The field of pathology strongly depends on the employment of special stains which allow detailed visualization of the tissue specimen collected from a patient. Special stains pertain to chromogenic reagents that could incorporate into a wide range of tissue specimens. There are certain special stains that could adhere to the entire tissue sample, while other may only bind to specific structures of cells such as the nucleus or cell membrane. Special stains are mainly used for immunohistochemical staining, which is the introduction of color to entire or specific parts of a cell or tissue.
It should be understood that special stains have also played an important role in other analytical assays such as flow cytometry, which is the separation of cells or even chromosomes based on inherent features. Special stains are also commonly employed in the technique known as in situ hybridization, which is based on the binding of deoxyribonucleic acid (DNA) probes to target sequences in a cell or tissue. In order to better appreciate the use of special stains, this report will describe a particular medical condition, as well as the importance of special stains in the study of its etiology and pathogenesis.
Special stains are essential components of pathology because these help in the detection and identification of pathogens that may have infiltrated tissues. In addition, special stains also facilitate in the diagnosis of cancer, as well as in monitoring cancer progression in a patient. These specific stains are strongly associated with the diagnosis of a particular disease. For example, the special stain known as mucicarmine is a highly effective reagent in demonstrating adenocarcinoma.
On the other hand, Giemsa stain is commonly used in classifying lymphocytes, which are the major cells involved in leukemia. There are also certain special stains that have high affinity to iron and thus are important in detecting hemochromatosis, which is also commonly known as iron deficiency. There are currently a huge number of special stains that are considered as general reagents in pathology. These reagents are generally used on tissue or cell specimens that have been fixed using preservatives such as formaldehyde or osmium tetraoxide.
Tissues are also required to be sturdy enough to undergo sectioning into thin slices and thus these specimens are embedded into paraffin wax. It has been earlier established that 80% of all tissues are made up of water and thus it is important that the water is removed from the specimen so that any adverse chemical reactions with the special stains are prevented. The removal of water is performed through the process of dehydration and this is technically induced by running the tissue specimen through a series of increasing ethanol concentrations.
The water removed from the tissues is then replaced in an infiltrating reagent, such as paraffin or resin. One of the most common special stains in pathology is hematoxylin and eosin (H&E). The chemical nature behind this special stain is associated with the bind of the reagent to polarized parts of the cytoplasmic region of the cell. This stain is so simple that it can be considered as a natural dye that allows the pathologist to visualize almost any type of tissue specimen under the microscope.
There are also other special stains that allow the visualization of other cellular components. Feulgen stain is frequently used in analyzing the DNA content of cells and these macromolecules are located within the nucleus. Silver stain, on the other hand, is commonly employed when there is a need to look at muscle tissue specimens. Silver has a high affinity to bind to muscle fibers and thus allowing easier access for further analysis by pathologists. Toluidine blue is usually added to blood specimens, especially when the mast cells are of interest to the analyst.
Mast cells are strongly associated with inflammatory conditions. Alzheimer’s disease is a neurodegenerative disease that commonly affects individuals of age 65 years and above. One of the main symptoms of this disease is dementia or memory loss. Pathological analysis has implicated the accumulation of protein deposits in the cortical region of the brains of patients diagnosed with this disease. The protein deposits were determined to be comprised of amyloid proteins, which are high complex sugar residues that inhibit the normal functioning of the brain.
The use of special stains that bind to these amyloid deposits has allowed pathologists and neuroscientists to visualize the brain tissue in finer detail. In addition, the special stains have also helped these professionals determine the progression of the disease based on the assessment of the amyloid deposits. According to Alafuzoff et al. (484), the employment of immunohistochemical analysis of hyperphosphorylated tau proteins in brain tissues of deceased Alzheimer’s patients validated their hypothesis that the amount of tau proteins is directly correlated to the degree of brain lesions that a patient has developed.
The special staining technique these investigators employed involved monoclonal antibodies which specifically reacted against the tau proteins, which are the identified antigens. Once an antigen-antibody reaction has occurred within the brain tissue specimen, a secondary antibody is introduced to the tissues for further immunolocalization. The secondary antibody employed in this assay was attached to a chromogen that could be visualized under regular microscope optics.
The special stain for tau proteins has thus allowed these researchers to assess Alzheimer’s brain tissues and compare these to normal brain specimens. Any differences between these two types of tissues are thus taken note of, especially with regards to the amount of tau proteins that have been deposited in the cortical region of the brain. The data collected from this analysis was also correlated with other physical signs in the patients. In another research study, special stains were employed in locating the exact site where amyloid plaques were deposited within astrocytes of brain tissues.
Immunoelectron microscopy efforts have shown that amyloid plaques were generated within the mitochondria of astrocytes (Petersen 13145). Visualization of the mitochondria using higher magnification indicated that these plaques were present in the cristae or the inner folds of mitochondria. In addition, the employment of highly reactive special enzyme stains showed that an internalization process is aggressively performed by the astrocytes, resulting in the accumulation of these proteins within the brain cells.
There are other research efforts conducted for independent investigators who have also attempted to screen for additional proteins that could provide more information on the pathogenesis of Alzheimer’s disease. Peroxiredoxin 6 is a promising target protein in immunohistochemistry because it allowed the visualization of protein markers that are specifically located in brain tissues that have reached pathological conditions (Power 611). This enzyme can be seen through the use of special stains that identify astrocytes.
In addition, the precise location of the proteins using special stains has been determined to be that around the nucleus. Immunohistological staining of this enzyme, together with the tau protein, has shown that these two proteins interact with each other, rendering the brain tissue susceptible to accumulation of protein plaques that promote memory loss. The staining of C9 complement proteins using the Bielschowsky special stain has also resulted in the understanding of how protein plaques in the brain influence the development of Alzheimer’s disease (Loeffler 9).