Sefer Tahkemoni

Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 201

Nicotine exposure during differentiation causes inhibition of N-myc expression

Background: The ability of chemicals to disrupt neonatal development can be studied using embryonic stem cells (ESC). One such chemical is nicotine. Prenatal nicotine exposure is known to affect postnatal lung function, although the mechanisms by which it has this effect are not clear. Since fibroblasts are a critical component of the developing lung, providing structure and secreting paracrine factors that are essential to epithelialization, this study focuses on the differentiation of ESC into fibroblasts using a directed differentiation protocol.Methods: Fibroblasts obtained from non-human primate ESC (nhpESC) differentiation were analyzed by immunohistochemistry, immunostaining, Affymetrix gene expression array, qPCR, and immunoblotting.Results: Results of these analyses demonstrated that although nhpESCs differentiate into fibroblasts in the presence of nicotine and appear normal by some measures, including H&E and SMA staining, they have an altered gene expression profile. Network analysis of expression changes demonstrated an over-representation of cell-cycle related genes with downregulation of N-myc as a central regulator in the pathway. Further investigation demonstrated that cells differentiated in the presence of nicotine had decreased N-myc mRNA and protein expression and longer doubling times, a biological effect consistent with downregulation of N-myc.Conclusions: This study is the first to use primate ESC to demonstrate that nicotine can affect cellular differentiation from pluripotency into fibroblasts, and in particular, mediate N-myc expression in differentiating ESCs. Given the crucial role of fibroblasts throughout the body, this has important implications for the effect of cigarette smoke exposure on human development not only in the lung, but in organogenesis in general. © 2013 Ben-Yehudah et al.; licensee BioMed Central Ltd

Multimodality Imaging of β-Cells in Mouse Models of Type 1 and 2 Diabetes

Objectiveβ-Cells that express an imaging reporter have provided powerful tools for studying β-cell development, islet transplantation, and β-cell autoimmunity. To further expedite diabetes research, we generated transgenic C57BL/6 "MIP-TF" mice that have a mouse insulin promoter (MIP) driving the expression of a trifusion (TF) protein of three imaging reporters (luciferase/enhanced green fluorescent protein/HSV1-sr39 thymidine kinase) in their β-cells. This should enable the noninvasive imaging of β-cells by charge-coupled device (CCD) and micro-positron emission tomography (PET), as well as the identification of β-cells at the cellular level by fluorescent microscopy.Research design and methodsMIP-TF mouse β-cells were multimodality imaged in models of type 1 and type 2 diabetes.ResultsMIP-TF mouse β-cells were readily identified in pancreatic tissue sections using fluorescent microscopy. We show that MIP-TF β-cells can be noninvasively imaged using microPET. There was a correlation between CCD and microPET signals from the pancreas region of individual mice. After low-dose streptozotocin administration to induce type 1 diabetes, we observed a progressive reduction in bioluminescence from the pancreas region before the appearance of hyperglycemia. Although there have been reports of hyperglycemia inducing proinsulin expression in extrapancreatic tissues, we did not observe bioluminescent signals from extrapancreatic tissues of diabetic MIP-TF mice. Because MIP-TF mouse β-cells express a viral thymidine kinase, ganciclovir treatment induced hyperglycemia, providing a new experimental model of type 1 diabetes. Mice fed a high-fat diet to model early type 2 diabetes displayed a progressive increase in their pancreatic bioluminescent signals, which were positively correlated with area under the curve-intraperitoneal glucose tolerance test (AUC-IPGTT).ConclusionsMIP-TF mice provide a new tool for monitoring β-cells from the single cell level to noninvasive assessments of β-cells in models of type 1 diabetes and type 2 diabetes

Multiresolution identification of germ layer components in teratomas derived from human and nonhuman primate embryonic stem cells

We propose a system for identification of germ layer components in teratomas derived from human and nonhuman primate embryonic stem cells. Tissue regeneration and repair, drug testing and discov-ery, the cure of genetic and developmental syndromes all may rest on the understanding of the biology and behavior of embryonic stem (ES) cells. Within the field of stem cell biology, an ES cell is not con-sidered an ES cell until it can produce a teratoma tumor (the ”gold” standard test); a seemingly disorganized mass of tissue derived from all three embryonic germ layers; ectoderm, mesoderm, and endo-derm. Identification and quantification of tissue types within ter-atomas derived from ES cells may expand our knowledge of abnor-mal and normal developmental programming and the response of ES cells to genetic manipulation and/or toxic exposures. In addition, because of the tissue complexity, identifying and quantifying the tis-sue is tedious and time consuming, but in turn the teratoma provides an excellent biological platform to test robust image analysis algo-rithms. We use a multiresolution (MR) classification system with texture features, as well as develop novel nuclear texture features to recognize germ layer components. With redundant MR transform, we achieve a classification accuracy of approximately 88%. Index Terms — Stem cell biology, multiresolution, classifica-tion, feature extractio

Recent Advances and Prospects in the Differentiation of Pancreatic Cells From Human Embryonic Stem Cells

Recent studies with human embryonic stem (hES) cells have established new protocols for substantial generation of pancreatic progenitors from definitive endoderm. These findings add to the efficient derivation of definitive endoderm, which is controlled by Wnt and Nodal pathways, and delineate a step forward in the quest for alternative β-cell sources. It also indicates that critical refining of the available strategies might help define a universal protocol for pancreatic differentiation applicable to several cell lines, therefore offering the possibility for transplantation of immune-matched or patient-specific hES–derived β-cells. We appraise here the fundamental role that bone morphogenetic protein, fibroblast growth factor, and retinoid signaling play during pancreas development, and describe a fundamental emergence of their combination in recent studies that generated pancreatic cells from hES cells. We finally enumerate some prospects that might improve further differentiation of the progenitor cells into functional β-cells needed in diabetes cell therapy

Encoding order and developmental dyslexia:a family of skills predicting different orthographic components

We investigated order encoding in developmental dyslexia using a task that presented nonalphanumeric visual characters either simultaneously or sequentially—to tap spatial and temporal order encoding, respectively—and asked participants to reproduce their order. Dyslexic participants performed poorly in the sequential condition, but normally in the simultaneous condition, except for positions most susceptible to interference. These results are novel in demonstrating a selective difficulty with temporal order encoding in a dyslexic group. We also tested the associations between our order reconstruction tasks and: (a) lexical learning and phonological tasks; and (b) different reading and spelling tasks. Correlations were extensive when the whole group of participants was considered together. When dyslexics and controls were considered separately, different patterns of association emerged between orthographic tasks on the one side and tasks tapping order encoding, phonological processing, and written learning on the other. These results indicate that different skills support different aspects of orthographic processing and are impaired to different degrees in individuals with dyslexia. Therefore, developmental dyslexia is not caused by a single impairment, but by a family of deficits loosely related to difficulties with order. Understanding the contribution of these different deficits will be crucial to deepen our understanding of this disorder

Preterm Delivery Disrupts the Developmental Program of the Cerebellum

A rapid growth in human cerebellar development occurs in the third trimester, which is impeded by preterm delivery. The goal of this study was to characterize the impact of preterm delivery on the developmental program of the human cerebellum. Still born infants, which meant that all development up to that age had taken place in-utero, were age paired with preterm delivery infants, who had survived in an ex-utero environment, which meant that their development had also taken place outside the uterus. The two groups were assessed on quantitative measures that included molecular markers of granule neuron, purkinje neuron and bergmann glia differentiation, as well as the expression of the sonic hedgehog signaling pathway, that is important for cerebellar growth. We report that premature birth and development in an ex-utero environment leads to a significant decrease in the thickness and an increase in the packing density of the cells within the external granular layer and the inner granular layer well, as a reduction in the density of bergmann glial fibres. In addition, this also leads to a reduced expression of sonic hedgehog in the purkinje layer. We conclude that the developmental program of the cerebellum is specifically modified by events that follow preterm delivery