Date of Award

Summer 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Karl H. Schoenbach

Committee Member

Juergen Kolb

Committee Member

Ravindra P. Joshi

Call Number for Print

Special Collections LD4331.E55 S33 2006

Abstract

Nanosecond pulsed electric fields (nsPEF) of megavolt per meter field strengths can interact with subcellular structures [1] and consequently trigger a variety of biological events. The exposure can induce apoptosis, as well as an array of differential "sub-lethal effects." One of the most sensitive and immediate responses is the increase in intracellular calcium concentration in pulsed cells [2], [3][4].We investigated the response of Jurkat cells (a human leukemic cell line) to nsPEFs of 60 ns duration and field strengths from 25 tol00 kV/cm. The development of the induced calcium response in individual cells was studied by spinning-disc confocal microscopy with the calcium indicator Fluo-4. The fast imaging rate of this system allowed us to record the development of fluorescence changes representing calcium mobilization with a temporal resolution of 5 ms exposure every 18 ms. Pulse-induced calcium release is electric field-dependent with the fluorescent response increasing as the electric field strength is raised from 25 to 100 kV /cm. The presence of extracellular calcium affected the calcium response of cells pulsed at 100 kV/cm, but there was no statistically significant difference at 25 and 50 kV /cm between cells pulsed in its presence or absence. The 18 ms temporal response was fast enough to resolve the spontaneous physiological response in non-pulsed cells, but not the response to pulses of 50 kV /cm and 100 kV /cm amplitude.

Whereas the temporal and spatial resolution in previous studies was not sufficient to observe the source of calcium after pulsing, results in this research suggest that the calcium signal originates from the endoplasmic reticulum. The effects of a second pulse were observed to investigate whether the stores could recover between pulses. The results show a second calcium response equivalent to or less than the magnitude of the first response upon applications of pulses with the same field strengths.

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DOI

10.25777/t5nd-5y77

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