    You correctly point out that there was nothing dogmatic about my 3000 year time frame…. So, let’s go with your 50,000… It does make for a more dramatic difference in appearance. But, probably the biggest impediment would be cultural standards. Think of a man’s attitude toward women in today’s middle east and multiply it by 1000 to get an inkling of what women faced in the “B.C”. Would you think many women would acquiesce to relations with a male that is, by today’s standards, a brutish pig? Would today’s man be able to connect with the women from then? Factor in competition from the contemporary men and women respectively.

    One thing to consider, it would not be a matter basing the entire thought experiment on whether one man from now would have sex with one women (or vice versa)…. In the schema of evolution, a slight preference can be enough to have causal influence. It is populations that evolve, not individuals.



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  • Laurie Bee, “It’s interesting to learn about why humans lost most of their body hair but what is also interesting is why we kept it in the places we have it now.”
    That is natures way of hiding the ugly parts when we get older.



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  • crookedshoes #10
    Dec 4, 2016 at 11:37 am

    Alan4,
    Very interesting, the physiological effects seem like the tip of the iceberg when you consider that many of the events in fertilization and embryonic development could be significantly impacted (and even impeded) when gravity is decreased by this drastic amount. Head/tail axis determination comes to mind.

    An interesting experiment which may throw some light on some of these gravitational effects is the ISS JAXA fish experiment.

    In some (but not all) respects, fish float so gravitational effects are different.

    https://www.nasa.gov/mission_pages/station/research/news/bone_health.html

    Aboard the International Space Station, however, astronauts have a much closer view of real finned friends, thanks to the Medaka Osteoclast investigation. Sponsored by the Japan Aerospace Exploration Agency (JAXA), the study will help scientists uncover new knowledge about human bone health in space and on Earth.

    Living in the Aquatic Habitat, the Medaka (Oryzias latipes) fish serve as a model for researching the impact of microgravity environments on osteoclasts — the cells responsible for the process by which bone breaks down during remodeling. Bone is living tissue that naturally breaks down and rebuilds as part of the way the human body functions. This remodeling process allows for growth and healing as we age. When the remodeling is out of balance, diseases such as osteoporosis can occur.

    Studies indicate osteoclasts are the culprits for the noted decrease in bone density experienced by astronauts while on orbit. “The phenomenon is considered due to the disruption of balance between the amount of newly formed bone and the amount of bone absorbed into the blood,” said Nobuyoshi Fujimoto, associate senior engineer at JAXA’s Space Environment Unitization Center. “Activation of the osteoclast is assumed to cause the decrease of bone mineral density in space; however the basic mechanism is still unknown.”

    Researchers selected the Medaka for many reasons. First, they are vertebrates, meaning they have bones and muscles. Research to understand the basic mechanisms of how osteoclasts work in microgravity for the fish may be helpful in understanding human bone change findings.

    The fish also are transparent, allowing scientists to view the inner workings of their bodies while they swim in space. The Medaka have a fully mapped genome, too, making it possible for scientists to identify changes in their genetic code from exposure to the space environment. The fish have established transgenic lines — modified DNA that passes down to their offspring — which adds to their usefulness in experiments.

    Researchers also are interested in the animals’ gravity sensing system. The fish understand “up” while living aboard station thanks to their instinctual dorsal light response. In other words, they sense the LED light at the top of the habitat in the same way they would sense the sun’s light while in water on Earth.

    Even though fish seem weightless when they swim in water on Earth, they still are impacted by gravity and buoyancy. While they appear to float in both settings, scientists anticipate behavioral changes due to microgravity.

    “The investigators’ hypothesis on gravitational effects is that the balance between the internal air bladder of the fish and other high density organs (e.g., head, teeth) will change in microgravity; tensions on the bone will also change and we can observe different responses in space than on Earth,” said Fujimoto.



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  • “Males will mate with anybody or anything for a quickie (even out of species and even inanimate objects)”
    Laurie, I am personally offended by this remark. Is that ok?



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  • I think pubic hair remained after the rest of body hair evolved out of existence because of clothes and possibly parasites because of the link to sex latterly co-opting oxytocin in the hormonal mix. The higher primates (notably bonobos) created socially recreational sex. This is part of making sex socially functional, enhancing mutuality, through grooming and making mating a little more akin to maternal bonding.

    Mammals but most particularly higher primates have C-tactile afferent nerves, dedicated to feelgood and oxytocin release. These nerves run from hair follicles and if large enough hairs still grow from them, these act as levers amplifying the touch/sense experience. Recent studies have shown that these very skinny slow nerves respond to a very narrow range of stroking speeds. Very lightly touch the hairs on the back of your head to see how specific the effect is. Oxytocin gets produced. Too fast or too heavy and its gone.

    We may suppose that preliminary pubic hair grooming might add in the pupil-dilating romance of oxytocin before those more tumescent hormones get started. Foreplay folks.



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  • True, Olgun.

    Axillary sex is a thing….

    Pubic hair and underarm hair are a great broadcaster of pheromones.

    This was the standard pubic hair theory. I prefer the new one. Probably both or all three contribute.



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  • Alf

    Laurie, I am personally offended by this remark. Is that ok?

    Don’t waste your valuable energy being offended. Is it your fault that you have all of that pesky testosterone surging through your brain 24/7? As a female of our species I can’t imagine what that’s like. The lesser levels of the stuff that I’ve had to contend with are aggravating enough and that doesn’t compare to what you guys have to deal with. Between testosterone and oxytocin, my free will in this life has been zero. Your system must be primed to act on any opportunity. From time to time a batch or two of sperm will be wasted here and there. Meh. No great loss in the scheme of things. Don’t tell the RCC I said so. 😉 There are plenty of features of female reproductive strategy that offend us if we let them. I’ve made my peace with the situation. Truth is more important than cozy comfort. All together, even with its flaws, human reproduction is a wildly successful system, otherwise, why would we be fretting and gnashing our teeth on that other thread about overpopulation wrecking the world? 🙂



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