Saturday, November 7, 2009

Mechanism of Parkinson's Disease

 Parkinson's disease is a neurological disease.
Participation of Niger locus (the heart of nigrostriatal brain's gray matter) resulting in lack of secretion of dopamine (neurotransmitter) involved in regulating movement. Lack of dopamine is the result of the destruction of neurons (nigrostriatal), which usually produces dopamine (dopaminergic neurons).
Historically, these lesions cause a decrease in dopamine secretion identified by Tretyakov in the medical thesis, he remained in Paris in 1919, about a century after the pioneering work of Parkinson's disease.

To understand this phenomenon, it is necessary to remember more about the first of neurons and neurotransmitters. Everyone knows that the brain consists of tens of billions of cells called neurons that communicate with each other through a very complex network. In other words, each neuron has the ability to receive information from thousands of other neurons, and in turn sends the new information received. This information is transmitted from one neuron to another by a joint (that is, in some kind of junction between two neurons) are called synapses. In other words, the synapse is a small space between two neurons and nerve impulses must pass. This crossing can be done only if the first neuron releases chemicals called neurotransmitters, which will be recognized by the neurons, and so on. This explains a little more than 50 neurotransmitters. Everyone has heard of the adrenaline, noradrenaline, acetylcholine, glutamate and dopamine is of course a matter of our concerns related to Parkinson's disease.
Returning to the substantia nigra neurons that secrete dopamine. Therefore, the dopaminergic neurons.
The number of neurons at this level is about 400 000. Knowing that there are tens of billions in the brain, we can imagine that this figure is very low.
We are now talking about other parts of the brain called the striatum. The striatum is a part of the basal ganglia of the brain. A core is gray gray mass of cells (usually present in the periphery to the cerebral cortex) in the middle of this white substance, like a seed planted in citrus pulp.

The relationship between the substantia nigra and the striatum is via an extension of the cell body located in the substantia nigra. In other words, there is communication between the two regions through the expansion of the neurons of the body (the main part of the neurons) are located in the substantia nigra.
Each neuron is located in the substantia nigra has several thousands of terminals with synapses. In this way, all the information arrives in the striatum is very high given the large number of synapses.
 
The number of neurons in the substantia nigra in patients not suffering from Parkinson's disease is about half a million. In Parkinson's disease, this number has gradually decreased. Initially some of the remaining neurons still have the ability to remove dopamine in adequate quantity for the patient presents no serious symptoms. But as to measure the evolution of the disease, these neurons are no longer able to provide, to bring enough dopamine in the striatum, which is used to function properly. In Parkinson's disease, which gradually inappropriate activation of the striatum. This dysfunction (damage) is not related to the number of receptors in the striatum, because they are in the quantity and quality. The problem is the number of neurons in the gray and inadequate because it produces abnormally low dopamine. Looked under the microscope of the substantia nigra, we see that the number of neurons is very low, which causes pale substantia nigra. Reduced number of neurons does not irregular. Indeed, there is a part of the substantia nigra and ± Neuron-rich, while other regions did not neurons.

Microscopic examination also helps to highlight another anomaly. There was the existence of Lewy bodies. Lewy is a neurologist who first described these bodies. A neurologist specializing in neurology studying the mechanisms of certain neurological diseases by examining cells that have failed and most often seen under the microscope. Small inclusions of Lewy bodies (foreign) which is found in neurons, round. For specialists: they are the center with hyaline eosinophilic and surrounded by a clear halo.

It is estimated that the destruction, which is a type of apoptosis (genetically programmed death) of neurons is about half before the first symptoms of Parkinson's disease appears. At the end of life, destruction affects approximately 80% stake in neurons of patients.
When neurons were observed in a phase of apoptosis by electron microscopy, we find that they have the following changes. First came the removal of body cells and condensation and fragmentation (fragmentation) of chromatin (the grouping of chromosomes in the nucleus). There was other damage cellular organelles such as endoplasmic reticulum and mitochondria, among others.

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