Masson's trichrome: A
three-color staining protocol used to differentiate cells
from surrounding connective tissue. Most recipes produce
red keratin and muscle fibers, blue or green collagen
and bone, light red or pink cytoplasm, and dark brown to
black cell nuclei. The trichrome is applied by immersion
of the fixated sample into Weigert's iron hematoxylin,
and then two different solutions.
Periodic acid-Schiff stain
(PAS): A staining method used primarily to identify
glycogen in tissues. The reaction of periodic acid
selectively oxidizes the glucose residues, creates
aldehydes that react with the Schiff reagent and creates
a purple-magenta color. A suitable basic stain is often
used as a counterstain. PAS staining is mainly used for
staining structures containing high proportion of
carbohydrate macromolecules (glycogen, glycoprotein,
proteoglycans), typically found in eg. connective
tissues, mucus, and basal laminae.
Alcian blue (AB):
Alcian blue is a phthalocyanine dye that contains
copper. The dye stains acid mucopolysaccharides and
glycosaminoglycans, for which it is one of the most
widely used cationic dyes; the stained parts are blue to
bluish-green. It is sometimes combined with H&E staining
and van Gieson staining methods. It bonds by
electrostatic forces with the negatively charged
macromolecules. By gradual increasing of the electrolyte
concentration used to wash the bound dye, one can
selectively identify neutral, sulphated, and phosphated
mucopolysaccharides.
Van Gieson stain: The
Van Gieson stain (Ira van Gieson, 1865-1913, an American
bacteriologist) is specific for collagen. This
combination permits you to distinguish two types of CT
elements in the wall of this artery: the black strands
are elastic fibers and the bright red material is the
reinforcing collagen. As with other combined stains, it
provides structural information that the single
components alone can't; and complements the general
structural stains such as H&E.
