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Methods in laboratory investigation. Identification and evaluation of histopathology at microelectrode puncture sites
Abstract:
Tissue puncture techniques using microelectrodes for various measurements have been criticized for producing undetermined degrees of tissue damage. Therefore, a method permitting routine identification of puncture tracks was developed to determine local microelectrode-induced injury. Rabbits were anesthetized and the femoral arteries surgically exposed. A 3-ml mixture of saline-India ink suspension was introduced through an ear vein. Oxygen-sensitive (pO2) microcathodes were advanced into and through the arterial wall at 10- or 20-micron intervals using a stepping microdrive to 150 to 450 micron and then withdrawn. The arteries were fixed in 10% formalin and gelatin embedded, and serial frozen sections (less than or equal to 15 micron) of the microelectrode puncture area were made. We observed within 5 minutes of microcathode withdrawal a dark, punctate, microscopic discoloration within the arterial wall. Histologically, ink distribution within the arterial wall demonstrated an acute permeability change: puncture depths generally less than 300 micron showed ink-lined microelectrode tracks (generally less than 2 micron wide) in the media, and greater puncture depths showed local hemorrhage and focal laminar accumulation of ink which extended from the track. The immediate adjacent area to microelectrode puncture depths less than 300 micron showed an apparent intact internal elastic lamina and media. Therefore, microelectrode damage has been shown to be primarily limited to microelectrode tissue tracks.
Insights
Microelectrode use in tissue puncture can cause damage. This study developed a method to visualize microelectrode tracks, showing damage is primarily confined to the puncture site, not widespread tissue injury.
Area of Science:
- Biomedical Engineering
- Histology
- Vascular Biology
Background:
- Microelectrode techniques for tissue measurements are widely used.
- Concerns exist regarding the extent of tissue damage caused by microelectrode insertions.
- A reliable method to identify and quantify microelectrode-induced injury is needed.
Purpose of the Study:
- To develop and validate a method for visualizing microelectrode puncture tracks in arterial tissue.
- To determine the extent and nature of local tissue damage resulting from microelectrode insertion.
- To assess the impact of puncture depth on arterial wall integrity.
Main Methods:
- Anesthetized rabbits underwent femoral artery exposure.
- A saline-India ink suspension was injected intravenously to trace puncture pathways.
- Oxygen-sensitive microcathodes were inserted into the arterial wall using a microdrive, followed by withdrawal.
- Arteries were fixed, sectioned, and examined histologically for ink distribution.
Main Results:
- Microscopic, dark discoloration (ink tracks) was observed within 5 minutes of microelectrode withdrawal.
- Puncture depths <300 microns revealed ink-lined tracks (<2 microns wide) in the media.
- Deeper punctures (>300 microns) resulted in local hemorrhage and ink accumulation extending from the track.
- Arterial tissue adjacent to shallow punctures (<300 microns) appeared intact.
Conclusions:
- Microelectrode-induced tissue damage is primarily localized to the direct puncture track.
- The developed India ink method effectively visualizes microelectrode pathways and associated acute permeability changes.
- This technique allows for the determination of microelectrode-induced injury extent in vascular tissue.