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Search Results: 1 - 10 of 28639 matches for " Jean-Pierre Abastado "
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Immune Microenvironment in Tumor Progression: Characteristics and Challenges for Therapy
Valerie Chew,Han Chong Toh,Jean-Pierre Abastado
Journal of Oncology , 2012, DOI: 10.1155/2012/608406
Abstract: The tumor microenvironment plays a critical role in cancer development, progression, and control. The molecular and cellular nature of the tumor immune microenvironment influences disease outcome by altering the balance of suppressive versus cytotoxic responses in the vicinity of the tumor. Recent developments in systems biology have improved our understanding of the complex interactions between tumors and their immunological microenvironment in various human cancers. Effective tumor surveillance by the host immune system protects against disease, but chronic inflammation and tumor “immunoediting” have also been implicated in disease development and progression. Accordingly, reactivation and maintenance of appropriate antitumor responses within the tumor microenvironment correlate with a good prognosis in cancer patients. Improved understanding of the factors that shape the tumor microenvironment will be critical for the development of effective future strategies for disease management. The manipulation of these microenvironmental factors is already emerging as a promising tool for novel cancer treatments. In this paper, we summarize the various roles of the tumor microenvironment in cancer, focusing on immunological mediators of tumor progression and control, as well as the significant challenges for future therapies. 1. Introduction The tumor microenvironment consists of cancer cells, stromal tissue, and extracellular matrix. The immune system is an important determinant of the tumor microenvironment. Indeed, the complex interplay between cancer cells and the host immune response has been extensively investigated in the past few decades. Several immunological deficiencies have been linked with enhanced tumor development in mouse models as well as in humans [1, 2]. The higher incidence of cancers in transplant patients receiving long-term immunosuppressive treatment is well documented [3–5]. Similarly, mice with compromised immune functions due to genetic modifications develop more tumors [6–9]. It is now well recognized that effective tumor surveillance by the immune system is critical to maintain homeostasis in the host. Despite exerting a key role in host protection, tumor surveillance by the immune system may eventually fail. As described in the three “Es” of cancer immunoediting, tumor cells are initially eliminated by the immune system before becoming clinically detectable. This is then followed by an equilibrium phase, where a selection process for less immunogenic tumor variants take place until the tumors finally “escape” the immune
Selection of Mesenchymal-Like Metastatic Cells in Primary Tumors – An in silico Investigation
Vipin Narang,Bindu Harish,Jean-Pierre Abastado,Alexandre Gouaillard
Frontiers in Immunology , 2012, DOI: 10.3389/fimmu.2012.00088
Abstract: In order to metastasize, cancer cells must undergo phenotypic transition from an anchorage-dependent form to a motile form via a process referred to as epithelial to mesenchymal transition. It is currently unclear whether metastatic cells emerge late during tumor progression by successive accumulation of mutations, or whether they derive from distinct cell populations already present during the early stages of tumorigenesis. Similarly, the selective pressures that drive metastasis are poorly understood. Selection of cancer cells with increased proliferative capacity and enhanced survival characteristics may explain how some transformations promote a metastatic phenotype. However, it is difficult to explain how cancer cells that disseminate can emerge due to such selective pressure, since these cells usually remain dormant for prolonged periods of time. In the current study, we have used in silico modeling and simulation to investigate the hypothesis that mesenchymal-like cancer cells evolve during the early stages of primary tumor development, and that these cells exhibit survival and proliferative advantages within the tumor microenvironment. In an agent-based tumor microenvironment model, cancer cell agents with distinct sets of attributes governing nutrient consumption, proliferation, apoptosis, random motility, and cell adhesion were allowed to compete for space and nutrients. These simulation data indicated that mesenchymal-like cancer cells displaying high motility and low adhesion proliferate more rapidly and display a survival advantage over epithelial-like cancer cells. Furthermore, the presence of mesenchymal-like cells within the primary tumor influences the macroscopic properties, emergent morphology, and growth rate of tumors.
Volatility Forecasting of Market Demand as Aids for Planning Manufacturing Activities  [PDF]
Jean-Pierre Briffaut, Patrick Lallement
Journal of Service Science and Management (JSSM) , 2010, DOI: 10.4236/jssm.2010.34045
Abstract: The concepts and techniques designed and used for pricing financial options have been applied to assist in scheduling manufacturing activities. Releasing a manufacturing order is viewed as an investment opportunity whose properties are similar to a call option. Its value can be considered as the derivative of the market demand mirrored in the selling price of the manufactured products and changes over time following an Itô process. Dynamic programming has been used to derive the optimal timing for releasing manufacturing orders. It appears advisable to release a manufacturing when the unit selling price come to a threshold P* given by the relation P* = β/(β–1) C with C = unit cost price. β is a parameter whose value depends on the trend parameter α and the volatility σ of the selling price, the discount rate ρ applicable to the capital appreciation relevant to the business context under consideration. The results have been successfully applied to the evolution of the quarterly construction cost index in France over ten years.
Chaos Appearance during Domain Wall Motion under Electronic Transfer in Nanomagnets  [PDF]
Donfack Gildas Hermann, Jean-Pierre Nguenang
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.33022
Abstract:

In this paper, we study the likelihood of chaos appearance during domain wall motion induced by electronic transfer. Considering a time-varying current density theory, we proceed to a numerical investigation of the dynamics. Using the dissipation parameter, amplitude and frequency of current density as control parameters; we show how periodic regime as well as chaotic regime can be exhibited in nanomagnetic systems. Numerical results allow setting up the periodicity and quasi-periodicity of system and chaotic phenomena occurring during magnetization switching process in nanomagnet through electronic transfer.

Traceability in Acceptance Testing  [PDF]
Jean-Pierre Corriveau, Wei Shi
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.610A005
Abstract:

Regardless of which (model-centric or code-centric) development process is adopted, industrial software production ultimately and necessarily requires the delivery of an executable implementation. It is generally accepted that the quality of such an implementation is of utmost importance. Yet current verification techniques, including software testing, remain problematic. In this paper, we focus on acceptance testing, that is, on the validation of the actual behavior of the implementation under test against the requirements of stakeholder(s). This task must be as objective and automated as possible. Our first goal is to review existing code-based and model-based tools for testing in light of what such an objective and automated approach to acceptance testing entails. Our contention is that the difficulties we identify originate mainly in a lack of traceability between a testable model of the requirements of the stakeholder(s) and the test cases used to validate these requirements. We then investigate whether such traceability is addressed in other relevant specification-based approaches.

DNA Nano Devices as a Biased Random Walk Process: A Case Study of Isothermal Ratchet?  [PDF]
Jean-Pierre Aimé, Juan Elezgaray
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.65045
Abstract: Computation and amplification processes based on Networks of Chemical Reactions are at the heart of our understanding of the regulation and error correction of life systems. The recent advances in DNA nanotechnology, with the creation of the modular structures origamis and the development of dynamical networks using the toe hold mediated strand displacement, open fertile areas to construct Hierarchical Cascades of Chemical Reactions with an increasing complexity inspired from systems in biology. DNA strands have the great advantage to design autonomous and homogeneous Networks of Chemical Reactions leaving aside companion chemical reactions as it occurs in biological systems. In the present paper, we use the Fokker Planck equation to extract predictions that address a wider class of systems beyond the case of diluted solutions. We introduce the concept of toehold strength and output strength that leads to an exponential square dependence of the toehold strength divided by the output strength on the escape rate and the probability for the output strand to leave the gate. We highlight the influence of the boundary conditions that may have an important consequence in confined environment when modular structures like origamis are employed.
A Comparison of Imaging Techniques to Monitor Tumor Growth and Cancer Progression in Living Animals
Anne-Laure Puaux,Lai Chun Ong,Yi Jin,Irvin Teh,Michelle Hong,Pierce K. H. Chow,Xavier Golay,Jean-Pierre Abastado
International Journal of Molecular Imaging , 2011, DOI: 10.1155/2011/321538
Abstract: Introduction and Purpose. Monitoring solid tumor growth and metastasis in small animals is important for cancer research. Noninvasive techniques make longitudinal studies possible, require fewer animals, and have greater statistical power. Such techniques include FDG positron emission tomography (FDG-PET), magnetic resonance imaging (MRI), and optical imaging, comprising bioluminescence imaging (BLI) and fluorescence imaging (FLI). This study compared the performance and usability of these methods in the context of mouse tumor studies. Methods. B16 tumor-bearing mice ( for each study) were used to compare practicality, performance for small tumor detection and tumor burden measurement. Using RETAAD mice, which develop spontaneous melanomas, we examined the performance of MRI ( mice) and FDG-PET ( mice) for tumor identification. Results. Overall, BLI and FLI were the most practical techniques tested. Both BLI and FDG-PET identified small nonpalpable tumors, whereas MRI and FLI only detected macroscopic, clinically evident tumors. FDG-PET and MRI performed well in the identification of tumors in terms of specificity, sensitivity, and positive predictive value. Conclusion. Each of the four methods has different strengths that must be understood before selecting them for use. 1. Introduction Studies in living animals are critical to oncology research, and many experimental models have been exploited for drug development and basic studies [1, 2]. Fast-growing tumors can be generated in mice by orthotopic or ectopic implantation of tumor cell lines. However, models exhibiting spontaneous oncogenesis better mimic human disease therefore, oncogene-driven or chemically induced tumor models have come into use more recently [3, 4]. In both spontaneous and transplanted tumor models, the most common readouts are primary tumor growth and metastatic spread, but accurate measurement of these parameters is challenging. Unlike necropsy, noninvasive imaging techniques could offer an ideal solution as they allow measurement of tumor burden in the whole body without the need to sacrifice the animal. This makes longitudinal studies possible, simultaneously reducing the number of animals required and producing more robust data. These technologies are also sensitive and accurate enough to detect microscopic nodules, whose importance in human disease prognosis is increasingly recognized [5, 6]. Several imaging techniques have recently become available for small animals [7]. These include 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) [8], T2-weighted
Skeletal involvement in the pathogenesis and outcomes of rheumatoid arthritis and osteoarthritis
Jean-Pierre Pelletier
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3571
Abstract: In RA, increased osteoclastic activity is responsible for the development of focal osteopenia/erosion and systemic osteoporosis. The increased osteoclast activity in RA has been demonstrated to be linked to a dysregulation of pathways including cell-cell interactions, cytokines, and the receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL) system. Recent studies have shown that joint erosion in RA is linked to a decrease in long-term physical function.Under OA conditions, the subchondral bone is the site of numerous dynamic morphological changes. These changes are associated with a number of local abnormal biochemical pathways related to the altered metabolism of osteoblasts and osteoclasts. At the early stages of the disease process, increased bone loss and resorption is observed with subchondral bone associated with local production of catabolic factors including cathepsin K and MMP-13. Moreover, OA osteoblasts present an abnormal phenotype resulting in increased production of growth hormones and catabolic factors. In addition, factors such as osteoprotegerin (OPG) and RANKL have been found to be expressed and modulated over time in human OA subchondral bone. Their synthesis varies from being reduced in early OA to being increased in the late stages of the disease. This finding may explain that in the early stages of OA, bone remodeling favors resorption and in the more advanced stages of the disease, bone formation is predominant.Magnetic resonance imaging (MRI) studies in knee OA patients have shown that the subchondral bone is frequently the site of signal alterations-bone marrow lesions (BML) - indicative of a great variety of morphological changes. BML and cartilage loss have been linked in several studies. Moreover, studies have identified, in OA patients, a number of risk factors for total knee replacement including BMLs.The paradigms regarding the role of bone lesions in arthritic diseases raise a number of important questions. A comprehensive
rich: An R Package to Analyse Species Richness
Jean-Pierre Rossi
Diversity , 2011, DOI: 10.3390/d3010112
Abstract: The paper describes rich, a new R package to perform species richness estimation and comparison. Species richness is the simplest surrogate for the more complex concept of species biodiversity. It is relatively easy to assess although estimations strongly depend on sampling intensity with the consequence that richness estimations should be standardized to perform valid comparisons. The R package rich allows such corrections as well as the computation of various statistics and implements different randomization tests to compare cumulative and average species richness of two communities. These tests are useful for ranking sites or communities which is a classical goal in restoration ecology and conservation biology.
Supramolecular Bioorganic Chemistry: Nucleic Acids Recognition and Synthetic Vectors for Gene Transfer
Jean-Pierre Vigneron
Molecules , 1999, DOI: 10.3390/40700180
Abstract: Our works on nucleic acids recognition and synthetic vectors for gene transfer have been reviewed.
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