More Than 100 ...
...Not Hermetically Sealed...

Description

Capillary blood vessels in the body are not hermetically sealed and chemicals in the blood can leak out into the surrounding tissue (and vice versa).

This is not the case in the brain, where such general leakage would disrupt message transmission. There is thus a blood-brain barrier where capillary cell walls are more tightly joined together.

Discussion

There is some transmission through the walls, though this is carefully managed and the walls are selectively permeable. If nothing from the blood could escape, then it would serve no purpose. For example glucose transporters that bring fuel for the brain are allowed through.

The blood-brain barrier is also weaker in the area postrema in the medulla, where vomiting is managed. In this way toxins in the blood can be monitored and the vomit reaction triggered as needed.

See also

Parts of the brain, Hindbrain

 

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The BBB Stands In...

The Blood-Brain Barrier - Treatment's Biggest Obstacle

The blood-brain barrier stands in the way of new drug development.

You may have heard of "antisense" technology, that so-called ultimate magic bullet of genetic science that promises to bind to disease-causing strands of messenger RNA and stop them dead in their tracks. Try to imagine antisense turned loose inside your skull, and now imagine kissing your depression or mania goodbye forever.

The catch? There are probably many, but the most obvious one is that any drug which targets any part of the brain must first cross the blood brain barrier (BBB). The name conjures up a kind of cross between the Berlin Wall and a coffee filter, but in fact refers to nearly 400 miles of narrow capillaries throughout the brain, all filled with tightly-packed endothelial cells that are exceedingly selective in what gets through. Endothelial cells are also present in capillaries in the body, but the spacing there poses no difficulty.

The BBB is to protecting the brain internally as the skull is to protecting it externally. The problem is the BBB does not differentiate what it keeps out. Life-saving chemicals, if they happen to be the wrong chemicals, simply won't get through. With very few exceptions, only small molecules soluble in fat clear the barrier. Alcohol, caffeine, and nicotine - all meeting this criteria - have a free pass. So do antidepressants. The problem is, according to William Pardridge MD of UCLA writing in the Jan Archives of Neurology, "small molecules are largely palliative medicines with often unfavorable safety profiles." There are no chronic diseases, other than infectious diseases, that are cured by small-molecule drug therapy.

Large-molecule drugs have the potential to cure patients with neurological disorders, he notes, but none of them can cross the blood brain barrier. The following paragraph is worth quoting in full:

"Despite the importance of the BBB to neuropathic agents, this area is underdeveloped in the neurosciences. To my knowledge, no pharmaceutical company in the world has a BBB drug delivery program! It is not unusual for an entire conference to be convened on a given neurologic disorder (eg brain tumors), with no discussion of targeting drugs through the BBB."

The blood brain barrier makes certain exceptions for allowing passage to large molecules and water-soluble molecules, and exploiting these exceptions is the key to developing new classes of drugs. One binding and transport system in the BBB, for example, permits water-soluble glucose into the brain and another mediates the bidirectional movement of large molecule peptides. According to Dr Partridge: "Based on the knowledge that these endogenous transport systems exist, drugs may be reformulated to enable transport into the brain via the endogenous BBB transporters."

A lab-made "chimeric peptide", for example, is half drug (which does not cross the BBB), and half "molecular Trojan Horse" (which does). The Trojan Horses are genetically-engineered proteins that have slipped through the BBB in lab animals.

Trojan Horses are also being constructed to slip through concealed genetic material. New Scientist reports that Dr Partridge and his team have been working on encasing genes in fatty spheres called liposomes, which are coated with a special polymer, to which certain antibodies are attached. The antibodies trick the brain-capillary receptors

 

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Brain Tissue Receives A...

The Blood Brain Barrier (the BBB)


  • The brain receives a constant 50ml of blood per 100g of brain tissue, per minute, no matter what the conditions. This is unlike the skeletal muscles or other organs, which have different blood flow requirements depending on how they are being used.
  • The circle of Willis works to distribute blood at an even pressure, even if one of the major arteries to the brain becomes occluded
  • With all of this blood coming in, what protects the brain from blood-borne drugs or other substances? The blood-brain barrier
  • The "barrier" is actually a series of tight junctions between the endothelial cells of the tunica intima. The blood vessels of the brain are the least permeable of all vessels due to the intercellular connections
  • Astrocytes participate in the barrier too. They cover the capillaries, and their "feet" help the endothelium to form the tight junctions.
  • The barrier is not absolute. Important nutrients such as glucose, amino acids and certain electrolytes move easily via facilitated diffusion. Wastes, such as urea and large proteins, drugs and other molecules cannot get through to the brain.
  • The barrier is not effective against smaller molecules, including fats, fatty acids, oxygen, carbon dioxide, alcohol (ethanol) and nicotine.

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The Blood Brain Barrier ("Keep Out")

 More than 100 years ago it was discovered that if blue dye was injected into the bloodstream of an animal, that tissues of the whole body EXCEPT the brain and spinal cord would turn blue. To explain this, scientists thought that a "Blood-Brain-Barrier" (BBB) which prevents materials from the blood from entering the brain existed. More recently, scientists have discovered much more about the structure and function of the BBB.

Anatomy of the BBB

 The BBB is semi-permeable; that is, it allows some materials to cross, but prevents others from crossing. In most parts of the body, the smallest blood vessels, called capillaries, are lined with endothelial cells. Endothelial tissue has small spaces between each individual cell so substances can move readily between the inside and the outside of the vessel. However, in the brain, the endothelial cells fit tightly together and substances cannot pass out of the bloodstream. (Some molecules, such as glucose, are transported out of the blood by special methods.)

 Glial cells (astrocytes) form a layer around brain blood vessels and may be important in the development of the BBB. Astrocytes may be also be responsible for transporting ions from the brain to the blood.

Functions of the BBB

The BBB has several important functions:

  1. Protects the brain from "foreign substances" in the blood that may injure the brain.
  2. Protects the brain from hormones and neurotransmitters in the rest of the body.
  3. Maintains a constant environment for the brain.

General Properties of the BBB

  1. Large molecules do not pass through the BBB easily.
  2. Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules, such as barbituate drugs, rapidly cross through into the brain.
  3. Molecules that have a high electrical charge are slowed.

The BBB can be broken down by:

  1. Hypertension (high blood pressure): high blood pressure opens the BBB.
  2. Development: the BBB is not fully formed at birth.
  3. Hyperosmolitity: a high concentration of a substance in the blood can open the BBB.
  4. Microwaves: exposure to microwaves can open the BBB.
  5. Radiation: exposure to radiation can open the BBB.
  6. Infection: exposure to infectious agents can open the BBB.
  7. Trauma, Ischemia, Inflammation, Pressure: injury to the brain can open the BBB.

Circumventricular Organs

There are several areas of the brain where the BBB is weak. This allows substances to cross into the brain somewhat freely. These areas are known as "circumventricular organs". Through the circumventricular organs the brain is able to monitor the makeup of the blood. The circumventricular organs include:

  • Pineal body: Secretes melatonin and neuroactive peptides. Associated with circadian rhythms.
  • Neurohypophysis (posterior pituitary): Releases neurohormones like oxytocin and vasopressin into the blood.
  • Area postrema: "Vomiting center": when a toxic substance enters the bloodstream it will get to the area postrema and may cause the animal to throw up. In this way, the animal protects itself by eliminating the toxic substance from its stomach before more harm can be done.
  • Subfornical organ: Important for the regulation of body fluids.
  • Vascular organ of the lamina terminalis: A chemosensory area that detects peptides and other molecules.
  • Median eminence: Regulates anterior pituitary through release of neurohormones.
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Cell Phone Use

The Blood-Brain Barrier

The second effect that I want to focus on, which has been proven in the laboratory, should by itself have been enough to shut down this industry and should be enough to scare away anyone from ever using a cell phone again. I call it the “smoking gun” of cell phone experiments. Like most biological effects of microwave radiation, this has nothing to do with heating.

The brain is protected by tight junctions between adjacent cells of capillary walls, the so-called blood-brain barrier, which, like a border patrol, lets nutrients pass through from the blood to the brain, but keeps toxic substances out. Since 1988, researchers in the laboratory of a Swedish neurosurgeon, Leif Salford, have been running variations on this simple experiment: they expose young laboratory rats to either a cell phone or other source of microwave radiation, and later they sacrifice the animals and look for albumin in their brain tissue. Albumin is a protein that is a normal component of blood but that does not normally cross the blood-brain barrier. The presence of albumin in brain tissue is always a sign that blood vessels have been damaged and that the brain has lost some of its protection.

Here is what these researchers have found, consistently for 18 years: Microwave radiation, at doses equal to a cell phone’s emissions, causes albumin to be found in brain tissue. A one-time exposure to an ordinary cell phone for just two minutes causes albumin to leak into the brain. In one set of experiments, reducing the exposure level by a factor of 1,000 actually increased the damage to the blood-brain barrier, showing that this is not a dose-response effect and that reducing the power will not make wireless technology safer. And finally, in research published in June 2003, a single two-hour exposure to a cell phone, just once during its lifetime, permanently damaged the blood-brain barrier and, on autopsy 50 days later, was found to have damaged or destroyed up to 2 percent of an animal’s brain cells, including cells in areas of the brain concerned with learning, memory and movement.1 Reducing the exposure level by a factor of 10 or 100, thereby duplicating the effect of wearing a headset, moving a cell phone further from your body, or standing next to somebody else’s phone, did not appreciably change the results! Even at the lowest exposure, half the animals had a moderate to high number of damaged neurons.

The implications for us? Two minutes on a cell phone disrupts the blood-brain barrier, two hours on a cell phone causes permanent brain damage, and secondhand radiation may be almost as bad. The blood-brain barrier is the same in a rat and a human being.

These results caused enough of a commotion in Europe that in November 2003 a conference was held, sponsored by the European Union, titled “The Blood-Brain Barrier — Can It Be Influenced by RF [radio frequency]-Field Interactions?” as if to reassure the public: “See, we are doing something about this.” But, predictably, nothing was done about it, as nothing has been done about it for 30 years.

America’s Allan Frey, during the 1970s, was the first of many to demonstrate that low-level microwave radiation damages the blood-brain barrier.2 Similar mechanisms protect the eye (the blood-vitreous barrier) and the fetus (the placental barrier), and the work of Frey and others indicates that microwave radiation damages those barriers also.3 The implication: No pregnant woman should ever be using a cell phone.

Dr. Salford is quite outspoken about his work. He has called the use of handheld cell phones “the largest human biological experiment ever.” And he has publicly warned that a whole generation of cell-phone-using teenagers may suffer from mental deficits or Alzheimer’s disease by the time they reach middle age.

Radio-Wave Sickness

Unfortunately, cell phone users are not the only ones being injured, nor should we be worried only about the brain. The following brief summary is distilled from a vast scientific literature on the effects of radio waves (a larger spectrum which includes microwaves), together with the experiences of scientists and doctors all over the world with whom I am in contact.

Organs that have been shown to be especially susceptible to radio waves include the lungs, nervous system, heart, eyes, testes and thyroid gland. Diseases that have increased remarkably in the last couple of decades, and that there is good reason to connect....

 

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The Web Your Health And Tech Friend

The West Entrance

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 "...these researchers have found, consistently for 18 years: Microwave radiation, at doses equal to a cell phone’s emissions, causes albumin to be found in brain tissue. A one-time exposure to an ordinary cell phone for just two minutes causes albumin to leak into the brain. "  (This article is below)

Studies have linked cell phone radiation to health problems such as headaches, high blood pressure, brain tumors, cancer, Alzheimer's, and more. There is a latency period for most diseases and it may take years and more studies before the required weight of evidence is established. But the effects are cumulative and precautions should be taken now before it is too late.

Here are some steps you can take to minimize the effects of cell phone radiation exposure:

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