During gastrulation, the cells, and consequently the organ anlagen, are repositioned according to their future arrangement along the anterio- posterior axis. The movements responsible, the... Show moreDuring gastrulation, the cells, and consequently the organ anlagen, are repositioned according to their future arrangement along the anterio- posterior axis. The movements responsible, the convergence and extension (CE) cell movements, are crucial for normal development and defects in their mechanism underlie human pathologies like spina bifida and Noonan syndrome. Collective polarization of the cells is essential for these morphogenetic. The coordination and regulation are governed by intricate signaling mechanisms. Tyrosine phosphorylation is one of such mechanisms. By either phosphorylation by protein-tyrosine kinases or dephosphorylation by protein-tyrosine phosphatases (PTPs) of tyrosine residues, many signaling proteins can be switched from active to inactive states. In this thesis, we focus on the role of ‘classical’ PTPs. We identified PTP-BL, Ptpn20, RPTPα and RPTPε as components of a system regulating cell polarity. Additionally, we identified via screening one additional PTP, ptprda, as essential for CE movements. Quantitative analysis and clear representation of the data is essential to modern day biology. Studying collective cell migrations requires the analysis of the net effect of cell polarization and/or displacements of a large number of cells within a tissue rather than measurements of a few individuals. An automated cell tracing algorithm was developed and an algorithm for the detection of cell membranes. Additionally, a novel method of graphical data representation is introduced. Show less
This thesis proposes several new algorithms including X-ray angiographic image enhancement, three-dimensional (3D) angiographic reconstruction, angiographic overlap prediction, and the co... Show moreThis thesis proposes several new algorithms including X-ray angiographic image enhancement, three-dimensional (3D) angiographic reconstruction, angiographic overlap prediction, and the co-registration of X-ray angiography with intracoronary imaging devices, such as intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The algorithms were integrated into prototype software packages that were validated at a number of clinical centers. The feasibility of using such software packages in typical clinical population was verified, while the advantages and accuracy of the proposed algorithms were demonstrated by phantoms and in-vivo clinical studies. In addition, based on the proposed approaches and the conducted studies, this thesis reports a number of findings including the impact of acquisition angle difference on 3D quantitative coronary angiography (QCA), the clinical characteristics of bifurcation optimal viewing angles and bifurcation angles, and the discrepancy of lumen dimensions as assessed by 3D QCA and by IVUS or OCT. Show less
