Thursday, March 6, 2014

Star Babies, the Next Generation

by Joseph Vacca

Have you ever really sat down to think about space, that final frontier? Have you ever wondered if one day you may live to see the human colonization of another planet; or maybe even recognize the first child born and raised in space? Well, for all of you active imaginative/sci-fi loving people out there, I am here to give you the low down on the development of space children.
So let’s start with the embryo development!


Embryo Development and baby’s first steps…
May not actually be possible… Sorry to start off on a downer, but it is true. The problem is with fertilization. In cow semen, the cytoskeletal composition that allows for the tail to correctly generate the force needed for propulsion is affected by low gravity environments [1]. It may not have the necessary power to be able to push into the zona pelucida of the egg. However, studies by NASA scientists have also found that the enzyme that phosphorylates the tail and causes motion also acts in a hyper activated state when at low gravity [2]. This means that, although sperm are more motile in space, they are also functionally unable to fertilize a viable oocyte.

Birth is quite another problem, without gravity to help expel the baby, those present will instead have to pull the baby out of the womb. And could you imagine the amount of free floating liquid, gross. As soon as the baby is out, it misses out on its first lesson, orientation.

In the inner ear there are two gravity-sensing areas, the saccule for vertical orientation and the utricle for horizontal orientation. These areas have hair cells within them that are surrounded by little crystals that are known as otoliths. On earth, gravity pulls these crystals down in the inner ear, thereby bending the hairs of the sensory cells downward.



Try not to bend over backwards thinking too hard about this one...

The sensory hairs can be bent in any direction, and the brain interprets the specific bending as specific orientations. However, in space fluid and objects are free floating; therefore, the otoliths cannot contact the hairs quite as well, leading to a loss in the perception of tilting [3]. This will interfere with the baby’s ability to distinguish up from down or movement from side to side. If ever returned to gravity the child would neither be coordinated nor balanced. This is because the neural pathways of the child have not developed to move the body in relation to gravity's pull.

They would probably end up looking something like this on earth

Neural development  
Have you ever heard of muscle memory when talking about a sport or repetitive activity? The same kind of “training” of your muscles must occur during the first few months of birth [4]. Rats born and raised for 16 days at extremely low levels of gravity never learn how to correct their orientation when placed on their backs. It was never necessary before. So when scientists brought the mice back to Earth and placed them on their backs, they were unable to “properly” right themselves by flipping their legs underneath them [4]. The weirdest thing about this discovery is that they continued to improperly turn over for up to a month after returning to Earth! To even further investigate the effect, mice neurons were stained to observe their presence and morphology. And just as expected, there was a lower number of motor neurons branching from the spinal cord to the muscles in the medial part of the body – these neurons are involved in righting the body’s orientation. This suggests that the rat’s motor system was biased towards adaptation to a totally different environment!


Life Alert doesn’t seem so bad now, does it?

These muscles had become used to the weightlessness of space. But 60% of our muscles are skeletal weight-bearing muscle, meant to hold our bodies up against the force of gravity [5]. You are using them just to stand/ sit while reading this. So what does all that muscle do if it has no use in space? Well not only do you not grow the same muscle size and composition as you would on Earth, but you also have weak branching of the nerves into the muscle cell as seen in rats [5]. This leads to a decrease in overall developmental function that cannot be recovered once returned to normal gravity conditions.

Muscle and Bones
Bones require constant stress in order to develop properly. Normally, in Earth’s gravitational pull this isn’t too much of a problem. However, when astronauts are exposed to long periods of time in space, their bones tend to atrophy, and appear similar to osteoporosis patients [6].



In developing children this could be even worse. Such soft bones would easily break and heal incorrectly. These bones would form much like bone formation in the disease, Rickets [7]. Rickets is formed by a lack of vitamin D in the diet, thereby causing poor bone formation. A child grown up is space may look like this:


I could continue on and on about the effects of low gravity on various aspects of the body, but I don’t want to bore you; instead I shall point you towards a great book if you are interested. It’s called The Neurolab Spacelab Mission: Neuroscience Research in Space and it explains all the tests they have done in rats and astronauts on development in space. I know this all seems daunting, but don’t fret, we are a long way off from any type of space travel that would require reproduction in space. However, it is good to think about these implications now so that by the time we are ready to travel to space we will be able to overcome the negative effects of lack of gravity.



Citations:
[1] Miller, K. (2002). Floating Fertility. NASA. Available at http://www.nasa.gov/vision/earth/livingthings/floating_fertility_prt.htm
[2] Tash, J.S., Kim, S., Schuber, M., Seiber, D., and Kinsey, W.H. (2001). Fertilization of sea urchin eggs and sperm motility are negatively impacted under low hypergavitational forces significant to space flight. Biol Repro 65(4):1224-31.
[3] Clement, G., Berthoz, A., Bernard, C., Moore, S., Curthoys, I., Dai, M., Koizuka, I., Kubo, T., and  Raphan, T. (2003). Perception of the Spatial Vertical During Centrifugation and Static Tilt.  In The Neurolab Spacelab Mission: Neuroscience Research in Space (ed. J.C. Buckley and J.L. Homick), pp. 5-10. Huston, NASA.
[4] Kalb, R., Hillman, D., DeFelie, J., Garcia-Segura, L.M., Walton, K.D., and Llinas, R.R. (2003). Motor System Development Depends on Experience: A microgravity study of rats.  In The Neurolab Spacelab Mission: Neuroscience Research in Space (ed. J.C. Buckley and J.L. Homick), pp. 95-103. Huston, NASA.
[5] Riley, D.A. and Wong-Riley, M.T.T. (2003) Neuromuscular Development Is Altered by Spaceflight.  In The Neurolab Spacelab Mission: Neuroscience Research in Space (ed. J.C. Buckley and J.L. Homick), pp. 105-109. Huston, NASA.
[6] NASA Science – Science News: Space bones. (2001). NASA. [March 4, 2014]. Available at http://science1.nasa.gov/science-news/science-at-nasa/2001/ast01oct_1/
[7] Bricker, N.S. (1979). Life beyond the Earth's Environment: The Biology of Living Organisms in Space. Washington: National Academy of Sciences. Print.

Pictures:

http://www.theinsidetrainer.com/wp-content/uploads/rickets-vitamin-D-deficiency.jpg

1 comment:

  1. New Diet Taps into Pioneering Plan to Help Dieters Lose 20 Pounds within Only 21 Days!

    ReplyDelete