Dehydration Flashcards
Dehydration
the procedure whereby calcium and lime salts are removed from tissues
When does dehydration done
After fixation adn before impregnation
Bones and decalcified tissues are cut with
fine fret-saw and trimmed with a hand razor
Appear as dark purple granular masses with lighter purple halos after hematoxylin staining
Microcalcification
The resistance when a tissue surface with small foci of calcification is sectioned with a microtome knife
Grating sensation
Remedy for grating sensation
Place the block face down on a cotton pad or gauze saturated with 10% HCl for approximately an hour
Calcium may be removed by
Acids, chelating agents, Ion exchange resins, and electrical ionization
Factors influencing the rate of decalcification
concentration, volume of decalcifying agent, temperature, mechanical agitation, sonificaton
Optimum temperature
18-30 degree Celsius
Impaired nuclear staining of Van Geison’s stain for collagen fibers
37 degree Celsius
Tissue will undergo complete digestion within 24-48 hours
55 degree Celsius
Most widely used agents for routine decalcification of large amounts of bony tissues. Stable, easily available, relatively inexpensive
Acid decalcifying agents
Most common and fastest decalcifying agent. Recommended for routine purposes
Nitric acid
Recommended concentration for nitric acid
5-10%
Recommended for urgent biopsy, and for needle and small biopsy
10% Aqueous Nitric Acid Solution
Recommended for urgent biopsies and less tissue distruction than 10% aqueous nitric acid
Formol Nitric Acid
Recommended for routine purposes
Perenyi’s Fluid
Most rapid decalcifying agent
Perenyi’s Fluid
It is inferior to nitric acid. Slower action greater distortion
Hydrochloric acid
may be recommended for surface decalcification of the tissue block
1% HCl solution with 70% alcohol
Usually contain HCl
Rapid proprietary solution
Usually contain buffered formic acid or formalin/ formic acid
Slow proprietary solution
moderately rapid decalcifying agent. It is recommended for teeth and small pieces of bone
Von Ebner’s Fluid
Moderate-acting decalcifying agent (addition of citrate accelerates decalcification)
Formic acid
Recommended for routine decalcification of postmortem research tissue and for small pieces of bones and teeth
Formic acid
It is the only weak acid used extensively as a primary decalcifying agent
Formic acid
Recommended for autopsy materials, bone marrow, cartilage, and tissue studied for research purposes
Formic Acid-Sodium Citrate Solution
Suitable only for small spicules of bone
Trichloroacetic acid
Suitable only for minute pieces of bone
Sulfurous acid
Decalcifies minute bone spicules both a fixative and decalcifying agent
Chromic acid (Flemming’s fluid)
Permits excellent nuclear acid cytoplasm staining
Citric acid-citrate buffer solution (pH 4.5)`
Substance which combine with calcium ions and other salts to form weakly dissociated complexes and facilitate removal of calcium salt
Chelating agents
Most common chelating agent
EDTA (Versene)
traditionally referred as Acid. Also used as anticoagulant and water softener.
EDTA (Versene)
A slow decalcifyng agent and also an excellent bone decalcifier for immunohistochemical or enzyme staining
EDTA
Ammonium form of polystrene resin
Ion exchange resin
Hastens decalcification by removing calcium ions from formic acid containing decalcifying solutions and not recommended for fluids containing mineral acids
Ion exchange resin
Ratio of Ion exchange resin
20-30 times the volume of the tissue
degree of decalcification measured by
physical or x-ray method
Is the process whereby positively charged calcium ions are attached to a negative electrode and subsequently removed from the decalcifying solution
Electrophoresis (Electrical ionization)
The priniciple is similar to that of chelating agents but utilizez electricity and is dependent upon a supply of direct current to remove calcium deposits
Electrophoresis
done by touching or bending the tissue with the fingers to determine consistency of tissues or pricking tissue with a fine needle or a probe
Physical or Mechanical test
very expensive and most ideal, most sensitive and most reliable method of determining extent of decalcification. Not recommended for mercuric chloride-fixed tissues
X-ray or radiological method
simple, reliable, and convenient method. Recommended for routine purposes by precipitation of insoluble calcium hydroxide or calcium oxalate
Chemical method (Calcium oxalate method)
The decalcifying agent is usually changed for
24-48 hours
Indicates that there is still calcium in the solution
Presence of cloudiness
Complete decalcification
Solution remains clear after 30 minutes
