Fixation Flashcards
Defined as the killing, penetration and hardening of tissues
fixation
Fixation also be defined as the alteration of tissues by stabilizing _ so that tissues become resistant to further changes
protein
primary goal of fixation:
secondary goal of fixation:
primary: preserve
secondary: harden & protect
fixation methods
— done in microbiology to fix bacterial smears
heat fixation (physical method)
fixation methods
— fixing neurochemical substances in brain like acetylcholine
microwave technique (physical method)
fixation method
— immerse/subject/place the specimen in chemical fixatives
chemical method
use as holding solutions for tissues to be transported to frozen sections or kidney biopsies for special processing
isotonic solution
concentration for EM & immunoEM
3% glutaraldehyde for EM
0.25% glutaraldehyde for immunoEM
temperature range that will accelerate fixation
37-56 deg C
fixative for EM; required volume is _ the volume of the specimen because it’s quite expensive
Osmium tetroxide; 5-10x
Autopsy materials should be fixed as soon after death as possible. If not possible, body must be placed in a _
mortuary ref (temp 4degC)
Human Brain must undergo _ washing out of blood by using _
INTRAVASCULAR PERFUSION ; Ringer’s lactate
_ should not be dissected before they are fixed
Eyes
Hard tissues (cervix, uterine, fibroid etc) must undergo _ immersing specimen in _
LENDRUM’S METHOD ; 4% aqueous phenol for 1-3 days
preserves glycogen
picric acid (Brasil’s)
liver/spleen fixative
formalin but Zenker’s fluid is better
“All fixatives that are available are additive fixatives except _”
acetone
alcohol
fixative for brain tissue for the diagnosis of rabies
Carnoy’s & Acetone
fixative NOT compatible with kidney
bouin’s
water-free (anhydrous) acetic acid that freezes and solidifies at about 17°C.
glacial acetic acid
acetic acid major effect
precipitate dna, which is split off from nucleoprotein
Excellent for trichrome staining & tissue photography
mercuric chloride
mercuric chloride for pituitary gland, BM, liver & spleen
contains potassium dichromate & 40% formaldehyde
helly’s fluid (zenker’s formol)
mercuric chloride for connective tissue & nuclei, liver & spleen
contains Glac Hac
zenker’s fluid
used to wash out excess mercuric fixatives
alcoholic iodine
mercuric fixatives leave
black mercury deposits
fixative temperature for EM & histochemistry
fixation temperature using autotechnicon
0-4 °Celsius - EM & histochem
40°Celsius- autotechnicon
fixative & temperature for rapid fixation of urgent biopsies
formalin @60deg C
fixative & temperature for fixing tissues w TB
formalin @100 deg C
slow down decomposition of tissue needs to be photographed and cannot be fixed immediately
refrigeration
types of fixative according to:
i. mechanism of action
additive and non-additive
types of fixative according to action
i. microanatomical
ii. cytological (cytoplasmic & nuclear)
iii. histochemical
allows the general microscopic study of tissue structures without altering the structural pattern and normal intercellular relationship of tissues
microanatomical
added to prevent precipitation of formaldehyde to white paraformaldehyde
10% methanol
CNS tissues & post-mortem tissues
10% formol saline
(w/ NSS & sodium chloride)
Tissues with iron pigments and elastic fibers
10% Neutral Buffered formalin
(NSS + sodium phosphate)
formaldehyde for lipids, neutral phospholipids
formol corrosive/ formol sublimate
used for:
fixing / preserving sputum specimen and MICROINCINERATION TECHNIQUE
Alcoholic formalin (Gendres)
mercuric chloride for tumor skin biopsies
contains TCA, Glac Hac & formalin
Heidenhain’s Susa
mercuric chloride for bone marrow
contains anhydrous sodium acetate
B5
for carbohydrates
1-2% Chromic acid
for lipids, mitochondria
Potassium dichromate (3%)
mitochondria, RBC containing colloid tissues
Regaud’s (Moller’s)
Rickettsiae & other bacteria, tissue necrosis
Orth’s fluid
picric acid can act as
- fixative
- decal
- stain
picric acid remedy for yellow color stain (major drawback)
50-70% alcohol
in book:
saturated soln of lithium carbonate in 70% alcohol, water. —> 70% ethanol, sodium thiosulfate, water
for embryos; pituitary biopsies & endometrial curettings
- Not for kidney structures
- Not compatible with feulgen’s (demonstrates DNA & RNA)
bouin’s (picric)
for GIT biopsies & endocrine tissues
Hollande’s soln (picric)
use as raw material in making shabu
acetone
Causes: glycogen polarization
alcohol
for fixing wet and dry smears, blood smears and BM tissues
methyl alcohol (100%)
recommended for touch preparations
isopropyl (95%)
for fixing chromosomes and lymph glands
- contains absolute alcohol, glacial HAC and chloroform
Carnoy’s
classified both as nuclear (to preserve nuclear proteins) and histochemical fixative (can preserve musopolysaccharides)
newcomer’s
CT mucins & umbilical cord
rossman’s
used to fix myelin and peripheral nerves and for processing neurological tissues
osmium tetroxide
solidifies @ about 17deg C
glacial acetic acid
