Living cells keep sensing the changes in their environments, mostly, via cell surface receptors for different ligands. Attachment-dependent cells are sensitive to alterations in extracellular matrix (ECM). ECM is not only required for cell survival, but also prerequisite for epidermal growth factor (EGF) to stimulate cell proliferation. The receptors for the majority of ECM components are integrins and the receptor for EGF is EGF receptor (EGFR). When bound by their ligands, integrins and EGFR induce signal transduction cascades composed of alternative pathways. A quantitative assessment of relative contributions of alternative pathways to one final cell signaling will help understand designing principles of the network. Unfortunately, a methodology for such assessment is still not available, partly because of lack of relatively mature mathematical models. On the other hand, in most biochemical cascades, existence of alternative pathways increases the complexity and thus the robustness of networks. The relationships between the topology and robustness of large-scale biochemical networks have been studied intensively recently. In small-scale networks, while feedback has been revealed as an important contributor for adaptation and robustness, the quantitative correlation between the topology/pathway redundancy of small networks and their robustness remains unknown. / In this thesis, apoptosis of bovine mammary gland epithelial cells was demonstrated to be induced when fibronectin, one of the major components of ECM, was degraded by overexpressed tPA via two potential ways: deprivation of attachment and the effects of fibronectin fragments. Secondly, a mathematical model for EGFR activation of the MAPK cascade, in which alternative pathways exist, was explored and it was found that the Shc-dependent pathway is both redundant and dominant. We hypothesize that the Shc-dependent pathway is important for EGFR to compete with other receptors, which need Shc to transduce cell signals; and this pathway is not aimed to increase the robustness of the EGFR cascade. Finally, for the general importance of alternative pathways to the network topology and robustness, several concepts have been proposed to decompose and quantitatively characterize the networks. We demonstrate that the pathnet score is a better assessment for robustness than the molecular connectivity.

Plants in the field are exposed to multiple stresses and their response to these various stresses determines their capacity to survive. Plants can use multiple signaling pathways and signals to mediate their response / for example, at least four different signal pathways have been identified for water-deficit stress (Shinozaki and Yamaguchi-Shinozaki, 1997 / Xiong et al., 2002). Different forms of stress may activate or utilize the same components, including proteins and other signaling molecules. Signaling molecules such as jasmonic acid (JA) are involved in multiple stress response and development in plants (Creelman and Mullet, 1995, 1997 / Turner et al., 2002). However it is the specific combination of various components of the signaling network coupled with spatial and temporal factors that allows the plant to mount a directed response to any given stress factors. Systemic defense responses thus provide an attractive model for the study of cell-to-to cell signal transduction pathways that operates over long distances (Lucas and Lee, 2004).<br /> <br /> Cellular and physiological evidence suggest the presence of a novel class of systemic mobile plant molecule that is recognized by antibodies against vertebrate atrial natriuretic peptides (ANPs). It has been demonstrated that a recombinant Arabidopsis thaliana natriuretic peptide analogue (AtPNP-A) molecule can induce osmoticumdependent water uptake into protoplast at nanomolar concentrations thus affecting cell volume and hence plant growth. In this study we confirm that active recombinant protein causes swelling in Arabidopsis mesophyll cell protoplasts (MCPs).

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 1, 2008) Includes bibliographical references.

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Marc d'Alarcao. Submitted to the Dept. of Chemistry. Includes bibliographical references (leaves 123-128). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--Ohio University, November, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 112-129).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 65-74). Also available in electronic version.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 133-169). Also available in electronic version.

Thesis (Ph.D.) - University of St Andrews, January 2008. / Restricted until 15th January 2009, during which time access is available with the consent of the Head of School.

Professional paper (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Michael Franklin. Includes bibliographical references (leaves 37-46).