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Secrets of Saliva

Exciting New Technology Can Detect Cancer And Other Serious Diseases

By Dr. David T.W. Wong

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Messengers Of Health And Disease — At The Nano Level

How do you know there's been an elephant in the fridge? Foot prints in the butter.

Believe it or not this analogy may be more appropriate than you think. It belies the size of things to come — going from macro, very large — to ridiculously small — the “nano” level.

Consider this: All life is made up of cells — about ten trillion of them in the human body, that's 10,000,000,000,000. Each cell is a small factory, which contains a control center, the nucleus. The nucleus is made up of 23 pairs of chromosomes, one part of the pair derived from your mom, and the other from your dad. The chromosomes are long chains, to which the genes are attached; they contain the code for the units of life.

Each gene is attached to a long chain-like molecule called DNA — deoxy-ribose-nucleic acid, that's the double helix or ladder shaped structure, to which four bases — A (adenine), T (thymine), C (cytosine) and G (guanine) are made. They are arranged in sequences that determine what each gene is and does. They are the rungs of the ladder with the paired bases making up the rungs — A joining with T, and C with G.

The first part of the process of protein manufacture is to copy the DNA. The double helix splits, almost like a zipper opening. Along each part of the unzipped area, RNA (ribonucleic acid), makes a mirror image of the split section, it acts like a caterpillar track rolling along in mud. In so doing it leaves an exact replica of itself. The imprint in the mud is the messenger, called messenger or mRNA. (The mRNA transfers this mirror image to transfer or tRNA. The tRNA is thus an exact replica of the DNA. tRNA is the template along which proteins are made.)

Remnants of mRNA along with other protein molecules are found in saliva. A protein measures just 3-10nm (nanometers).

For perspective, a nanometer is equal to one billionth of a meter, that's a 1,000,000,000th of a meter — very, very small. 2,000,000 nanometers would fit on a pinhead. We're now down at the level of the wavelength of light, 400-700 nm.

How Tiny Molecules Are Measured

Mass spectrometry.
A technique called mass spectrometry is the primary means of analyzing the types and amounts of different proteins in saliva.

A technique called mass spectrometry (“spectrum” – colored light; “metry” – measurement) is the primary means of analyzing the types and amounts of different proteins in saliva. Essentially, different molecules emit different, yet specific types of light, and just like fingerprints, they are unique. For example, this has enabled scientists to compare the proteins in saliva from healthy people to those with early-stage oral cancer.

Because diseases are not marked by just one protein or RNA molecule, but perhaps by more than 100, identifying them is a very complicated task. Laser technology has allowed the identification of thousands of salivary molecules from many individuals with speed and accuracy. Salivary samples are laid out in a grid, or array, on a palm-sized wafer made of quartz. A laser “reads” each position on the array and indicates what type of RNA is present in the sample and in what quantities.

Salivary samples.
Salivary samples are laid out in a grid on a palm-sized wafer made of quartz. A laser “reads” each position on the array and indicates what type of RNA is present in the sample and in what quantities.

Pushing The Frontiers Of Science

Importantly, we have now unraveled the mechanisms responsible for the development of biomarkers for systemic diseases in saliva and provided the scientific rationale for using saliva to detect these life-threatening conditions. As the field of salivary biomarker diagnosis grows, the biomarkers we are studying may prove to be just the tip of the iceberg — especially if one considers what can also be gleaned from other materials, such as blood, urine, spinal fluid, tears and more. It seems likely that biomarkers for certain diseases will prove to be more abundant in some types of samples than in others. Which works best for what? That question will undoubtedly remain under investigation in coming years. However, we are optimistic that saliva will continue to reveal secrets about the state of disease or health in both the mouth and the rest of the body. It's exciting to have such life-saving technology within — spitting distance!



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