<p> The studies described in this thesis explore the physiology of upper respiratory tract colonization by S. pneumoniae and S. pyogenes. We have shown that colonization is associated with biofilm formation and examined the effects of co-colonization on genetic exchange. Additional studies have investigated the virulence and inflammatory potential of biofilm bacteria, and identified factors influencing cellular egress from biofilm communities and the transition to acute disease. The remaining chapters explore the mechanism of action of the human milk protein lipid complex HAMLET and its potential for antimicrobial adjutancy.</p>

<p> The origins of pairs of monozygotic twins and higher order multiples, i.e. triplets, quadruplets, etc., have been extensively studied but still little is understood. To gain insight into this event, certain possible cell labeling schemes that model an organism&rsquo;s development are analyzed. The phenomenon of quadruplet twins is exposed during the process. We predict that monozygotic quadruplets are not really quadruplets but instead are two pairs of monozygotic twins where the pairs slightly differ. From the considered models, the probability of monozygotic twins is found to be (1/2)<i>^K</i>, and we discover from our analysis that the probability of monozygotic quadruplets, or triplets in the case of the death of an embryo, is (1/8)<i>^K</i>, where <i> K</i> is a species-specific integer representing the number of pairs of homologous chromosomes. This investigation into twinning provides a foundation for understanding the process of cell development through which the cell development mechanism is established. The failure of the internal cellular clock from this mechanism may play an important role in cancerogenesis. The parameter K may determine cancerization with a probability threshold that is approximately inversely proportional to the Hayflick limit, so exposure to small levels of ionizing radiation and chemical pollution may not produce cancer.</p>

<p> Tendons are important tissues with unique mechanical properties necessary for their function. Tendon injuries require lengthy rehabilitation, with adult healing resulting in mechanically inferior scar tissue. A more complete understanding of the development of embryonic tendon may lead to advances in the field of tendon tissue engineering and regeneration. Mechanical properties of embryonic tendon are not dependent on the same factors as mature tendon, and during early development, embryonic tendon cells are maintained at a high density. They also contain actin filaments that increase in organization and span cells. These results suggest the importance of a tendon progenitor cell (TPC) network to emerging tendon functional properties. We examine the proliferation and apoptosis activities of resident TPCs as contributors to cell density maintenance. We characterize the TPC network by visualizing points of cell-cell contact via cell membrane staining as well as staining for the actin cytoskeleton. Finally, we characterize various cell-cell proteins as crosslinks in the TPC network and compare their expression and distribution. These data provide a deeper understanding of embryonic tendon development and the role of cellular contributions to the emerging functional characteristics of tendon.</p>

Thesis (Ph. D.)--University of Michigan.

Thesis (Ph. D.)--University of Michigan.

<p> An estimated 1,735,350 new cancer diagnosis and 609,640 cancer related deaths are predicted to occur in the United States in 2018. To improve patient prognosis, biomarkers are needed to identify cancer in early stages. When diagnosed at an early stage, cancer is more likely to respond to treatments and patients have a higher survival rate. Consequently, there is an ever-present need to identify biomarkers that can aid in the detection of cancer. Additionally, there is a paradigm shift in the field of cancer treatment towards immunotherapy. Traditional cancer treatments include chemotherapy, radiation, and hormone therapy and are not cancer-specific, which leads to bystander effects on the patient&rsquo;s normal organs that often harm the patient and create unnecessary hardship. To alleviate this, immunotherapy utilizes a patient&rsquo;s own immune cells to attack and destroy cancer cells via cancer-specific biomarkers. These biomarkers are ideally on the surface of cancer cells and absent from the patient&rsquo;s normal cells to avoid healthy tissue destruction. With this new therapy, there is a recent push to find surface antigens for immunotherapy techniques. </p><p> This dissertation describes the characterization of HPRT as a diagnostic and therapeutic biomarker for the detection and possible treatment of hematological and solid malignancies. We describe the general upregulation of HPRT upon malignancy and show that this elevation in protein expression is independent of stage, which indicates that it would be useful as an early stage diagnostic companion tool. We have preliminarily linked the elevation in HPRT to a mutation in one of its prime transcription factors, p53. Specific mutation in p53 called Gain of Function mutations have shown to influence salvage pathway enzyme expression, and we have shown that mutations in p53 are relevant to the elevated levels of HPRT within several cancer types. In addition, we also found that HPRT associates significantly with the membrane of several cancer cell lines as well as patient samples. We found that HPRT has insignificant expression on normal cells, which suggests it may be useful as a targetable biomarker for immunotherapy. Throughout our analysis, we also determined that HPRT might have a role in immune regulation as an elevation of the protein correlates to the decrease of several pro-inflammatory genes involved in immune activation. The knowledge gained from the data presented in this dissertation have opened up new functions for HPRT outside of simple nucleotide production and have confirmed that HPRT has a unique role in cancer that has not been previously reported.</p><p>

<p> High incidence of prostate cancer is a major public health issue in the Western world, and bone metastasis is one of the final clinical consequences of prostate cancer progression. In an effort to understanding the molecular pathogenesis of this disease, numerous cell models have been developed, arising mostly from patient biopsies. The introduction of the genetically engineered mouse in biomedical research has allowed the development of murine models for the investigation of tumorigenic and metastatic processes. Current challenges to the field include lack of an animal model that faithfully recapitulates bone metastasis of prostate cancer.</p><p>

Gastrulation is a fundamental process that reorganizes the primary germ layers to shape the internal and external features of an early embryo. Morphogenetic movements underlying this process can be classified into a variety of different types of cellular movements. I will focus on investigating in this thesis two types of cell movements in the dorsal mesoderm; mediolateral cell intercalation and convergence and extension. During gastrulation, mesoderm cells send protrusions to gain traction on neighboring cells and the surrounding extracellular matrix; a process called mediolateral cell intercalation. Mesoderm cells use this type of cell movement to converge and extend the dorsal mesoderm tissue during gastrulation; a process called convergence and extension. These morphogenetic movements are essential to form the early embryo and are important for later development. There are a number of different proteins involved in regulating the morphogenetic movements during gastrulation. The Planar Cell Polarity Signaling Pathway helps establish individual cell polarity and is activated in dorsal mesoderm cells undergoing convergence and extension. In addition, dorsal mesoderm cells migrate by using integrin receptors and the surrounding extracellular matrix to correctly position the mesoderm in the embryo. I will focus my efforts on analyzing the function of ADAM proteins during Xenopus laevis gastrulation. The ADAM family of metalloproteases is important for a variety of biological processes. ADAM proteins function as ectodomain sheddases by cleaving membrane bound proteins involved in signal transduction, cell-cell adhesion, and cell-extracellular matrix adhesion. I will focus on investigating the roles of two ADAM family members; ADAM13 and ADAM19 during gastrulation. Both ADAM13 and ADAM19 are expressed in the dorsal mesoderm during gastrulation. Throughout early embryonic development, ADAM13 is expressed in the somitic mesoderm and cranial neural crest cells. ADAM19 is expressed in dorsal, neural and mesodermal derived structures such as the neural tube, notochord, the somitic mesoderm, and cranial neural crest cells. Since ADAM13 and ADAM19 are expressed in similar tissues, I investigated if both proteins functionally interacted. I show that a loss of ADAM13 protein in the embryo reduces the level of ADAM19 protein by 50%. In the opposite experiment, a loss of ADAM19 protein in the embryo reduces the level of ADAM13 protein by 50%. This suggests that both ADAM13 and ADAM19 are required to maintain proper protein levels in the embryo. This might be explained through their physical interaction in a cell. The ADAM19 Proform binds to the ADAM13 Proform in cultured cells. Through domain analysis, I show that ADAM19 binds specifically to the cysteine-rich domain of ADAM13. When co-overexpressed in a cell, the level of Mature ADAM13 (compared to the Proform) is reduced suggesting a complex form of regulation. I propose a few models that discuss how ADAM19 may function as a chaperone to stabilize and regulate the further processing of ADAM13 protein. Some of the unpublished work discussed in this thesis focuses on the roles of ADAM13 and ADAM19 in the dorsal mesoderm during gastrulation. Specific emphasis is made on investigating the axial mesoderm during notochord formation. I show that ADAM19 affects gene expression important for the A-P polarity of the notochord while ADAM13 does not. The changes in gene expression can be partially rescued by the EGF ligand Neuregulin1β, a known substrate for ADAM19 in the mouse. ADAM13 and ADAM19 are important for convergence and extension movements of the axial mesoderm during gastrulation. Specifically, a loss of ADAM13 or ADAM19 causes a delay in mediolateral cell intercalation resulting in a significantly wider notochord compared to control embryos. These defects occur without affecting dishevelled intracellular localization or the activation of the PCP signaling pathway. However, a loss of ADAM13 or ADAM19 reduces dorsal mesoderm cell spreading on a fibronectin substrate through α5β1 integrin. To conclude, the work presented in this thesis focuses on the similarities and differences of ADAM13 and ADAM19 in the early embryo. Although ADAM13 and ADAM19 are required for normal morphogenetic movements during gastrulation, my data suggests they have different functions. ADAM13 appears to function in regulating cell movements while ADAM19 appears to function in regulating cell signaling. I propose a few models that discuss how each ADAM metalloprotease may function in the dorsal mesoderm and contribute to convergence and extension movements during gastrulation.

Possible roles for wall-based enzyme activity in aging of daylily petals are presented. We are asking if daylily senescence is controlled in part by reactions associated with. We suggest that membrane changes leading to cell death may be induced in part by lipoxygrenase activity and by ROS that are increasing because of reduced effectiveness of certain protective enzymes. The flowers are insensitive to ethylene, but exogenous ABA prematurely upregulates events that occur during natural senescence, such as loss of differential membrane permeability, increases in lipid peroxidation and the induction of proteinase and RNase activities. The possibility is discussed that ABA is a constituent of the signal transduction chain leading to programmed cell death of daylily petals. Six daylily genes, whose levels increase during senescence, were isolated from a daylily cDNA library. Southern blot analysis showed that all six DSA genes, designated as DSA3, 4, 5, 6, 12 and 15, are members of multigene families. The GenBank database homology search suggested, that DSA3 belongs to the cytochrome P450 superfamily, DSA4 is an aspartic proteinase, DSA5 may be a water stress protein, DSA6 is a putative S-1 type nuclease, DSA12 is very similar to impedance induced protein, and DSA15 is a fatty acid elongase. The accumulation of dsag mRNAs, with the exception of DSA4, is accelerated 3.2 to 43 times in ABA treated prematurely senescing petals. Levels of DSA mRNAs in leaves are very low, less than 4% of the maximum detected in petals, and there is no significant change during senescence. Except for the gene for a putative impedance protein (DSA12), DSAs are also expressed at low levels in daylily roots. (Abstract shortened by UMI.)

The migration of the cranial neural crest is an essential part of cranio-facial development in every vertebrate embryo. The cranial neural crest (CNC) is a transient population of cells that forms the lateral border of the anterior neural plate. In the tailbud stage Xenopus embryo, the neural crest cells delaminate from the neural tube, and undergo a large-scale migration from the dorsal to ventral region of the embryo. The CNC travels along distinct pathways, and populates specific regions of the embryos face. Once the CNC ceases migrating, it differentiates into a variety of tissues that are essential for cranio-facial structure and function. Some of these tissues include bones, muscle, cartilage, and ganglia. The CNC receives a concert of signals from neighboring tissues during and after CNC migration as well as signals transmitted among CNC cells, which act together to determine the fate of each CNC cell. Therefore, the proper migration of the CNC is an essential part of cranio-facial development. What molecules are important for the process of CNC migration? As one might imagine, a milieu of different molecules and interactions are essential for this complicated embryological process to occur. The work presented in this dissertation will focus on the role of a cell adhesion molecule that is important for Xenopus CNC migration. Typically, the amount of cell adhesion decreases within tissues undergoing migration. This behavior is essential to allow fluidity within the tissue as it moves. However, cell adhesions are fundamental for cell migration to occur because the moving cells need a platform on which to mechanically propel themselves. These interactions can occur between the migrating cell and extracellular matrix molecules (ECM), or can happen between cells. The cranial neural crest utilizes both cell-ECM and cell-cell interactions during the process of migration. The amount of cell adhesion mediated by either of these mechanisms will depend on where the cell is located within the CNC. Cells located at the periphery of the CNC tissue, which is surrounded by a matrix of ECM, will have more cell-ECM interactions. Cells located deeper in the CNC tissue, where there is little ECM, will rely more on cell-cell interactions. The work presented in this thesis focuses on a cell-cell adhesion molecule that is part of the cadherin superfamily of molecules. With this in mind, these studies should be descriptive of the environment within the CNC, and to a less degree the environment between the CNC and the surrounding tissues. The work presented in this dissertation will focus on cadherin-11, which is a classical cadherin that is specifically expressed in the cranial neural crest during its migration. How does cadherin-11 function in the CNC during this process? The work presented here suggests that the main role of cadherin-11 in the CNC is to perform as a cell adhesion molecule. However, too much cell adhesion is inhibitory to migration. In this respect, many of the studies described in this work indicate that cadherin-11 mediated cell adhesion is tightly regulated during CNC migration. Here I show that cadherin-11 is extracellularly processed by ADAM metalloproteases, ADAM9 and ADAM13, which removes the adhesive domain of cadherin-11. This extracellular cleavage event occurs throughout CNC migration, and is likely the main mechanism that regulates cadherin-11 mediated cell adhesion. Cleavage of cadherin-11 by ADAMs does not seem to affect its ability to interact with cytoplasmic binding partners, β-catenin and p120-catenin. This observation supports the idea that the “purpose” of cadherin-11 cleavage is to regulate cell adhesion, and not to induce (cell autonomous) signaling events. Additionally, the secreted extracellular domain of cadherin-11 (EC1-3) retains biological activity. This fragment can bind to a number of cell surface molecules in tissue culture including full-length cadherin-11 and specific members of the ADAM family. This observation suggests that EC1-3 may interact with full-length cadherin-11 molecules in vivo, and inhibit cadherin-11 mediated cell adhesion during CNC migration. EC1-3 can rescue CNC migration in embryos that overexpress cadherin-11, further supporting this hypothesis. Many of the above observations have been published in my first-author paper entitled “Extracellular processing of cadherin-11 by ADAM metalloproteases is essential for Xenopus cranial neural crest migration” published in the journal Molecular Biology of the Cell in 2009. Some of the unpublished work in this dissertation further focuses on how EC1-3 effects CNC migration in an ex vivo environment. During these studies, the observation was made that overexpression of EC1-3 in a cranial neural crest explant produces abnormal directional movement. In these experiments, it appeared as though certain regions of the CNC explant were “attracting” other regions of the explant. The preliminary studies described in chapter IV are aimed at answering the question; does EC1-3 attract migrating CNC cells? Here, we generated a Matlab program in order to effectively quantify the amount of directional movement of CNC explants presented with a source of EC1-3. In addition to quantifying cell directionality, this program can also decipher between cells moving with random or directed motion, and measure the velocity of cell migration within certain coordinates. Therefore, this program should be useful other ex vivo studies that require the observation of these features. To conclude, the work presented in this dissertation suggests that the role of cadherin-11 during cranial neural crest migration is predominately based on the adhesive function. In order for CNC migration to proceed, the amount of cadherin-11 mediated cell-cell adhesion is tightly regulated throughout this process. These cell-cell interactions are likely important for “sheet” and “branch” migration where CNC cells maintain a lot of cell-cell cohesion.