Tissue Fixation Methods

Additive Fixation

Chemical constituents are taken into the tissue and become part of it, chemically reacting with tissue components to stabilize them for examination.

Non-Additive Fixation

The fixing agent stabilizes tissue by altering its chemical or physical properties without being incorporated into the tissue.

Duration of Fixation: 2-6 hours

Time frame within which tissue samples should be fixed to ensure proper preservation of structures.

Simple Fixatives

Fixatives composed of only one chemical component, used for specific desired effects without mixing multiple agents.

Compound Fixatives

Fixatives consisting of two or more chemical components, allowing for a broader range of tissue preservation and specific reactions.

Microanatomical Fixatives

Preserve tissue structures for microscopic study without altering their patterns or relationships.

Cytoplasmic Fixatives

Fixatives that specifically preserve cytoplasmic structures, excluding glacial acetic acid to avoid interference.

Histochemical Fixatives

Preserve cell and tissue constituents for specific staining methods in histochemistry, facilitating detailed biochemical studies.

Digitonin

A fixative used to demonstrate cholesterol in tissues.

Imidazole Osmium Tetroxide

An improved fixative for showing lipids in tissues at an ultrastructural level, enhancing lipid membrane preservation.

Alcoholic Fixatives

Recommended for fixing glycogen to preserve this carbohydrate in tissue samples.

Carbohydrate Fixation

Focuses on preserving carbohydrates like glycogen in tissues for examination.

Glycogen Fixation

Specifically preserves glycogen, a crucial energy-storage molecule in cells.

Rossman's Fluid / Cold Absolute Alcohol

Considered the most useful fixatives for glycogen preservation in tissue samples.

70% Alcohol

Used to restore the natural color of tissue samples post-fixation.

10% Formol-Saline

A simple microanatomical fixative recommended for central nervous system tissues and post-mortem examinations.

10% Neutral Buffered Formalin

A widely used fixative for long-term storage of surgical, post-mortem, and research specimens.

Formal-Corrosive

Recommended for routine post-mortem tissues to preserve structures and prevent degradation.

Alcoholic Formalin (Gendre's Fixative)

A combination fixative enhancing immunoperoxidase studies and electron microscopy results.

Glutaraldehyde

Widely used in electron microscopy to preserve fine cellular details.

Mercuric Chloride

A common metallic fixative that can leave black deposits on tissues, requiring proper washing for removal.

Heidenhain's Susa

Recommended for fixing tumor biopsies, particularly skin samples.

Zenker's Fluid

Contains mercuric chloride and glacial acetic acid, used for fixing liver, spleen, and connective tissue fibers.

Zenker-Formol

A microanatomical fixative suitable for organs like the pituitary gland, bone marrow, spleen, and liver.

B-5 Fixative

Commonly used for bone marrow biopsies due to its ability to preserve cellular details.

Orth's Fluid

Recommended for studying early degenerative processes, tissue necrosis, and infections like Rickettsia.

Regards (Muller's) Fluid

Preserves chromatin, mitochondria, and other cellular organelles but may deteriorate due to its acidic nature.

Lead Fixatives

Primarily used for preserving acid mucopolysaccharides in connective tissues.

Picrate Fixatives

Highly explosive when dry, producing excessive yellow staining.

Bouin's Solution

Recommended for fixing embryos and pituitary biopsies due to its strong preserving properties.

Brasil's Alcoholic Picroformol Fixative

An excellent fixative for glycogen preservation, less messy and more efficient than Bouin's solution.

Glacial Acetic Acid

Fixes nucleoproteins and counteracts shrinkage caused by other fixatives.

Alcoholic Fixatives (General)

Work by destroying hydrogen bonds, potentially causing glycogen granule polarization.

Methanol

Excellent for fixing blood and bone marrow smears, effective for dry and wet smears.

Ethanol

Used in cytologic smears, with lower concentrations capable of lysing red blood cells.

Carnoy's Fluid

Recommended for urgent biopsies, especially chromosomes, lymph glands, brain tissues, and rabies diagnosis.

Alcoholic Formalin

Useful for preserving sputum samples in respiratory diagnostics.

Newcomer's Fluid

Specialized fixative for preserving mucopolysaccharides and nuclear proteins.

Osmium Tetroxide Fixatives

Should be stored in dark bottles to prevent evaporation and reduction by sunlight, affecting tissue staining.

Flemming's Solution

Recommended for nuclear preparation, fixing nuclear structures including lipids.

Trichloroacetic Acid

Weak decalcifying agent for tissue sample preparation before sectioning.

Acetone

Commonly used for diagnosing rabies and preserving water-soluble enzymes.

Secondary Fixation

Placing tissues in a second fixative to enhance preservation for specific staining techniques.

Washing-Out Process

Removing excess fixative from tissues post-fixation to prevent artifacts.

Tap Water

Used to remove excess chromate, formalin, or osmic acid from fixed tissues.

50-70% Alcohol

Utilized to remove excess picric acid from tissues fixed in Bouin's solution.

Alcoholic Iodine

Used to remove excess mercuric chloride from tissues to prevent black deposits.