Question

Preparation of paraffin section

Answer 1

Where the best possible morphology is required, animals should be anesthesized and subjected to cardiac perfusion with saline, followed by

a 10% formalin flush. If biochemical studies need to be performed on the tissue, a 10% formalin flush should not be used as it may interfere with subsequent analysis.

For routine stains where perfusion is not required, tissue is sectioned and drop-fixed in a 10% formalin solution. Fixative volume should be 20 times that of tissue on a weight per volume; use 2 ml of formalin per 100 mg of tissue.

Due to the slow rate of diffusion of formalin (0.5 mm hr), tissue should be sectioned into 3 mm slices on cooled brain before transfer into formalin. This will ensure the best possible preservation of tissue and offers rapid uniform penetration and fixation of tissue within 3 hours.

Tissue should be fixed for a minimum 48 hours at room temperature.

After 48 hours of fixation, move tissue into 70% ethanol for long term storage.

Keep fixation conditions standard for a particular study in order to minimize variability. (Although set times are best, tissue may be fixed for substantially longer periods without apparent harm.

Answer 2

Creating great paraffin sections using a rotary microtome takes a great deal of skill and experience. "Microtomy and Paraffin Section Preparation" is a great training aid for new microtomists and is an excellent refresher for experienced operators. All of the essential aspects of cutting paraffin sections are covered, including:

Safety
Microtome setup
Microtome blades
Trimming, facing and roughing blocks
Techniques for consistent paraffin sections
Microtome maintenance
Common microtomy faults

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