Introduction: tracks. Astrocytes help to maintain the blood

Introduction:

Glial Fibrillary Acidic Protein (GFAP) is found in cells of
the Central Nervous System, and is an intermediate filament, meaning it takes
part in the communication between cells via gap junctions, as well as
maintaining the blood/brain barrier in the brain. Thus, it is expected that there
will be an abundance of GFAP in astrocytes. The purpose of this experiment was
to learn how to use immunohistochemistry (a technique using a labelled specific
antigen/antibody reaction to identify individual tissue components) in order to
recognise the distribution of GFAP in sections of the adult mouse brain.

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(95/100)

Materials and
Methods:

The protocol followed during this practical is attached and
was followed exactly as described with the exception of the addition of too
much DPX (more than two drops used) leading to difficulty in seeing parts of the
sample clearly through a microscope. During the practical itself, the instructor
made a few changes to the method, including washing the slide in TBS for only 3
minutes during step 5, and leaving the slide in the Haematoxylin for 15 seconds
instead of 30 in step 8.

(84/100)

Results:

It was expected that nearly every astrocyte would be stained
with GFAP, however, the actual proportion of astrocytes stained was less when
looked at under a microscope. The reason is discussed in the conclusions
section.

At a magnification of x4, it was
seen that the cerebral cortex in mice was smaller and less complex than in
humans, but the Olfactory bulb was larger. However, it was clear to see the
Hippocampus was stained very blue with Haematoxylin due to it being heavily
nucleated.

At a greater magnification, two different classes of
astrocytes were seen: fibrous and protoplasmic. Fibrous astrocytes are longer
and thinner than the star-shaped protoplasmic astrocytes; the former was much
more abundant in the observed specimen. It was observed that fibrous astrocytes
are associated with white matter specifically in the fornix and corpus callosum,
where there is an abundance of nerve fibre tracks. Astrocytes help to maintain
the blood brain barrier and regulate action potential transmission within the
brain. Astrocytes are closely associated with blood vessels that were also
visible through the microscope. Also seen were the astrocyte foot processes, which
make up the glia limitans, (appears as a thin brown border).

(196/200)

 

 

 

 

 

 

 

 

Conclusions:

Although it was expected that most astrocytes would be
stained with GFAP, only a small proportion of the total astrocytes were visible
due to the shortage of time. Furthermore, seeing the detailed differences
between fibrous and protoplasmic astrocytes was not expected due to GFAP
staining being unable to do so, but with more time, various techniques such as
antigen retrieval could have been used to identify most of these astrocytes.

Although the glia limitans was seen bordering the brain, it
was not seen on the surface of the frontal cortex as would have been expected.
This may have been because it had been cut off during the dissection process.

Overall, it can be concluded that GFAP is abundant in
astrocytes, although due to timing, the actual percentage of GFAP present in
mouse brains was unable to be identified.Introduction:

Glial Fibrillary Acidic Protein (GFAP) is found in cells of
the Central Nervous System, and is an intermediate filament, meaning it takes
part in the communication between cells via gap junctions, as well as
maintaining the blood/brain barrier in the brain. Thus, it is expected that there
will be an abundance of GFAP in astrocytes. The purpose of this experiment was
to learn how to use immunohistochemistry (a technique using a labelled specific
antigen/antibody reaction to identify individual tissue components) in order to
recognise the distribution of GFAP in sections of the adult mouse brain.

(95/100)

Materials and
Methods:

The protocol followed during this practical is attached and
was followed exactly as described with the exception of the addition of too
much DPX (more than two drops used) leading to difficulty in seeing parts of the
sample clearly through a microscope. During the practical itself, the instructor
made a few changes to the method, including washing the slide in TBS for only 3
minutes during step 5, and leaving the slide in the Haematoxylin for 15 seconds
instead of 30 in step 8.

(84/100)

Results:

It was expected that nearly every astrocyte would be stained
with GFAP, however, the actual proportion of astrocytes stained was less when
looked at under a microscope. The reason is discussed in the conclusions
section.

At a magnification of x4, it was
seen that the cerebral cortex in mice was smaller and less complex than in
humans, but the Olfactory bulb was larger. However, it was clear to see the
Hippocampus was stained very blue with Haematoxylin due to it being heavily
nucleated.

At a greater magnification, two different classes of
astrocytes were seen: fibrous and protoplasmic. Fibrous astrocytes are longer
and thinner than the star-shaped protoplasmic astrocytes; the former was much
more abundant in the observed specimen. It was observed that fibrous astrocytes
are associated with white matter specifically in the fornix and corpus callosum,
where there is an abundance of nerve fibre tracks. Astrocytes help to maintain
the blood brain barrier and regulate action potential transmission within the
brain. Astrocytes are closely associated with blood vessels that were also
visible through the microscope. Also seen were the astrocyte foot processes, which
make up the glia limitans, (appears as a thin brown border).

(196/200)

 

 

 

 

 

 

 

 

Conclusions:

Although it was expected that most astrocytes would be
stained with GFAP, only a small proportion of the total astrocytes were visible
due to the shortage of time. Furthermore, seeing the detailed differences
between fibrous and protoplasmic astrocytes was not expected due to GFAP
staining being unable to do so, but with more time, various techniques such as
antigen retrieval could have been used to identify most of these astrocytes.

Although the glia limitans was seen bordering the brain, it
was not seen on the surface of the frontal cortex as would have been expected.
This may have been because it had been cut off during the dissection process.

Overall, it can be concluded that GFAP is abundant in
astrocytes, although due to timing, the actual percentage of GFAP present in
mouse brains was unable to be identified. 

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