The Marvels of the Blood-Brain Barrier

Have you survived, or are you presently suffering from the “three week” head cold that is currently spreading like wild fire? This writer had it and even in a fevered state, like any good scientist, continued to ask questions. The “cold” related questions: why, with the sinus headache, constantly draining phlegm cough - things directly associated with the head - did the effects not spread to the brain tissue, mere millimetres away from all this infected goop? The answer, found after a minute of searching the web, is the Blood-Brain Barrier or BBB.

 

The human brain, like those of most animals with a spinal cord (which is essentially an extension of the brain) requires a stable environment, lots of oxygen and protection from the chemical chaos going on in the blood flowing through the circulatory system. It can’t function effectively when assaulted by hormone messages, changes in ion concentration, vibration, etc. So, the brain and spinal column, supported within the boney confines of the skull and spine, float in cerebral spinal fluid more commonly described as CSF. This straw colored fluid, very similar in composition to plasma, serves as shock absorber, nutrition highway, waste removal system and a pretty fine barrier to the rest of the body.

 

In fact, CSF effectively isolates the brain and spinal cord from the rest of the body, including systemic blood flow. It might seem impossible to believe that very little of the blood circulating around your body actually comes in direct contact with your brain. So, how then could all the blood rushing past fingers pressed to your carotid artery on the side of your neck not flow directly to the brain? Welcome to the marvels of the BBB.

Just above your jaw line leading up to the base of the skull, the carotid artery funnels down into an intricate network of smaller vessels and in a distance of less than a centimeter is fed through a maze of capillaries, the smallest blood vessel. Just outside the capillary wall, specialized endothelial and glial cells are aggregated so tightly that only the smallest things can get through: oxygen, carbon dioxide, glucose and substances like nicotine and alcohol, but not much else. That pesky cold virus can’t get through, neither can most bacteria and parasites. Opiates can get through but 95 % of prescription drugs cannot, including cancer fighting molecules used to fight brain tumors.

To put things in perspective about how truly effective the BBB really is, consider the approximately 5.5 litres of blood that fill our circulatory system. Each minute this amount is pumped throughout the body carrying oxygen and nutrients. Of the oxygen present in blood hemoglobin, 20 % goes to the brain, an organ that makes up less than 2% of body mass. And all of this blood and oxygen - that we may have envisioned flowing directly to the brain - is actually all diffused and filtered through the BBB. Quickly and most effectively. A natural engineering marvel.

 

For the most part the BBB functions effectively throughout our lives, however, there are things that can cause short and perhaps even long term disruptions. Exposure to microwaves, radiation, chronic high blood pressure, strokes and, yes, Alzheimer’s disease have been shown to have adverse effects on the filtration capabilities of the BBB.

 

As always, where we provide a suggestion or two for readers to further research the topics discussed in this column, this week proved difficult to find one that was not all scientific gobbledygook and the best we could find on the Blood-Brain Barrier is:

Differentiation of blood-brain barrier endothelial cells

Disinfection – Making Our Water Safe

In this modern age, in thriving communities, in developed countries, so many things in our lives are taken for granted.  Case in point: safe and abundant drinking water.

Safe and dare I say, abundant drinking water is generally considered the responsibility of municipalities and/or regional authorities, which in turn hold to quality and heath standards set at the provincial, federal and, increasingly, international levels. At a minimum, every civic authority must access, supply, remove sediment (clarify), disinfect, filter, and distribute drinking water to thirsty constituents and supply water for fire protection. Additionally, they are often held responsible to provide water for industry, agriculture and in some cases, surrounding communities.

Supply and distribution, accomplished to varying degrees since Roman times, are perhaps the easiest aspects of the drinking water equation – achieved by good old fashioned engineering. However, insuring that drinking water is clean and free of dangerous microbes is relatively new. In particular, disinfection, the act of effectively killing and rendering harmless dangerous microbes, was only accomplished on a grand scale just over one hundred years ago in Sweden with the identification of the element, Chlorine and its interesting cleansing properties, cities in Europe and then soon after, North America, started introducing it into water supplies. The effects on human health have been nothing less than phenomenal.  Deaths in the range of 250 per one hundred thousand due to typhoid, cholera, E coli and a number of the usual suspects, dropped off precipitously.

In order to be deemed acceptable to world standards and tight municipal budgetary constraints, water disinfection, only one part of a water cleansing strategy, must kill or neutralize essentially all pathogens in the water. 98% or greater kill rates are common targets. Disinfection needs to be automatic, easily and inexpensively maintained, relatively safe and above all, effective. An ideal system treats all the water for drinking, fire prevention, industrial and agricultural needs, and provides residual (long term) disinfection. So far the only disinfection methodology that comes even close to meeting these criteria is Chlorine, more commonly known as bleach.

Disinfection, including boiling of water, the increasingly popular ultra violet (UV) treatment, ozone treatment, and the most popular, chlorination, all work on microbial “baddies” including bacterial, viral, protozoan, etc., by disruption and destruction of their outer protective coatings. In the case of Chlorine, it is believed to create blister-like holes which allow the chemical to get inside the cell disrupting DNA formation, energy production and in relatively short order, killing the target microbes. It can take upwards of ½ hour of Chlorine exposure to achieve this “kill” effect.

Unfortunately, Chlorine with all its great disinfection capabilities, does not kill all microbes, particularly, those with tough outer skins such as cryptosporidium, and “baddies” like it that form spores and hard capsules. These microbes need to be filtered out by screens or by reverse osmosis.

And finally, if chlorination’s effectiveness against microbes is so good, the question has to be asked, “What is it doing to human cells once we drink it?” And the answer, thankfully, is that human cells are seldom found as single cells, like microbes, but as grouped cells, such as tissues and the sheer numbers of cells tend to provide protection. It is also important to recognise that the concentrations of Chlorine required to kill a single microbe cell are well within the safe limits for human health.  The only significant issue that research points out is the taste of bleach in our cups.

To better understand the effectiveness of Chlorine as a disinfectant in our water systems check out:

How does chlorine added to drinking water kill bacteria and other harmful organisms? Why doesn't it harm us?