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Heat fixation is used for the fixation of single cell organisms, most commonly bacteria and archaea. The organisms are typically mixed with water or physiological saline which helps to evenly spread out the sample. Once diluted, the sample is spread onto a microscope slide. This diluted bacteria sample is commonly referred to as a smear after ...
Endospore staining is particularly useful for identifying endospore-forming bacterial pathogens such as Clostridioides difficile. Prior to the development of more efficient methods, this stain was performed using the Wirtz method with heat fixation and counterstain.
Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. [1] The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884. [2]
Zenker's fixative is a rapid-acting fixative for animal tissues. It is employed to prepare specimens of animal or vegetable tissues for microscopic study. It provides excellent fixation of nuclear chromatin, connective tissue fibers and some cytoplasmic features, but does not preserve delicate cytoplasmic organelles such as mitochondria.
Tissue fixation is required for certain procedures such as antibody-linked immunofluorescence staining. Frozen sections are often prepared during surgical removal of tumors to allow rapid identification of tumor margins, as in Mohs surgery , or determination of tumor malignancy, when a tumor is discovered incidentally during surgery.
One of the main difficulties with IHC staining is overcoming specific or non-specific background. Optimisation of fixation methods and times, pre-treatment with blocking agents, incubating antibodies with high salt, and optimising post-antibody wash buffers and wash times are all important for obtaining high quality immunostaining.
An advantage of using this method, rather than regular positive stains like methylene blue or carbol fuchsin, is that prior fixation by heat or alcohol is not needed, so the organisms are seen in more lifelike shapes. Furthermore, negative staining with nigrosin can reveal some microorganisms that cannot be stained by regular methods.
Moeller staining involves the use of a steamed dye reagent in order to increase the stainability of endospores. Carbol fuchsin is the primary stain used in this method. Endospores are stained red, while the counterstain methylene blue stains the vegetative bacteria blue.