The Height of Pulses Seen on Impedance Counters is Proportional to Cell Volume
The height of pulses seen on impedance counters is directly proportional to cell volume (option D). This relationship forms the fundamental principle behind impedance-based cell counting and analysis technologies.
How Impedance Counters Work
Impedance counters operate on the Coulter principle, which measures changes in electrical resistance when particles pass through a small aperture. The mechanism works as follows:
- When cells suspended in a conductive fluid pass through a small aperture (orifice), they temporarily increase the electrical resistance across the aperture
- This resistance change is detected as a voltage pulse
- The height (amplitude) of this pulse is directly proportional to the volume of the cell passing through the aperture 1
Scientific Evidence Supporting Cell Volume Correlation
The relationship between pulse height and cell volume has been well-established in scientific literature:
- In aperture counters, particles flowing through a small orifice cause changes in electrical resistance that are translated into voltage pulses
- These signal pulses are collected into a spectrum of pulse heights by a multichannel pulse-height analyzer
- The channel number (voltage increment) spectrum is directly proportional to the volume distribution of the particles being measured 1
Why Other Options Are Incorrect
A. Number or concentration of cells
- While impedance counters can determine cell concentration, the pulse height itself corresponds to individual cell volume, not concentration
- Cell concentration is determined by counting the number of pulses over time, not by the height of each pulse
B. Hemoglobin density
- Hemoglobin density affects optical measurements but not impedance measurements
- Impedance counters detect changes in electrical resistance, which is primarily influenced by cell volume, not hemoglobin content
C. Nuclear complexity
- Nuclear complexity may influence certain cellular properties but does not directly determine the pulse height in impedance counters
- The electrical impedance change is primarily related to the total volume of the cell displacing conductive fluid
Applications of Impedance-Based Cell Volume Measurement
Impedance measurement technology has evolved to include:
- Electric cell-substrate impedance sensing
- Impedance flow cytometry
- Electric impedance spectroscopy 2
These technologies have applications in:
- Living cell counting and analysis
- Cell biology research
- Cancer research
- Drug screening
- Food and environmental safety monitoring 2
Advanced Applications in Cell Analysis
Recent developments have expanded impedance measurement capabilities:
- Dual-frequency impedance assays can analyze intracellular components at submicron levels 3
- Microfluidic impedance spectroscopy can perform quantitative analysis of subcellular structures 4
- Large-scale microelectrode arrays enable real-time, high-resolution impedance measurements of biological samples 5
The fundamental principle remains consistent across these applications: the height of the impedance pulse is proportional to the volume of the cell passing through the detection zone.