According to the Bloodless surgery: ultrasound cleans up operations, McCarthy, The Lancet “Focuses on the use of high-intensity focused ultrasound (HIFU) in medicine. Gail ter Haar, a physicist at the Royal Marsden Hospital in Surrey, England, and co-workers using HIFU to destroy cancer cells; How the ultrasound transducer works; Problems in bloodless HIFU surgery; The use of HIFU for cautery during standard surgery; How Lawrence Crum and colleagues of the Applied Physics Laboratory at the University of Washington in Seattle, Washington used HIFU.”
High-intensity focused ultrasound ablation HIFU – is a method based on local heating of tissue to a temperature of 50 ° – 90 °, caused by exposure to a focused high-intensity ultrasound. Under the influence of ultrasound, the gas is dissolved in the blood passes into the gaseous state and is converted into micro bubbles. Bursting the bubbles creates acoustic pressure of several thousand Pa and heated to a temperature of 2000-5000 ° C. in this case, the focus area of ultrasound – there is a rise in temperature to 90 º C. The method is widely used for liposuction and to treat various types of tumors.
There is much debate on the future implications of nanotechnology, because the challenges are similar to the development of new technologies, including questions about the toxicity and environmental impacts of nano materials and the potential effects on the global economy, as well as speculation about doomsday scenarios, (doomsday scenarios).
These questions led to debate among groups and governments regarding a regulation on nanotechnology.
The blood-brain barrier (BBB) is a physiological barrier between the bloodstream and central nervous system. BBB have all vertebrates. The main function of the BBB – is the maintenance of homeostasis of the brain. It protects the nervous tissue of circulating microorganisms, toxins, cellular and humoral immune systems, which perceive the brain tissue as foreign. BBB acts as a highly selective filter through which from the bloodstream into the brain receives nutrients, but in the opposite direction derived waste products of nerve tissue. However, the presence of blood-brain barrier makes treatment of many diseases of the central nervous system, since it does not skip a number of drugs.
Weight of the human brain is about 2% by weight of the body. In this case the oxygen consumption of the central nervous system is 20% of the total consumption of oxygen by the body. Also, in contrast to other organs, the brain has the lowest reserves of nutrients. Nerve cells can not meet their energy needs through anaerobic glycolysis alone. Cessation of blood flow to the brain for a few seconds leads to loss of consciousness, and after 10 minutes of coming death of neurons. These energy requirements are provided by the brain through active transport of oxygen and nutrients through the BBB.
Normal functioning of the brain may also only in terms of biochemical and electrolyte homeostasis. Fluctuations in pH, the concentration of potassium in the blood and other factors should not affect the state of the nervous tissue. Circulating in the bloodstream neurotransmitters must not penetrate into the nervous tissue, where they might alter the activity of neurons. Also, the brain must be protected from being hit by foreign agents such as xenobiotics and pathogens. BBB – it is also an immunological barrier, as it is impervious to many microorganisms, antibodies and white blood cells.
The system of blood vessels in the central nervous system has a number of structural and functional features that distinguish them from the vessels of other organs and tissues. These features provide the functionality of food, removing waste products and the maintenance of homeostasis. Violations of the BBB can cause central nervous system. A number of neurological diseases directly or indirectly is associated with damage to the BBB.
Until the late 20th century it was believed that the fetus and newborn blood-brain barrier is not formed in full extent and therefore does not fulfill its function. The reason for this is still widely held in views that are shortcomings of the earlier physiological experiments. The experiments consisted in the introduction of a protein associated with dyes or other markers of adult animals and embryos. The first such experiments were conducted in 1920. Bullets entered the embryos, penetrated the brain tissue and cerebrospinal fluid, whereas in the adult animal – no. In the course of these experiments it was admitted to a number of methodological errors (use of excessive amounts of input material, increasing the osmotic pressure), because of which occurred partial damage of the vascular wall and thus marker got into the brain. With the correct formulation of the experiments the marker passage through the vasculature has been reported.
During the evolution of nervous tissue from invertebrates to vertebrates on the one hand, and noted its increased acquisition activity in the central functions of organisms. On the other hand a large mass of the brain requires a better supply of nutrients and elimination of unnecessary and waste substances. This led to the development of a dense capillary network in the brain tissue. The next stage of evolution is the emergence of a protective barrier from circulating in the blood of toxic substances to neurons – xenobiotics and toxins.
In addition to the blood-brain barrier, there is also the blood-cerebrospinal fluid, which limits the central nervous system from the bloodstream. It is formed by the epithelial cells lining the intimate contact with the choroid plexus of ventricles of the brain. The blood-cerebrospinal fluid barrier also has a role in maintaining the homeostasis of the brain. Through it from the blood into surrounding brain cerebrospinal fluid coming vitamins, nucleotides and glucose. The total contribution of the blood-CSF barrier in the communication processes between the brain and the blood is low. The total surface of the blood-CSF barrier, choroid plexus in the ventricles of the brain approximately 5000 times less compared to the blood-brain area.