Astronauts sent into space by NASA and other space programmes constantly deal with several factors in order to survive in a zero-gravity field. Obviously in a non-gravity field like space with extremely alien conditions, it does get difficult to adapt and continue the basic necessary metabolic processes. Although not as fatal as to cause death or the severe harmful effects on human body, the absence of gravity does cause some significant changes to occur inside the human body. It should be noted that in space shuttles out in space, the gravity value is not exactly zero for that matter. It is present though at minor levels thus naming it as microgravity.
One phenomenon that has been widely observed into the astronauts is the frequent bone loss. Experiments were conducted on astronauts and crew members of space flight STS 76 by the lab of cell growth at University of California. The research involved study of gene growth and activation of normal osteoblasts (MC3T3-E1) in astronauts that were sent out into the space. The data obtained from the study revealed that the quiescent osteoblasts were slower to enter the cell cycle in microgravity and that the lack of gravity itself may prove to be a significant factor in bone loss in spaceflight.
Recent research work and studies have clearly demonstrated that microgravity appears to have an effect on signal transduction too. Based on the data collected from the crew members and astronauts of Soyuz, Skylab and Apollo Spaceship it has been concluded that under the influence of microgravity, the activation of lymphocytes gets depressed, while on the other hand, T-cell activation happens to get reduced. Microgravity also affects the functioning of PKC (Protein kinase C), although the other major processes that occur into the immune cells like the first activation signal, the patching and capping of conA binding membrane proteins seem to have no alterations whatsoever. These findings have clearly suggested that there could be gravi-sensitive receptors located upstream of PKC that happen to be affecting its functioning in microgravity environment. An experiment was conducted to demonstrate these alterations in which the T-cells were subjected to a DNA array analysis where simulated microgravity was provided by random positioning machine (RPM) and the results clearly showed a change in signal modulus of NF-kB and MAPK-signaling.
Further, the proliferative response of T-cells was found be diminished during the space flight. It is believed that this occurred due to a reduced expression of IL-2 receptor during simulated microgravity. Moreover, overall, a reduced capacity of T-cells for the production of cytokines is believed to be a major effect of microgravity on leukocytes during spaceflight.
Monocyte function impairment also takes place in microgravity. Microgravity causes impairment in monocyte function. Based on the data obtained from SLS-1 Space lab mission, the results obtained showed that the monocytes lost their ability to express IL-2 receptor. Also the ability to secret IL-1 was found to have diminished. A reduction in phagocytosis was also noticed when Kaur et al matched the data collected from the astronauts before and after a spaceflight with the control group data. The results were quite fascinating. On the basis of results, they demonstrated a decrease in phagocytosis and de-granulation capacity of the monocytes.
Based on a study carried out by Nasa that includes a series of experiments to carry out a research on the activity of a higher plant i.e. A. Thaliana in microgravity under the wise supervision of Alexander Dovzhenko et al. The aim of the research is to unequivocally identify those genes that are activated by gravity or in some way regulated. The results of this experiment can have a deep impact on today's practical agronomic purposes, for instance, architecture of root and shoot systems. It can be realised practically also to realize this potential for regulating plant growth in space. The research is using state-of-the-art tools to analyse the architecture of these pathways. Using techniques like DNA microchips and other molecular genetic technology as the prospective techniques, new quantitative and qualitative information on gravity-regulated gene expression would thus be gained. The experimentation in this study consists of study of the well-known flowering plant, Arabidopsis thaliana which is also known as mouse-ear cress or thale cress, a plant which is genetically associated to soybeans, cotton, vegetables and oil seed crops. A. thaliana has all the functions of a normal plant, and has become a useful and noble research model. The features that has made it an ideal model for the prospective research are its short life cycle, small size, neat seed production, and its tiny genome of about 110 Mb having 25.498 genes.
Therefore, one could profoundly conclude that microgravity do have some significant effect on the human body and basic underlying pathways mainly the signal transduction. By studying the effects of microgravity on live species like plants, microbes or humans for that matter, novel therapeutic and preventive strategies could be designed in order to help astronauts survive better in space.
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