Giemsa stain is a mixture of dyes used to highlight different cell types in blood smears or tissue slices. It is named after Gustav Giemsa and produces different colors depending on what it binds to. The staining process is useful in studying chromosomes and visualizing the differences between various blood cells.
Giemsa stain is a standardized mixture of dyes that makes different cell types stand out clearly in a blood smear or thin slice of tissue. This stain is named after the German chemist Gustav Giemsa, who first developed it for his work in the study of the malaria parasite, Plasmodium. To ensure that the technician examining the sample can obtain an accurate reading, the steps in the staining procedure must be standardized as well as the dye mix. Giemsa stain is called differential stain because it produces different colors depending on what it binds to, such as cytoplasm or DNA.
The formula of Giemsa stain has been adjusted over time to improve the stability of the dyes and the resulting colours. Current standard blends include methylene blue, eosin, and sometimes azure B. These dyes are often stored in a dry powdered form and mixed with water just before being used. If water is present in the dye mix before it is used, some of the compounds will oxidize and stain incorrectly.
The exact steps in the procedure for using the Giemsa stain can vary depending on the organism or cell type for which the sample is being tested, as well as the composition of the sample itself. A sample that will be stained with Giemsa stain is usually smeared or taped onto a glass slide immediately after collection. A thin blood smear is typically fixed by immersion in methanol, while a thick blood smear is simply allowed to dry completely at room temperature. The slide is then immersed in the stain for a specified amount of time and then rinsed with neutral pH water. Slides are allowed to air dry before viewing.
Due to the differential staining produced by the Giemsa stain, the cytoplasm of the plasmodium stains light blue while the DNA appears red or purple. Another parasite, Giardia lamblia, is pink-purple in color except for the DNA, which stains a very dark blue. Histoplasma capsulatum, a fungus, is found in its yeast form in human white blood cells and stains dark blue.
This staining process is also useful in studying chromosomes and visualizing the differences between various blood cells. A chromosome stains very dark blue in some sections and light blue in others. This causes a banding effect that helps geneticists find places where chromosomes have undergone unusual changes. Red blood cells stain pink, while granules in mast cells appear as purple dots. White blood cells stain various shades of blue, allowing the different types to be distinguished (basophils, eosinophils, neutrophils, and others).
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