Expression and function of mouse Sox17 gene in the specification of gallbladder/bile-duct progenitors during early foregut morphogenesis

In early-organogenesis-stage mouse embryos, the posteroventral foregut endoderm adjacent to the heart tube gives rise to liver, ventral pancreas and gallbladder. Hepatic and pancreatic primordia become specified in the posterior segment of the ventral foregut endoderm at early somite stages. The mechanisms for demarcating gallbladder and bile duct primordium, however, are poorly understood. Here, we demonstrate that the gallbladder and bile duct progenitors are specified in the paired lateral endoderm domains outside the heart field at almost the same timing as hepatic and pancreatic induction. In the anterior definitive endoderm, Sox17 reactivation occurs in a certain population within the most lateral domains posterolateral to the anterior intestinal portal (AIP) lip on both the left and right sides. During foregut formation, the paired Sox17-positive domains expand ventromedially to merge in the midline of the AIP lip and become localized between the liver and pancreatic primordia. In Sox17-null embryos, these lateral domains are missing, resulting in a complete loss of the gallbladder/bile-duct structure. Chimera analyses revealed that Sox17-null endoderm cells in the posteroventral foregut do not display any gallbladder/bile-duct molecular characters. Our findings show that Sox17 functions cell-autonomously to specify gallbladder/bile-duct in the mouse embryo.     

A nonlinear model with latent process for cognitive evolution using multivariate longitudinal data

Cognition is not directly measurable. It is assessed using psychometric tests, which can be viewed as quantitative measures of cognition with error. The aim of this article is to propose a model to describe the evolution in continuous time of unobserved cognition in the elderly and assess the impact of covariates directly on it. The latent cognitive process is defined using a linear mixed model including a Brownian motion and time-dependent covariates. The observed psychometric tests are considered as the results of parameterized nonlinear transformations of the latent cognitive process at discrete occasions. Estimation of the parameters contained both in the transformations and in the linear mixed model is achieved by maximizing the observed likelihood and graphical methods are performed to assess the goodness of fit of the model. The method is applied to data from PAQUID, a French prospective cohort study of ageing.     

小鼠体内脾脏,骨髓及精原细胞姐妹染色单体交换的比较研究

本文对几种化学诱变剂诱发小鼠体内脾脏、骨髓和精原细胞的SCE进行了比较研究,同时分析了几类常见化合物在小鼠脾脏细胞中诱发SCE的活力。结果显示诱变剂在脾脏细胞中诱发SCE比骨髓和精原细胞敏感。几类化合物都能显著地诱发小鼠脾脏SCE的增加,与对照相比差异显著(P<0.05)或极显著(P<0.01),说明利用小鼠脾脏细胞检测环境诱变物是相当灵敏的。     

Occurrence of unusual heterogeneous lipid-containing granule-storing cells in the main excretory duct epithelium of the male mouse submandibular gland

Summary The fine structure of the main excretory duct epithelium of the male mouse submandibular glands was investigated by scanning and transmission electron microscopy. Three principal cell-types were observed: type I and II, and basal cells. This epithelium was characterized by the presence of intercellular canaliculi. Type-I cells were the most numerous. They had an abundance of mitochondria, well-developed Golgi apparatus, a few electron-lucent lipid-containing granules and poorly developed basal infoldings. These cells were also characterized by many glycogen granules throughout the cytoplasm and abundant smooth endoplasmic reticulum in the apical cytoplasm. Type-II cells were the second most numerous. Their most characteristic feature was the presence of abundant heterogeneous lipid-containing granules having acid phosphatase activity at the periphery. They were concentrated in the infra- and supranuclear cytoplasm. The granules may be derived from mitochondrial transformation and seem to be a special kind of secondary autolysosome. Type-II cells also contained abundant mitochondria throughout the cytoplasm, much smooth endoplasmic reticulum in the apical cytoplasm, a well developed Golgi apparatus adjacent to the heterogeneous lipid-containing granules and no basal infoldings. Basal cells were situated adjacent to the basal lamina. They had a large nucleus and the cytoplasm was filled with glycogen granules.     

Heart-specific Deletion of CnB1 Reveals Multiple Mechanisms Whereby Calcineurin Regulates Cardiac Growth and Function

Calcineurin is a protein phosphatase that is uniquely regulated by sustained increases in intracellular Ca²⁺ following signal transduction events. Calcineurin controls cellular proliferation, differentiation, apoptosis, and inducible gene expression following stress and neuroendocrine stimulation. In the adult heart, calcineurin regulates hypertrophic growth of cardiomyocytes in response to pathologic insults that are associated with altered Ca²⁺ handling. Here we determined that calcineurin signaling is directly linked to the proper control of cardiac contractility, rhythm, and the expression of Ca²⁺-handling genes in the heart. Our approach involved a cardiomyocyte-specific deletion using a CnB1-LoxP-targeted allele in mice and three different cardiac-expressing Cre alleles/transgenes. Deletion of calcineurin with the Nkx2.5-Cre knock-in allele resulted in lethality at 1 day after birth due to altered right ventricular morphogenesis, reduced ventricular trabeculation, septal defects, and valvular overgrowth. Slightly later deletion of calcineurin with the α-myosin heavy chain Cre transgene resulted in lethality in early mid adulthood that was characterized by substantial reductions in cardiac contractility, severe arrhythmia, and reduced myocyte content in the heart. Young calcineurin heart-deleted mice died suddenly after pressure overload stimulation or neuroendocrine agonist infusion, and telemetric monitoring of older mice showed arrhythmia leading to sudden death. Mechanistically, loss of calcineurin reduced expression of key Ca²⁺-handling genes that likely lead to arrhythmia and reduced contractility. Loss of calcineurin also directly impacted cellular proliferation in the postnatal developing heart. These results reveal multiple mechanisms whereby calcineurin regulates cardiac development and myocyte contractility.     

Stability and structural constraints of random brain networks with excitatory and inhibitory neural populations

The stability of brain networks with randomly connected excitatory and inhibitory neural populations is investigated using a simplified physiological model of brain electrical activity. Neural populations are randomly assigned to be excitatory or inhibitory and the stability of a brain network is determined by the spectrum of the network’s matrix of connection strengths. The probability that a network is stable is determined from its spectral density which is numerically determined and is approximated by a spectral distribution recently derived by Rajan and Abbott. The probability that a brain network is stable is maximum when the total connection strength into a population is approximately zero and is shown to depend on the arrangement of the excitatory and inhibitory connections and the parameters of the network. The maximum excitatory and inhibitory input into a structure allowed by stability occurs when the net input equals zero and, in contrast to networks with randomly distributed excitatory and inhibitory connections, substantially increases as the number of connections increases. Networks with the largest excitatory and inhibitory input allowed by stability have multiple marginally stable modes, are highly responsive and adaptable to external stimuli, have the same total input into each structure with minimal variance in the excitatory and inhibitory connection strengths, and have a wide range of flexible, adaptable, and complex behavior.     

Parental genome composition and genetic classifications of derivatives from intergeneric crosses of Festuca mairei and Lolium perenne

Intergeneric hybridization between Festuca and Lolium has been a long-term goal of forage and turfgrass breeders to generate improved cultivars by combining stress tolerance of Festuca and rapid establishment of Lolium. However, wide-distance hybridizations usually result in the wild genome being eliminated from the hybrid due to incomplete chromosome pairing and crossovers. In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were used to detect the parental genome composition of F₁ hybrids and backcross, generated from crosses between Festuca mairei St. Yves (Fm) and Lolium perenne L. (Lp). Each of the hybrids exhibited integration of Fm and Lp genomes with varying levels of Fm/Lp genome ratios. However, cluster and principle component analyses of the progeny consistently revealed four groups depending on the amount of genome introgression from both parents. The parental genome composition and classifications of intergeneric progeny would be useful for breeding material selection. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Random amplification of polymorphic DNA versus pulsed field gel electrophoresis of SmaI DNA macrorestriction fragments for typing strains of vancomycin-resistant enterococci

Genetic typing of vancomycin-resistant enterococci (VRE) can be performed using a variety of methods, but comparative analyses of the quality of these methods are still relatively scarce. We here compare random amplification of polymorphic DNA (RAPD) analysis with pulsed field gel electrophoresis (PFGE) of DNA macrorestriction fragments as examples of two of the recent and well-accepted molecular typing methods. For the latter method, empirical guidelines for the interpretation of the DNA fingerprints have been proposed in the international literature. Based on our experimental analyses, we define similar criteria for RAPD fingerprinting. A collection of 100 strains of VRE, comprising Enterococcus faecium, Enterococcus faecalis, Enterococcus avium, Enterococcus gallinarum and Enterococcus casseliflavus, was assembled. Fifty isolates were Dutch, another 50 were isolated in the UK. Strains were selected on the basis of previously determined putative identity, close relatedness or uniqueness. The strains were analysed using well-standardised RAPD and PFGE protocols. Resulting fingerprints were interpreted with computerised methods involving band positioning and we show that typing of VRE by PFGE and RAPD generates highly congruent DNA fingerprint clustering. When the proposed international criteria for interpretation of PFGE fingerprints were applied in our case, 86% PFGE homology as discriminating value between close relatedness and uniqueness, a 75% homology cut-off for the comparison of the RAPD-generated DNA fingerprints revealed essentially identical strain clusters. As a spin-off it is revealed that strains from the different species can be efficiently discriminated, that strains from the UK and The Netherlands form separate clusters and that strains from veterinary origin can be identified separately as well.     

Testing the correlation for clustered categorical and censored discrete time-to-event data when covariates are measured without/with errors

In the analysis of clustered categorical data, it is of common interest to test for the correlation within clusters, and the heterogeneity across different clusters. We address this problem by proposing a class of score tests for the null hypothesis that the variance components are zero in random effects models, for clustered nominal and ordinal categorical responses. We extend the results to accommodate clustered censored discrete time-to-event data. We next consider such tests in the situation where covariates are measured with errors. We propose using the SIMEX method to construct the score tests for the null hypothesis that the variance components are zero. Key advantages of the proposed score tests are that they can be easily implemented by fitting standard polytomous regression models and discrete failure time models, and that they are robust in the sense that no assumptions need to be made regarding the distributions of the random effects and the unobserved covariates. The asymptotic properties of the proposed tests are studied. We illustrate these tests by analyzing two data sets and evaluate their performance with simulations.     

癌组织中的遗传不稳定性的RAPD分析(简报)

肿瘤仍然是导致人类死亡的重要原因,由于缺乏深刻了解癌症的发生机制,尽管在过去25年中肿瘤的诊断和治疗都取得很大的进展,但肿瘤病人的存活率并没有显著的提高。目前有很多癌基因和抑癌基因如P16、P53、P73、ras、DCC和RB等