Expansion On The Recent Discoveries Concerning Nitric

Oxide Essay, Research Paper

Expansion on the Recent Discoveries Concerning Nitric Oxide

as presented by Dr. Jack R. Lancaster

Nitric Oxide, or NO, its chemical representation, was until recently not

considered to be of any benefit to the life processes of animals, much less

human beings. However, studies have proven that this simple compound had an

abundance of uses in the body, ranging from the nervous system to the

reproductive system. Its many uses are still being explored, and it is hoped

that it can play an active role in the cures for certain types of cancers and

tumors that form in the brain and other parts of the body.

Nitric Oxide is not to be confused with nitrous oxide, the latter of

which is commonly known as laughing gas. Nitric oxide has one more electron than

the anesthetic. NO is not soluble in water. It is a clear gas. When NO is

exposed to air, it mixes with oxygen, yielding nitrogen IV dioxide, a brown gas

which is soluble in water. These are just a few of the chemical properties of

nitric oxide. With the total life expectancy of nitric oxide being from six to

ten seconds, it is not surprising that it has not been until recently that it

was discovered in the body. The compound is quickly converted into nitrates and

nitrites by oxygen and water. Yet even its short-lived life, it has found many

functions within the body. Nitric oxide enables white blood cells to kill tumor

cells and bacteria, and it allows neurotransmitters to dilate blood vessels. It

also serves as a messenger for neurons, like a neurotransmitter. The compound

is also accountable for penile erections. Further experiments may lead to its

use in memory research and for the treatment of certain neurodegenerative

disorders. One of the most exciting discoveries of nitric oxide involves its

function in the brain. It was first discovered that nitric oxide played a role

in the nervous system in 1982. Small amounts of it prove useful in the opening

of calcium ion channels (with glutamate, an excitatory neurotransmitter) sending

a strong excitatory impulse. However, in larger amounts, its effects are quite

harmful. The channels are forced to fire more rapidly, which can kill the cells.

This is the cause of most strokes. To find where nitric oxide is found in the

brain, scientists used a purification method from a tissue sample of the brain.

One scientist discovered that the synthesis of nitric oxide required the

presence of calcium, which often acts by binding to a ubiquitous cofactor called

calmodulin. A small amount of calmodulin is added to the enzyme preparations,

and immediately there is an enhancement in enzyme activity. Recognition of the

association between nitric oxide, calcium an calmodulin leads to further

purification of the enzyme. When glutamate moves the calcium into cells, the

calcium ions bind to calmodulin and activate nitric oxide synthase, all of these

activities happening within a few thousandths of a second. After this

purification is made, antibodies can be made against it, and nitric oxide can be

traced in the rest of the brain and other parts of the body. The synthase

containing nitric oxide can be found only in small populations of neurons,

mostly in the hypothalamus part of the brain. The hypothalamus is the

controller of enzyme secretion, and controls the release of the hormones

vasopressin and oxytocin. In the adrenal gland, the nitric oxide synthase is

highly concentrated in a web of neurons that stimulate adrenal cells to release

adrenaline. It is also found in the intestine, cerebral cortex, and in the

endothelial layer of blood vessels, yet to a smaller degree.

Although the location of nitric oxide was found by this experimentation,

it wasn?t until later that the function of the nitric oxide was studied. Its

tie to other closely related neurons did shed some light on this. In Huntington?

s disease up to ninety-five percent of neurons in an area called the caudate

nucleus degenerate, but no daphorase neurons are lost. In heart strokes and in

some brain regions in which there is involvement of Alzheimer?s disease,

diaphorase neurons are similarly resistant. Neurotoxic destruction of neurons

in culture can kill ninety percent of neurons, whereas diaphorase neurons remain

completely unharmed. Scientists studied the perplexity of this issue.

Discerning the overlap between diaphorase neurons and cerebral neurons

containing nitric oxide synthase was a good start to their goal. First of all,

it was clear that there was something about nitric oxide synthesis that makes

neurons resist neurotoxec damage. Yet, NO was the result of glutamate activity,

which also led to neurotoxicity. The question aroused here is, how could it go

both ways? One supported theory is that in the presence of high levels of

glutamate, nitric oxide-producing neurons behave like macrophages, rele

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