(PALM 306) Exam 3 objectives Flashcards
Overview of fixation Aqueous Fixatives
Acetic Acid (6)
-Non additive, Coagulant
-Reacts with nucleic acids
-rapid penetration rate
-lyses RBCS, causes cellular swelling, can dissolve calcifications due to acidity and leach iron
-used to counteract shrinking effects of other fixatives
-common household chemical, used under fume hood, stored in chemical cabinet
Picric Acid (11)
-additive coagulant
-reacts with nucleic acids by denaturing and solubilizing
-reacts w proteins by inhibiting enzyme activity
-reacts with carbohydrates, particularly glycogen
-very slow penetrations’ rate
-causes extreme shrinkage
-can dissolve small calcification and leach iron
-must be rinsed out with alcohol or will result in poor staining
-used a fixative and stains yellow
-used for trichrome staining because it is receptive to dyes
-explosive in dry form
Chromic Acid (5)
-Additive Coagulant
-slow penetrations’ rate
-reacts with nucleic acids and proteins
-reacts with carbohydrate by oxidizing them
-reacts with lipids by insolulizing them
Zinc Salts (6)
-Additive Coagulant
-use a replacement for mercury
-used for advance staining
-can clog processor lines, use 5-20% acetic acid to remove. Prevent by using a formulation that is approved routine processing
-forms in tissue
-zinc sulfate is preferred over zinc chloride because it is not as toxic/hazardous
Cupric Salts (3)
-Additive Coagulant
-stabilized RBC membranes
-added to fixatives to prevent lysis of RBCs
Mercuric Chloride (7)
-Additive Coagulant
-reacts with nucleic acids and proteins
-has exceptional nuclear detailing, inhibits enzyme activity
-mercury pigmentation cannot be prevented, but can be removed using iodine, then rinsing with sodium thiosulfate
- used for hematopoietic tissues and lymphoid tissues
-rarely used today due to health hazards
-very corrosive, health hazard, toxic, special documentation and disposal required
Potassium dichromate (9)
- Additive non coagulant, unless used on acid solution, then acts as chromic acid
-reacts with nucleic acids by solubilizing them, reacts with proteins and carbohydrates
-will react with some hormones produced in the adrenal medulla, to produce a yellow brown pigment (chromaffin reaction, cant be prevented or removed)
-Rapid penetration rate
-soft tissue shrinks after processing
-chromate pigment is a brown pigment, CAN be prevented but not completely removed
-prevent by rinsing tissue well with running water
-partially remove by treating tissue with acidic alcohol
- used to increase tissue affinity for acid dye
Osmium tetroxide (9)
-additive non coagulant
-reacts with nucleic acids and proteins
-insolublizes lipids–they appear black
- inhibits enzyme activity
-extremely slow penetration arte
- decreased affinity for acid dyes
-used primarily for EM as a post fixative
-very hazardous, vapors can fix exposed tissues (nasal passages and eye)
-must be used under the hood
Glyoxal (12)
- additive non coagulant
- reacts with nucleic acids and proteins
-rapid penetration rate
-breast microcalcifications are dissolved
-interferes with staining of helicobacter pylori
-causes RBCs to lysis
-loss of eosinophil granules
-iron leaching
-advance staining is hampered
-Acid free neutral pH solutions are recommended
used as a a formaldehyde replacement, fixes quicker and is less toxic
-no odor, skin irritant, not regulated by OSHA, can be poured down the sink
Glutaraldehyde (11)
-Additive non coagulant
-reacts with nucleic acids and proteins
- reacts with lipids but still has lipid loss
-slow penetration rate
- tissue must be thin to allow complete penetration of fixative
-inhibits advanced staining
-overhardenes with prolonged exposure (2 or less hours recommended)
-cannot use with some carbohydrates special stains because unbound aldehyde groups can cause nonspecific staining
-typically used for EM
-unstable, pH drops when exposed to oxygen, incompatible with oxidizers, should be handled same way as formaldehyde
-sensitizer of respiratory and digestive tract, and the skin
Paraformaldehyde (5)
-additive non coagulant
-reacts similarly to formaldehyde
-Used for EM to demonstrate ultrastructure preservation
-typically used for extensive crosslinking, results in better ultrastructure
-phosphate buffer and sodium hydroxide added to adjust pH to 7.2-7.3 and osmolarity before use
Formaldehyde (11)
- Additive non coagulant
- reacts with proteins to form methylene bridges
-Traps nucleic acids
-only reacts with proteins, poor fixative of nucleic acids
-has rapid penetration, but slow crosslinking
-crosslinking can mask protein antigens for IHC staining
-causes less shrinkage but hardens tissue more than aqueous fixatives
-Acid hematin or formalin pigment forms when you have to acidic of a PH
-prevent by maintaining a neutral PH with buffer salts
-remove by treating the tissue with alcoholic picric acid acid or alkaline alcohol
-most commonly used fixative in histopathology labs
What does formaldehyde combine with, what does it form, what happens if what it forms polymerizes, how can you prevent/fix that?
Formaldehyde combines with water ,forming methylene hydrate, if this polymerizes it forms paraformaldehyde, which can clog processor lines
It can be prevented by adding methanol to the formaldehyde, or removed by high temperatures which can break down the large polymers.
Denaturation is important in fixation because it can cause proteins to become _______ and ________
inactive and insoluble
Which type of fixative will chemically react to form a mesh like permeable network in tissue
Additive Coagulant
Select the two fixatives that insolublize lipids
osmium tetroxide and chromic acid
Select the two fixatives that insolublize lipids
osmium tetroxide and chromic acid
Select the fixatives that dissolve small calcifications and leach iron
Acetic Acid and Picric acid
Select the fixatives recommended for EM
Paraformaldehyde
Osmium Tetroxide
Gluteraldehyde
what fixative lyses RBCs and can be used to counteract shrinking/ cause swelling
acetic acid
What fixative is used as a stain also and stains yellow
picric acid
