Effects of Chronic Administration of Nickel on Memory Function, Hippocampal Neuronal Morphology and Oxidative Stress Factors in Male Adult Rats

Introduction: Nickel (Ni) is a toxic heavy metal that can damage the brain structure, especially the hippocampus which is an important complex brain structure with a major role in memory and learning. Recent studies showed that heavy metals can alter some brain functions and disrupt hemostasis in central nervous system (CNS). The role of chronic Ni administration on memory and leaning, survival of neurons in CA1 hippocampus and the level of oxidative stress marker in rats. Materials and Methods: In total 24 rats (n=6) were allocated to four groups: Group (I): vehicle received intraperitoneal (IP) normal saline (0.9% NaCl), Group (II, III ,IV): received 0.25 mg/kg, 0.5 mg/kg and 1 mg/kg IP NiCl2 for eight weeks, respectively. During this timespan, the rats were examined in the Morris water maze and novel object recognition test to evaluate memory and learning. Finally, the hippocampus of the rats was extracted and survived neurons were evaluated by Nissl staining; oxidative stress was determined using malondialdehyde (MDA) level and catalase enzyme activity. Results: Results showed that dose-dependent Ni administration decreased memory and leaning in behavioral studies and caused degenerative and morphological changes in neurons by elevating MDA and catalase enzyme activity as the most important oxidative stress markers. Conclusion: Ni induces changes in the structure of hippocampal neurons and disrupts memory and learning function in hippocampus in adult rats by an increase in oxidative markers

Un portrait de la compréhension du concept de la fraction : une étude exploratoire en Iran

Cette étude a comme origine une inquiétude à propos de la qualité des apprentissages en mathématiques des élèves iraniens à la suite des résultats préoccupants que ceux-ci ont obtenus dans l'étude internationale TIMSS. Ne pouvant embrasser toute l'étendue du champ des mathématiques scolaires, nous avons choisi de nous concentrer sur un concept, celui de fraction. Notre objectif de recherche a donc été, dans un premier temps, d'évaluer la compréhension de la notion de fraction, notamment dans le sens partie/tout retenu de la liste d'interprétation de Kieren (1980), chez des élèves Iraniens. Il s'est aussi prolongé, même si cela est d'abord apparu comme une visée secondaire, du côté de l'enseignement. Nous voulions savoir quelles conceptions des mathématiques et de leur apprentissage sont véhiculées par les enseignants. Les participants à notre étude ont été, d'une part, trois groupes d'élèves, soit 249 sujets, de quatrième et de cinquième années du primaire et de la première année du secondaire junior, et, d'autre part, 35 enseignants du primaire. Pour traiter de la compréhension chez nos élèves, des questionnaires adaptés à chacun des trois groupes ont été construits à partir d'une entrevue préliminaire. Les questions s'appuient sur les critères du tableau de compréhension de la fraction établis dans le cadre du modèle constructiviste élargi de Bergeron et Herscovics (1988). Une analyse a priori a permis de définir des catégories pour ranger les réponses fournies par les élèves. Cette analyse a priori a été complétée par une hiérarchisation des réponses qui traduit le niveau de compréhension atteint. Des études de fréquences des réponses regroupées à l'intérieur de chacune des catégories a conduit à un portrait d'ensemble de la compréhension manifestée par les élèves. Afin de connaître les conceptions des enseignants des mathématiques, un questionnaire a aussi été élaboré sur leur manière d'aborder l'enseignement de la fraction. Les réponses à ce questionnaire ont été regardées suivant deux perspectives, pédagogique et mathématique. Pour l'analyse à caractère pédagogique, une grille a été construite autour des modes de représentation privilégiés par les maîtres et autour des rôles réservés au maître et à l'élève. En parallèle, nous avons posé un jugement mathématique sur les réponses fournies par l'enseignant. Les conclusions sont encourageantes. On peut d'abord retenir que les résultats obtenus par les élèves iraniens ayant participé à l'étude sont nettement meilleurs que ce à quoi on pouvait s'attendre, notamment à la suite du TIMSS : malgré quelques faiblesses autour de certains aspects du concept de fraction, beaucoup d'élèves ont fait preuve d'une · compréhension satisfaisante. De même, les enseignants se sont montrés beaucoup moins dogmatiques, magistraux et formels qu'on ne le craignait : dans l'enseignement de la fraction, les maîtres interrogés affirment laisser une large place à l'utilisation du matériel ou de représentations graphiques. Les maîtres se réservent par ailleurs un rôle important tout au long des démarches d'enseignement et d'apprentissage. Notre étude montre donc que l'apprentissage et l'enseignement du concept de la fraction en Iran donne des résultats positifs, même s'il peut être amélioré, comme partout ailleurs. Mais surtout, cette thèse, qui garde un caractère exploratoire, ouvre des voies prometteuses pour l'étude de l'enseignement et l'apprentissage des mathématiques, que ce soit en Iran ou ailleurs

Active Nucleosome Displacement: A Theoretical Approach

AbstractThree-quarters of eukaryotic DNA are wrapped around protein cylinders forming so-called nucleosomes that block the access to the genetic information. Nucleosomes need therefore to be repositioned, either passively (by thermal fluctuations) or actively (by molecular motors). Here we introduce a theoretical model that allows us to study the interplay between a motor protein that moves along DNA (e.g., an RNA polymerase) and a nucleosome that it encounters on its way. We aim at describing the displacement mechanisms of the nucleosome and the motor protein on a microscopic level to understand better the intricate interplay between the active step of the motor and the nucleosome-repositioning step. Different motor types (Brownian ratchet versus power-stroke mechanism) that perform very similarly under a constant load are shown to have very different nucleosome repositioning capacities

Stochastic model for nucleosome sliding in the presence of DNA ligands

Heat-induced mobility of nucleosomes along DNA is an experimentally well-studied phenomenon. A recent experiment shows that the repositioning is modified in the presence of minor-groove binding DNA ligands. We present here a stochastic three-state model for the diffusion of a nucleosome along DNA in the presence of such ligands. It allows us to describe the dynamics and the steady state of such a motion analytically. The analytical results are in excellent agreement with numerical simulations of this stochastic process.With this model, we study the response of a nucleosome to an external force and how it is affected by the presence of ligands.Comment: 10 pages, 8 figures, submitted to Eur. Phys. J.

Biosorption of Nickel (II) from Aqueous Solutions onto Pistachio Hull Waste as a Low-Cost Biosorbent

There are many different industrial wastewater containing heavy metals that contribute to environmental pollution and raw agricultural waste is an effective adsorbent for the removal of heavy metals. The adsorption behavior of pistachio hull powder (PHP) as a low-cost adsorbent, with respect to nickel (II) ions, has been studied in order to consider its application to the purification of metal finishing wastewater. In this work, adsorption of nickel on pistachio hull has been studied by batch techniques. The adsorption depends on the process time, the pH of the solution, initial concentration of metals and the adsorbent concentration in the suspension. The kinetics of adsorption were relatively fast, reaching equilibrium for less than 60 minutes. Kinetic and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-second order and Freundlich model, respectively. The maximum Langmuir adsorption capacity was 14 mg/g. The optimum pH required for maximum adsorption was found to be 4-6. The initial concentration of the adsorbate and the concentration of pistachio hull strongly affect the process. No influence of particle size was evidenced. A degree of adsorption higher than 75% can be achieved for nickel (II) ions

Assessing the Satisfaction Level of Rehabilitation Trainers and Students from the Clinical Internship Assessment Checklist

Background: Valid assessment and validation indices are very important to evaluate and teach students, especially in clinical education settings. Considering the fact that rehabilitation science fields have about 1200 h of clinical education, planning of clinical skills training and how to evaluate them is important to improve the quality of education. Due to the importance of clinical skills teaching, clinical logbooks are used in various medical sciences in the world and some of the fields of medical sciences in Iran. This study was conducted to design and evaluate a clinical logbook for rehabilitation fields. Methods: Students [153] and trainers [43] surveys were conducted on how to evaluate clinical units. The clinical training logbooks of reputable rehabilitation universities of the world were studied and clinical activity logbooks for different rehabilitation fields were designed and administered in the clinical education and governance council meetings. Then, the level of satisfaction of trainers and students with the evaluation method was investigated using the logbook. Results: The results of this research showed a significant increase in students’ satisfaction with the assessment of internship and improvement of the quality of clinical education (above 80%) (P=0.02). Content validity results for the questionnaire were above 68% and Cronbach’s coefficient alpha was 75%. Conclusion: Given the similarity of internship courses throughout Iran, the logbook can be used in rehabilitation fields in the country by discipline to evaluate the clinical dimension of rehabilitation courses

Subject-specific knee ligaments modeling approaches in finite element analysis: 1D and 3D

Knee ligaments are among the most complicated structures and have a large effect on knee biomechanics. There are different approaches to model the knee ligaments in FE models. In the knee joint, ligaments have been commonly modelled as 1D spring elements; moreover, some studies modelled the ligaments as 3D constitutive elements [2]. Using springs reduces computational costs compared to constitutive models of the ligaments. In turn, constitutive models closer approximate the anatomy, and facilitate the prediction of local quantities and interactions with surrounding tissues, such as wrapping [1]. To the best of our knowledge, there is no direct/practical comparison study between two FE ligament modelling approaches. The aim of this study is to develop and compare two separate subject-specific finite element knee models in terms of ligament modelling approaches, based on cadaveric validation experiments

Strontium-and cobalt-doped multicomponent mesoporous bioactive glasses (MBGS) for potential use in bone tissue engineering applications

Mesoporous bioactive glasses (MBGs) offer suitable platforms for drug/ion delivery in tissue engineering strategies. The main goal of this study was to prepare strontium (Sr)-and cobalt (Co)-doped MBGs; strontium is currently used in the treatment of osteoporosis, and cobalt is known to exhibit pro-angiogenic effects. Sr-and Co-doped mesoporous glasses were synthesized for the first time in a multicomponent silicate system via the sol-gel method by using P123 as a structure-directing agent. The glassy state of the Sr-and Co-doped materials was confirmed by XRD before immersion in SBF, while an apatite-like layer was detected onto the surface of samples post-immersion. The textural characteristics of MBGs were confirmed by nitrogen adsorption/desorption measurements. In vitro experiments including MTT assay, Alizarin red staining, and cell attachment and migration showed the cytocompatibility of all the samples as well as their positive effects on osteoblast-like cell line MG-63. Early experiments with human umbilical vein endothelial cells also suggested the potential of these MBGs in the context of angiogenesis. In conclusion, the prepared materials were bioactive, showed the ability to improve osteoblast cell function in vitro and could be considered as valuable delivery vehicles for therapeutics, like Co2+ and Sr2+ ions