Formalin and paraffin-fixed tissue is an invaluable research resource. Formaldehyde fixation has been the method of choice for tissue preservation in pathology for more than a century.
In addition to tissue structure, the cellular content of proteins and nucleic acids is maintained through cross-linking between and within proteins in tissues. This provides stability of the tissue sample during long-term storage, usually at room temperature.
When any type of tissue is removed, it is sent to a pathology laboratory for processing, examination, and diagnosis. This material is processed using a well-known technique, namely paraffin-embedded tissue.
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The method allows the production of slides that can be subjected to histological analysis. After diagnosis, the remaining paraffin blocks are stored almost indefinitely.
Materials and methods
Paraffin blocks including tissues from various lymphatic organs were selected: nasopharyngeal tonsils, tonsils, and lymph nodes. The good blocks were molded in cellulose-agar medium and thin disks were made from the blocks and placed in liquid culture tubes.
The beam is then cleaned of surface paraffin and then the fabric inside is carved to provide a lubricating material. Slides containing samples from each sample were subjected to staining to test for the presence of acid and alcohol-resistant acid (AARB).
In tonsils and lymph nodes stored in paraffin blocks, only handling bacterial contamination can be detected. Blocks embedded in paraffin appear to remain a safe and easy way to store tissue samples.