38 Questions
What is the recommended angle between the blade edge bevel and the block?
2-5 degrees
Why is it necessary to trim the edges of the block with a sharp razor blade?
To ensure the upper and lower edges of the block are parallel to the edges of the knife
What should be the orientation of the block when placing it on the cassette holder?
The greater axis is perpendicular to the edge of the knife
What is the initial section thickness set for coarse cutting?
15 microns
Why should xylene not be used to clean the knife?
It often leaves an oily remnant on the knife
What should be done with the trimmed block after coarse cutting?
It should be returned to the cold plate for 1-2 minutes
Why is it necessary to remove wax debris from the knife?
To prevent subsequent sections from sticking to the knife
What should be done with the knife after removing wax debris?
It should be moved to an unused area or a new disposable blade should be installed
What is the primary function of the knife tilt in a rotary microtome?
To adjust the knife angle
What is the purpose of the cassette clamp or block holder?
To hold the paraffin block in place
What is the function of the coarse hand wheel in a rotary microtome?
To move the block holder toward or away from the knife
What is the safety feature of the advancement hand wheel?
It is equipped with a safety lock to prevent accidental block movement
What is the recommended temperature for the water bath in a rotary microtome?
56°C or just below the melting point of paraffin wax
What is the purpose of putting paraffin blocks on a cold surface before sectioning?
To harden the cut surface
What is the recommended frequency for cleaning the water bath?
Every day
What is the function of the face plate in a rotary microtome?
To guide the ribbons away from the blade and towards the operator
What is the purpose of gently breathing upon the sections?
To eliminate static electricity and facilitate the removal of the ribbon from the blade
What is the recommended way to transfer cut sections to the surface of the water bath?
By transferring the cut sections to the surface of the water bath
Why should certain types of pens be avoided when labeling slides?
Because they have non-alcohol-resistant ink
At what temperature should slides be stored for immunohistochemistry?
4°C
What is the range of section thickness that can be achieved with this method?
1.0 - 60.0 µm
What is an advantage of this method in terms of tissue adaptation?
It is easy to adapt to all types of tissues (hard, fragile, or fatty)
What is an advantage of the technological advances in the automation of this method?
It improved section quality and increased productivity and occupational safety
How can the slides be dried after collection?
By drying them horizontally on a warm plate for 10 minutes
What is a major disadvantage of using a rotary microtome?
It is not suitable for cutting large blocks
What is a precaution that can be taken to avoid danger when using a rotary microtome?
Using a knife guard/protector
How should metal parts of the rotary microtome be cleaned after use?
With xylol
What type of microtome is suitable for cutting hard and brittle materials such as bone?
Saw microtome
Why is it important to dry the knife holder of the rotary microtome after use?
To prevent rust formation
Why is it important to cover the rotary microtome when not in use?
To prevent accumulation of dust and dirt
What is the name of the microtome named after its inventor?
Minot microtome
What is the main function of the micrometer screw in a rotary microtome?
To advance the block holder
What is the purpose of the retracting action in a rotary microtome?
To produce a flat face to the tissue block
What is the name of the part that anchors the knife holder to the microtome stage?
Knife holder base
What is the purpose of the operating handle in a rotary microtome?
To rotate the hand wheel
What is the range of thickness that can be cut by a semi-automated rotary microtome?
0.5 to 2.0 um
What is the name of the platform that has rails that secure the knife holder base?
Microtome base plate
How many motors does a fully automated rotary microtome have?
Two
Study Notes
Rotary Microtome
- Also known as Minot microtome, named after its inventor Professor
- Most widely used microtome design globally
- Mechanism: hand wheel rotates 360 degrees, moving the specimen vertically past the cutting surface (knife edge) and returning to the starting position
Types of Rotary Microtomes
- Manual: completely operated by the operator
- Semi-automated: auto-cut microtome with built-in motor drive, foot and hand control, and accessories for cutting thin sections (0.5-2.0 um thickness)
- Fully automated: two motors driving both fine and coarse advance hand-wheels, example: automated cryostate
Mechanism of Block Advancement
- Retracting or non-retracting
- Retracting action moves the tissue block away from the knife on upstroke, producing a flat face to the tissue block
Rotary Microtome Parts
- Base
- Cassette or block holder
- Block adjustment screw
- Knife holder
- Blade clamps
- Angle of tilt adjustment
- Thickness gauge
- Operating handle
- Face plate
- Waste tray
Rotary Microtome Operation
- Fill the water bath with water and heat to 56°C or just below the melting point of paraffin wax
- Harden the cut surface of the paraffin block on a cold surface (e.g., refrigerated cold plate or ice cubes)
- Fit and adjust the knife: install a disposable blade, set angle between the blade edge bevel and the block (2-5 degrees), and lock the blade in place
- Trim the edges of the paraffin block with a sharp razor blade
- Fit the cassette paraffin block onto the cassette holder of the microtome
- Advance the block until it is in contact with the edge of the knife
- Set the section thickness (around 15 microns)
- Coarse cut the block until the whole surface of the embedded tissue can be cut
- Lock the microtome hand-wheel
Sectioning
- Return the trimmed block to the cold plate for 1-2 minutes
- Set the section thickness to 4-5 um
- Remove wax debris from the knife with alcohol
- Move to an unused area on the blade or install a new disposable blade
- Install the cassette paraffin block onto the cassette holder again
- Cut a series of paraffin sections
- Gently breathe upon the sections to eliminate static electricity
- Flatten the sections and facilitate the removal of the ribbon from the blade
- Separate the ribbon from the knife edge with a paint brush or forceps
Floatation
- Transfer the cut sections to the surface of the water bath
- Gently separate the floating sections on the water bath with pressure from the tips of forceps
- Collect sections on a clean glass slide
- Label slides with a histo-pen or pencil
Advantages and Disadvantages
- Advantages: section thickness range (1.0-60.0 um), stable and less vibration, excellent for routine and research work, ability to cope with harder tissue, easy adaptation to all types of tissues, ideal for cutting serial sections, cutting large blocks, and adjustable cutting angle
- Disadvantages: complex design, initial cost is relatively higher, knife can be dangerous to the operator, and not suitable for cutting large blocks
Care of the Rotary Microtome
- Brush away accumulated paraffin and tissue with a soft brush
- Wipe clean all metal parts with xylol
- Avoid continuous application of xylol to the rest of the machine
- Dry the machine carefully, especially the knife holder
- Keep the machine well oiled to prevent rust formation
- Keep the moving parts of the microtome lubricated
- Cover the microtome when not in use to prevent accumulation of dust and dirt
Learn about the mechanism and features of Rotary Microtomes, also known as Minot Microtomes, widely used in laboratories around the world.
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