8,476 Works

Scanning Near-Field Optical Microscopy of Living Cells in Liquid, Elaboration of New SNOM Probes and Detection Methods

Kanat Dukenbayev
The aim of the present PhD thesis is the elaboration of new, home-made Scanning Near-field Optical Microscope (SNOM or NSOM), and the demonstration of its great potential for high-resolution topography and fluorescence investigations of soft and solid samples, as well as the possibility to work in air and liquid environments showing high-resolution topographical and fluorescence abilities to investigate soft and solid samples. The first chapter starts from with the description of the general idea of...

PyroMEMS: Improved Fabrication Methods and Ignition Reliability

David De Koninck
Generating large force/displacement actuators at the millimeter and sub-millimeter scales remains an important challenge for microsystems engineers. One promising solution is to integrate high-energy density solid propellant fuels in microsystems (pyroMEMS) to generate high-pressure, high-temperature combustion gases. However, integrating combustible materials within microsystems is non-trivial: solid propellant fuels are generally integrated manually into the device during back-end processing leading to large variability in the device performance. The goal of this thesis was to improve pyroMEMS...

Ecological response of tree saplings to simulated climate change along an elevational gradient (CLIMARBRE)

María Paula Sanginés De Cárcer
Switzerland will face higher temperature increases than the global average, which will have strong impacts on the mountain ecosystems. How tree species will respond to future climate change scenarios, and what mechanisms will they adopt, remains as a gap of knowledge in ecological research. Foresters will have to make short-term decisions and plan future managements under the great uncertainty of climate change and they demand answers to know if the current species will cope with...

Mechanical orchestration of tissue remodeling

Pierre-Jean Wipff
After organ injury, a complex sequence of events is triggered to heal the tissue and to form a scar. Myofibroblasts, specialized contractile and secretory fibroblasts, are one of the many cell types that participate in the remodeling process. Myofibroblasts are responsible for tissue regeneration and tissue contraction, facilitating wound closure. However, uncontrolled occurrence of the myofibroblastic phenotype leads to pathological excessive extracellular matrix (ECM) secretion and aberrant tissue contraction, characteristic of severe diseases such as...

Interactions of silver and polystyrene nanoparticles with algae

Xiaomei Li
Nanoparticles have various physicochemical properties attributed by their small dimensions. The global production of nanoparticles lead to a raised concern for their environmental impacts. Algae are of highly ecological importance functioning as primary producers for almost all aquatic life. In the present thesis, interactions of nanoparticles with different fresh water algal strains were examined. First, the toxicity and uptake of citrate-coated silver nanoparticles (AgNP) and AgNO3 were examined in the alga Euglena gracilis, which has...

Stem cells of stratified epithelia:a generic stem cell?

Daniel-Alexandre Littman
Squamous stratified epithelia tissues are self-renewing, which quality implies the existence of stem cells. In skin the presence of bona fide multipotent stem cells has been demonstrated by long-term, serial grafting assays. We isolated, cultivated and expanded clonogenic keratinocytes from stratified epithelia of rodents (mouse and/or rat cornea, hairy and glabrous skin, oesophagus, buccal cavity and vagina). Just like mutipotent stem cells present in skin, clonogenic epithelial cells present in the stratified epithelia of rodents...

Deciphering the subcapsular epithelial cells in human fetal and postnatal thymus

Diane Sophie Elodie Hemon
Most papers related to thymus focus on the cortical and medullary epithelial cells whereas the subcapsular layer is ignored. In this thesis, we are providing new informations about the subcapsular thymic epithelial cells (TECs) by comparing them to cortical TECs, medullary TECs, Hassall's corpuscles (HCs) and the epidermis. We have demonstrated that TECs located in the subcapsular region are polarized cells adhering to an organized basement membrane and that they are interconnected in a tridimensional...

Modelling Architecture Styles

Anastasia Mavridou
Software systems tend to increase over time in size and complexity. Their development usually spans a long period of time and often results in systems that are hard to understand, debug and maintain. Architectures are common means for organising coordination between components in order to build complex systems and make them manageable. They allow thinking on a higher plane and avoiding low-level mistakes. Grouping architectures that share common characteristics into architecture styles assists component re-use...

Microwell and impedance-based approaches to isolate single cells for life sciences

Georges Muller
Cellular heterogeneity is ubiquitous in any cell population. Understanding these variations is key to answering fundamental questions in immunology, developmental biology, cancer or stem cell biology. For instance, single-cell in vitro and in vivo assays have been used to formally demonstrate the properties of stem and cancer cells.. Current strategies for single-cell isolation involve a trade-off between simplicity of use and single-cell yield. Moreover, few of these methods allows the traceability of the single-cell isolation...

From the early steps of whisker formation to its evolutionary disappearance: the (curious) case of Prdm1 and its regulation

Pierluigi Giuseppe Manti
Whiskers (also known as vibrissae) are sensory organs that are thought to have first appeared in Therapsida, a group of synapsids that includes mammals and evolutionary ancestors like the Thrinaxodon(1). They are highly conserved among mammals to the notable exception of the higher primates and are important for behavior, especially for nocturnal animals and the ones living in burrows(2). Furthermore, the mechanoreceptors of the vibrissae signal to the primary somatosensory cortex, where a discrete and...

Temperature impacts human epidermal stem cell behaviour through thermoTRPs and mTOR signalling

Johannes Alexander Mosig Rodriguez

Understanding engraftment of cultured epidermal stem cells

Nicolas Grasset
The epidermis and its appendages protect our body from environmental hazards. Cells generated in the basal layer continuously replace the terminally differentiated keratinocytes that are shed off the epidermal surface. Long-term renewal depends on specific tissue cells, called stem cells. The epidermis can efficiently repair itself when wounded, thanks to the proliferation, migration and differentiation of the stem cells and their progeny. In extensive full-thickness burns, restoration of the epidermal barrier can only be achieved...

A balancing act between stratification and EMT in cultured human thymic epithelial cells

Matteo Pluchinotta
The thymus is the primary organ for T cell differentiation and maturation. Its stroma forms a characteristic sponge-like 3D structure mainly composed of thymic epithelial cells. Despite of this unconventional epithelial architecture, TECs express markers associated with epidermal specification and differentiation. We have uncovered that the human thymus contains a population of clonogenic TECs that can be extensively expanded in a culture system originally developed for skin keratinocyte stem cells. In vitro, human TECs (hTECs)...

Capturing epidermal stemness

Andrea Zaffalon
Regenerative medicine aims to replace or regenerate tissues or organs to re-establish their normal function. In 1975, Rheinwald and Green developed a technique to isolate and amplify epidermal stem cells. Their discovery led to the development of cultured epidermal autografts (CEA), the first regenerative therapy using cultured cells. Adult stem cells are the working force behind tissue homeostasis and repair. Through constant division and specialization, they produce enough daughter cells to maintain tissue architecture and...

Inferring the age and strength of mutations evolving under positive selection

Nicky Louise Ormond
A fundamental goal of population genetics is to determine and quantify the interplay of mutation, natural selection, genetic drift and migration in shaping allelic frequency changes that underpin evolution-ary change. In this dissertation, I present computational, empirical and experimental approaches to address this goal. In the first chapter, I develop an approximate Bayesian computation (ABC) approach that co-estimates the selection strength and age of fixed beneficial mutations in single populations, by integrating a range of...

Innovative strategy of corneal epithelium regeneration using fabricated soft contact lens containing cavities for stem cells transplantation

Julien Graber
Transplantation of donor cornea is widely performed with a high success rate to treat patients with impaired corneal transparency. However the limited number of donors has led scientists to search for new technologies and treatments, including stem cell therapies. We have developed a device that permits the transplantation of stem cells onto the cornea in order to regenerate a functional epithelium. It is shaped as a contact lens and it possesses cavities in its internal...

Acquisition et recalage informatique d'images confocales de tissus denses:application à l'étude de la papille folliculaire de vibrisse de souris

Nicolas Fête
Analysis of the 3D structure of a biological sample is an important step to model cell and tissue dynamics. As a model system, we set up to determine the number of nuclei in a follicular papilla using confocal imaging and 3D computer reconstruction. The follicular papilla is a small mesenchymal ovalshape structure localized at the basis of the hair follicle that is particularly important for hair follicle morphogenesis, and the size of which varies during...

The Role of LEKTI in the Fate Determination of Keratinocyte Stem Cells

Alessandro Wataru Amici
SPINK5 (serine protease inhibitor Kazal-type 5) encodes the proteinase inhibitor LEKTI (lympho-epithelial Kazal-type related inhibitor). In skin, LEKTI expression is restricted to the stratum granulosum of the epidermis and the inner root sheath of hair follicles. Mutations that create premature termination codons in SPINK5 have been reported as the cause of Netherton syndrome (NS), a human autosomal recessive disorder characterized by congenital ichthyosis with defective cornification, a specific hair shaft defect known as trichorrexis invaginata...

Epithelial stem cells and mechanical signal transduction:a functional unit?

Vincent Bernard Cattin
Hair follicles are cutaneous structures characteristic of mammals. These sensitive organs cycle and contain multipotent epithelial stem cells which are implicated in hair growth and hair cycle. A single whisker follicle of the rat hosts up to 1500 stem cells, many more than necessary to regenerate the entire follicle throughout the animal's life. These cells are preferentially located in the most innervated region of the hair follicle. We hypothesised that stem cells might have an...

Mammalian TOR as a central modulator of the transcriptional response of keratinocyte stem cells to small temperature variations

Fahd Azzabi Zouraq
Being in the layer at the interface of the body with the outside world, keratinocyte stem cells constantly adapt and respond to environmental cues such as temperature and oxygen. However, until now, experiments involving temperature have only examined cold and heat shocks. Here, our work illustrates that small variations of temperature (~1°C) are enough to affect colony size of keratinocyte stem cells and alter expression of some genes involved in various signalling pathways. The promoter...

Exploring the potency of normal and pathological human thymic epithelial cells

Tiphaine Mélodie Chantal Arlabosse
Thymic epithelial cells (TECs) are organised in a unique 3D network that is critical for the development of efficient and self-tolerant T-cells. We report for the first time that the human thymus of all ages, even old and involuted, contains a significant number (up to 30%) of clonogenic TECs with extensive growth potential. All clonogenic TECs derive from a common EpCAM+ precursor, which within 48h in culture undergoes a molecular switch and gives rise to...

A Semantic Framework for Architecture Modelling

Eduard Baranov
Architectures are common means for organising coordination between components in order to build complex systems and to make them manageable. They allow thinking on a higher plane and avoiding low-level mistakes. Architectures provide means for ensuring correctness-by-construction by enforcing global properties characterising the coordination between components. In this work, we consider the following questions of architecture modelling: 1) how to model architectures; 2) how to compose them if several properties enforced by different architectures are...

New Algorithmic Paradigms for Discrete Problems using Dynamical Systems and Polynomials

Damian Mateusz Straszak
Optimization is a fundamental tool in modern science. Numerous important tasks in biology, economy, physics and computer science can be cast as optimization problems. Consider the example of machine learning: recent advances have shown that even the most sophisticated tasks involving decision making, can be reduced to solving certain optimization problems. These advances however, bring several new challenges to the field of algorithm design. The first of them is related to the ever-growing size of...

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