5.-  Integrative Conclusion

I would like to point out some basic conclusions from this short essay.

1.- Oxygen is the most essential element for life, and it affects living processes in a more fundamental way than any other element present in food, air or water.
Great efforts are placed in selecting appropriate foods, nutrients, vitamins, minerals and chemicals like pesticides,  medicines etc. None of these  elements which we might clearly visualize, touch, smell and analyze, have the slightest importance to our lives if compared with oxygen, an invisible element that we don't see, cannot touch or smell, but that we breath 15.000 times per day (no matter if we are asleep, tired, thirsty at rest or very busy).

2.- The amount of  oxygen that penetrates cells, depends on the external oxygen concentration of the air we breathe. At higher altitudes and in mountains,  oxygen pressure could be as low as 16%. At sea level oxygen pressure is 20.9%. Higher environmental oxygen means that  each and every cell of the body will have to cope with more oxygen. Excess oxygen reacts within cells to produce reactive and toxic oxygen radicals.  Against them, the body has a battery of enzymatic defenses. These defenses are not always enough or  functioning properly.  Damage might occur then  at  cellular levels.

3.- Ageing is controlled by  neuro-endocrine and genetic information.

In this paper I have presented evidence to support the idea that there is a fundamental ageing clock, between the hypothalamic and dopaminergic brain areas, which is extremely sensitive to oxygen toxicity. I have presented a sequence of chemical reactions, induced by oxygen surplus, which progressively destroys cells of the dopaminergic system,  responsible for the regulation of various hormones secretions, including  growth hormone. In my dissertation I present additional data to correlate the initiation of the process of ageing with the end of the period of growth, the latter being mainly determined by secretions of growth hormone.