Braiton Lugano
more than 1 week ago
What is the fixation as applied in histology?
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more than 1 week ago
In histology, fixation refers to the process of preserving biological tissues by preventing decay and maintaining their structure and integrity. This is typically done by immersing the tissue in a fixative solution, such as formaldehyde or glutaraldehyde, which cross-links proteins and other molecules within the tissue to prevent degradation. Fixation is an essential step in preparing tissues for further processing and analysis, such as staining, sectioning, and microscopy.
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Google Gemini AI
more than 1 week ago
Fixation is a vital step in histology, where biological tissues are preserved for further analysis and study. It involves treating the tissue samples with chemical agents, known as fixatives, to halt biological processes, prevent deterioration, and preserve the cellular structures and molecules.
The primary objectives of fixation in histology are:
Coagulation: Fixatives cause the proteins in the tissue to coagulate or precipitate, creating a stable and rigid structure. This prevents enzymatic degradation and preserves the tissue's overall architecture.
Cross-linking: Some fixatives, such as formaldehyde, form cross-links between proteins and other molecules, further stabilizing the cellular structures. This helps maintain the tissue's integrity during subsequent processing.
Inactivation of Enzymes: Fixatives can inactivate endogenous enzymes that could lead to tissue autolysis or degradation. By suppressing enzymatic activity, fixatives help preserve the tissue's biochemical composition.
Preservation of Antigens: Fixation can preserve tissue antigens, which are important for immunohistochemical or immunolabeling techniques used in histology. Fixatives can prevent the denaturation of antigens and allow for their specific binding with antibodies.
Different fixatives have varying properties and are selected based on the intended applications and the nature of the tissue being preserved. Common fixatives used in histology include:
Formaldehyde: Widely used due to its ability to cross-link proteins and preserve tissue morphology. It is commonly used in a range of concentrations (4-10%).
Glutaraldehyde: A strong fixative that provides excellent preservation of ultrastructure. It is often used for electron microscopy.
Ethanol: An alcohol-based fixative that dehydrates the tissue and precipitates proteins. It is commonly used in combination with other fixatives.
Paraformaldehyde: A water-soluble form of formaldehyde that is less irritating and can penetrate tissues more easily.
Carnoy's Fixative: A mixture of ethanol, chloroform, and acetic acid that provides rapid fixation and good preservation of nucleic acids.
Bouin's Fixative: A mixture of picric acid, formaldehyde, and acetic acid that is commonly used for histological examination of embryos and fetuses.
Zamboni's Fixative: A mixture of picric acid, formaldehyde, and calcium chloride that is specifically designed for the preservation of neuroglia and nerve tissues.
The choice of fixative and fixation method depends on various factors, including the type of tissue, the desired level of preservation, and the downstream applications. The fixation process typically involves immersing the tissue sample in the fixative solution for a specific duration, followed by subsequent processing steps such as dehydration, embedding, and sectioning.
The primary objectives of fixation in histology are:
Coagulation: Fixatives cause the proteins in the tissue to coagulate or precipitate, creating a stable and rigid structure. This prevents enzymatic degradation and preserves the tissue's overall architecture.
Cross-linking: Some fixatives, such as formaldehyde, form cross-links between proteins and other molecules, further stabilizing the cellular structures. This helps maintain the tissue's integrity during subsequent processing.
Inactivation of Enzymes: Fixatives can inactivate endogenous enzymes that could lead to tissue autolysis or degradation. By suppressing enzymatic activity, fixatives help preserve the tissue's biochemical composition.
Preservation of Antigens: Fixation can preserve tissue antigens, which are important for immunohistochemical or immunolabeling techniques used in histology. Fixatives can prevent the denaturation of antigens and allow for their specific binding with antibodies.
Different fixatives have varying properties and are selected based on the intended applications and the nature of the tissue being preserved. Common fixatives used in histology include:
Formaldehyde: Widely used due to its ability to cross-link proteins and preserve tissue morphology. It is commonly used in a range of concentrations (4-10%).
Glutaraldehyde: A strong fixative that provides excellent preservation of ultrastructure. It is often used for electron microscopy.
Ethanol: An alcohol-based fixative that dehydrates the tissue and precipitates proteins. It is commonly used in combination with other fixatives.
Paraformaldehyde: A water-soluble form of formaldehyde that is less irritating and can penetrate tissues more easily.
Carnoy's Fixative: A mixture of ethanol, chloroform, and acetic acid that provides rapid fixation and good preservation of nucleic acids.
Bouin's Fixative: A mixture of picric acid, formaldehyde, and acetic acid that is commonly used for histological examination of embryos and fetuses.
Zamboni's Fixative: A mixture of picric acid, formaldehyde, and calcium chloride that is specifically designed for the preservation of neuroglia and nerve tissues.
The choice of fixative and fixation method depends on various factors, including the type of tissue, the desired level of preservation, and the downstream applications. The fixation process typically involves immersing the tissue sample in the fixative solution for a specific duration, followed by subsequent processing steps such as dehydration, embedding, and sectioning.
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