(M) HT Lab L1-L2

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Formalin

FIXATION

The standard 10% neutral buffered solution that penetrates tissue well but is relatively slow; considered the best overall fixative.

10% Formol-Saline

FIXATION

The simple aldehyde fixative specifically recommended for the fixation of central nervous tissues and the histochemical examination of post-mortem tissues.

10% Neutral Buffered Formalin

FIXATION

The aldehyde fixative that prevents the precipitation of acid formalin pigments, making it the best fixative for tissues containing iron pigments and for elastic fibers.

Formol-Corrosive (Formol-Sublimate)

FIXATION

The compound aldehyde fixative recommended for routine post-mortem tissues that preserves cytologic structures and blood cells well, but forms mercuric chloride deposits.

Glutaraldehyde

FIXATION

The aldehyde fixative used at 2.5% for small fragments or needle aspirates and 4% for larger tissues; considered the best fixative for routine light microscopy (LM) and electron microscopy (EM).

Mercuric chloride

FIXATION

The metallic fixative base that produces rapid and even fixation, permits brilliant staining of nuclear and connective tissue fibers, but has poor tissue penetration and forms pigment precipitates.

Zenker's Fluid

FIXATION

The metallic fixative containing glacial acetic acid (which gives it an affinity for nuclear chromatin); recommended for liver, spleen, connective tissue fibers, and nuclei.

Zenker-Formol (Helly's solution)

FIXATION

The metallic and cytoplasmic fixative recommended for pituitary gland, bone marrow, and blood-containing organs (e.g., spleen, liver); produces brown pigments due to RBC lysis if tissues are immersed for more than 24 hours.

Heidenhain's Susa solution

FIXATION

The metallic fixative known as an excellent cytologic and nuclear fixative, highly recommended for tumor biopsies of the skin.

Potassium dichromate

FIXATION

The 3% aqueous chromate fixative that preserves lipids and mitochondria at pH 4.5-5.2, and preserves cytoplasm, chromatin bodies, and chromosomes if acidified.

Chromic acid

FIXATION

The 1-2% aqueous chromate fixative that acts to precipitate proteins and preserve carbohydrates.

Regaud's (Moller's) Fluid

FIXATION

The chromate and cytoplasmic fixative recommended for the demonstration of chromaffin tissues (phaeochromocytoma), mitochondria, mitotic figures, Golgi bodies, RBCs, and colloid-containing tissues.

Orth's Fluid

FIXATION

The chromate and cytoplasmic fixative recommended for the demonstration and study of early degenerative processes and tissue necrosis.

Lead fixative (Lead acetate)

FIXATION

The 4% aqueous metallic fixative recommended for acid mucopolysaccharides and fixing connective tissue mucin, but forms an insoluble carbonate when exposed to carbon dioxide.

Picric Acid

FIXATION

The simple fixative used as a 1% strong saturated solution that is excellent for glycogen demonstration and imparts a yellow color for easy detection of small fragments, but is highly explosive when dry.

Bouin's solution

FIXATION

The picric acid-containing microanatomical and nuclear fixative that preserves glycogen and provides a useful yellow stain for small biopsy fragments, but removes ferric iron from blood pigments and causes RBC hemolysis.

Brasil's Alcoholic Picroformol Fixative

FIXATION

The microanatomical fixative considered excellent for glycogen preservation that is known to be better and less messy than Bouin's solution.

Alcohol

FIXATION

The group of simple fixatives typically used in 70-100% concentrations that act as both fixing and dehydrating agents by rapidly denaturing and precipitating proteins (lesser concentrations cause cell lysis).

100% Methyl alcohol

FIXATION

The simple alcoholic fixative recommended for fixing dry and wet smears, blood smears, and bone marrow tissues.

Ethyl alcohol

FIXATION

The alcoholic fixative used to fix blood, tissue films, and smears; it preserves glycogen, nucleoproteins, and nucleic acids, and is used for histochemistry and enzyme studies.

Carnoy's Fluid

FIXATION

The most rapid fixative (1-3 hours) recommended for fixing chromosomes, lymph glands, and urgent biopsies; provides good nuclear differentiation but dissolves fats, lipids, and myelin.

Alcoholic Formalin (Gendre's) Fixative

FIXATION

The alcoholic fixative that reduces fixation time to one-half, coagulates mucus (making it highly useful for sputum), and provides better preservation of glycogen.

Newcomer's Fluid

FIXATION

The simple fluid recommended for fixing mucopolysaccharides and nuclear proteins; it is classified as both a nuclear and a histochemical fixative.

Osmium tetroxide (Osmic Acid)

FIXATION

The simple pale yellow powder fixative that stabilizes conjugated fats and lipids permanently, is used for ultrathin sectioning in EM, fixes myelin well, but has an acid vapor that can cause conjunctivitis and blindness.

Flemming's Solution

FIXATION

The osmium tetroxide-based nuclear fixative that permanently fixes fat, is excellent for nuclear structures like chromosomes, and uniquely requires less than 10 times the volume of the tissue to be fixed.

Flemming's Solution Without Acetic acid

FIXATION

The osmium tetroxide-based cytoplasmic fixative that omits a specific acid in order to improve the cytoplasmic detail of the cell; recommended for structures like mitochondria.

Glacial Acetic acid

FIXATION

The simple fixative that solidifies at 17°C, fixes nucleoproteins and chromosomes, and counteracts tissue shrinkage by causing tissue swelling, but destroys mitochondria and Golgi elements.

Trichloroacetic acid

FIXATION

The simple fixative that precipitates proteins, counteracts tissue shrinkage, can be used as a weak decalcifying agent, and softens dense fibrous tissues.

Acetone

FIXATION

The histochemical and simple fixative used at ice-cold temperatures (-5°C to 4°C), recommended for the study of water-diffusible enzymes (e.g., phosphatases and lipases) and used in fixing brain tissues for the diagnosis of rabies.

Heat

FIXATION

The physical (non-chemical) method of fixation that utilizes thermal coagulation of tissue proteins, employed for frozen tissue sections and the preparation of bacteriologic smears.

Formalin with "Post-Chroming"

FIXATION

The compound fixative technique classified under cytoplasmic fixatives that involves primary fixation in formalin followed by secondary preservation in a chromate solution (without glacial acetic acid).

Ethyl alcohol (Ethanol)

DEHYDRATION

What is the best dehydrating agent recommended for routine dehydration that mixes with water and many inorganic solvents?

Methyl alcohol (Methanol)

DEHYDRATION

Which dehydrating agent is primarily used for blood and tissue films, and for smear preparations, but is toxic to the body?

Butyl alcohol

DEHYDRATION

Which slow dehydrating agent is utilized in plant and animal micro-techniques because it produces less shrinkage and hardening than ethanol?

Anhydrous Copper Sulfate

DEHYDRATION

What substance serves as an indicator to ensure complete dehydration and accelerates the process by removing water from the dehydrating fluid?

Acetone

DEHYDRATION

Which cheap, rapid-acting dehydrating agent is used for urgent biopsies (½ to 2 hours) and is more miscible with epoxy resins than alcohol, despite being highly volatile, removing lipids, and causing considerable shrinkage?

Dioxane (Diethylene Dioxide)

DEHYDRATION

Which excellent dehydrating and clearing agent produces less tissue shrinkage and allows tissues to be left in it for long periods, but has a toxic vapor and causes tissues to ribbon poorly?

Running tap water

DEHYDRATION

What must tissues treated with a chromate fixative (e.g., Regaud's or Moller's fluid) be thoroughly washed in prior to treatment with Dioxane to remove the chromate?

Dioxane, Anhydrous Calcium oxide, Water, Calcium oxide, and Quicklime

DEHYDRATION

In Weiseberg's Method for dehydration, what specific chemicals are used to process the tissue wrapped in a gauze bag?

Cellosolve (Ethylene Glycol Monoethyl Ether)

DEHYDRATION

Which rapid dehydrating agent allows tissues to be stored for months without producing hardening or distortion, but is toxic and combustible at 110-120°F?

Triethyl Phosphate

DEHYDRATION

Which dehydrating agent removes water very readily, produces minimum shrinkage, and is specifically used to dehydrate sections and smears following certain stains?

Tetrahydrofuran (THF)

DEHYDRATION

Which agent both dehydrates and clears tissues, dissolves many substances including fats, and improves most staining procedures, but has an offensive odor and may cause conjunctival irritation?

Nitric acid

DECALCIFICATION

What is the most commonly used and fastest acid decalcifying agent that is recommended for routine purposes, though it can inhibit nuclear stain and destroy tissues?

10% Aqueous Nitric acid solution and Formol-Nitric acid

DECALCIFICATION

Which two specific rapid-acting acid decalcifying solutions impart a yellow color with Nitrous acid, which can impair the staining reaction of tissues?

Perenyi's Fluid

DECALCIFICATION

Which slow decalcifying agent for dense bones also softens tissues simultaneously?

Phloroglucin-Nitric acid

DECALCIFICATION

What is the most rapid decalcifying agent, which requires the acid to be subsequently removed by 3 changes of 70% to 90% ethanol?

Hydrochloric Acid

DECALCIFICATION

Which slow decalcifying acid produces good nuclear staining but causes greater tissue distortion on the decalcified section?

Formic Acid

DECALCIFICATION

What is the only weak acid used extensively as a primary decalcifying agent, providing better nuclear staining and less tissue distortion for routine postmortem or research tissues?

Sodium Citrate

DECALCIFICATION

In Formic Acid-Sodium Citrate solution, what chemical accelerates decalcification by chelating the calcium?

Trichloroacetic Acid

DECALCIFICATION

Which weak, very slow-acting acid provides good nuclear staining and does not require washing out?

Sulfurous Acid

DECALCIFICATION

Which specific chemical is classified as a very weak decalcifying agent?

Chromic acid (Flemming's fluid)

DECALCIFICATION

Which fluid acts as both a fixative and decalcifying agent, but inhibits nuclear staining with hematoxylin, undergoes reduction, and forms insoluble pigments when dehydrated with alcohol?

Citric Acid-Citrate Buffer solution (pH 4.5)

DECALCIFICATION

Which agent produces excellent nuclear and cytoplasmic staining without cell or tissue distortion, but acts as a too-slow decalcifying agent?

Von Ebner's fluid

DECALCIFICATION

Which moderately rapid acting fluid does not require washing out before dehydration?

Ethylenediaminetetraacetic acid (EDTA)

DECALCIFICATION

What is the most common chelating agent used for detailed microscopic studies that binds calcium to form an insoluble non-ionized complex, offering excellent staining results but acting very slowly?

Ion-exchange Resins

DECALCIFICATION

What substance hastens decalcification by removing calcium from formic acid-containing solutions, but is not recommended for fluids containing mineral acids like Nitric or Hydrochloric acid?

Concentrated NH4OH and Saturated (NH4)2C2O4

DECALCIFICATION

When measuring the extent of decalcification chemically (detecting calcium via precipitation), what specific solutions are added to the discarded fluid?

Saturated Li2CO3 / 5-10% NaHCO3

POST-DECALCIFICATION

To reduce the effects of decalcifying agents on staining, what chemicals are used to immerse the decalcified bone?

Formol saline w 15% sucrose / PBS w 15-20% sucrose

POST-DECALCIFICATION

What fluids are used for storing decalcified tissues during post-decalcification at 4°C?

Perenyi's fluid, 4% Aqueous Phenol, Molliflex, 2% HCl, and 1% HCl in 70% alcohol.

POST-DECALCIFICATION

Which specific reagents and fluids are used explicitly as tissue softeners?