Microtome Guide

Microtome Guide

Microtomes are used to make very thin tissue samples from paraffin blocks

How to use a Microtome

In general, the Microtome device consists of two parts. A part which Fixes the prepared block and a Microtome blade or Tissue sectioning blade. The part on which the tissue block is fixed is connected to a Micrometer handle (hand wheel). This handle moves forward or backward by a few microns in each rotation of the Microtome handle. There are different types of Microtomes, but the best type is that the mold is fixed on the Microtome wheel. As a result, it constantly moves in one direction, and thus the sections form narrow bands.

 To make a section from paraffin tissue blocks, the blocks must first be prepared Then adjust the Microtome correctly. Rotary Microtome is the most common tool used to make sections. Before making the sections, the paraffin blocks should be prepared. The blocks are then removed from the mold using a stainless steel knife or disposable blades .So that there is paraffin with a thickness of 3 mm around the tissue. The surfaces of the molds should be smooth and parallel to each other. In addition, the tissue must be completely inside the block. On sectioning, the blade must be completely sharp  to prevent cracks or breakage of the molds. The mold should be fixed to the Microtome base so that its longitudinal axis is parallel to the Microtome blade.

Fix the Microtome blade firmly in the desired location. The degree of its deviation should be carefully determined and appropriate. All bolts on the Microtome blade must firmly fixed. Then It should be cut from the surface of the block until the entire surface of the tissue be next to the Microtome. Then the final cut is done. For normal tissues, the cutting thickness of the machine is usually set between three to five microns. Hold the cut tissue with the left hand when sectioning. Forceps can also be used for this purpose. The sections should be striped, smooth and with wrinkle. The tissue sections are placed on the slide after being flattened in a water bath.
Making a good sections depends on the personal experience and familiarity of the technician or operator with the tools used. Therefore, operators must be well trained for this.

The results of the work mainly depend on the sensitivity and performance of the Microtome blade. So every technician should know how to use and maintain a Microtome blade. One of the most important points in sectioning is to maintain the right sectioning angle. This angle is usually between five to ten degrees.

When the sections are not acceptable and the samples are not well processed, the tissue block and blade could be cooled with ice. In the case of hard samples such as nails and tendons, a softening agent can be used. There are now sprays for this purpose that are sprayed on the surface of the tissue

Maintenance

• The body, base and blade of the Microtome should be cleaned daily after each work cycle(A xylene-impregnated gas band can be used to remove paraffin)
• When The Microtome is not used, The Microtome blade must be removed and the Microtome latch locked.
• Microtome lubrication should be performed by a technician at regular intervals.
• The permanent Microtome blade should always be carried and stored in its own box so its edges will not damage.
• Microtome blades, if not disposable, should be sharpened periodically when necessary.

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Microtome Quality Control

Tissue blocks should be cut into strips and they should be Be perfectly flat with no wrinkles or tear lines (just like getting paper out of a printer)

In microscopic examination, the sections should not have longitudinal scratches or transverse non-uniformity and In addition, the determined tissue thickness should be appropriate for the study methods and the degree of Microtome adjustment.

Note:

As a general rule, Microtome blades should always be perfectly sharp and clean.

Microtome safety

• Ensure that the Microtome toggle is locked when the Microtome is not in use.
• Place the protector on the Microtome blade when the tissue sectioning operation is not performed.
• Transport the permanent Microtome blade in their special boxes.
• Never touch the Microtome blade without proper protection (special gloves)