Hematology & Histology

Silver and Iron Stains

Iron Stain

Bone marrow is the main site of iron utilization in the body, where it is incorporated into hemoglobin during red blood cell formation. Under normal conditions, iron deficiency rarely happens. Loss of iron from the body mainly occurs from chronic bleeding due to ulcers, cancer or in females by menstruation. When iron stores in the bone marrow become depleted, insufficient hemoglobin is produced and anemia develops. Iron deficiency may be demonstrated by the absence of stainable iron in the bone marrow. The Perls prussian blue stain for ferric iron is considered one of the first classical histochemical reactions. Deposits of loosely bound iron in erythrocytes, bone marrow and tissue stain an intense blue when treated with potassium ferrocyanide and dilute hydrochloric acid. 

Silver Stain

Silver staining techniques rely on basic chemical reactions for the microscopic examination of microorganisms, melanin, carcinoid tumors, nerve fibrils and basement membranes. Microorganisms fall into two primary classifications, bacterial and fungi. One major group of bacteria are spirochetes, recognized by their distinct corkscrew shapes. A member of the genus Treponema is responsible for the disease of syphilis and the species Borrelia burgdorferi is the causitive agent for the tick-borne Lyme disease. Spirochetes are argyrophilic, i.e., they will absorb silver ions from a silver salt solution, but they need a separate reducing solution to reduce the absorbed silver ions to a visible metallic state. Fungi are a diverse family of single cell and multi-cellular organisms with cell walls composed of chitin and glycoproteins. Pneumocystis carinii is an opportunistic fungus known to cause a fatal pneumonia in immunocompromised individuals. The number of immunocompromised patients is increasing because of the use of chemotherapy and the epidemic of human immunodeficiency virus. The principle laboratory method for the detection of P. carinii is the direct visual examination of a specimen, usually obtained by bronchoscopy or an induced sputum specimen. An oxidation-reduction silver stain is commonly performed on these specimens. Carbohydrates are first oxidized by periodic acid to convert chitin in the fungal walls to aldehydes. Specimens are then treated with an ionic silver solution. The newly formed aldehyde groups reduce the silver ions to elemental silver, depositing visible silver on the fungal walls. Silver staining methods can be 10-100 times more sensitive than various staining techniques that rely on dyes that must penetrate a cell.


Iron Stain Kit

Silver Stain Kit