Gravity Research on Plants: Use of Single-Cell Experimental Models

Future space missions and implementation of permanent bases on Moon and Mars will greatly depend on the availability of ambient air and sustainable food supply. Therefore, understanding the effects of altered gravity conditions on plant metabolism and growth is vital for space missions and extra-terrestrial human existence. In this mini-review we summarize how plant cells are thought to perceive changes in magnitude and orientation of the gravity vector. The particular advantages of several single-celled model systems for gravity research are explored and an overview over recent advancements and potential use of these systems is provided

PI Stabilization for Congestion Control of AQM Routers with Tuning Parameter Optimization

In this paper, we consider the problem of stabilizing network using a new proportional- integral (PI) based congestion controller in active queue management (AQM) router; with appropriate model approximation in the first order delay systems, we seek a stability region of the controller by using the Hermite- Biehler theorem, which isapplicable to quasipolynomials. A Genetic Algorithm technique is employed to derive optimal or near optimal PI controller parameters

Using computer tablets to assess preference for videos in children with autism

Using computer tablets, we assessed preference for videos in five children with autism spectrum disorder (ASD). Then, we provided access to most preferred and less preferred videos contingent on sitting on one of two chairs within a concurrent schedule design. All participants spent consistently more time sitting on the chair associated with the video selected the most often during the preference assessment, indicating that practitioners may use the tablet-based assessment procedure to identify potential video reinforcers for children with ASD in applied settings

Modification de polysaccharides naturels pour l'obtention de nouveaux excipients pharmaceutiques (Liants, délitants et agents de libération contrôlée)

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Prevalence of stereotypy in individuals with developmental disabilities: a systematic review

Although many researchers have examined the prevalence of stereotypy in individuals with developmental disabilities, the results of previous studies have not been aggregated and analyzed methodically. Thus, we conducted a systematic review of studies reporting the prevalence of stereotypy in individuals with developmental disabilities. Our results indicated that the average prevalence of stereotypy across studies was 61 % and that individuals with autism spectrum disorders had the highest reported prevalence (i.e., 88 %) across specific diagnoses. Children and adults generally had similar overall prevalence measures, but the specific forms varied with age and diagnosis. Studies using the Repetitive Behavior Scale-Revised and the Autism Diagnostic Schedule-Revised generally reported higher estimates of prevalence of specific forms of stereotypy when compared to the Behavior Problem Inventory. However, the latter seemed more sensitive than the Aberrant Behavior Checklist for overall prevalence. Studies with a low risk of bias found a lower prevalence of stereotypy than those with a high risk of bias. Our systematic review underlines the importance of continuing research efforts to improve the assessment and treatment of stereotypy in individuals with developmental disabilities

Cell wall composition regulates cell shape and growth behaviour in pollen tubes

L’une des particularités fondamentales caractérisant les cellules végétales des cellules animales est la présence de la paroi cellulaire entourant le protoplaste. La paroi cellulaire joue un rôle primordial dans (1) la protection du protoplaste, (2) est impliquée dans les mécanismes de filtration et (3) est le lieu de maintes réactions biochimiques nécessaires à la régulation du métabolisme et des propriétés mécaniques de la cellule. Les propriétés locales d’élasticité, d’extensibilité, de plasticité et de dureté des composants pariétaux déterminent la géométrie et la forme des cellules lors des processus de différentiation et de morphogenèse. Le but de ma thèse est de comprendre les rôles que jouent les différents composants pariétaux dans le modelage de la géométrie et le contrôle de la croissance des cellules végétales. Pour atteindre cet objectif, le modèle cellulaire sur lequel je me suis basé est le tube pollinique ou gamétophyte mâle. Le tube pollinique est une protubérance cellulaire qui se forme à partir du grain de pollen à la suite de son contact avec le stigmate. Sa fonction est la livraison des cellules spermatiques à l’ovaire pour effectuer la double fécondation. Le tube pollinique est une cellule à croissance apicale, caractérisée par la simple composition de sa paroi et par sa vitesse de croissance qui est la plus rapide du règne végétal. Ces propriétés uniques font du tube pollinique le modèle idéal pour l’étude des effets à courts termes du stress sur la croissance et le métabolisme cellulaire ainsi que sur les propriétés mécaniques de la paroi. La paroi du tube pollinique est composée de trois composantes polysaccharidiques : pectines, cellulose et callose et d’une multitude de protéines. Pour comprendre les effets que jouent ces différents composants dans la régulation de la croissance du tube pollinique, j’ai étudié les effets de mutations, de traitements enzymatiques, de l’hyper-gravité et de la gravité omni-directionnelle sur la paroi du tube pollinique. En utilisant des méthodes de modélisation mathématiques combinées à de la biologie moléculaire et de la microscopie à fluorescence et électronique à haute résolution, j’ai montré que (1) la régulation de la chimie des pectines est primordiale pour le contrôle du taux de croissance et de la forme du tube et que (2) la cellulose détermine le diamètre du tube pollinique en partie sub-apicale. De plus, j’ai examiné le rôle d’un groupe d’enzymes digestives de pectines exprimées durant le développement du tube pollinique : les pectate lyases. J’ai montré que ces enzymes sont requises lors de l’initiation de la germination du pollen. J’ai notamment directement prouvé que les pectate lyases sont sécrétées par le tube pollinique dans le but de faciliter sa pénétration au travers du style.One of the most important features characterizing plant cells and differentiating them from animal cells is the cell wall that surrounds them. The cell wall plays a critical role in providing protection to the protoplast; it acts as a filtering mechanism and is the location of many biochemical reactions implicated in the regulation of the cell metabolism and the mechanical properties of the cell. The local stiffness, extensibility, plasticity and elasticity of the different cell wall components determine the shape and geometry of the cell during differentiation and morphogenesis. The goal of my thesis is to understand the role played by the different cell wall components in shaping the plant cell and controlling its growth behaviour. To achieve this goal, I studied the pollen tube, or male gametophyte, as a cellular model system. The pollen tube is a cellular protuberance formed by the pollen grain upon its contact with the stigma. Its main purpose is to deliver the sperm cells to the female gametophyte to ensure double fertilization. The pollen tube is a tip-growing cell characterized by its simple cell wall composition and by the fact that it is the fastest growing cell of the plant kingdom. This makes it the ideal model to study the effects of drugs, mutations or stresses on cellular growth behaviour, metabolism and cell wall mechanics. The pollen tube cell wall consists mainly of proteins and three major polysaccharidic components: pectins, cellulose and callose. To understand the role played by these components in regulating pollen tube growth, I investigated the effects of mutations, enzymatic treatments, hyper-gravity and omni-directional gravity on the pollen tube cell wall. Using mathematical modeling combined with molecular biology and high-resolution electron and fluorescent microscopy I was able to show that the regulation of pectin chemistry is required for the regulation of the growth rate and pollen tube shape and that cellulose is crucial for determining the pollen tube diameter in the sup-apical region. Moreover, I investigated the role of the pectate lyases, a group of pectin digesting enzymes expressed during pollen tube development, and I showed that this enzyme activity is required for the initiation of pollen germination. More importantly, I directly showed for the first time that the pollen tube secretes cell wall loosening enzymes to facilitate its penetration through the style

Comparison of tablet-delivered and instructor-delivered teaching on receptive identification in children with autism spectrum disorders

The purpose of our study was to compare the effectiveness of tablet- and instructor-delivered teaching (i.e., prompting and reinforcement) on the receptive identification of one-word concepts in children with autism spectrum disorders (ASDs). To this end, we embedded a multielement design within a multiple probe design to compare the effectiveness of the two instructional modalities in seven participants. Two of the seven participants showed generalization on all concepts in fewer instructional trials following instructor-delivered teaching, whereas the remaining five participants had mixed results depending on the concept. In total, the participants showed more rapid generalization with the instructor for 14 of the 19 concepts taught. Our results suggest that tablets should not systematically replace instructor-delivered prompting and reinforcement, but that they may be used to provide supplementary teaching to children with ASD

The Occurrence of Major Viruses Infecting Zucchini Squash (Cucurbita pepo L.) in Morocco

Zucchini squash, Cucurbita pepo L., is one of the most economically important vegetable crops in Morocco. Virus diseases are a major factor in limiting production of zucchini squash in the country. During the growing seasons 2015, 2016 and 2017, the main areas of field-grown cucurbit production in Morocco (Loukkos, Gharb, Bouznika, Doukkala and Souss) were surveyed for the occurrence and distribution of viruses of zucchini squash. A total of 38 commercial fields were visited and inspected for symptoms of virus diseases and 415 leaf samples were collected from plants showing virus-like symptoms for laboratory analyses. ELISA technique was used to detect the following viruses: Zucchini yellow mosaic virus (ZYMV), Squash mosaic virus (SqMV), Cucumber mosaic virus (CMV), Papaya ringspot virus-watermelon strain (PRSV-W) and Cucurbit aphid-borne yellows virus (CABYV). The obtained results showed that virus diseases were widely distributed in the country with an infection rate of 77.6%, especially in the region of Loukkos where 85% of the tested plants were infected by at least one virus. To the best of our knowledge, this isthe first study on the occurrence and geographical distribution of viruses infecting zucchini squash in Morocco. This study provides valuable information, which could be beneficial and of great interest for the researchers, growers and the plant protection services for planning future strategies to control virus diseases of zucchini squash in Morocco