103 research outputs found
Nicotiana sylvestris, a model plant for cell biology: organelle movement and retrotransposon mutagenesis
No full textNicotiana sylvestris is a diploid tobacco plant that is amenable to laboratory manipulation including facile transformation of nuclear and plastid (chloroplast) genomes. In three separate studies, I used this model organism to observe biological processes with evolutionary and biotechnological implications. The first addresses the mechanisms of horizontal gene transfer by demonstrating cell-to-cell movement of plastids. We grafted Nicotiana sylvestris plants with selectable transgenic plastid genomes to Nicotiana tabacum plants with selectable transgenic nuclear markers. Grafting triggers formation of new cell-tocell contacts, creating an opportunity for organelle movement between the plant cells. I present evidence for cell-to-cell movement of the entire 161-kb plastid genome in these plants, most likely in intact plastids. Acquisition of plastids from neighboring cells provides a mechanism by which cells may be repopulated with functioning organelles. My second objective was to determine whether exceptional pollen transmissionof plastids is accompanied by paternal mitochondria transmission in Nicotiana sylvestris. Plastids and mitochondria in Nicotiana are normally both inherited from the maternal parent. We observed that plastids from the N. sylvestris father were transmitted at a low (~0.002%) frequency via pollen. The plants that inherited paternal plastids did not carry paternal mitochondrial DNA, indicating that leakage of plastids via pollen can produce plant lines with unrelated plastids and mitochondria. My third objective was to observe the behavior of an individual high-copy retrotransposon in N. sylvestris, its native host. Long terminal repeat (LTR) retrotransposons are major components of the nuclear genomes of plants, animals and fungi. The “copy-and-paste” life cycle of retrotransposons accounts for their accumulation in host genomes and permits the assumption that LTRs are identical at the time of insertion. Our objective was to experimentally determine if an introduced synthetic element would interact with native high-copy elements during retrotransposition. I present evidence that S-TNT1 co-packaged with native TNT1 elements to produce hybrid insertions with swapped LTRs and multiple recombinations within the gag-pol gene. We can best explain our observations by dimerization and co-packaging of TNT1 gRNAs in the cytoplasm, followed by template-switching during minus-strand DNA synthesis, which we term the “mixand- paste” pseudodiploid mating system for LTR-retroelements.Ph. D.Includes bibliographical referencesIncludes vitaby Gregory N. Thysse
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Development of a Laser-Induced Cavitation Bubble Mechanotransduction Platform
No full textDevelopment of a Laser-Induced Cavitation Bubble Mechanotransduction PlatformBy Bryce G WilsonDoctor of Philosophy in Chemical and Biomolecular Engineering
University of California, Irvine, 2023
Professor Vasan Venugopalan, Co-Chair
Professor Elliot L. Botvinick, Co-ChairWe present the development of an optical platform for the stimulation and visualization of cellular mechanotransduction using the initiation and measurement of laser induced cavitation bubbles in conjunction with biological microscopy. This work builds from our lab’s previous demonstration of the use of micro-cavitation bubbles (µCB) to generate impulsive fluid shear stresses1 and elicit cellular mechanotransduction in 2D cell culture. This work also demonstrated that cavitation induced fluid flow could be observed as a basis for a high-throughput molecular screening of drugs related to mechanotransduction1. In this thesis we focus on expanding the use of laser induced cavitation bubbles to examine cellular mechanotransduction in 3D engineered tissues. Given the importance of the mechanical properties of the microenvironment in which the cells reside we also demonstrate how the measurement of cavitation dynamics can be used to determine the mechanical properties of the medium in which the cells reside. We demonstrate the use of Laser-Induced Cavitation Rheology (LICR) to measure viscoelastic properties of soft matter at high strain-rates. Experimentally captured cavitation dynamics are compared to theoretically modelled cavitation dynamics to fit for elastic modulus (η) and material failure strain (εf). We demonstrated the capability of detecting the predicted increased elastic modulus with increasing hydrogel density in both an amorphous PEG gel (6%, 7%) and a biologically derived fibrin gel (2.5mg/ml, 10mg/ml). Importantly, in this work cavitation dynamics were retrieved via time-resolved photography. Therefore, experimentally derived cavitation dynamics were the result of “averaged” dynamics over hundreds of cavitation events in their respective gels 2.
A crucial cornerstone to deploying LICR in 3D biological samples is the capability of measuring cavitation dynamics from single cavitation events in order to remove variability due to spatial heterogeneity in the 3D sample. We demonstrated an interferometric method to provide single-shot measurements of cavitation bubble dynamics with nanoscale spatial and temporal resolution. In comparison to time resolved photography which has noise on the order of microns we have shown interferometric spatial and temporal resolution on a nanoscale. Interferometrically derived dynamics are shown to match theoretical cavitation dynamics for bubbles between 25um and 150um.3
Finally, we demonstrate the use of laser generated cavitation bubbles to provide direct cellular mechano-stimulation in 3D hydrogels. We embedded fluorescently engineered Normal Healthy Dermal Fibroblasts (NHDF) in both amorphous polyvinyl alcohol (SLOPVA) hydrogels and biologically derived fibrous collagen hydrogels and observed intracellular calcium responses following exposure to a single 250µm diameter laser generated single cavitation bubble. We found that the spatial extent of cellular signaling is more extensive in cells embedded in fibrous collagen ECM gels in contrast to those embedded in amorphous gels (SLOPVA). We also found increased mechanosensitivity in collagen hydrogels in cells that were oriented along the bubble’s radial axis vs those oriented perpendicular to this axis. We found that extracellular calcium was required for intracellular calcium signalling to occur.
Overall, we demonstrated a non-invasive local tunable impulsive mechanical stimulus within 3D tissue models. Collectively, these results establish our technology as a promising multi-faceted tool to study mechanotransduction in 3D microenvironments. This platform presents an approachable and versatile combination of technologies for the investigation of mechanosignaling pathways and their associated material properties
The relationship between Ford, Kipling, Conan Doyle, Wells and British propaganda of the First World War
No full textPhDThis thesis resituates the war-writing of Ford Madox Ford, Rudyard Kipling, Arthur
Conan Doyle and H.G. Wells in relation to official British propaganda
produced during the First World War. Examining these authors' institutional
connections with propaganda that was authorised by the British government locates
some of their texts within a network of materials that were deployed to justify
Britain's involvenlent in the war. The British government, via the War Propaganda
Bureau, approached major literary figures to assist in its plan to compete
vigorously with Germany to win American support. Positioning Ford's condemnation
of Prussian culture within this institutional context reveals that his officially
commissioned books functioned as a part of the larger yet-covert government
project to influence American intellectual opinion. Although wary that Kipling's
chauvinism might offend some readers, the British government reprinted and
distributed his denunciations of the 'Hun'. Kipling was given access to censored
letters from Indian soldiers in order to assist him in depicting the Imperial forces as
united. The result, The Eyes of Asia (1918), was a set of fictional texts by Indian
soldiers celebrating French and English civilisation in contrast to German barbarism.
In addition to official propaganda, these authors produced pro-war stories, poems, and
articles independent of direct government commission. Conan Doyle's formal call for
men to volunteer to defend their country, and his public denunciations of German
atrocities, were followed by his recruitment of Sherlock Holmes to repel a possible
German invasion ("His Last Bow" (1917)). Adding to his support for the war in his
journalism and war-time fiction, Wells was appointed the Head of Enemy Propaganda
for the newly formed Ministry of Information. He resigned almost immediately
following disagreements over government strategy. This project situates historically
and examines critically these authors' differing roles in relation to British propaganda
efforts during the First World War
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"A Government of Men": Responsible Government and the Rule of Law in the Progressive Era
No full textThe Massachusetts Constitution of 1780 famously declares that the principle of the separation of powers will bind the commonwealth, “to the end it may be a government of laws and not of men.” The idea of “a government of laws” expresses the Enlightenment ideal of an impersonal form of rule that substitutes abstract justice for the capriciousness of personal rule and is associated with two distinguishing features of American constitutionalism: the separation of powers and judicial review of administration and legislation. A century after Adams wrote, however, the ideal of “a government of laws” came under attack by a new trend in political thought. In place of a government of laws, a group of turn-of-the-century thinkers that included Woodrow Wilson, Frank Goodnow, Henry Jones Ford, and Herbert Croly advocated a system of government that, by uniting rather than separating legislative and executive power and by reducing judicial control of government, sought to enable an elected executive to hold real responsibility and, accordingly, to be held responsible by voters—what some of them called “a government of men.” Their vision of government was encapsulated in the idea of responsible government. The archetype of responsible government was British parliamentarism, or responsible cabinet government. As theorized and advocated by the American school of responsible government, a range of reform ideas from presidential representation, the unitary executive, and the executive budget, to weakened judicial review of legislation and even, for some, the popular recall of state governor, properly understood, were part of a project to establish some approximation of parliamentary government within the constraints of the American context—what is here called “parliamentarism with American characteristics.” This dissertation offers the first full account of that project.
It does so in six chapters. Chapter 1 begins the story in the 1880s with the idea of formally parliamentarizing the American constitution by giving cabinet members seats in Congress, famously supported by a young Woodrow Wilson but also less famously by Gamaliel Bradford in a modified form. Chapter 2 follows Wilson in his pivot away from the Cabinet-in-Congress idea towards ways of achieving responsible government within the existing system through transformation of the presidency. It traces the development of this idea of responsible presidential government in the writings of James Bryce, Ford, Wilson, and Croly in the context of the transformation of the presidency by the three “progressive presidents,” Roosevelt, Taft, and Wilson. Chapter 3 considers how the principle of responsible presidential government extended from the executive’s leadership of the legislature to its control over the administration in Frank Goodnow’s pioneering scholarship in public administration and administrative law. Chapter 4 extends the analysis to the judicial power by asking just how far the school of responsible government meant to take its critique of a “government of laws” through an examination of the diversity of their views on judicial review of legislation and administration. Chapter 5 situates the school of responsible government in the context of the progressive-era debate over direct democracy and representative government, exploring their varying assessments of the direct primary, initiative, referendum, and recall. Chapter 6 offers an account of the New York Constitutional Convention of 1915, which under the leadership of Henry Stimson synthesized the main principles of responsible government as developed by the figures studied in chapters 1-5 and applied them in a concrete set of constitutional amendment proposals.Governmen
Schooling for 'lesser beings'
No full textUsing Edward Said’s notion of ‘lesser beings’, it is argued that the political culture of schooling for Maori was and still is part of a pervasive Western European intellectual climate and culture which has a quite recent history, and which provided powerful support for the notion of Europe possessing a categorical superiority over all other continents, which in turn justified imperialism or neo-colonialism as civilising missions.
Racism and violence were endemic in colonialism and, despite the claimed moral high ground, were endemic in Aotearoa/New Zealand. War was eulogised in the Native School system more than once. The rise and demise of the World War II Maori War Organisation is illustrative of the rejection of Maori aspirations. There were still no Maori in the senior echelons of the Maori Department in 1972.
The Native, later Maori, School system was overtly designed to 'Europeanise' Maori children and therefore Maori society. Individualism was deeply embedded in English and set-tler thinking, whilst communal, ‘communist’ Maori society was to be destroyed.
The thesis examines images of colonialism, empire and imperialism in fiction and non-fiction, New Zealand and British, for adults and children, and notes the attitudes of think-ers like J S Mill and Darwin, of children’s authors Jules Verne and G H Henty, and of New Zealand author William Satchell. The images continue, pervasive and endemic, in recent adult novels. Science also played a role, as did history.
Ranginui Walker, who is Maori, is the only historian to have written a history of New Zea-land which addressed the issue of waste lands, an issue on which Pakeha historians have a blind spot. New Zealand encyclopedia do not index ‘waste land’ or ‘confiscation’. Only two Waikato histories deal adequately, or even accurately, with confiscation, the central episode in the history of the Waikato. Tourist material is equally illustrative.
The Native Schools section of the Education Department ran the Native Schools like a fiefdom, operating in legislative and regulatory black holes for the first thirty years and for much of the time after that. Teachers were moved around at will.
The practice of James H Pope, the first inspector of Native Schools, is closely and critically examined, and negatively assessed. His official writings were consistently derogatory of Maori, and his decisions in respect of Te Kopua Native School were at times detrimental to the pupils. Pope was a product of his times.
The Te Kopua record is closely scrutinised, and the practice of the Education Department is frequently found wanting. It is probable that the establishment of the school was aimed to destabilise King Country Maori, not to benefit the children. It is a story of Maori co-operation and contribution.
Part Two is a detailed partial biography of Te Kopua, it being argued that until there is a significant corpus of studies of Native Schools a valid history of the Native/Maori School system and of schooling for Maori is not possibl
The ApolloTech chariot: Photodynamic therapy light delivery device for treating sub-cutaneous cancers
No full textPovești „vechi” în haine „noi” – o lectură a romanului Cruciada copiilor de Florina Ilis
No full textFocusing on the success of Florina Ilis’ novel The children’s crusade, this article explores its potential as a literary contribution in a broader global discourse, as it could be considered “literary Romanian capital” in a discussion about world literature. While the book draws on clichéd stereotypes of Romanian society from the early 2000s, including the Ceaușescu era and the challenging transition from communism to democracy, the author uses a universal language of trauma. This allows for a wider audience to engage with the themes presented in the novel. Thus, her story becomes part of a global collection of works exploring the theme of the “children’s crusade” (including George Zabriskie Gray, Marcel Schwob, Lucian Blaga, Jerzy Andrzejewski, Thea Beckman, Gregory J. Rinaldi, Karleen Bradford, Kathleen McDonnell, Bryce Courtenay, Mario Vargas Llosa, Tullio Avoledo, amongst others). Considering the connection between continuity and innovation in Romanian literature, 75 years following Lucian Blaga’s play, with the same title, Florina Ilis employs a plot with medieval roots in her novel, which has fascinated writers worldwide, to deliver a unique perspective, in a new discourse
Feeding pre-school children : negotiating good motherhood through food
No full textFood retains a central importance in family life, which extends beyond its nutritional necessity. Through in-depth interviews with 39 mothers of pre-school children, this study focuses on how mothers negotiate the complex and competing priorities of feeding their children. Mothers are expected to feed their children, according to expert definitions of appropriate nutrition, whilst taking account of individual food preferences and structural constraints. The ways that feeding children intersects with the construction of ‘good’ mother or how mothers negotiate external information and advice on feeding their children has not been the focus of much research. This research considers these issues at a time when government policy remains focused on health, lifestyles and obesity. This study shows that mothers feel the responsibility of motherhood strongly whilst accepting their accountability. It also shows that feeding children is one of the main concerns of mothers of young children and one that occupies a great deal of time. By talking to mothers of different ages and living in different social circumstances, this study shows that all mothers accept the links between food and health and all take account of these links as they look to their children’s future health. All mothers seek external sources of information and advice but sources differ with mothers’ age and social class. Expertise is found not to be the preserve of those with formal qualifications as mothers talked of how expertise is negotiated. Mothers therefore work hard to negotiate their own versions of good motherhood through their food decision-making. By focusing on the aspects of feeding children that are considered the most important at any given time, mothers are able to negotiate their own sense of good motherhood
Searching for Keynes: An Essay on the Political Economy of Fiscal Policy, with Application to Canada, 1870-2000 - revised version
No full textKeynes' General Theory (1936) is arguably one of the most important books of the twentieth century. His ideas for stabilizing the aggregate economy have profoundly influenced economic theory as well as popular opinion about what governments can and should do with respect to the business cycle. On the other hand, whether Keynesian theory has substantially altered the course of public policy remains an open question. In this paper we identify the elements required for any investigation of the impact of Keynes' ideas on policy choices and then conduct our own 'search for Keynes', applying an intertemporal spatial voting framework to study the fiscal history of the Government of Canada from 1870 to 2000. The long time series allows the construction of a counterfactual – one of several essential elements - showing what governments would have planned to do ‘after Keynes’, if Keynes' ideas had not in fact been present. Our results suggest that textbook Keynesianism is identifiable in the Canadian data.Keynesianism, spatial voting, permanent versus transitory policy, political equilibrium, liquidity constraints
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