Alan Rosenthal

Bio: Alan Rosenthal is an academic researcher from University of Toronto. The author has contributed to research in topics: Authoring system & Iterative design. The author has an hindex of 5, co-authored 7 publications receiving 163 citations. Previous affiliations of Alan Rosenthal include University Health Network.

A multimedia system for authoring motion pictures

Abstract: MAD (Movie Authoring and Design) is a novel design and authoring system that facilitates the process of creating dynamic visual presentations such as motion pictures and lecture-demonstrations. MAD supports the process by enhancing the author's ability to structure and modify a presentation and to visualize the ultimate result. It does this by allowing both top-down design and bottom-up creation with a hierarchical multimedia document representation; by supporting the flexible inclusion and combination of words, images, sounds, and video sequences; and by providing realtime playback of the best approximation to the ultimate presentation that can be produced at any stage of the design process. MAD represents a paradigm shift from traditional methods of authoring and producing motion pictures. Its development therefore requires in-depth observation of a variety of users working on a variety of filmmaking projects. After describing the key concepts underlying MAD and the current, second-generation prototype software, we describe a number of interesting applications of MAD. In doing so, we review how we have worked with users in an iterative design process and how studies of the work of these users have informed key design issues.

Transition of aortic endothelial cells from resting to migrating cells is associated with three sequential patterns of microfilament organization.

Abstract: The endothelial cell is unique because it must undergo a transition from a resting cell with a cytoskeleton organized for barrier function to one which promotes cell translocation following denuding endothelial injury. Since actin microfilaments are critical for both maintaining the integrity of the resting monolayer and for optimum reendothelialization, we carried out a detailed study of the organization of microfilaments as the cell undergoes the transition from a resting to a translocating cell. We used an in vitro model in which a linear wound was made in a confluent monolayer of porcine aortic endothelial cells. The complex reorganization of actin microfilament bundles following injury and their relationship to microtubules and vinculin was studied in cells at the wound edge using immunofluorescent scanning laser confocal microscopy and time-lapse videomicroscopy. In the resting confluent monolayer, microfilaments were present as a dense peripheral band (DPB) located toward the upper part of the cell and as central microfilament bundles at the substratum. Three distinct stages of microfilament reorganization occurred sequentially during early repair. Stage 1 followed wounding and involved the reduction of the DPBs of microfilaments and associated peripheral cell-cell vinculin plaques. This was associated with rapid forward actin-based lamellipodia extrusions and cell elongation. Low-dose cytochalasin, which did not disrupt the morphology of microfilament bundles, reduced elongation. Stage 2 was characterized by central microfilaments behind the lamellipodia distributed parallel to the wound edge with vinculin plaques at their tips. This was associated with prominent spreading at the front of the cell which enhanced the extent of coverage of the denuded wound area. Stage 3 was characterized by the orientation of central microfilaments perpendicular to the wound edge with vinculin plaques at their tips and was associated with the initiation of cell translocation. There was no specific structural association between central microfilaments and microtubules as the former were toward the substratum while the latter were toward the center and upper part of the cell. Thus, the sequential appearance of the three patterns of microfilament distribution define the cytoskeletal events that regulate the reestablishment of endothelial integrity following denuding endothelial injury.

Immunosuppressive agents and endothelial repair : prednisolone delays migration and cytoskeletal rearrangement in wounded porcine aortic monolayers

Abstract: Endothelial denudation at areas of predilection to atherosclerosis is balanced by an active repair process that may be inhibited under conditions of accelerated atherosclerosis. After cardiac transplantation, the accelerated atherosclerotic process that develops may be enhanced by immunosuppressive agents that have nonspecific effects on cell signaling, proliferation, and response to injury. To study subtle effects of cyclosporine A, azathioprine, and 6α-methylprednisolone on normal endothelial repair processes, confluent porcine endothelial monolayers were denuded in the presence of clinically relevant concentrations of these agents. The rate of endothelial wound repair was compared and the effects on cell spreading, proliferation, and the cytoskeleton assessed. 6α-Methylprednisolone at concentrations of 1.25 to 50 μmol/L was associated with a transient 30% to 60% inhibition of endothelial wound repair. This was associated with increased cell size at the wound edge and a delay in centrosomal reorientation toward the wound, without any effect on cell proliferation. Cyclosporine and azathioprine in clinically relevant concentrations did not affect endothelial repair. Thus, corticosteroids transiently inhibit endothelial cytoskeletal alterations that are important in endothelial repair after a denuding injury.

MAD: a movie authoring and design system

Abstract: MAD (Movie Authoring and Design) is a novel design and authoring system that facilitates the process of creating dynamic visual presentations. MAD aids this process by simultaneously allowing easy creation and modification of structured motion pictures and visualization of the result of the modifications. The principles behind MAD include hierarchical multimedia document representation, the flexible inclusion and combination of words, images, sounds, and video sequences, and real-time playback of a rough version of the final film at any time in the process. MAD represents a paradigm shift both from traditional methods of authoring and producing motion pictures and from modem multimedia authoring tools. Its development therefore required in-depth observation of a variety of users working on a variety of film-making projects. This demonstration will present the key concepts underlying MAD, demonstrate the current, second-generation prototype software, and review how we have worked with users in an iterative design process and how studies of the work of these users have informed key design issues.

The Emerging Role of Valve Interstitial Cell Phenotypes in Regulating Heart Valve Pathobiology

Abstract: The study of the cellular and molecular pathogenesis of heart valve disease is an emerging area of research made possible by the availability of cultures of valve interstitial cells (VICs) and valve endothelial cells (VECs) and by the design and use of in vitro and in vivo experimental systems that model elements of valve biological and pathobiological activity. VICs are the most common cells in the valve and are distinct from other mesenchymal cell types in other organs. We present a conceptual approach to the investigation of VICs by focusing on VIC phenotype-function relationships. Our review suggests that there are five identifiable phenotypes of VICs that define the current understanding of their cellular and molecular functions. These include embryonic progenitor endothelial/mesenchymal cells, quiescent VICs (qVICs), activated VICs (aVICs), progenitor VICs (pVICs), and osteoblastic VICs (obVICs). Although these may exhibit plasticity and may convert from one form to another, compartmentalizing VIC function into distinct phenotypes is useful in bringing clarity to our understanding of VIC pathobiology. We present a conceptual model that is useful in the design and interpretation of studies on the function of an important phenotype in disease, the activated VIC. We hope this review will inspire members of the investigative pathology community to consider valve pathobiology as an exciting new frontier exploring pathogenesis and discovering new therapeutic targets in cardiovascular diseases.

Passive capture and structuring of lectures

Abstract: Despite recent advances in authoring systems and tools, creating multimedia presentations remains a labor-intensive process. This paper describes a system for automatically constructing structured multimedia documents from live presentations. The automatically produced documents contain synchronized and edited audio, video, images, and text. Two essential problems, synchronization of captured data and automatic editing, are identified and solved.

Altered Shear Stress Stimulates Upregulation of Endothelial VCAM-1 and ICAM-1 in a BMP-4– and TGF-β1–Dependent Pathway

Abstract: Objective— Hemodynamics has been associated with aortic valve (AV) inflammation, but the underlying mechanisms are not well understood. Here we tested the hypothesis that altered shear stress conditions stimulate the expression of cytokines and adhesion molecules in AV leaflets via a bone morphogenic protein (BMP)- and transforming growth fact (TGF)-β1–dependent pathway. Methods and Results— The ventricularis or aortic surface of porcine AV leaflets were exposed for 48 hours to unidirectional pulsatile and bidirectional oscillatory shear stresses ex vivo. Immunohistochemistry was performed to detect expressions of the 4 inflammatory markers VCAM-1, ICAM-1, BMP-4, and TGF-β1. Exposure of the aortic surface to pulsatile shear stress (altered hemodynamics), but not oscillatory shear stress, increased expression of the inflammatory markers. In contrast, neither pulsatile nor oscillatory shear stress affected expression of the inflammatory markers on the ventricularis surface. The shear stress–dependent expression of VCAM-1, ICAM-1, and BMP-4, but not TGF-β1, was significantly reduced by the BMP inhibitor noggin, whereas the TGF-β1 inhibitor SB431542 blocked BMP-4 expression on the aortic surface exposed to pulsatile shear stress. Conclusions— The results demonstrate that altered hemodynamics stimulates the expression of AV leaflet endothelial adhesion molecules in a TGF-β1– and BMP-4–dependent manner, providing some potential directions for future drug-based therapies for AV diseases.

The role of transcription-independent damage signals in the initiation of epithelial wound healing

Abstract: Wound healing is an essential biological process that comprises sequential steps aimed at restoring the architecture and function of damaged cells and tissues. This process begins with conserved damage signals, such as Ca2+, hydrogen peroxide (H2O2) and ATP, that diffuse through epithelial tissues and initiate immediate gene transcription-independent cellular effects, including cell shape changes, the formation of functional actomyosin structures and the recruitment of immune cells. These events integrate the ensuing transcription of specific wound response genes that further advance the wound healing response. The immediate importance of transcription-independent damage signals illustrates that healing a wound begins as soon as damage occurs.