Fixation Flashcards
breakdown of tissue due to enzyme activity
autolysis
breakdown of tissue by bacterial action
putrefaction
physical agent in fixation
heat
primary function of a general purpose fixative
stabilize proteins
best preservation of staining properties during long term storage
70% ethanol
good fixative
makes tissues more permeable to subsequent reagents
universal fixative
NBF
10% formalin contains what percentage of formaldehyde
4
Formic acid present
create formalin pigment
mail specimens in what fixative
Michel or formalin
when neutral solutions of formalin are prepared by storing the solution over calcium or magnesium carbonate, the fluid drawn off for fixation becomes…
acidic
formalin pigment forms
pH fall below 6
an unknown pigment in a tissue section that can be bleached with a saturated alcoholic solution of picric acid is
formalin
10% neutral buffered formalin constituents
37-40% formalehyde, sodium phosphate monobasic and dibasic
Helly solution
mercuric chloride, potassium dichromate and 37-40% formalehyde
Zenker Solution
Mercuric chloride, potassium dichromate and glacial acetic acid
Carnoy
Chloroform, glacial acetic acid and 70% alcohol
Bouin
Picric acid, 37-40% formaldehyde and glacial acetic acid
Flemming
1% chromic acid, 2% osmium tetroxide and glacial acetic acid
Zamboni
Picric acid, paraformaldehyde, sodium phosphate monobasic and dibasic
B-5
Mercuric chloride, sodium acetate, and 37-40% formaldehyde
Orth Solution
potassium dichromate, sodium sulfate, and 37-40% formaldehyde
Hollande
Cupric acetate, picric acid, formaldehyde and acetic acid
mercuric chloride pigment is removed by
an iodine-sodium thiosulfate sequence
tissue fixed in hollande solution must be
must be stored in 70% alcohol
acetic acid is useful because
it counteracts the shrinkage effect of other reagents like picric acid
Zinc salts added to formalin
provide superior nuclear detailing
which of the following require washing with water before processing.
A: Carnoy
B. Bouins
C. NBF
D: Zenker
ZENKER
coaguate tissue proteins
zinc salts, mercuric chloride, picric acid
when zinc salts replace mercuric salts in fixatives
tissue must be treated with iodine
disadvantage of formalin
it interacts with hemoglobin at an acid pH
purpose of methanol in formaldehyde
retard the polymerization of formaldehyde
Baker calcium formalin
is used for the preservation of phospholipids
absolute alcohol recommended for
blood smears, glycogen, urate crystals
preserved well by ethanol
glycogen
Bouins is good for and is a mordant to
connective tissue stains like trichrome
tissue fixed in bouins should be washed with
50% alcohol
when a specimen is microwaved in saline
tissue proteins are denatured
Carnoy solution is best for
glycogen
one characteristic of carnoy solution is it
hemolyzes red blood cells
Zenker is good for
PTAH staining
characteristic of bouins is that
improperly washed tissue blocks undergo undesirable changes
characteristic of Zenker is that
is excellent for tissues requiring the feulgen reaction
Advantage of Zenkers
tissue stains great with trichrome stains
Helly solution great for
bone marrows
characteristic of helly solution
must be washed out before processing
Orth recommended for
chromaffin granules in the adrenal medulla
disadvantage of osmium tetroxide
interferes with staining
characteristic of zamboni fixative
good for EM
which has a mordanting effect on tissue
Zenkers and Bouin’s
recommended for EM
Zamboni, 2% buffered gluteraldehyde, formalin-gluteraldehyde
fixative for blood smears
methanol
CNS tissue to be stained with silver and gold tech should be fixed in
formalin ammonium bromide
pheochromocytoma should be fixed in
orth
uric acid crystals are preserved only when fixed in
absolute alcohol
improper fixation
mobilization of cytoplasmic proteins
coagulant fixatives
change the protein spongework into meshes through which paraffin can easily pass
formaldehyde in helly
reduces the chromate salt present in the solution
when alcohol is substituted as the diluent of formaldehyde solution the result is
faster fixation
a fixative containing potassium dichromate is
indicated for fixation of cytoplasm with out precipitation
mercuric chloride is used alone as a fixative it
penetrates poorly and causes excessive tissue shrinkage
tissue treated in what must be post-treated for mercury pigment
b-5
action of acetic acid
coagulated nucleoproteins and lyses RBC’s
acetic acid in fixatives
dissolves some cytoplasmic organelles
when enzyme histochemical studies are required
fewer diffusion artifacts will be seen in tissue fixed before freezing
when sucrose is used to treat tissue for enzyme histochemical studies
the solution should contain 30% sucrose and 1% gum acacia
for histochemical and most histological techniques it is necessary to bring the pH of formalin to neutral because
it neutralizes the formic acid present
steps of fixation for EM with gluteraldehyde
glutaraldehyde, phosphate buffer, sucrose solution, osmium tetroxide
Zamboni for EM
must be prepared weekly
lipid histochemistry fixative
calcium formalin
when preparing a fixative solution containing paraformaldehyde, the paraform, must be heated to 60 degrees prior to adding 1M NaOH in order
to dissociate the paraformaldehyde to formaldehyde
Immunoenzyme stains for vimentin are negative this indicates
overfixation in a formalin fixative
osmium is a good fixative for tissues for EM because it
fixes phospholipids so that they are not dissolved
urate crystals
do not use water based fixatives
