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"Fixation" is a process of stabilization important for anatomical study of biological tissue. To achieve this goal, one must arrest the decomposition caused by tissue enzymes and decay; it is usually desirable also to harden the tissue for convenient handling. The two basic approaches involve physical methods (rapid heating or quick-freezing) and/or chemical methods. Nearly all chemical methods were originally developed for the leather tanning industry, which faces similar problems.

The most widely-used chemical fixative is 4% formaldehyde gas dissolved in water or buffer. This (moderately toxic) agent rapidly penetrates tissue and (more slowly) denatures proteins, arresting enzymatic degradation. It also cross-links proteins, leading to tissue hardening. Glutaraldehyde, a di-aldehyde which cross-links very effectively, is often used for electron microscopy. A wide range of other chemical fixatives are sometimes used, including organic chemicals like tannic acid, picric acid, and absolute alcohol, and (highly toxic) inorganic fixatives like potassium dichromate, mercuric chloride, and osmium tetroxide. Their mechanisms of action are poorly-understood, but generally involve denaturation of protein.

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State the disadvantage of using 10 percent formal-saline in fixation?

One disadvantage of using 10 percent formal-saline in fixation is that it may lead to tissue shrinkage and hardening, which can affect the quality of histological staining and make it difficult to analyze cellular structures accurately. Additionally, formaldehyde is a potential carcinogen and exposure to its fumes can pose health risks to laboratory personnel if not handled properly.


What is the Ratio of fixative volume to tissue?

The typical ratio for fixative volume to tissue is 10:1, meaning 10 times the volume of fixative compared to the volume of the tissue. This ensures proper fixation and preservation of the tissue structure for further analysis. Adjustments to this ratio may be needed depending on the tissue size and fixative used.


Why does it take long to fix fatty tissue in histology?

Fixing fatty tissue in histology takes longer because lipids are not easily preserved by standard fixation methods, which often rely on formaldehyde or alcohol. These fixatives can dissolve or extract fats, leading to poor tissue morphology and loss of structural integrity. Special techniques, such as using osmium tetroxide or employing freeze-drying, may be needed to adequately preserve adipose tissue for accurate microscopic examination. Additionally, the processing time for these methods can extend the overall fixation duration.


What is fixation in specimens?

Fixation in specimens is a process used in biology and medicine to preserve the structure of cells and tissues. It involves treating the specimen with a fixative solution that immobilizes cell and tissue components, preventing decay and maintaining their original structure for further analysis under a microscope. Fixation is a crucial step in preparing samples for techniques such as histology, immunohistochemistry, and electron microscopy.


What is the principle of complement-fixation test?

The principle of complement-fixation test involves the detection of antibodies by measuring the ability of a patient's serum to fix and consume complement in the presence of a specific antigen. If antibodies are present in the sample, they will fix complement, leading to a decrease in complement activity that can be detected. This test is often used to diagnose infections such as syphilis and certain viral diseases.

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State the disadvantage of using 10 percent formal-saline in fixation?

One disadvantage of using 10 percent formal-saline in fixation is that it may lead to tissue shrinkage and hardening, which can affect the quality of histological staining and make it difficult to analyze cellular structures accurately. Additionally, formaldehyde is a potential carcinogen and exposure to its fumes can pose health risks to laboratory personnel if not handled properly.


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What is the Ratio of fixative volume to tissue?

The typical ratio for fixative volume to tissue is 10:1, meaning 10 times the volume of fixative compared to the volume of the tissue. This ensures proper fixation and preservation of the tissue structure for further analysis. Adjustments to this ratio may be needed depending on the tissue size and fixative used.


Why does it take long to fix fatty tissue in histology?

Fixing fatty tissue in histology takes longer because lipids are not easily preserved by standard fixation methods, which often rely on formaldehyde or alcohol. These fixatives can dissolve or extract fats, leading to poor tissue morphology and loss of structural integrity. Special techniques, such as using osmium tetroxide or employing freeze-drying, may be needed to adequately preserve adipose tissue for accurate microscopic examination. Additionally, the processing time for these methods can extend the overall fixation duration.