The purpose of this study was twofold: 1) to present experimental data on changes in permeability of fibers during irradiation using Na22 as the tracer isotope, and 2) to attempt to correlate these findings with the electrical changes observed.

The purpose of this study was (1) to measure the changes in water flux in isolated roots exposed to n-DSA and its mono-methly ester (m-MDSA) using a photometric technique in the absence of an externally applied suction and (2) to measure the flux of Na and K in similarly treated roots using a flame photometric method.

The title of this thesis requires some explanation. The term "microcapsules" is a coinage of my own. The Concise Oxford Dictionary gives several definitions of "capsule" (from Latin capsa, a case). Two of these definitions are relevant to my usage: a capsule is a "membranous envelope (Physiol.)" or a "gelatine envelope enclosing pill (Med.)". A "semipermeable aqueous microcapsule" is therefore an envelope of semipermeable membrane enclosing a very small aqueous compartment. At this point it may be useful to discuss also the terms "membrane" and "semipermeable". [...]

No description available.

The aim of the study is to investigate the causal relationship between membrane-damaging activity and antibacterial action of cardiotoxins from Naja naja atra (Taiwan cobra) cardiotoxin 3 (CTX3) and Naja nigricollis (Egyptian cobra) toxin gamma. Compared with that on Escherichia coli (E. coli, Gram-negative bacteria), CTX3 showed a greater growth inhibition on Staphylococcus aureus (S. aureus, Gram-positive bacteria). Antibacterial avtivity of toxin gamma toward E. coli and S. aureus was similar. Bactericidal action of cardiotoxins positively correlated with increase in membrane permeability of bacterial cells. Morphological examination showed that cardiotoxins disrupted the integrity of bacterial membrane. Cardiotoxins showed similar binding capability with lipopolysaccharide (LPS) and lipoteichoic acid (LTA), and destabilization of LPS layer and inhibition of LTA biosynthesis on cell wall promoted bactericidal effect of cardiotoxins on E. coli and S. aureus, respectively. CTX3 notably permeabilized model membrane of S. aureus and toxin gamma had similar activity on the permeabilization of bacterial model membrane used. Membrane-damaging activity of cardiotoxins was inhibited by either LPS or LTA, while increasing concentrations of cardiotoxins counteracted the inhibitory action of LPS and LTA. Oxidation of Met residues on loop II of cardiotoxins simultaneously attenuated membrane-permeabilizing activity and bactericidal effect of cardiotoxins. Taken together, our data indicate that antibacterial action of cardiotoxins depend on their ability to induce membrane permeability.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 96-104).

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [126]-169).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [114]-152).

Electroporation-based treatments are motivated by the response of biological membranes to high- intensity pulsed electric fields. These fields rearrange the membrane structure to enhance the membrane's diffusive permeability, or the degree to which a membrane allows molecules to diffuse through it, is impacted by the structure, composition, and environment in which the cell resides. Tracer molecules have been developed that are unable to pass through intact cell membranes yet enter permeabilized cells. This dissertation investigates the hypothesis that the flow of such molecules may be used to quantify the effects of the electrical stimulus and environmental conditions leading to membrane electroporation. Specifically, a series of electrical pulses that alternates between positive and negative pulses permeabilizes cells more symmetrically than a longer pulse with the same total on-time. However, the magnitude of this symmetric entry decreases for the shorter alternating pulses. Furthermore, a method for quantitatively measuring the permeability of the cell membrane was proposed and validated. From data near the electroporation threshold, the response of cells varies widely in the manner in which cells become permeabilized. This method is applied to study the transient cell membrane permeability induced by electroporation and is used to demonstrate that the cell membrane remains permeable beyond 30 min following treatment. To analyze these experimental findings in the context of physical mechanisms, computational models of molecular uptake were developed to simulate electroporation. The results of these simulations indicate that the cell's local environment during electroporation facilitates the degree of molecular uptake. We use these models to predict how manipulating both the environment of cells during electroporation affects the induced membrane permeability. These experimental and computational results provide evidence that supports the hypothesis of this dissertation and provide a foundation for future investigation and simulation of membrane electroporation. / PHD / Electroporation is a biophysical process in which intense electric fields permeabilize bilayer membranes. The degree to which a membrane allows molecules to diffuse through it is called its diffusive permeability, and is impacted by the structure, composition, and environment in which the cell resides. This dissertation investigates the hypothesis that the flow of molecules into cells through their membranes may be used to quantitatively study the effects of the electrical stimulus and environmental conditions leading to membrane disruption. Here, I demonstrate that the cellular response to pulsed electric fields is affected by the waveform of the applied electrical stimulus. Specifically, a series of electrical pulses that alternates between positive and negative pulses permeabilizes cells more symmetrically than a longer pulse with the same total energized time. However, the total molecular uptake decreases for the shorter alternating pulses over the longer pulse. A method for quantitatively measuring the permeability of the cell membrane using a fluorescent tracer molecule is also developed and validated. This method is applied to show how cell membrane permeability changes following electroporation. To analyze these findings, computational models of molecular flow through the cell membrane are developed. These simulations indicate that the cell’s surrounding environment during electroporation dramatically impacts the degree of molecular uptake. We use these models to predict how manipulating both the environment of cells during electroporation affects the induced membrane permeability. These experimental and computational results provide a foundation for future investigation and simulation of membrane electroporation.