Current Scientific Inventions And Technologies Biology Essay

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Many current scientific inventions and technologies that are now part of the daily life could only be imagined in the past and were the object of science fiction stories. Many of those that were considered impossible and highly opposed by scientists later caused a revolution in the science world (examples?). At present time, when science is rapidly progressing, some ideas that now seem to be unrealistic for the scientific community draw a lot of attention in the society. One of those is cryonics - an idea of extending human life by "cheating death".

Cryonics is preservation of a human (or animal) body or for example just the brain at extremely low temperatures (typically -196°C) with hopes of future revival. People who wish to cryogenically preserve their body are often people who suffer and die from diseases that cannot be cured with present medical knowledge. Such people see cryonics as a possibility to come back to life in the future when technology will develop so that their diseases can be cured. However, the changes that occur in the body during the cryonisation procedure cannot be reversed and the idea of cryonics seems to have no real scientific proof and be only supported by the hopes of future development of medicine and nanotechnology. Despite that around 200 people have been cryogenically frozen (Holwey K., 2010) already. Currently several companies around the world offer their services in cryopreservation, those are: Alcor (USA), Kriorus (Russia) and Cryonics Institute (USA). Prices for their services range from $28,000 to $155,000.

Our project idea fits the semester theme because cryonics causes disagreement in the scientific society and nevertheless is viewed as a potential cure by the ordinary people who choose to invest in it. This might be a result of certain aspects of cryonics present in everyday life (movies, books and mass media) and speculation on the future scientific development. In this project we are going to analyze scientific and societal aspects of cryonics, therefore our main problem formulation is:

What evidences/proofs justify/reject the idea of cryonics in the scientific community and in society?

Sub questions:

What are the origins of cryonics?

Which ethical and religious aspects are involved?

What is present statistical, financial and legal information?

What would "post-awakening" life of the patients be?

Cryonics

History

The word 'cryonics' originated from Greek 'kryos', meaning icy cold. This idea is first mentioned by a college physics teacher Robert Ettinger in his book The Prospect of Immortality published in 1962. Therefore he is regarded as the 'father of cryonics'.

The first cryonics organization, the Life Extension Society was founded by Evan Cooper in December 1963(Ben best, A History of Cryonics). In the late 70s of the 20th century, there were about six cryonics organizations in the United States. But not many people could afford cryopreservation due to its expansive cost; therefore, most of the cryonics organizations closed down in the following 10 years. Today, there are only three companies left: Alcor, KrioRus and the Cryonics Institute.

The first cryonics patient was a 73 year old psychology professor named James Bedford. He has been frozen in liquid nitrogen since January 12, 1967(Ben best, A History of Cryonics). Now his body is well preserved in Alcor Life Extension Foundation.

Companies and prices and statistics

There are currently several profit and non-profit companies related to cryonics, but only three of them offer the storage of bodies: Alcor (since 1972), the Cryonics Institute (since 1976) and KrioRus (since 2005). Other companies such as the American Cryonics Society, EUCrio or Suspended Animation, Inc. only offer perfusion with the cryoprotectants, standby (which consists in waiting for the death of the patient and cooling down of the body as soon as death occurred) and transport to a storage facility (cryonics.org).

In order to participate in a cryonic suspension program, a patient must fulfill three requirements: first he has to become a member of a chosen cryonics company by doing the necessary paperwork and paying a membership fee. Then he must give an authorization so that the company legally owns his body. And finally pay a fee to the company, which includes suspension, storage and revival. Some companies not only offer cryopreservation of the whole body, they offer preservation of only the brain (neurocryopreservation), and also of the patient's pet. Those fees are really high (Table 1), and therefore cryonic companies suggest their patient to have a life insurance, that could help to pay.

Table 1: Prices in US dollar for whole body preservation, neurocryopreservation, and pet cryopreservation for different companies. Those prices do not include neither the membership fee, nor the eventual standby and transport fees. (alcor.org, kriorus.ru, cryonics.org)

 

Whole Body Preservation

Neurocryopreservation

Pet Cryopreservation

Alcor

150.000

70.000

_ 

Cryonics Institute

28.000 or 35.000

_

>5.800

KrioRus

30.000

10.000

_ 

Laws and regulations

Since cryonics is not recognized as a medical practice, patients must be legally dead before the cryopreservation protocol is started. The criteria used to pronounce legal death differ between countries, in some case legal death can be pronounced if 'only' the brain is dead, in other, the heart and lungs must also be dead.

Of course cryonics is associated with political and legal issues. As mentioned earlier, in the USA, cryonic patients have to authorize the companies to own their body after their death, this is made possible by the Uniform Anatomical Gift Act (UAGA), individuals can choose to donate their organs or have their body dissected for the study of sciences, and in our case to be used in a cryonic suspension program. Therefore, this UAGA allows companies to own the bodies, just as an organ transplantation company can possess organs, making their status legal in the United States.

In order to avoid autopsy after their death, cryonics patients wear bracelets, necklaces or even tattoos providing information to the coroner (Figure 1). Some cryonauts also joined a "religion" in order to avoid autopsy The Society for Venturism, "Having an autopsy is strongly against the beliefs of the Society for Venturism (www.venturism.info)", the members of this religion are offered a card stating their opposition to an autopsy (www.venturist.info). Because euthanasia is illegal for cryonics purposes, a natural death is required.

Figure 1: Tattoo for a coroner (Romain T, 2010)

Chemical/biochemical principles of freezing

Problems for organisms that encounter low temperature environment:

Changes in membrane and protein structure;

Changes in electrolyte concentrations (and other solutes);

Changes in metabolism.

Effects of low temperature on the cells

Lipids

Cell membranes can exist in two phases: a liquid crystalline phase and a more ordered gel state. During the cooling the viscosity of the membrane increases and with further cooling results in phase separation.

Proteins

Cold denaturation temperatures of proteins are lower than the equilibrium freezing point of water, i.e. below -15°C. Denaturation of proteins at low temperatures is often reversible (e.g. tubulin; irreversible - urease, phosphofructokinase - breaks into 2 dimers). When cooling a number of stabilizing and destabilizing factors are important:

Stabilizing factors - hydrophobic interactions, hydrogen bonding, salt bridges, van der Waals interactions;

Destabilizing factors - core repulsion, configurational entropy, salvation effects.

Processes occurring during freezing

Cryopreservation of cells by freezing and vitrification is currently achievable, the procedure consists in exposing the cells to cryoprotective agents, before cooling them to extremely low temperatures (at first -70°C) and then storing them at -196°C.

Cooling

t°<below usual temperature of activity. [Stupor state - animal becomes sluggish and eventually stops moving when chill coma state is reached. (Only cold adapted animals survive this state for a longer period of time). ]ß shouldn't this be in the 'freezing tolerance in nature' part?

Freezing

Temperature < melting point of organism's body fluids. Nucleation ice crystals - particles that act as nuclei for formation of the ice crystals, may occur at any temperature below this point. If ice is not formed when t=melting point of organism's body fluids solution is supercooled or undercooled and is metastable ß Define maybe? . Crystallization spontaneously occurs when water molecules aggregate into ice nuclei (homogeneous nucleation) or around the surface that lowers the activation energy of crystallization (heterogeneous nucleation). A sufficient number of water molecules form a cluster called an "embryo ice crystal", which at a critical size becomes nucleus in the nucleation process.

Factors affecting nucleation process: t° (increased nucleation probability at lower t°), V of the sample (larger volume à higher probability of ice embryo formation, therefore larger volumes freeze closer to a melting point t°), presence of nucleating agents, a certain volume of supercooled state that is frozen at a time. If the temperature is further decreased during nucleation, eventually the eutectic point is reached when the ice and the solutes begin to precipitate simultaneously.

When ice formation is triggered (usually in the extracellular fluid: in the gut, tissues, in solution, in blood or in hemolymph), these fluids become increasingly concentrated, and as a result, an osmotic pressure difference between the internal and external liquids will develop, causing the water to run outside of the cells. This osmotic pressure difference is due to the difference in the intracellular and extracellular vapor pressure. Water has a higher vapor pressure than ice, and the cells being supercooled while the extracellular solution is freezing; the vapor pressure inside the cells is higher compared to that of the extracellular solution. The dehydration of the cells by losing water is then induced in order to lower the vapor pressure inside the cells and therefore maintaining vapor pressure equilibrium (Mazur, 1970). Freezing may also be initiated due to the contact with external ice (inoculation). Freezing can be seen as drying - since more and more water molecules are removed from solution and form ice.

The osmotic pressure (P) is given by Van't Hoff equation:

P = MRT

M being the molarity (molar concentration, in mol/L), R is the gas constant (R = 8.314472 J/(molÃ-K) or R = 8.205746 Ã- 10-2(LÃ-Atm)/(molÃ-K).) and T the thermodynamic absolute temperature in Kelvin. Thereby the dimension of Π becomes: or

With this equation we can find the pressure on each side of the membrane, and then get the total pressure on the membrane as the difference in pressure ∆Π, by subtracting those two pressures, if both concentrations are known. Here the concentration of the extra-cellular solution is higher than that of the intra-cellular solution. The cell is consequently in a hypertonic environment, and this leads to the flow of the intra-cellular water outside of the cells in order to re-establish the vapor pressure equilibrium state.

Increase in solute concentration also causes changes in pH, affects enzymatic activity and may lead to precipitation or denaturation of proteins, changes in membrane potential and membrane transport. Intracellular freezing is lethal in most cases; however, cooling might affect various kinds of cells differently. Generally, as water moves from the cell due to osmosis, cells shrink. When cell volume decreases to a minimal volume, cell membrane begins to rest on the intracellular structures, causing hydrostatic stress and eventually breaking the membrane. Also growing ice crystals may tear the cells ß sentence not complete??

The cooling rate is an important factor regarding the outcome of the freezing procedure. Indeed, cooling too slowly gives time to the water to flow outside of the cells and therefore triggers the osmotic pressure difference damaging the cells' sutructure (Zhao et al., 2006). And cooling too rapidly will not permit the water to run out of the cells, but the risk of intracellular ice formation will be increased because all of the cells' content will freeze immediately (Zhao et al., 2006). Slow cooling is the method that has been chosen in many cryopreservation protocols. This choice was made followingg Mazur's water transport equation (Mazur, 1963):

This equation presents the cooling rate (B) in function of the volume of intracellular water , the temperature (T), and some other parameters which can be found in table 2 below:

Table 2: Other parameters (constants, variables) involved in Mazur's water transport equation.

Symbol

Meaning

Units

b

Temperature coefficient of permeability constant

Degree-1

Tg

Temperature

K

T

Temperature

K

A

Area of the cell

µ2

R

Gas constant

µ3xatm/(mol.degree)

Kg

Permeability constant at temperature Tg

µ3/(µ2.min.atm)

n2

Omsoles of solutes cell

Moles

v10

Molar volume of pure water

µ3/moles

V

Volume of water in cell

µ3

B

Rate of temperature change

K/min

Therefore, the optimal cooling rate would be fast enough to reduce the time during which water would flow out of the cells, and slow enough to prevent intracellular ice formation (Figure 2).

Firgure 2: Different cryopreservation methods: freezing and vitrification. During freezing ice is initially formed in the extracellular solution. The longer time the cooling takes, the more time water has to move outside of the cells. The cells also become concentrated at slower cooling rates as they are pushed together by the forming ice (A, B). Maximum cell viability is usually achieved at an intermediate cooling rate (B) that balances osmotic dehydration and the risk of intracellular ice formation. Rapid cooling (C) permits intracellular ice formation and usually leads to cell death upon rewarming. Very slow cooling (A) may lead to excessive cell dehydration and cell death. In contrast, right side (D), cells cryopreserved by vitrification undergo neither ice formation nor shrinkage due to dehydration and most of the cells should be viable

An optimal cooling rate that would increase survival rate of the cells depends on water permeability of the membrane, cell surface to volume ratio hydraulic conductivity (Wikipedia: describes the ease with which water can move through pore spaces or fractures and depends on the intrinsic (ß define) permeability of the material and on the degree of saturation). Cells with higher membrane permeability to water and high surface to volume ratio can endure higher rates of cooling since water leaves the cells faster and risks of intracellular freezing due to supercooling of intracellular fluid is decreased. Figure 3 shows that the cooling rate depends on the type of cells.

Figure 3: Percentage of survival for different types of cells (marrow stem cells, yeast, hamster cells and human red cells (RBC) frozen to -196°C) in function of the cooling rate. The optimal cooling rate varies according to the cell type (Mazur 1970).

Processes occurring during vitrification

An alternative to freezing and its related disadvantages would be vitrification. It consists in the solidification of water (or water-based solution) without the formation of ice crystals which damage the cells during freezing procedures. During vitrification, the formation of both intracellular and extracellular is avoided (Figure 2).

Some liquids can avoid the formation of crystals if they are cooled to temperatures much lower than their melting temperature, this is more likely to happen when the liquid is viscous and when the cooling happens rapidly. While being cooled to extremely low temperatures, this liquid will meet its glass transition temperature, at which the change from the liquid phase to solid phase occurs. When in a glass state, a solution is still technically liquid, but is too cool to flow (Brockbank et al., 2003). Indeed, throughout cooling at lower and lower temperatures, the molecules will remain in the same disorganized way as they are when in a liquid state. Nevertheless, the physical properties of the 'liquid' are now comparable to those of a solid. Therefore, the molecules are held in the same pattern through the whole process (Fig. 4). The 'solid liquid' obtained is defined as glass (Wowk B, 2010). In figure 5, the kidney at the right of the picture has been vitrified, it looks like glass, no ice crystals are present; the kidney at the left is frozen, the white colour is due to the ice crystals that have been formed during cooling.

Vitrification is not observed in animals under natural conditions (Ramløv H, 2000); indeed, the water present in the cells is not viscous enough to undergo the process of vitrification. This is why some cryoprotective agents (CPAs) such as glycerol have to be used in order to increase the intracellular solution's viscosity and therefore prevent the ice crystal formation.

a) b)

Figure 4: Yellow molecules represent cryoprotectants, blue color represent water and the red are solutes. Molecules organization in warm, and vitrified states (www.alcor.org)

a)Solution at warm temperature.

b) Vitrified solid state. Organisation of the molecules is in the same pattern as in the warm liquid state.

Figure 5: Frozen and vitrified kidney (alcor.org)

Thermodynamical aspects of cooling

Simply as we know, one can keep food for a longer time in the fridge, and even longer in the freezer. Just imagine, if we try to lower the temperature to an Infinite low temperature, then can we keep it close to an infinite long time?

Here we can use Arrhenius equation to prove this hypothesis.

k = Ae-Ea/RT (Exponential equation)

k - reaction rate constant;

A - the frequency factor, which is an empirical relationship between temperature and rate coefficient; (wikipedia.org, 2010)

e - an irrational constant approximately equal to 2.718281828;

Ea - the activation energy, which is the minimum energy required in order to start the chemical reaction, with the unit of kilojoules per mole; (wikipedia.org, 2010)

R - the molar gas constant, which the value is 8.314 J/(mol K);

T - the thermodynamic temperature, which T1 is the initial temperature, T2 is the final temperature.

First put logarithm on both sides:

ln k = (-Ea/RT) + ln A (Logarithmic equation)

ln k1 = (-Ea/RT1) + ln A

ln k2 = (-Ea/RT2) + ln A

To remove the frequency factor A, we need to combine the two equations as above.

ln k1 - ln k2 = ((-Ea/RT1) + ln A) - ((-Ea/RT2) + ln A)

As we know ln(a)-ln(b)=ln(a/b), so

ln k1 - ln k2 = ln (k1/k2)= ((-Ea/RT1) + ln A) - ((-Ea/RT2) + ln A)

ln (k1/k2)= -Ea/RT1 + ln A + Ea/RT2 - ln A

ln (k1/k2)= Ea/RT2 - Ea/RT1

ln (k1/k2) = (Ea/R)*(1/T2 - 1/T1)

Then we can get the rate of two reaction rates in different temperature.

k1/k2 = e(Ea/R)*(1/T2 - 1/T1) (Integral equation)

Here we are using the lactate dehydrogenase from rabbit muscle as an example enzyme. Burning one thermochemical calorie of lactate dehydrogenase releases 54,810 J/mol energy (Benjamin P. Best, 2008). To compare two reaction rates k1 and k2, we need to calculate them in different temperature which T1 = 313 K (40 °C), T2 = 303 K (30 °C).

Therefore:

k1/k2 = e((54,810 J/mol)/(8.314 J/(mol K)))*(1/303 K -1/313 K) = 2.004

According the result, we can find out that, when the temperature dropping down 10 K (or 10 °C), the reaction rate in low temperature will be half of the normal reaction rate. Human body temperature is about 37 °C (310K) under normal circumstances. The thermodynamic temperature of liquid nitrogen is 77K. There is about 230K Temperature difference. That means the reaction rate in normal human body is 9 octillion (9*1027) times faster than in liquid nitrogen.(Benjamin P. Best, 2008)

Also any material's size will change as it undergoes a temperature change. During freezing and vitrification, the temperature of a tissue or an organ, or even a whole body in cryopreservation is lowered to a great extent, and will make the material shrink. And as it is impossible to cool a body uniformly, the temperature on the outside of it will be lower than that of the inside. But the outside of the body will not be able to shrink as it should because the inside does not have the same temperature and therefore no shrinkage will be induced at that same time; and so, it will be compressed by the shrinkage of the outside (Taylor et al., 2003).

Cryoprotectants

Glycerol used to be the most commonly used cryoprotectant; however, it has been shown that its toxicity to the cells is really high. Dimethyl sulfoxide (DMSO), and its great ability to penetrate the cells' membrane later replaced glycerol and was used for the cryopreservation of the very first patient, James Bedford.

There are now two main categories of cryoprotectants, the penetrating, and non- penetrating ones (Table 3). Penetrating cryoprotectants are used to protect the cells and tissue, by replacing some of the water they contain and thus increasing the viscosity in the cells, preventing the formation of ice crystals and making the vitrification process easier by inducing the transition to the glass state (Kuleshova LL et al., 2007). Whereas, the non-penetrating protectants, which prevent water from flowing outside of the cells and the occurring of osmotic damages by acting outside of the cells and making the membrane less permeable (Kuleshova LL et al., 2007). Some natural anti-freeze proteins can be used in addition to these cryoprotectants, their role is to inhibit ice nucleation.

Nevertheless, most of these solutions are toxic to the cells, and particularly the low molecular weight agents. The toxicity depends on different parameters, such as the time of exposure, and concentration.

Table 3: Classification of cryoprotectants (Kuleshova LL et al., 2007).

TREHALOSE?

Freezing tolerance in nature

Strategies used by cold tolerant animals:

Freeze tolerant animals - survive ice formation in the tissues;

Freeze avoiding animals - tolerate low temperatures without crystallizing their body fluids

Adaptations

Adaptations to temperature below body fluid melting point developed by ectothermic animals are given in table 4:

Table 4: Adaptations to temperatures below melting point of the body fluids (Ramløv H, 2000)

To remove nucleating agents during the cold periods, some freeze-avoiding animals stop eating and empty their gut in autumn in this way increasing their SCC (supercooling capacity).

One of the most important mechanisms in ectothermic animals that allows adaptation to low temperatures is the ice formation control, which is a complete avoidance of ice formation (and inoculation) or control of the site of ice formation, temperature of crystallization, the amount of ice formed and recrystallization control (recrystallization - formation of bigger ice crystal from the smaller ones).

Figure 6: Adaptations of ice formation control (Ramløv H, 2000)

To control ice formation ectotherms synthesize various substances (see Figure 6). To be effective in ice formation control these substances need to have specific properties:

High solubility in aqueous solution;

Non-toxic properties and non-reactivity with other macromolecules even in high concentrations;

Should be compatible solutes;

Have to counteract protein denaturation due to cold, dehydration and high ionic concentrations.

Low molecular weight substances found in large concentrations in cold-adapted ectotherms: polyols, sugar alcohols, (most commonly glycerol), sugars (trehalose, glucose) and free amino acids (proline). These substances are found in large concentrations and lower the rate of ice formation and its amount. (Mechanism of ice formation control?)

Proteinaceous substances that control ice formation - INA (ice nucleating agents) and antifreeze proteins.

INA work by causing ice formation via heterogeneous nucleation at relatively high temperatures (below melting point of intracellular fluids). INAs probably provide template for embryonic ice crystal formation and growth, and therefore ensure freezing of supercooled liquid.

Antifreeze proteins - found in polar fishes and invertebrates inhabiting exposed to cold. Antifreeze proteins prevent freezing by recognizing embryonic ice crystals before they grow into larger crystals thus stabilizing metastable supercooled state. Antifreeze proteins interact with specific crystal planes on ice crystals and inhibit recrystallization. Types of antifreeze proteins:

Glycoproteins (2,6 to 36 kDa);

Type I antifreeze proteins (3300-5000Da, alanine rich);

Type II antifreeze proteins (~14kDa, cysteine rich);

Type III antifreeze proteins (~7000Da, lack histidine and tryptophan)

Type IV antifreeze protein (?) - LS-12 from Myoxocephalus octodecimspinosis.

Antifreeze proteins are found not only in freeze avoiding but also in freeze tolerant animals. Antifreeze substances were first described by Ramsay in 1964.

Organ preservation

Patients who have chosen cryonics will undergo similar procedures, to some extent, as the ones used for organ preservation before transplantation. Freezing and vitrification techniques have been developed for organ transplantation. Another simplest method is called hypothermic preservation. This last technique consists in keeping the organs in a cold environment with the help of ice-filled bags, and machines pumping perfusion liquid at 0°C to 4°C into the organ keeping its metabolism (ion-pump activity, synthesis of ATP...) running, by delivering oxygen and substrates (Mukherjee S, 2010). ßPerfusion liquid explanation necessary or not (what liquids, effects on the cells..)?? However this technique cannot be used for the purpose of cryonics, since it only allows keeping the organ viable for up to 72h for a canine kidney (Leuvenink et al., 2009) and for human organs, a maximum time of 5 hours for the heart, up to 50 hours for kidneys, and 12 to 15 hours for pancreas and liver (Mukherjee S, 2010).

Cryonics follows the same principle as organ preservation: cooling down the organ in order to slow down its metabolism and therefore preventing its degeneration due to a lack of oxygen delivery to the cells. Freezing or vitrification of the organ has to occur immediately after death of the donor. [In organ transplantation, there are two important phases regarding the temperature, the warm ischemic phase, and the cold ischemic phase. Ischemia is a lack of blood supply to an organ. The warm ischemic phase is the time during which the organ remains at body temperature, from the stop of the blood flow through the organ until it is cooled down. And the cold ischemia time is defined by the duration of the time between the moment the organ is cooled down until it is back to physiological temperature during transplantation.

During the warm ischemia time, the organ can be damaged, and therefore; the time it takes for the organ to regain its normal function after transplantation can be extended or the organ could also never recover. For this reason, this phase has to be as short as possible; this is why between the removal and the transplantation in the receiving body, the organ has to be preserved at low temperature.] ß really necessary?

Before freezing or vitrification can be performed, the blood in the organs has to be flushed out with cryoprotectants. During both of these processes, the organ is first cooled down and perfused with cryoprotectants at low temperature (4°C).

Then, for the freezing procedure, the organ is placed in a cryocontainer. This container in which the organ is placed will be cooled in a freezer at around -70°C. Lastly, the cryocontainer is moved to another freezer which temperature is close to -150°C (Dittrich et al, 2010). However, freezing is associated with ice crystals formation, and damages made to the cells causing fractures to occur, separating cells from each other and disrupting their membranes, causing the organ to break into pieces. Another difficulty related to freezing resides in freezing every single cell of an organ; an organ being made of different cell type, and each type having specific freezing requirements for a better preservation of its functions (Mukherjee S, 2010). Therefore, we can hardly imagine freezing a whole body.

The other option, vitrification, seems to be the most promising method for cryopreservation of both organs, and entire bodies. It consists in converting the liquids present in an organism into a glass state at very low temperature, avoiding ice formation (Fahy et al,. 2009). After flushing and replacing the blood with cryoprotectants, the organ is cooled down in liquid nitrogen at -196°C.

Procedures in cryonics

Companies offering their services in cryopreservation follow strict procedures for preparation of the patients' body for cryonisation. Procedures start immediately after the patient has been pronounced legally dead to prevent damage due to stopped blood flow. First patients breathing and blood flow are artificially restored by heart-lung resuscitator. The following protective medications are administered into the blood flow (Alcor, www.alcor.org):

Free radical inhibitors

NOS (nitric oxide synthase) inhibitors

PARP (Poly ADP-ribose polymerase) inhibitors

Excitotoxicity inhibitors

Anticoagulants

Pressors

pH buffers

Anesthetic

The temperature of the body is lowered to a few degrees above freezing point of water and the blood is replaced by organ preservation solution and the patient is transported to cryonisation facility. Later all the remaining blood is washed out and the concentration of cryoprotectants is first gradually increased to half final concentration and then rapidly increased to the target concentration. Then the body is cooled down as quickly as possible by circulating nitrogen gas at -125°C. After this procedure the body has been vitrified and is further cooled to -196°C.

Ethics

7.1 Medical Ethics

Although the cooling procedure is starting after the patient's legal death, people are still thinking about if the doctor will try to save the patients or just let them pass away? Well, for some reason, if the patient is suffering an intense pain and he does not have any hope to wake up again, and if his relatives also agree to stop all medical treatment. Then in most of the countries, the doctor is allowed to remove the medical ventilator or increase the dose of the analgesics, so the patient will die without pain.

There is also an option called euthanasia, which is a deliberate intervention undertaken with the express intention of ending a life, to relieve intractable suffering. And it is legal in Belgium, Luxembourg, the Netherlands, Switzerland and the U.S. states of Oregon and Washington (Euthanasia, wikipedia.org, 2010).

7.2 Religion

Some religious people believe that, when people die, the heart will stop beating, the soul will leave their bodies. If a person has been cryopreserved and revived later. Where does the soul go?

Well, people who have been cryopreserved are not completely dead, they just fall asleep deeply. If the religious people agree for the organ transplantation, then cryonics is as if the people are under anesthesia, and waiting for their surgery.

Discussion

Cryonics is a controversial subject in both a social and a scientific context. It is the source of conflicts between husband and wives, when one does not approve or understand the choice of the other to be cryonised.

If cryonics is to be proven to actually work sometime in the future, then the definition of "dead" for the patients changes, they cannot be considered as dead since they will be revived. Therefore these people should not get money from their life insurances and most of the people who could afford cryopreservation only by using this money will not be able to pay for it anymore.

There is also the question of the "post-awakening" life of the patients. They will not have any money, home, family, friends and job.

Besides the ethical problems, cryonics has some major biological issues that would serve as a proof of ineffectiveness of such technology.

The process of preparing human body for cryopreservation is based on introduction of cryoprotective substances that normally do not exist in human body and therefore can have a toxic effect on the organism of the patient. Unlike humans, freeze tolerant animals have developed adaptations on the cellular level in the process of evolution and therefore it is unreasonable to assume that such features of the cells can be achieved by only introducing cryoprotectants after death.

COULD 100% OF CELLS SURVIVE FREEZING?? WHAT IF ONLY 70% SURVIVE??(BRAIN DAMAGE?)

Perspectives

Cryopreservation by vitrification presents some problems, such as the toxicity of the cryoprotectants. Alternative methods, such as isochoric preservation which requires less cryoprotectants than regular cryopreservation are currently being experimented (Preciado JA, Rubinsky B., 2010). An isochoric process is a constant volume process, therefore it takes place in a sealed container. It consists in using high pressures so the ice formation is avoided (Rubinsky et al., 2005).

Also, the use of a solution made of several cryoprotectants is currently being developed. It has been shown in experiments on mouse ovarian tissue that the use of several cryoprotectants is smaller concentration decreases their toxicity and also improves their efficiency (Zhang et al., 2010).

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