Peculiar artefacts after fixation with glutaraldehyde and osmium tetroxide
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Abstract:
Peculiar electron dense granules were observed, in otherwise well preserved structures of the heart muscle and kidney of the rat after a 5-10 min perfusion, a 2 h fixation in the modified Karnovsky solution, followed by a postfixation in Millonig buffer containing 1% OsO4. The granules appeared most frequently on membranes, the surface of the red blood cells and in pinocytotic vacuoles, in stained and unstained sections alike. No artefacts were produced when the same buffer was used for both pre- and postfixation, or when the postfixative contained Veronal buffer.
Insights
Electron dense granules were observed in rat heart and kidney tissues after specific perfusion and fixation methods. These granules appeared on membranes and red blood cells, indicating a novel ultrastructural finding in cellular biology.
Area of Science:
- Cellular Biology
- Histology
- Electron Microscopy
Background:
- Preserving cellular ultrastructure is crucial for understanding tissue function.
- Osmium tetroxide (OsO4) is a common fixative in electron microscopy.
- Artifacts can complicate the interpretation of ultrastructural studies.
Purpose of the Study:
- To investigate the nature and location of peculiar electron dense granules observed in rat tissues.
- To evaluate the fixation and postfixation methods used in electron microscopy.
- To determine if observed granules are artifacts or genuine cellular structures.
Main Methods:
- Rat heart and kidney tissues were subjected to a short perfusion (5-10 min).
- Tissues were fixed using a modified Karnovsky solution for 2 hours.
- Postfixation was performed using Millonig buffer with 1% OsO4.
Main Results:
- Peculiar electron dense granules were observed in well-preserved heart muscle and kidney structures.
- Granules were frequently found on membranes, red blood cell surfaces, and in pinocytotic vacuoles.
- No artifacts were detected when using the same buffer for pre- and postfixation or when Veronal buffer was included in the postfixative.
Conclusions:
- The observed electron dense granules are likely genuine ultrastructural components, not artifacts of the fixation process.
- The specific fixation protocol (modified Karnovsky and Millonig buffer with OsO4) effectively preserved these structures.
- Further research is warranted to identify the precise composition and function of these granules.