Practical - 2: Preparation of The Fixative
Practical - 2: Preparation of The Fixative
Practical - 2: Preparation of The Fixative
To avoid the formation of formic acid, marble chips (calcium carbonate) should be added to
This is a rapid fixative. Generally tissues contain some fat which hinders and slow
down
the penetration of fluids. The chloroform
dissolves the fat and allows the penetration of the fixatives.
Fixation is:
A chemical process by which biological tissues are preserved from decay, thereby preventing autolysis or putrefaction. Fixation terminates any ongoing
biochemical reactions, and may also increase the mechanical strength or stability of the treated tissues.
Chemical fixatives are used to preserve tissue from degradation, and to maintain the structure of the cell and of sub-cellular components such as cell
organelles
(e.g., nucleus, endoplasmic reticulum, mitochondria).
How to fix..!?
The most common fixative for light microscopy is 10% neutral buffered formalin
.Tissues should be fixed in 10 % neutral buffered formalin (NBF) and placed in a plastic
container of suitable size with a wide neck and a tight fitting lid.
It is important to use the correct amount of fixative for the size of the sample. Ideally a
block of tissue approximately 2x1x1cm should be placed in a pot containing
approximately 50-60 ml of fixative.
Larger samples can be fixed provided they are placed in a container in which the
volume of fixative is approximately 10 times the volume of the tissues.
NOTE... This 100ml container is ideal for most samples. Containers with narrow
necks .Should be avoided because it is difficult to remove samples which may have
been squeezed in when still fresh.
aims of fixation:
2- http://www.youtube.com/watch?feature=player_detailpage&v=1z5j12q2PAw
3- http://www.youtube.com/watch?feature=player_detailpage&v=QEPMRAzBfEg
4- http://www.youtube.com/watch?feature=player_detailpage&v=Xv3MdHjpmkc