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The main purpose of this research proposal is to demonstrate the direct effects of the chemical composition of the atmosphere on human life span.
The fact that most organisms respire and give off carbon dioxide and that the oxygen used must be replaced by photosynthesis is common knowledge. The quantities involved are enormous. The 10.18 kg of oxygen present in the Earth's atmosphere is virtually all the result of photosynthesis. The high concentration is maintained despite the continual removal of oxygen in oxidative processes.
The Earth's atmosphere is actively maintained and regulated by life on the surface, which is the biosphere. Each square meter of the Earth surface is covered by 60.000 moles of oxygen gas. Animals and bacteria do not consume all the oxygen produced through photosynthesis so every year a certain amount of oxygen is added to the atmosphere. The present content of oxygen in dry air at sea level is 20.95%. The other main components are nitrogen 78.08%, Carbon dioxide 0.03% and Argon 0.93%
The idea that the earth's atmospheric oxygen has been increasing throughout its history could be determined quantitatively only in the present century, when modern physics, physical chemistry, biology and genetics, has been applied to the processes of the Earth, its hydrosphere and its atmosphere, in relation to geologic and paleontological observation.
In the Cambrian period, approximately 400 million years ago, oxygen increased from 0.1 to 1 percent of present atmospheric level. This level is called the "Pasteur point" of oxygen. At this level, organisms adapted from fermentation to respiration. After the Cambrian Period, there was an explosive expansion of photosynthesis, and the rate of oxygen production increased radically. Thereafter oxygen levels rose rapidly. (Table 4, Page 65)
In present times, the increase in atmospheric oxygen is about 0.04 percent per year. Geological data have provided evidence that oxygen has been increasing in the Earth's atmosphere at variable rates since the Paleozoic Era.
It is the purpose of this research to analyze at which levels these increments in atmospheric oxygen switched from beneficial to detrimental for human life.
The free radical theory of ageing, first suggested by Harman in 1956 proposed that accumulation of degradative changes with age collectively known as senescence, may be due largely to free radical reactions within the cell. Free radicals e.g. O2, are highly reactive because they have an unpaired electron in an outer orbit. As a consequence, they cause a great deal of cell damage. Oxygen is intimately associated with free radical production (as the most frequent substrate); one might predict that the best indicator of the rate of free radical production would be cellular metabolism. Harman has further speculated that mitochondria, because they are the ultimate oxygen sink and therefore determine the rate of oxygen uptake, are the 'biological clock' within the body. Mitochondria not only regulate the rate of oxygen uptake and therefore the rate of free radical production, but they are also the primary recipient of the free radical damage.
In addition, there is now evidence that total mitochondria volume is directly proportional to oxygen consumption both within a given muscle as well as in the entire animal.
Simply stated, the free radical theory of aging postulates that by-products of oxygen consumption, especially the hydroxyl free radical .OH, cause cellular damage. High concentrations of inorganic peroxides such as H2O2 which are themselves byproducts of oxygen consumption increase the risk of hydroxyl free radical production. Therefore, reducing oxygen consumption could lengthen life, by the method of slowing free radical production.
Until now the free radical theory of ageing has been tested in living systems by modifying the self defenses against oxygen damage. The protective enzymes against free radical damage have been experimentally activated. Increased activity of the enzymes catalase, peroxidase, and superoxide dismutase (SOD), produces a decrease in cellular free radicals. Ingestion of anti-oxidants like -tocopherol, carotenoids and urate, have produced a slight extension of maximum life span in several species experimentally tested.
The aims of the present proposal is to stimulate more research and experimental work to confirm that main increases in life span could not be reached unless oxygen pressure, the leading source of free radical damage, is attenuated in the environment. Activation of the anti-oxidant defenses alone, although it can provide some help is not able by itself, to produce any significant increase in maximum human life span.
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