Introduction: tracks. Astrocytes help to maintain the blood

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Last updated: May 13, 2019

Introduction:Glial Fibrillary Acidic Protein (GFAP) is found in cells ofthe Central Nervous System, and is an intermediate filament, meaning it takespart in the communication between cells via gap junctions, as well asmaintaining the blood/brain barrier in the brain.

Thus, it is expected that therewill be an abundance of GFAP in astrocytes. The purpose of this experiment wasto learn how to use immunohistochemistry (a technique using a labelled specificantigen/antibody reaction to identify individual tissue components) in order torecognise the distribution of GFAP in sections of the adult mouse brain. (95/100)Materials andMethods:The protocol followed during this practical is attached andwas followed exactly as described with the exception of the addition of toomuch DPX (more than two drops used) leading to difficulty in seeing parts of thesample clearly through a microscope. During the practical itself, the instructormade a few changes to the method, including washing the slide in TBS for only 3minutes during step 5, and leaving the slide in the Haematoxylin for 15 secondsinstead of 30 in step 8. (84/100)Results:It was expected that nearly every astrocyte would be stainedwith GFAP, however, the actual proportion of astrocytes stained was less whenlooked at under a microscope. The reason is discussed in the conclusionssection. At a magnification of x4, it wasseen that the cerebral cortex in mice was smaller and less complex than inhumans, but the Olfactory bulb was larger.

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However, it was clear to see theHippocampus was stained very blue with Haematoxylin due to it being heavilynucleated. At a greater magnification, two different classes ofastrocytes were seen: fibrous and protoplasmic. Fibrous astrocytes are longerand thinner than the star-shaped protoplasmic astrocytes; the former was muchmore abundant in the observed specimen.

It was observed that fibrous astrocytesare associated with white matter specifically in the fornix and corpus callosum,where there is an abundance of nerve fibre tracks. Astrocytes help to maintainthe blood brain barrier and regulate action potential transmission within thebrain. Astrocytes are closely associated with blood vessels that were alsovisible through the microscope. Also seen were the astrocyte foot processes, whichmake up the glia limitans, (appears as a thin brown border).(196/200)        Conclusions:Although it was expected that most astrocytes would bestained with GFAP, only a small proportion of the total astrocytes were visibledue to the shortage of time. Furthermore, seeing the detailed differencesbetween fibrous and protoplasmic astrocytes was not expected due to GFAPstaining being unable to do so, but with more time, various techniques such asantigen retrieval could have been used to identify most of these astrocytes. Although the glia limitans was seen bordering the brain, itwas 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 inastrocytes, although due to timing, the actual percentage of GFAP present inmouse brains was unable to be identified.Introduction:Glial Fibrillary Acidic Protein (GFAP) is found in cells ofthe Central Nervous System, and is an intermediate filament, meaning it takespart in the communication between cells via gap junctions, as well asmaintaining the blood/brain barrier in the brain. Thus, it is expected that therewill be an abundance of GFAP in astrocytes.

The purpose of this experiment wasto learn how to use immunohistochemistry (a technique using a labelled specificantigen/antibody reaction to identify individual tissue components) in order torecognise the distribution of GFAP in sections of the adult mouse brain. (95/100)Materials andMethods:The protocol followed during this practical is attached andwas followed exactly as described with the exception of the addition of toomuch DPX (more than two drops used) leading to difficulty in seeing parts of thesample clearly through a microscope. During the practical itself, the instructormade a few changes to the method, including washing the slide in TBS for only 3minutes during step 5, and leaving the slide in the Haematoxylin for 15 secondsinstead of 30 in step 8. (84/100)Results:It was expected that nearly every astrocyte would be stainedwith GFAP, however, the actual proportion of astrocytes stained was less whenlooked at under a microscope. The reason is discussed in the conclusionssection. At a magnification of x4, it wasseen that the cerebral cortex in mice was smaller and less complex than inhumans, but the Olfactory bulb was larger. However, it was clear to see theHippocampus was stained very blue with Haematoxylin due to it being heavilynucleated.

At a greater magnification, two different classes ofastrocytes were seen: fibrous and protoplasmic. Fibrous astrocytes are longerand thinner than the star-shaped protoplasmic astrocytes; the former was muchmore abundant in the observed specimen. It was observed that fibrous astrocytesare associated with white matter specifically in the fornix and corpus callosum,where there is an abundance of nerve fibre tracks. Astrocytes help to maintainthe blood brain barrier and regulate action potential transmission within thebrain. Astrocytes are closely associated with blood vessels that were alsovisible through the microscope. Also seen were the astrocyte foot processes, whichmake up the glia limitans, (appears as a thin brown border).(196/200)        Conclusions:Although it was expected that most astrocytes would bestained with GFAP, only a small proportion of the total astrocytes were visibledue to the shortage of time.

Furthermore, seeing the detailed differencesbetween fibrous and protoplasmic astrocytes was not expected due to GFAPstaining being unable to do so, but with more time, various techniques such asantigen retrieval could have been used to identify most of these astrocytes. Although the glia limitans was seen bordering the brain, itwas 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 inastrocytes, although due to timing, the actual percentage of GFAP present inmouse brains was unable to be identified. 

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