In space gravity is the most notable absence and this is already seen to cause stress on the human body. Astronauts up in space tend to face skeletal complications, lower bone mineral density and a fluid shift that results in dizziness, higher blood pressure and more side effects. Calcium is probably the first mineral that they begin losing right after launch and it starts within 10 days of being in space. However, the molecular mechanism that causes such changes in a zero gravity environment is what has remained elusive.
In order to study the effects of minimal gravity, in 2014 a fish travelled abroad the ISS or International Space Station. Instantly observable was the reduction in bone density the moment the fish entered a microgravity environment. This fish astronaut was a newly hatched medaka fish, which is a Japanese rice fish that is mostly found along the southeast Asian corridor. It is a commonly preferred fish for toxicology research as well as in other areas of biological research. However, the reason for choosing this species of fish is because of skeletogenesis that closely resembles humans.
The team from Tokyo did real time remote live imaging of fluorescent signals from osteoclasts and osteoblasts of the fish from one day after it being exposed to microgravity on the ISS. What they found was a significant increase in osteoclast and osteoblast based DsRed and GFP signals after only one day. This growth continued all the way up to eight days.
All such findings pointed in one direction – microgravity has an immediate effect on osteoclasts and osteoblasts, especially the gene expressions of them. This research has already paved the path forward for a new scientific field that experts are now calling gravitational biology. Basically, it is the science of studying the effects of zero gravity or micro-gravity on life forms in space.
The fish actually spent a total of six weeks on earth at the launch site before it was embedded in a special kind of gel that would allow it to endure the voyage from Earth to ISS. The next two months was spent on ISS where the fish was reared. During the first eight days, the fish spent time under a fluorescence microscope as the scientists began observing just how quickly fish bone cells began to degenerate as opposed to a control group of fish maintained on Earth.