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This theory argue that decrements in a system so essential to survival and homeostasis, as neurons and hormones must play a profound role in the regulation of age changes. Critics of this theory say that it is not universal, and that all organisms that age do not have complex neuroendocrine systems. Also cells isolated from endocrine factors and nervous system stimulus will also age, replicate and die.
The hypothesis on ageing presented in this dissertation, is in agreement with the idea that the neuroendocrine system provides vital control and regulator elements, that modulate age changes, but that it represents only an effect, not the cause, of ageing. I intend to demonstrate that ageing is universally caused by biological damage due to chemical oxidations occurring in different types of living cells. In advanced forms of life damaging oxidations and autooxidations occurs mainly in oxygen sensitive cells of the nervous system which have direct control over the endocrine system.
The cause and main inducer of biological oxidations and their toxic by-products, is excessive atmospheric oxygen. High atmospheric oxygen, causes accelerated development, shortening life span. Oxygen, the main source of cell energy, controls the ageing process of all living organisms even those without neuroendocrine system.
The ageing human central nervous system, is mainly affected by neuronal oxidations and autooxidations. The importance of oxygen and its effect on the central nervous system is illustrated by the fact that the human brain represents only 2 percent of the total body weight, but the brain's rate of oxygen utilization (50 milliliters per minute) accounts for 20 percent of the total oxygen utilization. Oxygen constitutes the main source of energy for brain cells. A slight increase in environmental oxygen pressure has a crucial effect in neurons, since much of the oxygen we breath is supplied to the brain.
The neuroendocrine theory of ageing places at the top of the age regulator system, neurons that through chemical signals influence the endocrine system. Growth hormone for example, that plays a crucial function in ageing and development, is secreted by the pituitary, that in turn, receives a signal from the hypothalamus, the latter, sequentially receives signals from central neurons, secreting the neurotransmitter dopamine. Therefore dopamine appears to be the main biological clock that indicates when growth hormone be released and when to cease its secretion.
In this dissertation, and also in my research proposal, I present the idea of surplus, environmental oxygen, imposing redundant oxygen into brain cells. Oxidative waste products evolved from oxygen like superoxide, hydrogen peroxide and superoxide radical, accumulate in brain cells and do serious injury to them. These damaging oxygen by-products, burn up oxygen sensitive neurons, impairing the secretion of vital neurotransmitters. The cessation in the synthesis of basic neurotransmitters, signals the termination of the synthesis of specific hormones. These are events representing the initiation of the process of human ageing.
It has been demonstrated that the complex auto-oxidations of dopamine in the striatum (part of the human brain), causes the production of substantial quantities of toxic free radicals and highly reactive quinones that create serious damage to dopaminergic neurons. The present idea is that these changes occur as a natural consequence of the ageing process. Accordingly, substances that prevent oxidations, namely antioxidants, are recommended to slow down the ageing process.
My hypothesis adds to these, that anti-oxidants are capable of providing only minimal protective effect. Oxidative damage to brain cells could only be substantively reduced if there is a radical decrease in environmental oxygen.
In summary, the present hypothesis does not disagree with the neuroendocrine theory of ageing and recognizes the important role of hormones and brain chemical transmitters in switching on and off, clocks that regulates development and ageing.
My hypothesis adds that neuroendocrine clocks are controlled by secretions of neurons whose survival depends on the amount of oxidation damage received in specific areas of the brain. Oxygen in excess, will terminate the life of some type of active brain cells more quickly, impairing the biosynthesis of its neurotransmitters. By lowering the number of cells synthesizing that brain transmitter, the secretion of the related-induced hormone or chemical messengers will consequently decrease, representing the visible signal for the ageing and developmental changes in tissues and cells.
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