FREE ESSAY ON MAD COW

MAD COW

Who would of thought that eating hamburgers, steaks and drinking milk could produce an
epidemic disease? These types of food are frequently eaten for their appealing tastes and
nutritional values. The discovery of Creutzfeld Jakob Disease (CJD) has been a long and
remarkable one. The cause of this disease is a mutated prion protein within the brain
that can be either inherited or acquired. These mutations create sponge like holes that
destroy the brain. As a result, the disorder gives both behavioural and muscular problems
to infected individuals Experiments and discoveries to this disease have led to a further
understanding of the diversity of proteins. 
In the 1960s, D. Carleton Gadjusek studied the behaviour of a native population in Papua,
New Guinea. This population had been eating the brains of dead relatives and as a result,
contracted a fatal neurodegenerative disease. When autopsies were taken from the
population who died, they appeared to have a distinct pathology. The central brain tissue
resembled a sponge with a lot of regions containing microscopic holes. The results of
this disease appeared similar to persons affected with CJD. 
In 1968, D. Carleton Gadjusek injected an infected biopsy of brain with this disorder
into a laboratory animal. As a result, the animal developed this disease. At this time,
the biopsy was thought to contain a virus. 
At the University of California, Stanley Pruisner and colleagues proposed that agent for
this disease was a prion. A prion is a protein version of viruses without the genetic
information. Once the prion has entered the body, the normal proteins are mutated. The
gene for the normal protein is expressed within normal brain tissue and encodes a protein
that resides at the surface of nerve cells. The function is unknown. The mutated prion
version of the protein accumulates within nerve cells, forming aggregates that kill
cells. The normal protein is soluble in salt solution and is destroyed by protein-eating
molecules, known as enzymes. However, the mutated prion protein is insoluble and the
protein digestion. 
Based on these differences, one might expect these two forms of the prion protein to be
composed distinctly different sequences of amino acids, but this is not the case. Prions
are proteins, a diverse group of macromolecules. Proteins are capable of a wide variety
of functions and activities. This is due to the great variety of structures. Proteins are
polymers of amino acids known as polypeptides. These amino acids are the structural
building blocks of proteins. Amino acids have a single carbon linked to: an amino group,
a carboxylic acid group and a side chain. These side chains vary in structure and
determine the chemical properties of the amino acids. 
Each protein has a unique and highly ordered structure that is highly specific with the
molecules it interacts with. The assortment of the twenty amino acids are important
because of the activities the protein can perform in terms of both the intramolecular
interactions and intermolecular interactions. Intramolecular interactions are the forces
within a molecule. It could be thought of as intramural collegiate activities,
interactions within a molecule. Intermolecular interactions could be thought of as
intermediate collegiate activities, interactions outside the molecule and this. 
During the process of protein synthesis for the normal and mutated prion, special bonds
known as peptide bonds form a polypeptide chain. There are several levels of organization
that can describe the structure and reactivity of this prion protein. The primary
structure is the specific linear sequence of amino acids that constitute the chain. For
both the normal and mutated proteins, the primary structure is the same. This sequence of
amino acids is very important in both the structure and function of the proteins. 
Even though the primary structure of any protein is unique, the secondary structure of
many different proteins can be the same. These are selected regions that have protein
structures that are repeated throughout the polypeptide chain. In terms of the secondary
structure, both the normal and mutated proteins are still the same. With respect to the
secondary structure, hydrogen bonding is a very important type of intermolecular force
that determines the structure. One type is the alpha helix that is a right-handed coil
that is threaded in the same direction as a standard wood screw. The helical structure of
a polypeptide results from hydrogen bonds between elements of peptide bonds that are
distributed along the backbone of the chain. Another type of is beta-pleated sheet that
are completely extended and lie next to one another. They are stabilized by hydrogen
bonds between the elements of the peptide linkage. 
Tertiary structure of proteins is a result of the folding and twisting of polypeptides
through intermolecular interactions. This results in the creation of specific shapes of
polypeptide molecules. The intermolecular interactions are a result of hydrogen, ionic
and covalent interactions. The chemical nature of side chains on individual amino acid
determines how the molecule folds and packs in three dimensions. At this point, this is
where the normal and mutated proteins differ in their structure. Moreover, both proteins
have the same primary and secondary structure, however, it is the tertiary structure that
is different. This level of organization changes the role that the protein plays in an
organism; from normal protein to a life-threatening mutated protein. 
The mutated prion protein can be both inherited and acquired. When the mutated prion is
an organism, the normal prions are mutated. Stanley Pruisner proposed a mechanism where
mutated prion protein acts as a template for the normal protein to mutate. The mutated
prion protein happens to be susceptible to folding incorrectly normal proteins and this
accumulation happens to cause the death of cells in which it occurs. In an experiment to
test this mechanism, the addition of a small amount of normal prions with small amount
mutated prions form, showed that all of the components were expressed as the mutated
form. Thus, the mutated prion protein initiates a chain reaction that mutates the normal
prion. 
In the late 1980s and early 1990s, scientists believed that mad cow disease (scientific
name Bovine Spongiform Encephalopathy, BSE) only affected cattle. At this point, the mad
cow disease was believed to be an inherited disorder. However, during the mid-1990s, a
deadly version of mad cow disease known as Creutzfeldt-Jakob disease (vCJD) infected the
people of UK. After this incident, experts believed the disease was also transmitted
through the food chain. To date, fifty-six people in the U.K. died by vCJD. 
Several scientists in England and Switzerland have been studying the scrapie disease, a
disease similar to vCJD and BSE, in mice. In the experiment, mutated prions were injected
into the bellies of mice. The prions initially infected the spleen and lymph. Signals
were initiated from a molecule called Lymphotoxin (LT) alpha/beta on the surface of
immune cells to the spleen and lymph's immune cells. These signals mutated the normal
prions to the disease-causing ones. If these signals were somehow blocked, then the
normal prions will not be mutated. Scientists tested this hypothesis by injecting a
molecule that forms a bond to lymphotoxin-alpha/beta into the injected mice. The molecule
blocked any signals from immune cells to the spleen and lymph's immune cells. By
preventing the prion from mutation, the disease did not spread as fast. In addition, when
the mutated prion was blocked from the central nervous system, there will be no sign of
the disease. As a result, the mice who were treated with this molecule seem to develop
the scrapie disease much later than the untreated mice. 
Even though scientists have not developed a cure for the disease, these findings show a
lot of promise to the medical community. If the disease is treated at its initial stages,
the disease could be suppressed and eventually it could be cured. Ultimately, each new
discovery about a disease is a step closer to the ultimate goal, a cure for a disease. 
Bibliography
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