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Direct localised measurement of electrical resistivity profile in rat and embryonic chick retinas using a microprobe

Harsha Kasi
Harsha Kasi
, 
Robert Meissner
Robert Meissner
, 
Alexandre Babalian
Alexandre Babalian
, 
Harald van Lintel
Harald van Lintel
, 
Arnaud Bertsch
Arnaud Bertsch
 and 
Philippe Renaud
Philippe Renaud
   | Dec 31, 2010
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Article Category: Articles
Published Online: Dec 31, 2010
Page range: 84 - 92
Received: Dec 14, 2010
DOI: https://doi.org/10.5617/jeb.149
© 2010 Harsha Kasi, Robert Meissner, Alexandre Babalian, Harald van Lintel, Arnaud Bertsch and Philippe Renaud, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

A schematic of the electrodes with dimensions to scale.
A schematic of the electrodes with dimensions to scale.

Fig. 2

Photograph of the device used. (Left) The plastic base is used to facilitate attachment to a micromanipulator (not shown) for assisting in precise insertion of the electrodes into the retina. (Right) The narrow polyimide shaft consisting of the electrodes is the part that is inserted in the retina preparation.
Photograph of the device used. (Left) The plastic base is used to facilitate attachment to a micromanipulator (not shown) for assisting in precise insertion of the electrodes into the retina. (Right) The narrow polyimide shaft consisting of the electrodes is the part that is inserted in the retina preparation.

Fig. 3

An electrical equivalent representing the electrode and tissue components based on Cole model for measured tissue impedance. ZCPE_E is the constant phase element (CPE) representation of the electrodes. Rintra is the effective resistance offered by the intracellular fluid. ZCPE_T is the he CPE part of the tissue impedance. Rtissue is the resistive part of the tissue impedance. CPAR is the parasitic capacitance between the electrodes through the polyimide passivation.
An electrical equivalent representing the electrode and tissue components based on Cole model for measured tissue impedance. ZCPE_E is the constant phase element (CPE) representation of the electrodes. Rintra is the effective resistance offered by the intracellular fluid. ZCPE_T is the he CPE part of the tissue impedance. Rtissue is the resistive part of the tissue impedance. CPAR is the parasitic capacitance between the electrodes through the polyimide passivation.

Fig. 4

Bode plot at a certain depth in the retina and the corresponding fit using the electrical equivalent. The tissue resistance is identified at the peak resistance frequency (PRF), the point at which the phase is closest to 0°.
Bode plot at a certain depth in the retina and the corresponding fit using the electrical equivalent. The tissue resistance is identified at the peak resistance frequency (PRF), the point at which the phase is closest to 0°.

Fig. 5

Experimental apparatus consisted of (i) an Eppendorf 5171 micromanipulator that displaces the microprobe vertically (z-axis) in steps of 10μm, (ii) an Agilent 4294A impedance analyser for recording impedance/phase spectra for each probed retinal depth. (iii) a plastic petri-dish containing the isolated retinal slice placed on a block of Agar gel (1% in Ringer’s solution) submerged in Ringer’s solution.
Experimental apparatus consisted of (i) an Eppendorf 5171 micromanipulator that displaces the microprobe vertically (z-axis) in steps of 10μm, (ii) an Agilent 4294A impedance analyser for recording impedance/phase spectra for each probed retinal depth. (iii) a plastic petri-dish containing the isolated retinal slice placed on a block of Agar gel (1% in Ringer’s solution) submerged in Ringer’s solution.

Fig. 6

Bode plot in Ringer’s solution and the corresponding fit using the electrical equivalent replacing the tissue component by a simple resistor representing the solution resistance. The solution resistance is extracted from the modified model fit. Knowing the resistivity of the medium, an experimental cell constant of 225cm-1 was calculated. From fitting, the magnitude of ZCPE_E was found to be 3.154×× 10-10 Ωα-1⋅Fα, where α=0.85.
Bode plot in Ringer’s solution and the corresponding fit using the electrical equivalent replacing the tissue component by a simple resistor representing the solution resistance. The solution resistance is extracted from the modified model fit. Knowing the resistivity of the medium, an experimental cell constant of 225cm-1 was calculated. From fitting, the magnitude of ZCPE_E was found to be 3.154×× 10-10 Ωα-1⋅Fα, where α=0.85.

Fig. 7

PRF shift observed at various depths in a rat retina. As the PRF shifts from the right to left, the impedance increases with increasing depth into the retina (from the retinal ganglion cell towards photoreceptor layer). Depth is normalised to 100% retinal depth. A 10% retinal depth corresponded to an approximate microprobe displacement of 14μm in the retina
PRF shift observed at various depths in a rat retina. As the PRF shifts from the right to left, the impedance increases with increasing depth into the retina (from the retinal ganglion cell towards photoreceptor layer). Depth is normalised to 100% retinal depth. A 10% retinal depth corresponded to an approximate microprobe displacement of 14μm in the retina

Fig. 8

Mean resistivity (±SD) vs. percentage depth profile of three rat retina samples which are extracted from 14-16 day old postnatal wild-type juvenile rats.
Mean resistivity (±SD) vs. percentage depth profile of three rat retina samples which are extracted from 14-16 day old postnatal wild-type juvenile rats.

Fig. 9

PRF vs. resistivity plots for the three rat experiment trials. A large deviation for resistivity at a particular PRF between the trials was observed.
PRF vs. resistivity plots for the three rat experiment trials. A large deviation for resistivity at a particular PRF between the trials was observed.

Fig. 10

Mean resistivity (±SD) vs. percentage depth profile of five chick embryo retina samples of which three are extracted from E18 and two from E12. E18 have a higher peak mean resistivity than the E12 chick trials.
Mean resistivity (±SD) vs. percentage depth profile of five chick embryo retina samples of which three are extracted from E18 and two from E12. E18 have a higher peak mean resistivity than the E12 chick trials.

Fig. 11

PRF vs. resistivity plots for the five embryonic chick trials. In general, a good reproducibility of resistivities at a particular PRF in the trials was observed.
PRF vs. resistivity plots for the five embryonic chick trials. In general, a good reproducibility of resistivities at a particular PRF in the trials was observed.
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