Fixation in histology slides - The Veterinary Site

Fixation in histology slides


Types Of Fixation:
(by MAAZ AHMED SIDDIQUI)
       Fixation of tissues can be done by two methods.
       PHYSICAL METHODS
       CHEMICAL METHODS
       PHYSICAL FIXATION:
       It includes methods like Heating,Microwaving and Freeze drying which are independent methods.
       HEAT FIXATION:
       In this method heat is used to kill the microorganisms.The slide is gripped by tongs and passed through Bunsen burner flame several times to kill the microbes.This method generally preserves the overall morphology but the internal structure might change.
NON-COAGULANT OR CROSS LINKED FIXATIVE:
These fixatives act by creating covalent bonds between proteins in tissues.This anchors the soluble protein to cytoskeleton and lends extra rigidity to the tissues.Preservation of transient or fine cytoskeletal structures is best achived by a pretreatment using microwave before Cross linked fixation.Example includes Formaldehyde,Glutaraldehyde and other aldehydes, metal salts like mercuric and zinc chloride and other compounds like Osmium tetraoxide.
      FORMALDEHYDE FIXATIVE
Formaldehyde in its 10% natural form is the most commonly used fixative in diagnostic pathology.Pure formaldehyde is a vapour that when dissolved in water form 37-40% Formaldehyde.This aqueous solution is known as Formalin.The usual 10% Formalin used in fixation of tissues contains 4% weight to volume of Formaldehyde.The reactions however are complex.
FORMALDEHYDE FIXATION: (continued)
In an aqueous solution formaldehyde forms Methylene Hydrate.It undergoes several side chain reactions to form reactive Hydroxymethyl side groups.
Formaldehyde also reacts with nuclear proteins and nucleic acids.penetrates between nucleic acid and  protein and stabilizes the nucleic acid and protein shell.
      GLUTARALDEHYDE FIXATION:
Less is known about its reaction mechanism in the fixation.But it is suggested that it reacts in the same way as does Formaldehyde.And it hasn’t been widely used in biological reactions or fixation.It is a functional Aldehyde that in aqueous form Polymerises forming Cyclic and oligomeric compounds.
Extensive cross linking by Glutaraldehyde results in better preservation of  Ultra structure but negatively impacts the
immunohistochemical methods and slows the penetration by Fixatives



Fixation in histology slides Fixation in histology slides Reviewed by Maaz ahmed siddiqui on 06 May Rating: 5

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