Stains are used to enhance the preparation and make selected elements
easier to distinguish. Choice of stain will depend on the tissue and
the object of the examination.
Giemsa: a mixture of
methyline blue and eosin - the appearance is unsurprisingly similar to,
but not identical to the appearance under H&E and Wrights stain.
H&E:
Haematoxylin and Eosin.
Haematoxylin has a deep blue-purple
color and stains nucleic acids by a complex, incompletely understood
reaction. It stains the cell nucleus well enough to distinguish varying
cell-type- and cancer-type-specific patterns of condensation of
heterochromatin (hematoxylin staining) that are diagnostically
important.
Eosin is pink and stains proteins nonspecifically. It stains,
cytoplasm, extracellular matrix and nuceoli.
In a
typical tissue, nuclei are stained blue, whereas the cytoplasm and
extracellular matrix have varying degrees of pink staining. A clear
area of cytoplasm near the nucleus represents the Golgi zone.
Papanicolaou Stain: This
histology stain is used mainly on cytological specimens. Cells in smear
preparations can be stained with Pap staining. Gynecological smears
(Pap smears), sputum, urine, cerebrospinal fluid, abdominal fluid,
pleural fluid, synovial fluid, semminal fluid and fine needle
aspiration samples can all be stained with a Pap stain. This staining
technique involving five dyes in three solutions.
- Nuclear stain: haematoxylin for cell nuclei.
- Counterstain 1: Orange G, for
keratin. Its original role was to stain the small cells of keratinizing
squamous cell carcinoma present in sputum.
- Counterstain 2: contains three (or two)
elements
- Eosin Y
stains the superficial epithelial squamous cells, nucleoli, cilia, and
red blood cells.
- Light
Green SF yellowish stains the cytoplasm of all other cells.
- Bismarck
brown Y stains nothing and in contemporary formulations it is
often omitted.
Periodic Acid-Schiff (PAS): This
histology stain is particularly useful for staining glycogen and other
carbohydrates, but is useful for many things. It is often used to show
glomeruli, basement membranes, and glycogen in the liver. PAS stains
glycogen, mucin, mucoprotein, and glycoproteins magenta. The nuclei
will stain blue. Collagen will stain pink.
Vital stains: Stains applied to living tissue. Divided into
supravital (introduced to living
tissue that has been removed from the body, but before cessation of the
chemical life of the cells) and
intravital
(absorbed by living cells after injection into the body) stains.
Wright's stain: Methylene blue
(blue dye) has a positive charge and stains acidic granules as well as
RNA and DNA all of which have negative charges; Eosin (a red dye) has a
negative charge and so stains some granules and hemoglobin which are
basic with positive charges, a red colour.
