What is the primary fixative used for transmission electron microscopy (TEM) tissue preparation?

Prepare for the CAMLPR Specimen Collection Competency Test. Practice with diverse question sets including multiple-choice and flashcards. Each question includes hints and explanations to help you become proficient before the exam.

Glutaraldehyde is used as the primary fixative to preserve tissue ultrastructure for transmission electron microscopy. It rapidly penetrates tissue and forms strong covalent crosslinks between proteins, creating a stable network that locks in fine cellular details such as membranes, organelles, and cytoskeletal structures. This robust protein crosslinking is essential for withstanding the dehydration and resin-embedding steps that follow and for producing sharp, reliable ultrastructural images. In TEM prep, glutaraldehyde is typically used in a buffered solution (often around 2–2.5%) at low temperatures to optimize preservation. After this initial fixation, osmium tetroxide is applied as a postfix fixative to fix lipids and boost membrane contrast, complementing the protein-focused stabilization from glutaraldehyde. The other fixatives mentioned—formalin (for light microscopy), Bouin's solution (contains picric acid and can introduce artifacts and embedding issues), and osmium tetroxide used alone—do not provide the same level of protein crosslinking or overall ultrastructural fidelity required for TEM.