Eyespots and Macular Pigments Extracted from Algal Organisms Immobilized in Organic Matrix with the Purpose to Protect Astronaut?s Retina (Night Vision) is a study on the response of microalgae strains (that contain eye spots similar to the human retina) to space radiation in order to obtain results applicable to future nutrition programs for astronauts.Principal Investigator(s)
Biosensor Srl, Rome, , Italy
Institute of Crystallography CNR, National Research Council, Rome, , Italy
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Italian Space Agency (ASI)Research Benefits
Information PendingISS Expedition Duration
March 2011 - September 2011Expeditions Assigned
27/28Previous ISS Missions
Increment 23/24 is the first planned mission for the Night Vision experiment.
One of the main problems for astronauts exposed to long-duration space flight is the exposure to ionizing radiation and the consequent oxidative stress. One of the organs affected by ionizing radiation is the human retina. Moreover, the continuous changes in light due to the movement of the International Space Station (ISS) can lead astronauts to experience various dawns and sunsets over 24 hours. These phenomena cause troubles and difficulties in maintaining the rhythm of sleeping and the vision is particularly difficult in missions external to the ISS.
Lutein (substance found in vegetables that protect against cell damage) and zeaxanthin (substance usually found in yellow/orange fruits and vegetables, as well as egg yolks) are the pigments present in both the macula and lens of the human eye which are also referred to as macular pigments (MPs). They belong to the family of xanthophylls (yellow and orange pigments found in plants, animal fats and egg yolks) which are oxidized derivatives of carotenes, including several compounds. Both carotenes and xanthophylls belong to a class of polyisoprenoids (synthetic molecules). MPs? effects on the human body include the improvement of visual function, and the protection from photo-induced damage, as they act as filters for blue light and shield short-wave radiation. Epidemiological studies have shown a strong correlation between the levels of lutein and zeaxanthin in eye tissues, serum and blood plasma, with a reduced incidence of oxidative stress associated with age and macular degeneration pigment. MPs cannot be synthesized by the organism and must be introduced via the diet. There are other xanthophylls that also play an important role in protecting visual apparatus. The unicellular alga Chlamydomonas reinhardtii possess only one chloroplast that is in contact with an orange organelle called eyespot; similar to the human retina. As the human retina, the algal eyespot presents macular pigments involved in perception of light and a similar organization. Other algae with similar eyespots include Chlamydomonas nivalis and Haematococcus pluvialis.
This project proposes the study of resistance to ionizing radiation of algae and Chlamydomonas reinhardtii genetic mutants that accumulate various quantities of macular pigments in the eyespots. The extracts of eyespots will also be immobilized in alginate (salt from alginic acid) and their antioxidant effects will be evaluated for future nutrition programs in space. These immobilized matrices will be analyzed by means of X-ray (powder X-ray diffraction, XRD) to study the relationship between organization and functionality of the eyespots.
One of the organs mostly affected by cosmic radiation is the visual apparatus; in particular, the central and peripheral photoreceptors of the retina. The global vision in astronauts is disturbed in the perception of colors and movements. The result is that the vision during the night exploration is particularly disturbed. Recent studies on the ISS suggest that a unique ionizing heavy particle can hit one or plus photoreceptors in the retina, including damage to other eye tissue, such as the lens. The mechanism of oxidation at retina level is not known in detail. One hypothesis is that the damage is generated from a genetic damage in the lens epithelial cells, including the destruction of normal cellular life cycle, apoptosis (cell death), abnormal differentiation of cells and cellular disorganization.
The Department of Aviation Medicine is particularly interested in increasing the visual efficiency of astronauts as the number of working hours is reduced as a result of reduced visual fatigue. To understand what happens inside astronauts? eyes, scientific literature proposes several models in vivo and in vitro as to study the high ocular pressure in the retina and in the optical nerve, which occurs during oxidative stress. For the in vivo studies, an empiric model based on guinea pigs is used, causing ocular hypertension by injecting methylcellulose in front of the eyes. In guinea pigs, or humans affected by oxidative stress, eye neural tissue degenerates with a cell death program.
Previous investigations were conducted which studied the effects of ionizing radiation on the photosynthesis of several microorganisms. Various radioactive sources and facilities were used in radiation simulation studies. The results provided useful information on the radiation environment in Low Earth Orbit (LEO) monitored during the Foton M3 (robotic spacecraft used by Russia and the European Space Agency (ESA) for research conducted in the microgravity environment of Earth orbit) mission in 2007. The data was obtained by a couple of active spectrum-dosimeters that measured in real-time, the deposited energy spectrum by the incident ionizing particle, the particle flux and the absorbed dose behind different shielding. As a whole, this analysis indicated very quiet and low solar activity being the total dose measured on the silicon detectors. Green alga was found to be the less sensitive photosynthetic microorganism tested. Previous experiments demonstrated that the consequence of space stress on microorganisms seemed to be inversely correlated to cell dimensions. It appeared that large cell cross-sections, with their content of lipids, antioxidants and enzymes; could partially shield internal structures; however, other possible factors could account for the higher sensitivity observed in green algae.
In order to unravel the response of the photosynthetic apparatus to real space conditions, stratospheric balloon flights and Foton M2 and M3 space missions were successfully exploited. The organisms observed to be tolerant to ionizing radiation in the simulation studies, were used for the real space condition experiments. Investigators found that the effect of the ionizing radiation on the activity of PSII (Photosystem II - a protein complex) was enhanced in space, compared to that observed in ground based facilities. The PSII activity, the growth rate and the survival ability of the tested organisms were altered even at low doses.
The experiment is important since it addresses a possible future nutrition program for the astronauts against oxidative damage in the space environment.Earth Applications
The results of the Night Vision experiment can be transferred to a food integration program that will promote the consumption of foods necessary to prevent conditions that damage the eyes (e.g. Macular Degeneration).
A short-duration (Space Shuttle) crewmember is needed to open the Nomex Bag inside the Shuttle, exposing the three sample containers to environmental light. Night Vision samples are required to be returned to the PI for analysis at R+24 hours.Operational Protocols
Beginning with the experiment in the middeck locker, the crewmembers will open the Nomex Bag containing three containers. The Nomex bag is divided into three parts since the containers of the experiment are three independent containers. After opening, the unrolled Nomex bag will be fixed with Velcro at the wall inside the Shuttle; with the frontal part (the one with polycarbonate window), facing the crewmember that will operate the experiment; for this reason, the biological material inside the containers will be exposed to environmental light. The biological module is constituted by 16 hermetically closed static cells. The sample holder lid is designed for visible light and made by polycarbonate. The cells in the special containers have a life expectancy from 3 weeks to 3 months.
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Esposito D, Faraloni C, Margonelli A, Pace E, Pace E, Torzillo G, Zanini A, Zanini A, Giardi MT. The effect of ionizing radiation on photosynthetic oxygenic microrganisms for survival in Space flight revealed by automatic Photosystem II-based biosensors. Microgravity Science and Technology. 2006; 18: 215-218.
Damasso M, Dachev TP, Falzetta G, Giardi MT, Rea G, Zanini A, Zanini A. The radiation environment observed by Liulin-Photo and R3D-B3 spectrum-dosimeters inside and outside Foton-M3 spacecraft. Radiation Measurements. 2009; 44: 263-272.
Bertalan I, Esposito D, Torzillo G, Faraloni C, Johanningmeier U, Giardi MT. Photosystem II Stress Tolerance in the Unicellular Green Alga Chlamydomonas reinhardtii under Space Conditions. Microgravity Science and Technology. 2007; 19: 122-127.