McGill University Thèses et mémoires publiés en 2004

Quebec knew a long tradition of regionalistic literature since the novel of the soil, tradition with which the writers of Quebec broke for a long time. However, certain writers still practice a regionalistic form of literature, which does not have anything to see with the novel of the soil. Within the literary institution, the regionalistic writers of today seem to belong to a sphere of distinct production. In order to delimit the space occupied by the contemporary regionalistic writers, we based ourselves on the theory of the literary field of Pierre Bourdieu and the theory of the institution of the …  Read more

Malaria is a worldwide disaster that is still killing two million lives annually. The recent rise of the epidemic is mainly attributed to the emergence of resistance to the most effective, affordable and safe antimalarial, chloroquine. Unfortunately, neither the mechanism of action of these 4-aminoquinolines nor the basis of chloroquine resistance is well understood. It has been noted that a known channel blocker, verapamil, is able to modulate chloroquine resistance. In this study, a chemical biology approach was taken to gain some light into these mechanisms. The design, synthesis and characterization of fluorescent and photoreactive probes, analogues of chloroquine and …  Read more

Emerging methods of combinatorial chemistry involve receptor assistance to combine synthesis and screening. Binding to the receptor alters either the thermodynamics or kinetics of synthesis. Dynamic combinatorial chemistry uses reversible synthesis where binding to the receptor shifts the equilibrium to make more of the best binders. In target-accelerated synthesis, binding of the starting materials to the receptor speeds up the synthesis of the best-binding compounds. We report a new receptor-assisted method---pseudo-dynamic combinatorial chemistry---where binding to a receptor slows the destruction of the best-binding compounds. In pseudo-dynamic libraries, synthesis and destruction of library members are separate, irreversible reactions. Extending the destruction …  Read more

Different types of zinc bicrystals were tested under creep conditions. Observations of grain boundary sliding along boundaries with different misorientations were made. It was established that Sigma = 9 coincidence boundary slides faster than boundaries of general type. Grain boundary sliding along coincidence boundary was activated at higher stress and only in the presence of intragranular slip. Sliding along coincidence and near-coincidence boundaries is accompanied by regular boundary migration whereas sliding along general boundary is not. The sliding-migration behavior of coincidence boundaries was explained in terms of DSC-dislocations associated with steps. Sliding along general boundaries was described in terms of …  Read more

One of the key issues with online multiplayer games is game play fairness. In both centralized and decentralized architectures the ordering of command messages from clients for execution is an important issue that impacts fairness and response time of game play. Recently, a fair-ordered message exchange protocol (FMEP), based on "reaction" times was proposed to order command messages for a client-server model. This thesis presents a cheat controlled protocol (CCP) that can be used to control cheating in the FMEP. We examined the performance of the CCP by emulating wide-area game play scenarios on the Planet-Lab. The results from the …  Read more

Light gauge steel frame/wood panel shear walls are more commonly being used in the residential and low-rise building markets. However in Canada, no design guide for these shear walls has been published. Furthermore, although laboratory investigations that cover the performance of light gauge steel frame/wood panel shear walls with different sheathing material have been carried out, no analytical methods have been developed to predict the in-plane stiffness and strength of light gauge steel/wood panel shear walls based on member and connection properties. This thesis has two main objectives. One is to investigate the performance characteristics of various configuration light gauge …  Read more

Thin film transistors with different polymers (PTFTs) as active channel layers have been fabricated and studied in this work. Three different fabrication procedures were used to fabricate long and short channel PTFTs on silicon substrates and long channel PTFTs on glass substrates. It has been shown that the success rate of fabrication of PTFTs on glass substrates with anodic Al 2O3 gate dielectrics is higher than that on silicon substrates with thermally grown SiO2 gate dielectrics. The characteristics of PTFTs fabricated using several polymers were studied. Among them, the ones based on regioregualr poly[3-hexylthiophene-2.5diy] (RR-P3HT) have the best performance with …  Read more

This thesis is devoted to the studies of structural and magnetic properties of Pd/Fe multilayers with the principal goal of determining the extent to which the Pd layers are polarised by the Fe atoms and the average moment induced on each Pd atom. Although Pd/Fe multilayers have been the subject of several previous studies, no consensus on the behavior of magnetically polarised Pd has emerged. This work has the novel feature of applying a wide range of characterization techniques on the same sample. These techniques included x-ray diffraction, conversion electron Mossbauer spectroscopy (CEMS), magnetometry and polarised neutron reflectometry. Ag/Fe multilayers …  Read more

The current study was conducted for evaluating the effects of two different strategies viz., phase control and cycle control, on the microwave/air drying process. A phase-controlled electrical power regulator was developed and connected in series with the original cycle-controlled power regulator of an existing domestic microwave oven. The microwave oven was further modified such that combined microwave and convectional drying can be accommodated. The system performance was evaluated. It was observed that phase-controlled power regulator could be successfully used for quasi-continuous (fast-switching) power regulation with the maximization of power efficiency. The degradation of output microwave power was recorded and the …  Read more

Biofilm communities were cultivated in rotating annular bioreactors using water from the South Saskatchewan River. The impacts of seasonal variations, nutrients, pollutants and dissolved oxygen on the activity and composition of the biofilms were assessed by using a combination of microcosm assays and molecular biology techniques. The seasonal pattern in nitrification, denitrification and hexadecane mineralization, and in the occurrence of nirK in the South Saskatchewan River biofilms was: fall greater than winter, which was equivalent to spring. Hexadecane mineralization was higher in fall 1999 than in fall 2001, denitrification was similar in these two years, and no seasonal pattern of …  Read more

Most current applications and uses of liquid crystalline materials involve surfaces and interfaces. Prominent examples are high performance carbonaceous mesophase fibers, liquid crystal polymer fibers, and thermoplastic/liquid crystal polymer in-situ composites. Fundamental surface science and engineering principles are needed to optimize and design fibers and composites derived from liquid crystalline precursors. Currently non-equilibrium liquid crystal surface phenomena are not well understood. Force balance equations describing static and dynamical interfacial phenomena are available but have not been adequately used to describe the mechanics of fiber and film microstructures. This thesis explores the mechanics and stability of nematic liquid crystalline fibers embedded …  Read more

Although modern system operating speed and performance largely benefit by the advanced technology, designing the system level test circuitry is still a great challenge. Traditional ad-hoc or informal design practice is not adequate, and an early well planned testing scheme is required to meet the concerns raised by the increasing size and complexity of the system. Moreover, many high speed communication issues, including BER testing, jitter measurement and jitter injection, also need to be considered due to the increasing need for newly developed high speed interconnect architectures such as PCI Express, Fibre Channel and InfiniBand. In this thesis, a disciplined …  Read more

Theory of mind (ToM) is the knowledge that other people have minds, thoughts, beliefs and values different from our own. Patients with schizophrenia are generally thought to be impaired at tasks requiring this ability. Frith (1992) has proposed that specific signs and symptoms of schizophrenia are associated with dysfunction in ToM ability. The purpose of the present study was to investigate the role of thought disorder in theory of mind and to tease out the electrophysiological correlates of this phenomenon. Participants partook in an intention attribution task, during which event-related potentials (ERPs) were recorded. Patients with high ratings of thought …  Read more

Copper has been recently used as an interconnecting material since it has high conductivity and good electromigration failure resistance. Recent studies show the close relationship between texture and reliability of Cu damascene interconnects. However, textural and microstructural evolutions of Cu damascene interconnects as function of substrate texture, current density, line width and annealing process are still not well understood. At first, to understand the influence of substrate texture and electroplating conditions on the texture and surface morphology of Cu electrodeposits, three different polycrystalline copper specimens were used as substrates and electrodeposits were plated using different current densities. The mechanism of …  Read more

Replication Protein A (RPA) is required for DNA recombination, repair and replication in all eukaryotes. RPA participation in these pathways is mediated by single-stranded DNA binding and protein interactions. We have identified a novel RPA protein interactor, Replication Protein Binding Trans-Activator (RBT1), in a yeast two-hybrid assay employing the second subunit of human RPA (RPA32) as bait. RBT1-RPA32 binding was confirmed by glutathione S-transferase pull-down and co-immunoprecipitation. Fluorescence microscopy indicates that over-expressed green fluorescence protein-tagged RBT1 is localized to the nucleus in vivo. RBT1 mRNA expression, determined by semi-quantitative RT-PCR, is significantly higher in cancer cell lines MCF-7, ZR-75, SaOS-2 …  Read more

Polystyrene-b-poly(acrylic acid) block copolymers can self-assemble in selective solvents to form aggregates of different morphologies, including spherical micelles and vesicles. The ability of spherical micelles to solubilize (incorporate) 2-nitrodiphenylamine, a model hydrophobic but polar dye molecule, is investigated. The solubilization capacity of the micelles is evaluated as a function of the dye concentration, and the results are explained by treating solubilization as an adsorption process. The location of the incorporated molecules within the micelle is also examined, and the interfacial region of the micelle is identified as the solubilization site. Vesicles prepared from polystyrene-b-poly(acrylic acid) in dioxane/water mixtures undergo fusion …  Read more

The present study examined the discrepancy in the literature regarding the absence of gender differences in the stability of same-sex close friendships. One hundred and twenty children and adolescents (60 females and 60 males) from three grade levels (5, 7, and 9) participated in the study. An interview measure was developed to assess for the level of intimacy, the social context in which the friendship occurred (dyad vs. group), and perceptions of equality of achievement for both current and former same-sex close friendships. Intimacy and equality are features most closely associated with the social context of girls' same-sex friendships. It …  Read more

The motivation for this thesis is the paper by Paul L. Canner [The American Statistician, vol. 23, no. 5, pp. 39--40 (1969)] in which it was noted that in simple linear regression it is possible for the generalized least squares regression line to lie either entirely above or entirely below all of the observed data points. Chapter I builds on the observation that in Canner's model the ordinary least squares and generalized least squares regression lines are parallel, which led us to introduce a new measure of efficiency of ordinary least squares and to find conditions for which the total …  Read more

The presence of peak points in constant strain rate flow curves is generally considered to indicate the onset of dynamic recrystallization (DRX). However, not all materials display clear peaks when tested under these conditions. It has been suggested that DRX is initiated when the strain reaches a critical value epsilonc that is related to the peak strain epsilonp and that this critical strain can be detected from the inflection point in plots of the strain hardening rate theta against stress sigma, regardless of the presence or absence of peaks. This is of importance because many works regarding DRX have been …  Read more

In this thesis we study the theory of equations over a free group. We consider basic notions in combinatorial group theory including free groups and free constructions. Using these tools and recent results involving fully residually free groups, we classify solutions to one-variable systems of equations over a free group. We examine some more sophisticated results involving splittings, and obtain a new theorem that describes solutions to two-variable systems of equations over a free group.  Read more

Mammalian cortical neurogenesis is a highly regulated developmental process. The main factors involved in this regulation are the bHLH family of transcription factors, of which the Hes family of Notch effector proteins play a major role. Hes1 acts as a transcriptional repressor by recruiting the co-repressor Gro/TLE and functions to prevent differentiation of progenitors into neurons. Recently, a novel member of the Hes family, Hes6, has been identified. This protein was shown to have an opposite function to Hes1, promoting differentiation of progenitor cells into neurons. The goal of the present project was to determine whether Hes6 might also have …  Read more

Genetic improvement of timothy digestibility by breeding requires an effective and reliable selection procedure. The general objective of this study was to evaluate the concentrations of four fiber components (neutral detergent fiber, acid detergent fiber, acid detergent lignin, hemicellulose, and cellulose) and four ratios involving these concentrations (acid detergent lignin over hemicellulose, acid detergent lignin over cellulose, acid detergent lignin over the sum of hemicellulose and cellulose and hemicellulose over cellulose) as selection criteria to improve timothy digestibility without affecting plant biomass. Selected genotypes and populations derived from them were evaluated in a field experiment. Significant variability was observed among …  Read more

The focus of this dissertation is the teacher education program of Nunavut, until 1999 the eastern part of the Northwest Territories. Through interviews and personal experience as a participant observer within the program, this longitudinal qualitative case study, influenced by social constructivist theory, of the Nunavut Teacher Education Program attempts to provide an account of the program's growth and development, its strengths and its weaknesses and possibilities for the future. However, in order to locate the program in its time and place, it is necessary to examine the nested contexts of traditional, colonial and post-colonial worlds from which and in …  Read more

The McGill Paleoclimate Model (MPM) was used to simulate the past and future glacial inceptions. This model of intermediate complexity was first run between 122 and 80 kyr BP (Before Present). After some parameter tuning, the MPM simulated the last glacial inception at 119 kyr BP. The recent addition of a vegetation component in the model led to an improvement of the results, especially for the ice sheet distribution over Eurasia. The MPM was then run to simulate projections of the climate for the next 100 kyr and possibly the next glacial inception. When forced by a constant atmospheric CO2 …  Read more

This thesis examines Sephardic melodies that were adopted into the liturgy of the Ashkenazic Jews in London during the early twentieth century. The work begins by presenting a history of Sephardic and Ashkenazic Jews from the time they settled in England to the end of the nineteenth century. Through an analysis of social and religious changes taking place among English Jews of the nineteenth century, this thesis explicates reforms in the synagogue service that led to the inclusion of polyphonic music into the synagogue and eventually, to the incorporation of Sephardic melodies into Ashkenazic synagogue practice. The attempt to canonize …  Read more

Magnetic quantum cellular automata (MQCA) have been proposed as an alternate computing architecture. Single domain magnetic particles represent "1" or "0"; their stray field interaction controls the propagation and manipulation of information. An inherent requirement for an MQCA system is to know the conditions under which nanomagnets switch between the purely "up" (1) and the purely "down" (0) state, and to control this reproducibly. As a first step to study this, arrays of two types of permalloy particles were designed, simulated, fabricated and imaged, and their switching distributions ascertained. Individual particles were "peanut"-shaped, to investigate the effect of a shape …  Read more

The synthesis, characterization, and assembly of thiol-stabilized gold nanoparticles in 2- and 3-dimensions are the focus of this thesis. Assemblies of gold nanoparticles in 2-dimensions were prepared by the reduction of gold(I)-thiolate thin films on carbon and silicon surfaces. These films were reduced by direct exposure to an electron beam. The electron beam-induced growth of gold nanoparticles was observed in-situ in a transmission electron microscope. Electron beam lithography of the gold(I)-thiolate films allowed for the fabrication of sub-50 nm arrays of small gold nanoparticles (from 2 to 6 nm in diameter). Variation in the electron dose allowed for a variation …  Read more

The neurobiological model of Post-Traumatic Stress Disorder, based upon the neurobiological model of fear-conditioning, states that the amygdala is hyperactivated, while other, inhibiting structures, like the Anterior Cingulate Cortex (ACC), are hypoactivated, therefore not fully inhibiting the amygdala. Two structural neuroimaging studies have examined the ACC volume to try to comprehend the hypoactivation of the ACC observed in subjects suffering from PTSD. Yamasue et al. (2003) found a lower grey matter density in the ACC of subjects with PTSD. Rauch et al. (2003) found a lower volume of the affective division of the ACC in subjects with PTSD compared to …  Read more

Molecular Dynamics simulations often involve the numerical integration of pair-wise particle interactions with a constant, step size method. Of primary concern in these simulations is the introduction of error in velocity statistics. We consider the simple example of the symplectic Euler method applied to two-particle collisions in one dimension governed by linear restoring force and use backward error analysis to predict, these errors. For nearly all choices of system and method parameters, the post-collision energy is not conserved and depends upon the initial conditions of the particles and the step size of the method. The analysis of individual collisions is …  Read more

The potential use of stem cells for therapy depends on our ability to optimize differentiation conditions to best take advantage of their multipotentiality. Skin derived precursor cells (SKPs) are recently described adult stem cells that have been shown to differentiate into both neuronal and mesodermal cell types in vitro. We asked specifically whether they could be induced to differentiate into skeletal muscle. An accurate assay for detecting skeletal muscle was first developed, using RT-PCR, immunocytochemistry and Western blotting. We then used traditional differentiation methods, and found that SKPs could differentiate into cells expressing an immature skeletal muscle phenotype, as determined …  Read more

On examining novels written in Quebec after the 1950s, surprisingly some common themes emerge. One finds progressively increasing references to the themes of the book, the library, and the author. In this thesis, we study the fictional work of Gerard Bessette and Jacques Poulin, two authors who make abundant references to the universe of the book. Their characters read, write, work and even live in libraries and bookshops. We will discuss the concept of the library, in order to clarify various key issues. Our definition of the library will include any place where books are read or stored. In other …  Read more

Two processes may lead to genetic divergence among populations. One is mediated by geography, whereby physical barriers and geographic distance limit gene flow among populations, resulting in divergence due to drift or mutation. Another is ecological speciation, whereby populations adapt to their local environments via natural selection, and gene flow is impeded by selection against dispersers in favor of adapted residents. I used natural populations of guppies (Poecilia reticulata) to determine the relative influence of these two processes in the structuring of populations. If geography is playing a strong role, I predicted that gene flow would be greatly impeded by …  Read more

My thesis examined the implications of life history and ecology for population-level responses of the European long-snouted seahorse ( Hippocampus guttulatus Cuvier 1829) to habitat alteration, exploitation and a recommended minimum size limit for seahorse management. The research employed a mark-recapture study, underwater visual censuses (UVCs) and catch data from an unrelated experimental sampling program in the Ria Formosa Lagoon (southern Portugal). These small-bodied fish are characterized by rapid growth rate, early age at maturity, high natural mortality, short generation time, short life span and multiple spawnings per year, traits that are usually associated with resilience to exploitation. However specialized …  Read more

The objective of this study is to assess current distributional patterns of species within a community, while taking into account species' evolutionary histories, as reflected in their phylogenetic relationships. The hypothesis is that closely related species segregate along environmental gradients, either due to historic evolutionary divergence of their niches, or to ecological processes presently occurring within a community. Distribution along environmental gradients was compared to phylogenetic structure of the 27 sedge species (Cyperaceae) growing in the subarctic fen communities of Schefferville, northern Quebec. Field data suggest that within these fens, sedges mostly differentiate along gradients of rooting depth and pH. …  Read more

Iteratively computing and discarding a set of convex hulls creates a structure known as an "onion". In this thesis, we show that the expected number of layers of a convex hull onion for n uniformly and independently distributed points in a disk is theta( n23 ). Additionally, we show that in general the bound is theta( n2d+1 ) for points distributed in a d-dimensional ball. Further, we show that this bound holds more generally for any fixed, bounded, full-dimensional shape with a non-empty interior. The results of this thesis were published in Random Structures and Algorithms (2004) [1].  Read more

A central question in the field of Obsessive-Compulsive Disorder (OCD) is the role of symptom-related dysfunctional beliefs thought to underlie symptoms. This study examines change in symptoms and related dysfunctional beliefs during Cognitive Behavior Therapy (CBT) with 32 previously treatment resistant OCD patients. Three questions were examined: (a) What is the relationship between dysfunctional beliefs and symptoms at pre-treatment; (b) How much change occurs in symptoms, and related beliefs, during specialized CBT; and (c) What is the relationship between change in cognitive and symptom variables. On average, symptoms and related beliefs of symptomatic-responders resolved to within normal limits following treatment. …  Read more

This dissertation consists of three essays each of which considers a political economy problem. In the first essay, we study a local government who can engage in both grabbing hand and helping hand activities with respect to the firms under its jurisdiction. We find that there are two dynamic paths for this economy. It can either stagnate or take off, i.e., grow without bound. The path actually taken depends on three variables: If the initial capital stock, tax share of the local government, or the cost of covering up corruption is sufficiently high, the economy takes off. Otherwise it stagnates. …  Read more

One of the main objectives of the next generation of mobile communications is to provide cost-effective transmission of broadband multimedia services over time-varying, frequency-selective fading, band-limited wireless channels. Orthogonal Frequency Division Multiplexing (OFDM) with dynamic resource allocation is one of the potential techniques to improve the system spectral efficiency. In this work, efficient dynamic resource allocation algorithms are developed for downlink OFDM mobile cellular systems to support multimedia traffic. User channel responses are considered in the dynamic resource allocation to reduce interference and hence, to increase the system spectral efficiency while maintaining different Quality-of-Service (QoS) requirements. Performance of the proposed …  Read more

Subcortical band heterotopia (SBH) is a rare neuronal migration disorder, characterized by bilateral bands of neurons abnormally located in the cerebral white matter. It occurs mostly in females, 80% of whom harbor mutations in the DCX (Xg22.3-q23) gene. To determine whether males and females with SBH have a similar clinical spectrum and genetic basis, we analyzed and compared the clinical, imaging, and molecular features in 30 males and 60 previously reported females with SBH. The range of clinical phenotypes in males with SBH overlapped that in females. However, MRI studies revealed that some SBH subtypes such as incomplete posterior SBH, …  Read more

Beck's cognitive diathesis-stress theory has generated much research into the etiology of depression. Central to the theory are depressogenic schemata that interact with stressors, resulting in increases in depressive symptomatology. These schemata are commonly assessed using the Dysfunctional Attitudes Scale (DAS). Importantly, the DAS was not designed for use in children---it has been validated with adults and contains advanced language. Thus, the Child and Adolescent Dysfunctional Attitudes Scale (CADAS) was developed. Study 1 sought to psychometrically validate the CADAS. 453 children completed the CADAS item pool and measures assessing divergent validity. The CADAS was readministered 3 weeks later. Items were …  Read more

The segmenting of gravel-bed rivers into 'sedimentary links', characterized by single-sediment sources and downstream fining of alluvial sediments, is a relatively new technique which has had limited application. The sedimentary link concept has been primarily applied to alpine river environments where link formations are supplied by coarse sediment from active point sources. The purpose of this study is to apply the sedimentary link concept on the Ste Marguerite River in the Saguenay region of the Canadian Shield, where valley-segment deposits of coarse sediment from ancient glacial processes are dominant in forming links. Specifically, this study examines link-scale trends in surface …  Read more

This thesis is an introduction to the study of convexification problems involving smooth functions in the area of continuous mathematical programming. The results are applied to a real life problem in oil production. An improved model is formulated for the company which yields environmentally friendlier optimal solutions at the same profit level.  Read more

Arsenic trioxide (As2O3) is an effective drug for the treatment of acute promyelocytic leukemia (APL), but is less effective against other malignancies. Although the response of APL cells to AS 2O3 has been linked to degradation of the PML/RARalpha fusion oncoprotein characteristic of this disease, we present evidence that PML/RARalpha does not confer sensitivity to As2O3-induced apoptosis. In two arsenic-resistant APL cell lines, AsR2 and AsR3, that we established to study mechanisms of action of arsenic trioxide, PML/RARalpha expression was regulated normally by As2O3. However, both arsenic-resistant clones contained high glutathione (GSH) levels, and we found that GSH depletion dramatically …  Read more

In 1890, lawyers Samuel Warren and Louis Brandeis conceived of a "sacred" right, the right to "be let alone." They argued for this right as a measure of "retreat from the world" for protection of an individual's "inviolate personality." Their argument was born in response to intrusions made possible with technological developments in printing and photography. For over a 100-year period, the concept of privacy has received attention from a multi-disciplinary collection of scholars. Despite this significant attention, however, relatively little consideration has been paid to conceptualizations of privacy in the everyday. My dissertation utilizes the focus group method to …  Read more

The three dimensional structure of P-gp nucleotide binding sites is unknown but a high resolution crystal structure was solved for the homodimer of HiSP, the ATP binding subunit of the bacterial ABC transporter histidine permease. The main goal was to test the hypothesis that the nucleotide binding domains (NBD) of P-gp are structurally and functionally conserved with HisP with respect to key residues in intimate contact with the ATP molecule and possibly involved in catalysis. The strategy adopted involves the insertion of cysteine residues at the desired position in a cysteine-less protein backbone. A set of 14 mutants was generated …  Read more

Numerous groups, including ours, have found that retinoids potently inhibit the growth of breast cancer cells, but the mechanisms by which growth regulation is achieved remains unclear. Although several of the effects of retinoids in breast cancer have been linked to the insulin-like growth factor (IGF) system, their effects on key signaling molecules in the IGF type-I receptor (IGF-IR) pathway have not been well characterized. This thesis project examined the hypothesis that retinoids mediate their growth inhibitory effects by targeting specific members of the IGF-IR signal transduction pathway. Although we did not observe regulation of IGF-IR itself, we found that …  Read more

The objectives of this qualitative multiple case study are as follows: (a) identify the professional beliefs or representations of two student teachers before, during and after their last practicum in FSL (French as a second language) or in French immersion at a High School; and (b) study the evolution of these beliefs or representations during the student teaching period. The investigation was conducted by means of semi-structured interviews: of two student teachers; of two associate teachers; of one university supervisor; and of the student teaching coordinator. Other data, taken from the portfolio of the two student teachers, were also analysed. …  Read more

Tumors develop and progress as a result of alterations in oncogene and tumor suppressor genes. Knudson's two hit model predicts that cancer arises when both alleles of a tumor suppressor gene are inactivated. The insulin-like growth factor 2 receptor gene (IGF2R) is known to be a tumor suppressor for breast cancer, as mutations inactivating both alleles have been found in these tumors, consistent with its known functions in degrading insulin-like growth factor 2 (IGF2) and activating transforming growth factor beta1 (TGF-beta1), a growth inhibitor. Tumor suppressors can be inactivated by several means, such as genomic imprinting (a preferential silencing of …  Read more

Le taux de synthèse fractionée (TSF) du cholestérol (Ch) endogène est inversement proportionnel à la prise alimentaire du Ch à 4 mois (mo). L’objectif de cette étude était de verifier si ces différences du TSF persistent à 18 mo. Quarante-sept enfants ont reçu, dès la naissance, soit lait maternel (HM), jusqu’au sevrage (n=15), ou ont reçu de façon aléatoire soit du lait maternisé (CF), à base lait de vache (n=17), ou une formule modifiée par l’addition de Ch (MCF, n=15) durant 12 mo. Les HM, CF, et MCF contenaient respectivement 120, 80, 40 mg/L de Ch. À 4 mois, le …  Read more

Members of voltage-gated potassium channel subfamily 3 (Kv3) have been extensively demonstrated to play a significant role in facilitating function of "fast-firing" neurons in the central nervous system. Kv3.1 and Kv3.3 channels, members of Kv3 channel subfamily, have different distribution profiles on the regional level of brain and on the subcellular level of neurons in mammals and in weakly electric fish, according to mRNA hybridizations in situ and immunohistochemical analysis. In mammals, Kv3.1 channels are expressed in soma, axon and proximal dendrites as well as presynaptic membrane of "fast-firing" neurons. In weakly electric fish (Apteronotus), Kv3.1 channels are distributed in …  Read more