Factors associated with students' decisions to attend selected private postsecondary christian institutions

Turcotte, James Carlton University of North Texas 1995 해외박사

A structure-function analysis of Nudel, a protein required for Drosophila dorsoventral polarity

Turcotte, Cynthia Leclerc Yale University 2002 해외박사(DDOD)

Dorsoventral patterning of the Drosophila embryo requires Nudel, a large mosaic protein with a protease domain. Nudel also contains other recognizable motifs including multiple copies of the protein-protein binding LDL-A module, an RGD integrin binding motif, a C-terminal protease-like domain and several regions suitable for both N- and O-linked glycosylation including glycosaminoglycan (GAG) addition. Previous studies have implicated Nudel's protease domain as the trigger of a proteolytic cascade that activates the Toll signaling pathway to establish dorsoventral polarity in the embryo. However, the function of other regions of Nudel has been unclear. Mutant <italic>nudel</italic> alleles fall into 2 different phenotypic categories: class I alleles produce embryos that arrest early in development within fragile eggshells and class II alleles produce dorsalized embryos that lack all ventral and lateral structures. Previous sequencing of the protease domain of the class II <italic>nudel</italic> mutant alleles revealed that all but one, <italic>ndl<super>9</super></italic>, contain molecular lesions in conserved regions of the protease domain. Upon sequencing of the <italic> ndl<super>9</super></italic> allele, I detected an alteration of a cysteine just N-terminal to the protease domain. In other serine proteases, an analogous cysteine is involved in a crucial disulfide bond between regulatory and catalytic domains suggesting that the N-terminal region of Nudel may be required for proper function of the Nudel protein. In addition, I have investigated the potential role of the LDL-A modules in Nudel. Using 2D-gel electrophoresis and site-directed mutagenesis, I have obtained evidence that the N-terminal region of Nudel contains a site for glycosaminoglycan attachment that is required for dorsoventral patterning. Disruption of this site blocks a disulfide-based association between N- and C-terminal Nudel polypeptides and activation of Nudel's protease domain. I discuss how a GAG chain on Nudel is required for Nudel protease activation.

Ribonucleases as cancer and viral therapeutics: Role of Coulombic interactions

Turcotte, Rebecca Frances The University of Wisconsin - Madison 2008 해외박사(DDOD)

Ribonuclease A (RNase A) has served as a favorite model for protein chemists for decades, used for studies on synthesis, structure, folding, and enzymology. More recently, it was discovered that several members of the RNase A superfamily have interesting biological properties, including angiogenic, antimicrobial, antiviral, and cytotoxic effects. Indeed, one homologue, Onconase (ONC), is in late-stage clinical trials for the treatment of malignant mesothelioma. Several requirements must be met for a ribonuclease to be cytotoxic. First, the ribonuclease must retain conformational stability at physiological temperatures. It also must have intact catalytic activity. It must not interact with the cytosolic ribonuclease inhibitor protein (RI), which binds to members of the RNase A superfamily with extremely high affinity. Finally, a cytotoxic ribonuclease must be able to bind to the cell surface and enter the cytosol of cancer cells. This thesis focuses on the role of Coulombic interactions in two of these processes---cellular internalization and RI binding. ONC, the prototypical cytotoxic ribonuclease, is the model ribonuclease in this work. In C HAPTER 2, a systematic analysis of the role of positively charged surface residues in the cytotoxicity of ONC is described. This study supports a model in which positively charged residues on the surface of ONC influence the translocation of the protein from endosomes to the cytosol. In C HAPTER 3, a productive interaction between RI and ONC in a solution of low salt concentration is detected, providing the first direct measurement of the affinity of these proteins. The potential use of cytotoxic ribonucleases for their antiviral properties is described in CHAPTER 4. A zymogen that has the potential to specifically kill HIV-infected cells was created from RNase A. Activation of this zymogen is dependent on the interaction between two positively charged proteins, the zymogen and HIV protease. In this case, Coulombic interactions do not favor this activation, but potentially limit it. Finally, in C HAPTER 5, several potential future directions of this work are proposed.

An integrated optical platform for micromanipulation of cells and tissue in live animals

Turcotte, Raphael Boston University 2014 해외박사(DDOD)

The hematopoietic stem cell niche is a specialized bone marrow (BM) microenvironment where blood-forming cells reside. Interactions between these rare cells and their niche need to be studied at the single-cell level. While live animal cell tracking with optical microscopy has proven useful for this purpose, a more thorough characterization requires novel approaches. This can be accomplished by using an integrated optical platform for cell and tissue manipulations (cell transplantation and extraction) in the skull bone of live mice. The platform integrates a non-damaging laser ablation microbeam for bone removal and tissue cutting, optical tweezers for single cell trapping, and a video-rate scanning microscope. For single cell delivery, a narrow channel is ablated through bone under imaging guidance. Cells are then transferred from a micropipette into an optical trap, which brings cells into the BM through the channel. The survival and proliferation of implanted cells can be tracked in vivo by imaging. For cell extraction after laser bone thinning, different approaches can be implemented and three of them are presented.

Temporal and Spatial Distribution of Imidacloprid and the Arthropod Fauna Associated with Eastern Hemlock, Tsuga canadensis (L.) Carr

Turcotte, Richard M ProQuest Dissertations & Theses West Virginia Univ 2016 해외박사(DDOD)

Eastern hemlock, Tsuga canadensis (L.) Carr (Pinales: Pinaceae), is an important component of both the urban and forest landscape of the eastern United States. Eastern hemlock has been heavily impacted by the introduction of the hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae). Two goals of this research were (1) to determine the effect of treatment timing (spring versus fall) and application method (tree injection versus soil injection) on the spatial and temporal distribution of imidacloprid the primary insecticide used to treat A. tsugae and (2) to assess the impact of application method and timing of imidacloprid treatments on the arthropods associated with eastern hemlock. The results of this study showed that xylem fluid concentrations of imidacloprid were significantly (P < 0.05) higher for spring applications than for fall applications, and for trunk injections than soil injections in the first year post treatment. A diverse group of arthropods, making up 393 species, were collected by branch beating the lower crowns of eastern hemlock. No significant (P > 0.05) differences in arthropod abundance were found between imidacloprid treated and control trees and application methods. An extensive literature review revealed 484 native and exotic arthropods from three different taxonomic classes and 21 different orders associated with eastern hemlock in North America. A total of five arthropod species were eastern hemlock dependent, and are likely to experience local extirpation as a result of declining and dying eastern hemlock. In addition, an assessment of the impact of application method and timing of imidacloprid treatments on the spider communities were carried out because spiders are the primary arthropod predator present in the crown of eastern hemlock. No significant (P > 0.05) differences in spider abundance were found between imidacloprid treated and control trees and application methods. This study provides fundamental information to aid the conservation and management of eastern hemlock and biodivisity at risk due to extensive applications of imidacloprid.

Intimate Data in-the-Moment: Embodied Collaborative Pedagogical Encounters of Golf Instructors with Data

Turcotte, Nate The Pennsylvania State University ProQuest Dissert 2020 해외박사(DDOD)