FAULTS-IN-SECTION-CUTTING-TISSUE-PROCESSING

Faults During Section Cutting

  • Sections Expand or Disintegrate

    • Reason: Poor impregnation of tissue

      • Remedy: Re-process tissue on water bath

    • Reason: Water temperature too high in the flotation bath

      • Remedy: Turn down the temperature of flotation bath

  • Sections Roll Into a Coil Instead of Remaining Flat on Knife Edge

    • Reason: Blade dull

      • Remedy: Use a new blade

    • Reason: Rake angle too small

      • Remedy: Reduce blade tilt if clearance angle is excessive

    • Reason: Section too thick

      • Remedy: Reduce section thickness

    • Reason: Dull knife/blade edge

      • Remedy: Re-sharpen the knife/blade or replace it with a new one

  • Sections Fail to Form Ribbons

    • Reason: Surfaces and edges of the block are not parallel

      • Remedy: Re-trim the block

    • Reason: Paraffin wax is too hard

      • Remedy: Coat horizontal edges of the block with wax of lower melting point

    • Reason: Knife is tilted too much

      • Remedy: Reduce the tilt

Faults During Section Cutting

  • Sections are Compressed, Wrinkled, or Jammed

    • Reason: Knife is blunt or dull

      • Remedy: Re-sharpen the knife

    • Reason: Paraffin block is warm and soft

      • Remedy: Cool the block on ice water until firm

    • Reason: Sections are too thin

      • Remedy: Re-adjust thickness of section

  • Sections are Squashed

    • Reason: Bevel of knife is lost due to incorrect sharpening

      • Remedy: Re-sharpen using a knife back or automatic knife sharpener

    • Reason: A hole is formed in the section

      • Remedy: Re-embed in freshly filtered embedding medium wax if necessary

  • Sections Adhere to the Knife or Other Parts of the Microtome

    • Reason: Static electricity due to low atmospheric humidity

      • Remedy: Breathe out or blow gently on the block and knife to break up static electricity

Faults During Section Cutting

  • Ribbon is Split or Lengthwise Vertical Scratches are Seen on Sections

    • Reason: Nicks or damage on the knife edge

      • Remedy: Sharpen the knife

    • Reason: Knife edge is dirty

      • Remedy: Clean knife edge with xylene

    • Reason: Sections are lifted from the knife

      • Remedy: Reduce the tilt on the upstrokes

  • Sections of Unequal Thickness are Produced

    • Reason: Tilt of knife is too great or bevel is not cleared

      • Remedy: Reduce the tilt

    • Reason: Blocks are too large

      • Remedy: Cut blocks into smaller fragments

Faults During Tissue Processing

  • Brittle or Hard Tissues

    • Reason: Prolonged fixation

      • Remedy: Soften tissue by soaking in a small dish with detergent, phenol, or molliflex

    • Reason: Overheated paraffin oven

      • Remedy: Repeat dehydration with absolute alcohol then clear again

  • Tissue Shrinks Away from Wax

    • Reason: Insufficient dehydration and incomplete clearing

      • Remedy: Repeat the whole procedure when trimmed

  • Inadequate Processing of Fatty Tissues

    • Reason: Routine schedule and reagents may not process fat adequately

      • Remedy: Ensure complete fixation and use appropriate lipid solvents like acetone or isopropanol

  • Hard, Dense Tissues

    • Reason: Tough keratin component of certain tissues

      • Remedy: Treat fixed tissues using 4% aqueous phenol for 24-72 hrs to soften