Determination of intracellular conductivity from electrical breakdown measurements

Pilwat, G.; Zimmermann, U.

doi:10.1016/0005-2736(85)90125-7

Cited by 17 publications

(12 citation statements)

References 27 publications

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“…For yeasts, intact red blood cells and cultivated BHK cells, r i is in the range of 3-5 mS/cm. 18,30,40,41 Only earlier work reported a wider range of 2-9 mS/cm. 7 r i is therefore significantly lower than r m measured in this study ($18-21 mS/cm).…”

Section: Theoretical Backgroundmentioning

confidence: 97%

“…55,56 Differences in r i are most likely attributable to different ion concentrations in the cell's interior. 40 Based on the presented analysis, it is therefore assumed that significant changes in the intracellular environment (and hence, in r i ) occurred at the time of glutamine depletion. At that time, f C and De Fogale decreased in both batch cultivations.…”

Section: Multifrequency Permittivity Measurements and Analysis Of Calmentioning

confidence: 99%

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Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Ansorge

Esteban

Schmid

2009

Biotechnology Progress

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Lab and pilot scale batch cultivations of a CHO K1/dhfr À host cell line were conducted to evaluate on-line multifrequency permittivity measurements as a process monitoring tool. The b-dispersion parameters such as the characteristic frequency (f C ) and the permittivity increment (De max ) were calculated on-line from the permittivity spectra. The dual-frequency permittivity signal correlated well with the off-line measured biovolume and the viable cell density. A significant drop in permittivity was monitored at the transition from exponential growth to a phase with reduced growth rate. Although not reflected in off-line biovolume measurements, this decrease coincided with a drop in OUR and was probably caused by the depletion of glutamine and a metabolic shift occurring at the same time. Sudden changes in cell density, cell size, viability, capacitance per membrane area (C M ), and effects caused by medium conductivity (r m ) could be excluded as reasons for the decrease in permittivity. After analysis of the process data, a drop in f C as a result of a fall in intracellular conductivity (r i ) was identified as responsible for the observed changes in the dual-frequency permittivity signal. It is hypothesized that the b-dispersion parameter f C is indicative of changes in nutrient availability that have an impact on intracellular conductivity r i . On-line permittivity measurements consequently not only reflect the biovolume but also the physiological state of mammalian cell cultures. These findings should pave the way for a better understanding of the intracellular state of cells and render permittivity measurements an important tool in process development and control.

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Section: Theoretical Backgroundmentioning

confidence: 97%

Section: Multifrequency Permittivity Measurements and Analysis Of Calmentioning

confidence: 99%

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Ansorge

Esteban

Schmid

2009

Biotechnology Progress

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“…The oxygen gas concentration at the time of measurement did not have a statistically significant effect on blood resistivity, but incubation oxygen concentration did (P Ͻ 0.0001). Rheological changes alter blood resistivity (30,33) and may explain differences between normoxia-and hypoxia-incubated fetuses (21).…”

Section: Blood Resistivitymentioning

confidence: 99%

Effects of chronic hypoxia on cardiac function measured by pressure-volume catheter in fetal chickens

Jonker

Giraud

Espinoza

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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Hypoxia is a common component of many developmental insults and has been studied in early-stage chicken development. However, its impact on cardiac function and arterial-ventricular coupling in late-stage chickens is relatively unknown. To test the hypothesis that hypoxic incubation would reduce baseline cardiac function but protect the heart during acute hypoxia in late-stage chickens, white Leghorn eggs were incubated at 21% O2 or 15% O2. At 90% of incubation (19 days), hypoxic incubation caused growth restriction (-20%) and increased the LV-to-body ratio (+41%). Left ventricular (LV) pressure-volume loops were measured in anesthetized chickens in normoxia and acute hypoxia (10% O2). Hypoxic incubation lowered the maximal rate of pressure generation (ΔP/ΔtMax; -22%) and output (-57%), whereas increasing end-systolic elastance (ELV; +31%) and arterial elastance (EA; +122%) at similar heart rates to normoxic incubation. Both hypoxic incubation and acute hypoxia lengthened the half-time of relaxation (τ; +24%). Acute hypoxia reduced heart rate (-8%) and increased end-diastolic pressure (+35%). Hearts were collected for mRNA analysis. Hypoxic incubation was marked by decreased mRNA expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase 2, Na(+)/Ca(2+) exchanger 1, phospholamban, and ryanodine receptor. In summary, hypoxic incubation reduces LV function in the late-stage chicken by slowing pressure generation and relaxation, which may be driven by altered intracellular excitation-contraction coupling. Cardiac efficiency is greatly reduced after hypoxic incubation. In both incubation groups acute hypoxia reduced diastolic function.

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“…In addition to theory and modeling, various experimental approaches have been applied to measure cell interior and membrane properties. For instance, a voltage patch clamp was utilized to directly measure neuronal membrane capacitance [8] and intracellular conductivity was determined from cell membrane electric breakdown [9]. Despite all these efforts, the dielectric properties of many mammalian cells have yet to be determined accurately because of the vast variety of cell types; the values of those that have been reported in the literature vary widely [1,2,8,10].…”

Section: Introductionmentioning

confidence: 99%

Estimation of the physical properties of neurons and glial cells using dielectrophoresis crossover frequency

et al. 2016

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We successfully determine the ranges of dielectric permittivity, cytoplasm conductivity, and specific membrane capacitance of mouse hippocampal neuronal and glial cells using dielectrophoresis (DEP) crossover frequency (CF). This methodology is based on the simulation of CF directly from the governing equation of a dielectric model of mammalian cells, as well as the measurements of DEP CFs of mammalian cells in different suspension media with different conductivities, based on a simple experimental setup. Relationships between the properties of cells and DEP CF, as demonstrated by theoretical analysis, enable the simultaneous estimation of three properties by a straightforward fitting procedure based on experimentally measured CFs. We verify the effectiveness and accuracy of this approach for primary mouse hippocampal neurons and glial cells, whose dielectric properties, previously, have not been accurately determined. The estimated neuronal properties significantly narrow the value ranges available from the literature. Additionally, the estimated glial cell properties are a valuable addition to the scarce information currently available about this type of cell. This methodology is applicable to any type of cultured cell that can be subjected to both positive and negative dielectrophoresis.

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Determination of intracellular conductivity from electrical breakdown measurements

Cited by 17 publications

References 27 publications

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Effects of chronic hypoxia on cardiac function measured by pressure-volume catheter in fetal chickens

Estimation of the physical properties of neurons and glial cells using dielectrophoresis crossover frequency

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