Sonoporation, referring to transient membrane permeation phenomenon generated by acoustic cavitation, has spurred significant scientific interests for its potential applications in facilitating uptake of drugs and genes into living cells. With an increasing level of technical maturity in realizing sonoporation, scientists are trying to gain a deeper understanding of the cellular responses related to this biophysical phenomenon from the standpoint for drug/gene delivery. However, challenges and difficulties remain to be overcome including providing direct evidences for the microbubble-cell wave matter interaction mechanism, obtaining controllable sonoporation at the desired locations on the cell membrane, maintaining the viability of the sonoporated cells with high efficiency delivery outcomes and so on. Such a lack of scientific foundations has been recognized as a fundamental obstacle in substantiating the application merit of sonoporation. In this study, the overall objective is to stepwise unravel the cellular stress induced by microbubble-mediated sonoporation after resealing. To achieve it, two kinds of well-calibrated ultrasound exposure platforms are designed. One of them can be used for the in situ observation of the wave matter interaction ways during sonoporation via the confocal microscope. The other ultrasound exposure setup can be used for the studies of the sonoporation induced bio-effects which need many cells for analysis. With these designed and well calibrated ultrasound exposure platforms, new insights for the cellular impacts induced by sonoporation are provided. As demonstrated in vitro, sonoporation may inadvertently induce repressive cellular features even whilst enhancing exogenous molecule uptake. Both suspension-type (HL-60) and adherence-type (ZR-75-30) cells were employed in this investigation. They were routinely exposed to 1 MHz pulsed ultrasound with calibrated acoustic field profile and in the presence of microbubbles. The post-exposure morphology and the intracellular actin cytoskeletons dynamics of sonoporated cells were examined in situ using confocal microscopy. Furthermore, the cell-cycle progression kinetics of the viable sonoporated cells were analyzed using flow cytometer. Results show that, for both investigated cell types, viable sonoporated cells would exhibit membrane and nucleus shrinkage, intracellular lipid accumulation and actin deploymerization over a two hours period. On the other hand, as compared to the sham control cells, the deoxyribonucleic acid (DNA) synthesis duration of sonoporated cells is significantly lengthened as indicative of a delay in cell-cycle progression. These features are known to be characteristics of a cellular stress response, suggesting that sonoporation indeed constitutes itself as a cellular stress to living cells even after the cells are resealed. In terms of the implication of this work, this study has shown that sonoporation can be a significant cellular stress both short term and long term after ultrasound exposure. In particular, the intracellular homeostasisis found disrupted even with membrane resealing. Therefore, if sonoporation is to be used for drug delivery, efficiency may be a problem that really needs to be solved in optimizing sonoporation for drug/gene delivery purposes. On the other hand, it raises opportunities for developing other therapeutic applications via sonoporation. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Therapeutic ultrasound employs the acoustic energy carried by high-frequency mechanical wave to induce beneficial effects on living systems. This therapeutic approach is advantageous in that its energy could be remotely focused on the targeted tissue in a non-invasive manner. Although ultrasound therapy has been shown to be feasible and effective in both laboratory experiments and clinical trials, its safety and efficacy are still challenged by the lack of fundamental knowledge of how ultrasound wave exerts physical effects on the cell system and how the cell functionally responds to the ultrasound stimulation. Motivated by the above insight, this thesis aims to provide direct experimental evidence for illustrating the biophysical details of how ultrasound wave (alone or combined with microbubble) interacts with live cells. An acoustic experimental platform with well-calibrated ultrasound field and live-cell imaging modality was developed to observe ultrasound-cell interaction. Based on this platform, a series of single-cell studies was then conducted to monitor the structural and functional changes of the live cell as well as its fluorescently-labelled components over the course of ultrasound exposure. Results obtained in this thesis provided image-level evidence for characterizing the ultrasound-cell interactions in the following three aspects. First, it was found that low-intensity ultrasound pulsing could directly perturb the plasma membrane, the cytoskeletal network and the inner nucleus of live neuroblastoma cells. This cytomechanical perturbation would result in reversible and structural alternations of subcellular components. Second, low-intensity pulsed ultrasound, when applied on neuronal cells, could exert morphological impact through inducing neurite retraction and cell body displacement, and electrophysiological impact in the form of membrane depolarization and calcium influx. This finding verified the potential of ultrasound in modulating neuronal development and excitability. Last, the cell membrane perforation and resealing dynamics induced by the ultrasound-activated microbubble were visualized and characterized. The subsequent cellular responses to this ultrasound-induced sonoporation were also identified at both membrane and cytoskeleton levels. The significance of this study is to provide direct and solid experimental evidence for understanding the biophysical interactions between ultrasound wave and live cell. This advanced scientific interpretation is definitely crucial for establishing the cellular mechanisms of therapeutic ultrasound and for providing technical insights into ultrasound treatment. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Strawberry plants (Fragaria x annanasa D.) were grown in drip irrigated plots covered with gray/black plastic mulch at the Campus Agricultural Center, University of Arizona, Tucson, AZ. During the 1993-94 season varieties Chandler and Oso Grande were grown while in the 1994-95 season varieties Chandler and Selva were grown. Crop coefficients to estimate crop evapotranspiration for Chandler were determined on calendar day and growing degree day (GDD) basis. For the harvest period, the crop coefficients ranged from 0.35 for early March to 0.6 for early June. GDD were computed using 6 °C as the base temperature and 26 °C as the upper threshold temperature. Although GDD is useful to estimate water needs, it did not predict the starting date of harvest because other factors such as day length, transplanting date, and chilling period are involved. In the 1994-95 season, dry, medium and wet irrigation treatments were established for the Chandler. The well irrigated plants yielded 328 g/plant, equivalent to 21.2 metric tons/ha. The dry treatment received 33 % less water than the medium treatment and resulted 25% less yield. There were no statistical differences in yield between the medium and wet treatments, although the wet treatment received 33% more water than the medium treatment. The Oso Grande and Selva were tested and they yielded 46 and 22% less than Chandler, respectively. The harvest period extended for 70 to 100 days and premium size berries were produced during the first half of the harvesting season.

Greece, like many other countries, has experienced great changes in food supply, consumption patterns and health outcomes. Famous for its Mediterranean diet, it has actually undergone a modem nutrition transition, and now has high rates of overweight and obesity and increased incidence of non-communicable nutrition-related diseases. This study begins with that reality and the current failure of food policy and nutrition-related initiatives to tackle problems. The study explores whether and how social marketing could remedy this policy deficit and contribute to changing Greek food behaviour. The thesis describes a contextual review of the state of nutritional health, the food system and food policy in Greece and outlines social marketing theory and experience. Two studies were conducted to answer the research questions. The first was a case study conducted on a sample of undergraduate students through nine focus groups with fifty-nine Greek undergraduate students from eight Athenian education institutes to explore the influencers of eating behaviour, the impact of current initiatives and the potential of social marketing. A second study of thirty-two key stakeholders in significant positions in the Greek food system explored through semi-structured interviews the reactions of education institutes, civil society, government and food supply chain representatives to the Greek food situation and the potential of social marketing. The fieldwork studies found that social marketing was not likely to be a panacea but has potential for Greece. The first study found that eating decisions are complex, based on individual as well as environmental factors. Both studies highlighted policy failings in government, while the second study specified the problematic structure of the public sector and a reluctance to confront existing food culture. Both studies found potential for social marketing to help change Greek food culture but its utility depends on factors beyond the realm of food policy alone. Political will, suitably qualified people and changes in the food system are all necessary. The thesis concludes that social marketing would be enhanced by an integrated food policy framework and from a broader understanding of behaviour change in general and of the dynamics of eating behaviour in particular. A new model of this integrated approach is proposed. Greek food policy would be enriched by the citizen-centric approach of social marketing but only if the full 5 Ps that will include "Policy" are applied as the policy element is too easily marginalised. The thesis proposes that food policy be integrated around three dimensions of action: food safety and hygiene, nutrition and environment.

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Emerging adulthood is a time of significant change where behaviors are adopted that can have significant long term effects on health. The most dramatic increases in weight are occurring among emerging adults, especially those with some college education. Emerging adults are also at an increased risk for substance use and abuse. The current study examined the relationship between BMI and substance use among college students. Participants included 703 undergraduate students at a large public U.S. university (M age=20.6, 58.7% Non-Hispanic White, 59.8% female). Students completed an online survey with items on substance use behaviors such as smoking, alcohol use, marijuana use, and binge drinking. Tobacco, alcohol, marijuana use, and binge drinking were assessed with one question asking students how many days over the past month they had used the specific substance (range 0-30 days). Binge drinking was assessed using one question: “Over the last two weeks, how many times have you had five or more drinks of alcohol at a sitting?” Responses ranged from 0 to 10 or more times. Substance use behaviors were coded to no use/any use in the past month. Body mass index was calculated through the student’s self reported height and weight. BMI was significantly related to past month tobacco use with an odds ratio of 1.06 (95% CI: 1.01-1.12). Specifically, with every one unit increase in BMI, the odds of past month tobacco use increased by 6%. However, BMI was not significantly associated with past month alcohol use, marijuana use, or binge drinking (p>.05). As BMI increases, college students’ odds of using tobacco increase. This finding is particularly problematic given that weight gain is common among undergraduate students and cigarette use has been cited as a common weight management practice among this group as well. Future research should consider the role of BMI as a factor in decreasing tobacco use. / text

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

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