| Question |
Answer |
| This leaves tissue more receptive to staining than any other fixative reagent? |
Mercuric Chloride |
| This solution is isotonic exclusive of the formaldehyde, but may produce formalin pigment? |
10% Formalin Saline |
| Recommended especially for the fixation and preservation of phospholipids in tissues? |
Calcium Formalin |
| Recommended only for tissue of the CNS, especially when the Cajal astrocyte procedure is to be performed. This solution is very acidic, lyses RBC, and causes nuclei to give a direct positive Schiff reaction due to the Feulgen hydrolysis during fixation? |
Formalin Ammonium Bromide |
| This is probably one of the better formaldehyde solutions if one does not wish to prepare the buffered reagent? |
Acetate Formalin |
| Although this has been used widely as a fixative, it is not recommended because the solution becomes acidic after withdrawal from the storage bottle? |
10% Neutralized Formalin |
| This solution is recommended for routine formalin fixation. It has a pH of approximately 6.8 and it is hypotonic in the buffer ions present? |
10% Neutral Buffered Formalin (NBF) |
| This solution is isotonic in buffer ions and has a pH of approximately 7.2-7.4. It can be used as a dual purpose fixative, allowing electron microscopy on stored tissue? |
Modified Millonig Formalin |
| This solution is a compound fixative, but is categorized with the other formalin fixatives. It is useful as a fixative on tissue processors because in addition to fixation, the dehydrating process is also begun? |
Alcoholic Formalin |
| This solution is also an aldehyde, but it differs from formaldehyde in that it is a dialdehyde, with one aldehyde group on each end of the molecule? |
Glutaraldehyde |
| This additive fixative is not used frequently in the histopathology lab but is primarily used in the fixation of specimans for electron microscopy? |
Osmium Tetroxide |
| This is a very corosive chemical and all contact with metallic objects must be avoided if possible? |
Mercuric Chloride |
| This will attach to some lipids, rendering them insoluble, but it does not preserve lipids to the degree that osmium tetroxide does? |
Potassium Dichromate |
| Even though specimans for electron microscopy are fixed primarily in an aldehyde solution, they are post-fixed in this to ensure preservation of the lipids? |
Osmium Tetroxide |
| This chemical is unique in that it is the only substance used in histotechnique both as a fixative ingredient and as a stain? |
Picric Acid |
| This has recently found acceptance as a replacement for mercury since it does not have the associated hazards and it preserves tissue antigenicity, often making digestion procedures unnecessary. |
Zinc Salts |
| Rarely used alone for a fixation, Noncoagulant unless used in an acid solution, then it will act like chromic acid which is a coagulant. |
Potassium Dichromate |
| Superior nuclear detain and better paraffin infiltration are obtained with this than with formalin alone. |
Zinc Salts |
| Because less extraction of cellular elements occurs with this fixative, sectioning of the paraffin-embedded tissue may be slightly more difficult. |
Modified Millonig Formalin |
| Tissue may be stored indefinitely in this solution? |
Alcoholic Formalin |
| Techniques using Schiff reagent, such as periodic acid-Schiff (PAS) stain, cannot be used on tissue fixed with this solution because false-positive results are obtained. |
Glutaraldehyde |
| This is not used alone, but is used in compound fixatives because it is a very powerful protein coagulant and enhances staining by leaving the tissue very receptive to dyes. It's presence in tissue inhibits freezing, so frozen sections are difficult. |
Mercuric Chloride |
| This is most frequently used for the fixation of speciman's for electron microscopy as it preserves ultra-struture better than any of the aldehydes. It tends to overharden tissue, so fixation should not be prolonged for more than 2 hours. |
Glutaraldehyde |
| This can be used to fix small amounts of fat so that the fat will be maintained in sections during paraffin processing. |
Osmium Tetroxide |
| Because of the hazard associated with the use of this chemical, other metals have been tried as substitutes, but only zinc has found any acceptance. |
Mercuric Chloride |
| This is a sufficiently strong acid to hydrolyze nucleic acids. If stains for DNA and RNA are anticipated, any fixative containing this should be avoided. |
Picric Acid |
| A fixation pigment produced by this is one that cannot be prevented but can be removed. |
Mercuric Chloride |
| This preserves mitochondria by rendering the lipid component of the membranes insoluble in alcohol, but it readily dissolves DNA. |
Potassium Dichromate |
| This is a hypotonic and organic acid. In a dilute form, it is a common household chemical. Vinegar, which has been used for pickling for many years contains about 5% of this. |
Acetic Acid |
| This chemical causes less shrinkage to tissue even though it is hypertonic and not osmotically active. It preserves morphological details so that tissue is life-like. Penetrates rapidly but fixes slowly (up to 7 days). |
Formaldehyde |
| Since formaldehyde is not osmotically active, this solution is very hypotonic and may also produce formalin pigment. |
10% Aqueous Formalin |
| It's name means "bitter" in Greek. |
Picric Acid |
| A coagulating fixative that is toxic and explosive, penetrates tissue well, gives tissue a soft consistency and causes extreme shrinkage. (hypertonic effect) |
Picric Acid |
| This fixative is chemically stable and kept at room temperature. |
Formaldehyde |
Science Vocab 147928
