Matching Items (36)
Description
Specific dendritic morphologies are a hallmark of neuronal identity, circuit assembly, and behaviorally relevant function. Despite the importance of dendrites in brain health and disease, the functional consequences of dendritic shape remain largely unknown. This dissertation addresses two fundamental and interrelated aspects of dendrite neurobiology. First, by utilizing the genetic power of Drosophila melanogaster, these studies assess the developmental mechanisms underlying single neuron morphology, and subsequently investigate the functional and behavioral consequences resulting from developmental irregularity. Significant insights into the molecular mechanisms that contribute to dendrite development come from studies of Down syndrome cell adhesion molecule (Dscam). While these findings have been garnered primarily from sensory neurons whose arbors innervate a two-dimensional plane, it is likely that the principles apply in three-dimensional central neurons that provide the structural substrate for synaptic input and neural circuit formation. As such, this dissertation supports the hypothesis that neuron type impacts the realization of Dscam function. In fact, in Drosophila motoneurons, Dscam serves a previously unknown cell-autonomous function in dendrite growth. Dscam manipulations produced a range of dendritic phenotypes with alteration in branch number and length. Subsequent experiments exploited the dendritic alterations produced by Dscam manipulations in order to correlate dendritic structure with the suggested function of these neurons. These data indicate that basic motoneuron function and behavior are maintained even in the absence of all adult dendrites within the same neuron. By contrast, dendrites are required for adjusting motoneuron responses to specific challenging behavioral requirements. Here, I establish a direct link between dendritic structure and neuronal function at the level of the single cell, thus defining the structural substrates necessary for conferring various aspects of functional motor output. Taken together, information gathered from these studies can inform the quest in deciphering how complex cell morphologies and networks form and are precisely linked to their function.
ContributorsHutchinson, Katie Marie (Author) / Duch, Carsten (Thesis advisor) / Neisewander, Janet (Thesis advisor) / Newfeld, Stuart (Committee member) / Smith, Brian (Committee member) / Orchinik, Miles (Committee member) / Arizona State University (Publisher)
Created2013
Description
The academic literature on science communication widely acknowledges a problem: science communication between experts and lay audiences is important, but it is not done well. General audience popular science books, however, carry a reputation for clear science communication and are understudied in the academic literature. For this doctoral dissertation, I utilize Sam Harris's The Moral Landscape, a general audience science book on the particularly thorny topic of neuroscientific approaches to morality, as a case-study to explore the possibility of using general audience science books as models for science communication more broadly. I conduct a literary analysis of the text that delimits the scope of its project, its intended audience, and the domains of science to be communicated. I also identify seven literary aspects of the text: three positive aspects that facilitate clarity and four negative aspects that interfere with lay public engagement. I conclude that The Moral Landscape relies on an assumed knowledge base and intuitions of its audience that cannot reasonably be expected of lay audiences; therefore, it cannot properly be construed as popular science communication. It nevertheless contains normative lessons for the broader science project, both in literary aspects to be salvaged and literary aspects and concepts to consciously be avoided and combated. I note that The Moral Landscape's failings can also be taken as an indication that typical descriptions of science communication offer under-detailed taxonomies of both audiences for science communication and the varieties of science communication aimed at those audiences. Future directions of study include rethinking appropriate target audiences for science literacy projects and developing a more discriminating taxonomy of both science communication and lay publics.
ContributorsJohnson, Nathan W (Author) / Robert, Jason S (Thesis advisor) / Creath, Richard (Committee member) / Martinez, Jacqueline (Committee member) / Sylvester, Edward (Committee member) / Lynch, John (Committee member) / Arizona State University (Publisher)
Created2013
Description
Once perceived as an unimportant occurrence in living organisms, cell degeneration was reconfigured as an important biological phenomenon in development, aging, health, and diseases in the twentieth century. This dissertation tells a twentieth-century history of scientific investigations on cell degeneration, including cell death and aging. By describing four central developments in cell degeneration research with the four major chapters, I trace the emergence of the degenerating cell as a scientific object, describe the generations of a variety of concepts, interpretations and usages associated with cell death and aging, and analyze the transforming influences of the rising cell degeneration research. Particularly, the four chapters show how the changing scientific practices about cellular life in embryology, cell culture, aging research, and molecular biology of Caenorhabditis elegans shaped the interpretations about cell degeneration in the twentieth-century as life-shaping, limit-setting, complex, yet regulated. These events created and consolidated important concepts in life sciences such as programmed cell death, the Hayflick limit, apoptosis, and death genes. These cases also transformed the material and epistemic practices about the end of cellular life subsequently and led to the formations of new research communities. The four cases together show the ways cell degeneration became a shared subject between molecular cell biology, developmental biology, gerontology, oncology, and pathology of degenerative diseases. These practices and perspectives created a special kind of interconnectivity between different fields and led to a level of interdisciplinarity within cell degeneration research by the early 1990s.
ContributorsJiang, Lijing (Author) / Maienschein, Jane (Thesis advisor) / Laubichler, Manfred (Thesis advisor) / Hurlbut, James (Committee member) / Creath, Richard (Committee member) / White, Michael (Committee member) / Arizona State University (Publisher)
Created2013
Description
This is a study of scientific realism, and of the extent to which it is undermined by objections that have been raised by advocates of various forms of antirealism. I seek to develop and present a version of scientific realism that improves on past formulations, and then to show that standard antirealist arguments against it do not succeed. In this paper, I will first present my formulation of scientific realism, which conceives of theories as model-based and as fundamentally non-linguistic. I advocate an epistemic position that accords with indirect realism, and I review and assess the threat posed by theses of underdetermination. Next, I review and discuss three important views: the antirealist constructivist view of Thomas Kuhn, the realist view of Norwood Hanson, and the antirealist constructive empiricist view of Bas van Fraassen. I find merits and flaws in all three views. In the course of those discussions, I develop the theme that antirealists' arguments generally depend on assumptions that are open to question, especially from the perspective of the version of realism I advocate. I further argue that these antirealist views are undermined by their own tacit appeals to realism.
ContributorsNovack, Alexander Dion (Author) / Armendt, Brad (Thesis advisor) / Creath, Richard (Committee member) / French, Peter (Committee member) / Arizona State University (Publisher)
Created2013
Description
In somatic cells, the mitotic spindle apparatus is centrosomal and several isoforms of Protein Kinase C (PKC) have been associated with the mitotic spindle, but their role in stabilizing the mitotic spindle is unclear. Other protein kinases such as, Glycogen Synthase Kinase 3â (GSK3â) also have been shown to be associated with the mitotic spindle. In the study in chapter 2, we show the enrichment of active (phosphorylated) PKCæ at the centrosomal region of the spindle apparatus in metaphase stage of 3T3 cells. In order to understand whether the two kinases, PKC and GSK3â are associated with the mitotic spindle, first, the co-localization and close molecular proximity of PKC isoforms with GSK3â was studied in metaphase cells. Second, the involvement of inactive GSK3â in maintaining an intact mitotic spindle was shown. Third, this study showed that addition of a phospho-PKCæ specific inhibitor to cells can disrupt the mitotic spindle microtubules. The mitotic spindle at metaphase in mouse fibroblasts appears to be maintained by PKCæ acting through GSK3â. The MAPK pathway has been implicated in various functions related to cell cycle regulation. MAPKK (MEK) is part of this pathway and the extracellular regulated kinase (ERK) is its known downstream target. GSK3â and PKCæ also have been implicated in cell cycle regulation. In the study in chapter 3, we tested the effects of inhibiting MEK on the activities of ERK, GSK3â, PKCæ, and á-tubulin. Results from this study indicate that inhibition of MEK did not inhibit GSK3â and PKCæ enrichment at the centrosomes. However, the mitotic spindle showed a reduction in the pixel intensity of microtubules and also a reduction in the number of cells in each of the M-phase stages. A peptide activation inhibitor of ERK was also used. Our results indicated a decrease in mitotic spindle microtubules and an absence of cells in most of the M-phase stages. GSK3â and PKCæ enrichment were however not inhibited at the centrosomes. Taken together, the kinases GSK3â and PKCæ may not function as a part of the MAPK pathway to regulate the mitotic spindle.
ContributorsChakravadhanula, Madhavi (Author) / Capco, David G. (Thesis advisor) / Chandler, Douglas (Committee member) / Clark-Curtiss, Josephine (Committee member) / Newfeld, Stuart (Committee member) / Arizona State University (Publisher)
Created2012
Description
The present essay addresses the epistemic difficulties involved in achieving consensus with respect to the Hayek-Keynes debate. In particular, it is argued that the debate cannot be settled on the basis of the observable evidence; or, more precisely, that the empirical implications of the theories of Hayek and Keynes are such that, regardless of what is observed, both of the theories can be interpreted as true, or at least, not falsified. Regardless of the evidence, both Hayek and Keynes can be interpreted as right. The underdetermination of theories by evidence is an old and ubiquitous problem in science. The present essay makes explicit the respects in which the empirical evidence underdetermines the choice between the theories of Hayek and Keynes. In particular, it is argued both that there are convenient responses one can offer that protect each theory from what appears to be threatening evidence (i.e., that the choice between the two theories is underdetermined in the holist sense) and that, for particular kinds of evidence, the two theories are empirically equivalent (i.e., with respect to certain kinds of evidence, the choice between the two theories is underdetermined in the contrastive sense).
ContributorsScheall, Scott (Author) / Creath, Richard (Thesis advisor) / Armendt, Brad (Committee member) / French, Peter (Committee member) / Arizona State University (Publisher)
Created2012
Description
In 1997, developmental biologist Michael Richardson compared his research team's embryo photographs to Ernst Haeckel's 1874 embryo drawings and called Haeckel's work noncredible.Science soon published <“>Haeckel's Embryos: Fraud Rediscovered,<”> and Richardson's comments further reinvigorated criticism of Haeckel by others with articles in The American Biology Teacher, <“>Haeckel's Embryos and Evolution: Setting the Record Straight <”> and the New York Times, <“>Biology Text Illustrations more Fiction than Fact.<”> Meanwhile, others emphatically stated that the goal of comparative embryology was not to resurrect Haeckel's work. At the center of the controversy was Haeckel's no-longer-accepted idea of recapitulation. Haeckel believed that the development of an embryo revealed the adult stages of the organism's ancestors. Haeckel represented this idea with drawings of vertebrate embryos at similar developmental stages. This is Haeckel's embryo grid, the most common of all illustrations in biology textbooks. Yet, Haeckel's embryo grids are much more complex than any textbook explanation. I examined 240 high school biology textbooks, from 1907 to 2010, for embryo grids. I coded and categorized the grids according to accompanying discussion of (a) embryonic similarities (b) recapitulation, (c) common ancestors, and (d) evolution. The textbooks show changing narratives. Embryo grids gained prominence in the 1940s, and the trend continued until criticisms of Haeckel reemerged in the late 1990s, resulting in (a) grids with fewer organisms and developmental stages or (b) no grid at all. Discussion about embryos and evolution dropped significantly.
ContributorsWellner, Karen L (Author) / Maienschein, Jane (Thesis advisor) / Ellison, Karin D. (Committee member) / Creath, Richard (Committee member) / Robert, Jason S. (Committee member) / Laubichler, Manfred D. (Committee member) / Arizona State University (Publisher)
Created2014
Description
This thesis is concerned with the methodological role of intuitions in metaphysics. It is divided into two main parts. Part I argues that an academic field can only employ a method of gathering evidence if it has established some agreed-upon standards regarding how to evaluate uses of this method. Existing meta-philosophical disputes take the nature of intuitions to be their starting point. This is a mistake. My concern is not the epistemic status of intuitions, but rather how metaphysicians appeal to intuitions as a form of evidence. In order for intuitions to play a viable role in research they must be subject to certain constraints, regardless of whether they allow individual researchers to know that their theories are true. Metaphysicians are not permitted to use intuitions as arbitrarily having different evidential status in different circumstances, nor should they continue to use intuitions as evidence in certain disputes when there is disagreement amongst disputants about whether intuitions should have this evidential status.
Part II is dedicated to showing that metaphysicians currently use intuitions in precisely the sort of inconsistent manner that was shown to be impermissible in Part I. I first consider several competing theories of how intuitions function as evidence and argue that they all fail. As they are currently used in metaphysics, intuitions are analogous to instruments in the sciences in that they are taken to be a substantial non-inferential source of evidence for theories. I then analyze several major metaphysical disputes and show that the source of controversy in these disputes boils down to inconsistencies in how the different parties treat intuitions as evidence. I conclude that metaphysicians must abandon appeals to intuition as evidence--at least until the field can agree upon some general standards that can resolve these inconsistencies.
Part II is dedicated to showing that metaphysicians currently use intuitions in precisely the sort of inconsistent manner that was shown to be impermissible in Part I. I first consider several competing theories of how intuitions function as evidence and argue that they all fail. As they are currently used in metaphysics, intuitions are analogous to instruments in the sciences in that they are taken to be a substantial non-inferential source of evidence for theories. I then analyze several major metaphysical disputes and show that the source of controversy in these disputes boils down to inconsistencies in how the different parties treat intuitions as evidence. I conclude that metaphysicians must abandon appeals to intuition as evidence--at least until the field can agree upon some general standards that can resolve these inconsistencies.
ContributorsMusgrave, Shea (Author) / Creath, Richard (Thesis advisor) / Pinillos, Nestor A. (Committee member) / Kobes, Bernard W. (Committee member) / Arizona State University (Publisher)
Created2014
Description
Gays identity is usually cast in generics--statements about an indeterminate number of members in a given category. Sometimes these generic statements often get built up into folk definitions, vague and imprecise ways to talk about objects. Other times generics get co-opted into authentic definitions, definitions that pick out a few traits and assert that real members of the class have these traits and members that do not are simply members by a technicality. I assess how we adopt these generic traits into our language and what are the ramifications of using generic traits as a social identity. I analyze the use of authentic definitions in Queer Theory, particularly Michael Warner's use of authentic traits to define a normative Queer identity. I do not just simply focus on what are the effects, but how these folk or authentic definitions gain currency and, furthermore, how can they be changed. I conclude with an analytic account of what it means to be gay and argue that such an account will undercut many of the problems associated with folk or authentic definitions about being gay.
ContributorsBlankschaen, Kurt (Author) / Calhoun, Cheshire (Thesis advisor) / Pinillos, Angel (Committee member) / Creath, Richard (Committee member) / Arizona State University (Publisher)
Created2012
Description
After surveying the literature on the normativity of logic, the paper answers that logic is normative for reasoning and rationality. The paper then goes on to discuss whether this constitutes a new problem in issues in normativity, and the paper affirms that it does. Finally, the paper concludes by explaining that the logic as model view can address this new problem.
ContributorsCadenas, Haggeo (Author) / Pinillos, Angel (Thesis advisor) / Creath, Richard (Committee member) / Kobes, Bernard (Committee member) / nair, shyam (Committee member) / Arizona State University (Publisher)
Created2017