bluuebunny/crossref_metadata_2025 huggingface dataset:
Acute alcohol intoxication impairs top–down regulation of stroop incongruity as revealed by blood oxygen level‐dependent functional magnetic resonance imaging
Authors: Marinkovic Ksenija , Rickenbacher Elizabeth , Azma Sheeva , Artsy Elinor
Published: March 2011

Functional neuroanatomy of executive functions has been delineated in a large number of neuroimaging studies using conflict‐inducing tasks. The neural basis of alcohol's effects on cognitive control is poorly understood despite the evidence of impaired ability to evaluate competing demands and to inhibit maladaptive responses. To investigate the effects of moderate intoxication, healthy social drinkers participated in both alcohol (0.60 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions while being scanned using blood oxygen level‐dependent (BOLD) functional magnetic resonance imaging (fMRI). A modified four‐color Stroop task combined reading and color naming and used manual responses. Twenty subjects (10 women) were instructed to press a button corresponding to the font color except when a word was written in gray in which case they had to respond to the meaning of the word. Alcohol increased reaction times and a tendency to make more errors on incongruent trials. Behavioral indices of alcohol‐induced premature responding correlated with the current drinking levels and impulsivity traits, suggesting an interaction between alcohol effects and personality predispositions. A distributed frontoparietal cortical network was activated by incongruity. However, moderate alcohol inebriation selectively attenuated anterior cingulate cortex (ACC) activation during both high‐conflict trials and erroneous responses, indicating vulnerability of the regulative function subserved by the ACC. By disrupting top–down, strategic processing, alcohol may interfere with goal‐directed behavior, resulting in poor self control. The present results support models proposing that alcohol‐induced prefrontal impairments diminish inhibitory control and are modulated by dispositional risk factors and levels of alcohol consumption. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
The role of planum temporale in processing accent variation in spoken language comprehension
Authors: Adank Patti , Noordzij Matthijs L. , Hagoort Peter
Published: March 2011

A repetition–suppression functional magnetic resonance imaging paradigm was used to explore the neuroanatomical substrates of processing two types of acoustic variation—speaker and accent—during spoken sentence comprehension. Recordings were made for two speakers and two accents: Standard Dutch and a novel accent of Dutch. Each speaker produced sentences in both accents. Participants listened to two sentences presented in quick succession while their haemodynamic responses were recorded in an MR scanner. The first sentence was spoken in Standard Dutch; the second was spoken by the same or a different speaker and produced in Standard Dutch or in the artificial accent. This design made it possible to identify neural responses to a switch in speaker and accent independently. A switch in accent was associated with activations in predominantly left‐lateralized areas including posterior temporal regions, including superior temporal gyrus, planum temporale (PT), and supramarginal gyrus, as well as in frontal regions, including left pars opercularis of the inferior frontal gyrus (IFG). A switch in speaker recruited a predominantly right‐lateralized network, including middle frontal gyrus and prenuneus. It is concluded that posterior temporal areas, including PT, and frontal areas, including IFG, are involved in processing accent variation in spoken sentence comprehension. Hum Brain Mapp, 2012. © 2010 Wiley Periodicals, Inc.
The human dorsal premotor cortex facilitates the excitability of ipsilateral primary motor cortex via a short latency cortico‐cortical route
Authors: Groppa Sergiu , Schlaak Boris H. , Münchau Alexander , Werner‐Petroll Nicole , Dünnweber Janin , Bäumer Tobias , van Nuenen Bart F.L. , Siebner Hartwig R.
Published: March 2011

In non‐human primates, invasive tracing and electrostimulation studies have identified strong ipsilateral cortico‐cortical connections between dorsal premotor‐ (PMd) and the primary motor cortex (M1HAND). Here, we applied dual‐site transcranial magnetic stimulation (dsTMS) to left PMd and M1HAND through specifically designed minicoils to selectively probe ipsilateral PMd‐to‐M1HAND connectivity in humans. A suprathreshold test stimulus (TS) was applied to M1HAND producing a motor evoked potential (MEP) of about 0.5 mV in the relaxed right first dorsal interosseus muscle (FDI). A subthreshold conditioning stimulus (CS) was given to PMd 2.0–5.2 ms after the TS at intensities of 50‐, 70‐, or 90% of TS. The CS to PMd facilitated the MEP evoked by TS over M1HAND at interstimulus intervals (ISI) of 2.4 or 2.8 ms. There was a second facilitatory peak at ISI of 4.4 ms. PMd‐to‐M1HAND facilitation did not change as a function of CS intensity. Even at higher intensities, the CS alone failed to elicit a MEP or a cortical silent period in the pre‐activated FDI, excluding a direct spread of excitation from PMd to M1HAND. No MEP facilitation was present while CS was applied rostrally over lateral prefrontal cortex. Together our results indicate that our dsTMS paradigm probes a short‐latency facilitatory PMd‐to‐M1HAND pathway. The temporal pattern of MEP facilitation suggests a PMd‐to‐M1HAND route that targets intracortical M1HAND circuits involved in the generation of indirect corticospinal volleys. This paradigm opens up new possibilities to study context‐dependent intrahemispheric PMd‐to‐M1HAND interactions in the intact human brain. Hum Brain Mapp, 2012. © 2010 Wiley‐Liss, Inc.
Brain regions involved in human movement perception: A quantitative voxel‐based meta‐analysis
Authors: Grosbras Marie‐Hélène , Beaton Susan , Eickhoff Simon B.
Published: March 2011

Face, hands, and body movements are powerful signals essential for social interactions. In the last 2 decades, a large number of brain imaging studies have explored the neural correlates of the perception of these signals. Formal synthesis is crucially needed, however, to extract the key circuits involved in human motion perception across the variety of paradigms and stimuli that have been used. Here, we used the activation likelihood estimation (ALE) meta‐analysis approach with random effect analysis. We performed meta‐analyses on three classes of biological motion: movement of the whole body, hands, and face. Additional analyses of studies of static faces or body stimuli and sub‐analyses grouping experiments as a function of their control stimuli or task employed allowed us to identify main effects of movements and forms perception, as well as effects of task demand. In addition to specific features, all conditions showed convergence in occipito‐temporal and fronto‐parietal regions, but with different peak location and extent. The conjunction of the three ALE maps revealed convergence in all categories in a region of the right posterior superior temporal sulcus as well as in a bilateral region at the junction between middle temporal and lateral occipital gyri. Activation in these regions was not a function of attentional demand and was significant also when controlling for non‐specific motion perception. This quantitative synthesis points towards a special role for posterior superior temporal sulcus for integrating human movement percept, and supports a specific representation for body parts in middle temporal, fusiform, precentral, and parietal areas. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Effect of scanner in longitudinal diffusion tensor imaging studies
Authors: Takao Hidemasa , Hayashi Naoto , Kabasawa Hiroyuki , Ohtomo Kuni
Published: March 2011

The purpose of this study was to evaluate the effects of longitudinal drift in scanner hardware, inter‐scanner variability (bias), and scanner upgrade on longitudinal changes in global and regional diffusion properties using longitudinal data obtained on two scanners of the exact same model at one institution. A total of 224 normal subjects were scanned twice, at an interval of about 1 year, using two 3.0‐T scanners of the exact same model. Both scanners were simultaneously upgraded during the study period. The subjects were divided into four groups according to the combination of scanners used. With use of tract‐based spatial statistics, we evaluated the effects of scanner drift and inter‐scanner variability (bias) on global and regional fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) changes of the white matter. Even with scanners of the exact same model, inter‐scanner variability (bias) significantly affected longitudinal results. FA, AD, and RD of the white matter were relatively stable within the same scanner. We also investigated the effect of scanner upgrade on longitudinal FA, AD, and RD changes. The scanner upgrade included only software upgrade, not hardware upgrade; however, there was a significant effect of scanner upgrade on longitudinal results. These results indicate that inter‐scanner variability and scanner upgrade can significantly affect the results of longitudinal diffusion tensor imaging studies. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Age‐related changes in topological organization of structural brain networks in healthy individuals
Authors: Wu Kai , Taki Yasuyuki , Sato Kazunori , Kinomura Shigeo , Goto Ryoi , Okada Ken , Kawashima Ryuta , He Yong , Evans Alan C. , Fukuda Hiroshi
Published: March 2011

The aim of this study was to examine structural brain networks using regional gray matter volume, as well as to investigate changes in small‐world and modular organization with normal aging. We constructed structural brain networks composed of 90 regions in young, middle, and old age groups. We randomly selected 350 healthy subjects for each group from a Japanese magnetic resonance image database. Structural brain networks in three age groups showed economical small‐world properties, providing high global and local efficiency for parallel information processing at low connection cost. The small‐world efficiency and node betweenness varied significantly and revealed a U‐ or inverted U‐curve model tendency among three age groups. Results also demonstrated that structural brain networks exhibited a modular organization in which the connections between regions are much denser within modules than between them. The modular organization of structural brain networks was similar between the young and middle age groups, but quite different from the old group. In particular, the old group showed a notable decrease in the connector ratio and the intermodule connections. Combining the results of small‐world efficiency, node betweenness and modular organization, we concluded that the brain network changed slightly, developing into a more distributed organization from young to middle age. The organization eventually altered greatly, shifting to a more localized organization in old age. Our findings provided quantitative insights into topological principles of structural brain networks and changes related to normal aging. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Challenging a decade of brain research on task switching: Brain activation in the task‐switching paradigm reflects adaptation rather than reconfiguration of task sets
Authors: De Baene Wouter , Kühn Simone , Brass Marcel
Published: March 2011

In daily life, we permanently need to adapt our behavior to new task situations, requiring cognitive control. Such adaptive processes are commonly investigated with the task‐switching paradigm. Many fMRI studies have interpreted stronger activation for switch than repeat trials in fronto‐parietal brain areas as reflecting an active reconfiguration process in switch trials, tuning the cognitive system for proper task execution. From the single cell literature, however, one could deduce the alternative interpretation that switch‐specific activity reflects reduced brain activity in repeat trials due to adaptation. These alternative explanations cannot be distinguished by simply comparing brain activity in switch and repeat trials. Therefore, we used a parametric approach to examine which interpretation is more powerful to account for the data. In all areas of the fronto‐parietal network, adaptation explained the data better than reconfiguration. Therefore, our results call the classical reconfiguration interpretation into question and provide first evidence for adaptation of abstract task representations. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Dissociable neural imprints of perception and grammar in auditory functional imaging
Authors: Herrmann Björn , Obleser Jonas , Kalberlah Christian , Haynes John‐Dylan , Friederici Angela D.
Published: March 2011

In language processing, the relative contribution of early sensory and higher cognitive brain areas is still an open issue. A recent controversial hypothesis proposes that sensory cortices show sensitivity to syntactic processes, whereas other studies suggest a wider neural network outside sensory regions. The goal of the current event‐related fMRI study is to clarify the contribution of sensory cortices in auditory syntactic processing in a 2 × 2 design. Two‐word utterances were presented auditorily and varied both in perceptual markedness (presence or absence of an overt word category marking “‐t”), and in grammaticality (syntactically correct or incorrect). A multivariate pattern classification approach was applied to the data, flanked by conventional cognitive subtraction analyses. The combination of methods and the 2 × 2 design revealed a clear picture: The cognitive subtraction analysis found initial syntactic processing signatures in a neural network including the left IFG, the left aSTG, the left superior temporal sulcus (STS), as well as the right STS/STG. Classification of local multivariate patterns indicated the left‐hemispheric regions in IFG, aSTG, and STS to be more syntax‐specific than the right‐hemispheric regions. Importantly, auditory sensory cortices were only sensitive to the overt perceptual marking, but not to the grammaticality, speaking against syntax‐inflicted sensory cortex modulations. Instead, our data provide clear evidence for a distinction between regions involved in pure perceptual processes and regions involved in initial syntactic processes. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Altered motor network recruitment during finger tapping in boys with tourette syndrome
Authors: Roessner Veit , Wittfoth Matthias , Schmidt‐Samoa Carsten , Rothenberger Aribert , Dechent Peter , Baudewig Jürgen
Published: March 2011

In Tourette syndrome (TS), not only the tics but also the findings on deficits in motor performance indicate motor system alterations. But our knowledge about the pathophysiology of the motor system in TS is still limited. To better understand the neuronal correlates of motor performance in TS, 19 treatment‐naïve boys [age 12.5 (SD 1.4) years] with TS without comorbid symptomatology were compared to an age‐matched healthy control group [n = 16; age 12.9 (SD 1.6) years] in regard to brain activation during right‐hand index finger tapping by means of functional magnetic resonance imaging. Group differences were found mainly in the left (contralateral) precentral gyrus, which was less activated in boys suffering from TS and in caudate nucleus as well as in medial prefrontal cortex, which was more activated compared to healthy boys. These results show that even in the first years after the onset of the disorder, an altered brain network of motor performance is recruited. These alterations in brain regions frequently associated with TS are probably based on functional changes, which are discussed in terms of early compensatory mechanisms of the motor execution network. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.
Effects of morphine and alcohol on functional brain connectivity during “resting state”:A placebo‐controlled crossover study in healthy young men
Authors: Khalili‐Mahani Najmeh , Zoethout Remco M.W. , Beckmann Christian F. , Baerends Evelinda , de Kam Marieke L. , Soeter Roelof P. , Dahan Albert , van Buchem Mark A. , van Gerven Joop M.A. , Rombouts Serge A.R.B.
Published: March 2011

A major challenge in central nervous system (CNS) drug research is to develop a generally applicable methodology for repeated measurements of drug effects on the entire CNS, without task‐related interactions and a priori models. For this reason, data‐driven resting‐state fMRI methods are promising for pharmacological research. This study aimed to investigate whether different psychoactive substances cause drug‐specific effects in functional brain connectivity during resting‐state. In this double blind placebo‐controlled (double dummy) crossover study, seven resting‐state fMRI scans were obtained in 12 healthy young men in three different drug sessions (placebo, morphine and alcohol; randomized). Drugs were administered intravenously based on validated pharmacokinetic protocols to minimize the inter‐ and intra‐subject variance in plasma drug concentrations. Dual‐regression was used to estimate whole‐brain resting‐state connectivity in relation to eight well‐characterized resting‐state networks, for each data set. A mixed effects analysis of drug by time interactions revealed dissociable changes in both pharmacodynamics and functional connectivity resulting from alcohol and morphine. Post hoc analysis of regions of interest revealed adaptive network interactions in relation to pharmacokinetic and pharmacodynamic curves. Our results illustrate the applicability of resting‐state functional brain connectivity in CNS drug research. Hum Brain Mapp, 2011. © 2011 Wiley‐Liss, Inc.
Health status and the allocation of time
Authors: Podor Melinda , Halliday Timothy J.
Published: March 2011

We consider the relationship between health and time allocation in the American Time Use Survey. Better health is associated with large positive effects on home production and larger positive effects on market production, but less consumption of leisure. Theoretically, if market‐ and home‐produced goods are perfect substitutes, the positive correlation between health and home production implies that health exerts larger effects on home than on market efficiency. Notably, these correlations are higher for single people than for married people, perhaps reflecting a lack of market substitutes for the time of married people. Copyright © 2011 John Wiley & Sons, Ltd.
Liver receptor homolog-1 is critical for adequate up-regulation of Cyp7a1 gene transcription and bile salt synthesis during bile salt sequestration
Authors: Out Carolien , Hageman Jurre , Bloks Vincent W. , Gerrits Han , Gelpke Maarten D. Sollewijn , Bos Trijnie , Havinga Rick , Smit Martin J. , Kuipers Folkert , Groen Albert K.
Published: March 2011

Liver receptor homolog-1 (LRH-1) is a nuclear receptor that controls a variety of metabolic pathways. In cultured cells, LRH-1 induces the expression of CYP7A1 and CYP8B1, key enzymes in bile salt synthesis. However, hepatic Cyp7a1 mRNA levels were not reduced upon hepatocyte-specific Lrh-1 deletion in mice. The reason for this apparent paradox has remained elusive. We describe a novel conditional whole-body Lrh-1 knockdown (LRH-1-KD) mouse model to evaluate the dependency of bile salt synthesis and composition on LRH-1. Surprisingly, Cyp7a1 expression was increased rather than decreased under chow-fed conditions in LRH-1-KD mice. This coincided with a significant reduction in expression of intestinal Fgf15, a suppressor of Cyp7a1 expression, and a 58% increase in bile salt synthesis. However, when fecal bile salt loss was stimulated by feeding the bile salt sequestrant colesevelam, Cyp7a1 expression was up-regulated in wildtype mice but not in LRH-1-KD mice (+593% in wildtype versus +9% in LRH-1-KD). This translated into an increase in bile salt synthesis of +272% in wildtype versus +21% in LRH-1-KD mice.

Conclusion:

Our data provide mechanistic insight into a missing link in the maintenance of bile salt homeostasis during enhanced fecal loss and support the view that LRH-1 controls Cyp7a1 expression from two distinct sites, i.e., liver and ileum, in the enterohepatic circulation. (HEPATOLOGY 2011;)
RN181 suppresses hepatocellular carcinoma growth by inhibition of the ERK/MAPK pathway
Authors: Wang Suihai , Huang Xiang , Li Yue , Lao Haimiao , Zhang Ying , Dong Huimin , Xu Weiwen , Li Ji-Liang , Li Ming
Published: March 2011

The activation of oncogenes and the inactivation of tumor suppressor genes by mutations or chronic hepatitis virus infections play key roles in the pathogenesis of hepatocellular carcinoma (HCC). Here we report that RN181, a really interesting new gene finger domain-containing protein, was down-regulated in highly malignant cell lines and in tumor cells of 139 HCC clinical samples in comparison with adjacent normal liver tissues. The expression of RN181 was strongly associated with the pathological grade of HCC. Alterations of the expression of RN181 by retrovirus-transduced up-regulation and short hairpin RNA–mediated down-regulation demonstrated the function of RN181 as a tumor suppressor because it decreased the proliferation and colony formation of HCC cells in vitro and inhibited tumor growth in vivo by suppressing cell proliferation and enhancing cell apoptosis in xenografted tumors. Proteomic analyses showed that RN181 regulates the expression of many proteins that are important in many cellular processes. Statistical analyses identified 33 proteins with consistent changes (≥2-fold) in RN181-transformed cells. Ten of these proteins were up-regulated by RN181, and 23 were down-regulated. Representative proteins were validated by western blotting. Interaction network investigations revealed that 20 RN181-regulated proteins could integrate several key biological processes such as survival, metabolism, and mitogen-activated protein kinase (MAPK) pathways. Remarkably, 11 of the 33 proteins are associated with MAPK signaling in one or more ways. RN181 suppressed the tyrosine phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in cell lines and in tumor cells of xenografts and HCC clinical samples, and removing the suppression increased tumor growth.

Conclusion:

We have shown that RN181 suppresses the tumorigenesis of HCC through the inhibition of ERK/MAPK signaling in the liver. Our results provide new insights into the pathogenesis of HCC and may help with the development of novel therapeutic strategies. (HEPATOLOGY 2011;)
FLT3 mutation and expression did not adversely affect clinical outcome of childhood acute leukaemia—a study of 531 Southeast Asian children by the Ma‐Spore study group
Authors: Leow Shuangjie , Kham Shirley Kow‐Yin , Ariffin Hany , Quah Thuan Chong , Yeoh Allen Eng‐Juh
Published: March 2011

FMS‐like tyrosine kinase 3 (FLT3) is critical for normal haematopoiesis and have been reported to be expressed in the majority of acute myeloid and lymphoid malignancies. We correlated the impact of FLT3 mutations and its expression with age, WHO 2008 classification and treatment outcome in 531 childhood acute leukaemias. Of 150 acute myeloid leukaemia (AMLs), 18 (12%) harboured FLT3‐ITD while nine (6%) had FLT3‐TKD. FLT3‐ITD and ‐TKD were rare in acute megakaryoblastic leukaemia (AMKL; FLT3‐ITD 0/26, FLT3‐TKD 1/26) and children below 3 years (n = 2/48). Acute promyelocytic leukaemia (APL) with t(15;17);PML‐RARα (n = 7/18; 39%) harboured the highest frequency of FLT3 mutations, followed by myelomonocytic (n = 4/18; 22%) and AML with t(8;21);RUNX1‐RUNX1T1 (n = 2/21; 9%). FLT3 expression levels were also lowest in AMKL, both in Down's and non‐Down's (p = 0.002) followed by patients <3 years (p = 0.001). The rarity of FLT3 mutations and expression levels in AMKL were independent of age. Conversely, only 2% of childhood acute lymphoblastic leukaemia (ALL) harboured FLT3 mutations (ITD = 1/381; TKD = 6/381). FLT3 was highly expressed in hyperdiploid ALL (p < 0.001). Of the 121 AMLs with clinical history, there were no significant differences in 4‐year event‐free survival (EFS) (46% vs. 38%; p = 0.46) and overall‐survival (OS) (55% vs. 43%; p = 0.30) between FLT3‐wildtype and ITD+ patients. Similarly, FLT3 expression levels did not influence survival in AML in both the good risk and non‐good risk subgroups. FLT3 does not appear to be involved in the pathogenesis of AMKL, both in Down's and non‐Down's. Therapeutic targets using FLT3 inhibitors may not be useful in AMKL and in young children with AML. Copyright © 2011 John Wiley & Sons, Ltd.
In vitro assessment of macrophage attachment and phenotype on polymerized phospholipid bilayers
Authors: Page Jonathan , Heitz Benjamin A. , Joubert James R. , Keogh John P. , Sparer Tim , Saavedra S. Scott , He Wei
Published: March 2011

Phosphatidyl choline (PC)‐based materials have been found to be resistant to nonspecific protein adhesion in vitro. In this study, a PC‐based planar supported phospholipid bilayer composed of 1,2‐bis[10‐(2′,4′‐hexadienoyloxy)decanoyl]‐sn‐glycero‐3‐phosphocholine (bis‐SorbPC or BSPC) was generated on piranha‐treated silicon wafers by vesicle deposition. The bilayer was polymerized with redox initiation forming a stable 4‐nm thick coating. Polymerized lipid bilayers (PLBs) were characterized and tested for uniformity, with ellipsometry and contact angle. Cellular adhesion and morphological changes in RAW 264.7 macrophages were investigated in vitro on PLBs and compared to bare silicon controls. Fluorescent and scanning electron microscopy were used to observe changes in cellular morphology. The PLBs showed much lower cellular adhesion than bare silicon controls. Of the cells that attached to the PLBs, a very low percentage showed the same morphological expressions seen on the controls. It is hypothesized that proteins adsorb to the defects in the PLBs, caused by incomplete polymerization, and this mediates the observed minimal cellular attachment and morphological changes. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: , 2011.
Efficacy of desulfated heparin mitigating inflammation in rat burn wound model
Authors: Lakshmi Thiagavathi S. Ramyaa , Shanmugasundaram Natesan , Shanmuganathan Seetharaman , Babu Mary
Published: March 2011

During skin repair, leukocyte infiltration is the principal inflammatory response which is instrumental in triggering growth factor and cytokine signals that orchestrate together to recruit cells necessary for healing. In severe wounds like burn, when acute inflammation becomes chronic, intervention is required to control inflammation so as to hasten the process of healing. Heparin, a known anticoagulant also possesses anti‐inflammatory activity by its ability to interfere with the adhesion of leukocytes to the endothelium. Desulfated heparins (DSH) have subdued anticoagulant activity while possessing increased anti‐inflammatory activity. Among which 2,3 DSH is found to have marked potency as an anti‐inflammatory agent and has been utilized for this study. In this investigation, a controlled delivery system was designed by incorporating 2,3 DSH in microspheres and embedding in collagen matrix which could serve as a wound dressing in burns. In vivo evaluation of healing process was ascertained in rat burn wound model by qualitative and quantitative estimation of proinflammatory cytokines in serum and granulation tissue and collagen turnover was also assessed as healing progressed. The results of this study suggests that 2,3 DSH could be delivered in a controlled manner to regulate inflammatory events to hasten healing of burn wounds. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.
An assessment of transcriptional changes in porcine skin exposed to bromine vapor
Authors: Rogers James V. , Price Jennifer A. , Wendling Morgan Q. S. , Perry Mark R. , Reid Frances M. , Kiser Robyn C. , Graham John S.
Published: March 2011

Bromine is an industrial chemical that can cause severe cutaneous burns. This study was a preliminary investigation into the effect of cutaneous exposure to bromine vapor using a weanling swine burn model and microarray analysis. Ventral abdominal sites were exposed to a mean calculated bromine vapor concentration of 0.69 g L−1 for 10 or 20 min. At 48 h postexposure, total RNA from skin samples was isolated, processed, and hybridized to Affymetrix GeneChip Porcine Genome Arrays. Expression analysis revealed that bromine vapor exposure for 10 or 20 min promoted similar transcriptional changes in the number of significantly modulated probe sets. A minimum of 83% of the probe sets was similar for both exposure times. Ingenuity pathways analysis revealed eight common biological functions among the top 10 functions of each experimental group, in which 30 genes were commonly shared among 19 significantly altered signaling pathways. Transcripts encoding heme oxygenase 1, interleukin‐1β, interleukin 2 receptor gamma chain, and plasminogen activator inhibitor‐1 were identified as common potential therapeutic targets for Phase II/III clinical trial or FDA‐approved drugs. The present study is an initial assessment of the transcriptional responses to cutaneous bromine vapor exposure identifying molecular networks and genes that could serve as targets for developing therapeutics for bromine‐induced skin injury. © 2011 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:252–262, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20383
Arsenic induced progesterone production in a caspase‐3‐dependent manner and changed redox status in preovulatory granulosa cells
Authors: Yuan Xiao‐Hua , Lu Cai‐Ling , Yao Nan , An Li‐Sha , Yang Bai‐Qing , Zhang Chuan‐Ling , Ma Xu
Published: March 2011

Arsenic contamination is a principal environmental health threat throughout the world. However, little is known about the effect of arsenic on steroidogenesis in granulosa cells (GCs). We found that the treatment of preovulatory GCs with arsenite stimulated progesterone production. A significant increase in serum level of progesterone was observed in female Sprague–Dawley rats following arsenite treatment at a dose of 10 mg/L/rat/day for 7 days. Further experiments demonstrated that arsenite treatment did not change the level of intracellular cyclic AMP (cAMP) or phosphorylated ERK1/2 in preovulatory GCs; however, progesterone production was significantly decreased when cAMP‐dependent protein kinase (PKA) or ERK1/2 pathway was inhibited. This implied that the effect of arsenite on progesterone production may require cAMP/PKA and ERK1/2 signaling but not depend on them. Furthermore, we found that arsenite decreased intracellular reactive oxygen species (ROS) but increased the antioxidant glutathione (GSH) levels and mitochondrial membrane potential (ΔΨm) in parallel to the changes in progesterone production. Progesterone antagonist blocked the arsenic‐stimulated increase of GSH levels. Arsenite treatment induced caspase‐3 activation, although no apoptosis was observed. Inhibition of caspase‐3 activity significantly decreased progesterone production stimulated by arsenite or follicle‐stimulating hormone (FSH). GSH depletion with buthionine sulfoximine led to cell apoptosis in response to arsenite treatment. Collectively, this study demonstrated for the first time that arsenite stimulates progesterone production through cleaved/active caspase‐3‐dependent pathway, and the increase of GSH level promoted by progesterone production may protect GCs against apoptosis and maintain the steroidogenesis of GCs in response to arsenite treatment. J. Cell. Physiol. 227: 194–203, 2012. © 2011 Wiley Periodicals, Inc.
Synthesis and properties of multiblock copolymers of styrene and propylene oxide
Authors: Xie Hongquan , Chen Xin
Published: March 2011

Multiblock copolymers of styrene and propylene oxide were synthesized by coupling together poly(propylene glycol) and telechelic dihydroxy‐polystyrene with 2, 4‐toluene diisocyanate(TDI) as the coupling agent. The results showed that it was better to terminate the telechelic dihydroxy polystyrene with TDI first, then react with poly(propylene glycol). The copolymer obtained in this two‐step method contains less homopolymers than that obtained when all the three reagents reacted together in one step. The crude product can be purified by extractions with absolute ethyl alcohol and decalin in order to remove the unreacted poly(propylene glycol) and polystyrene, respectively. The purified products were characterized by IR, TH NMR, GPC, membrane osmometry, elemental analysis and shown to be multiblock copolymers of styrene and propylene oxide. The multiblock copolymer exhibits two transition temperatures(Tg's) and behaves like a thermoplastic elastomer at 20–30% polystyrene content. Addition or 2% of the copolymers to the blends of polystyrene and epichlorohydrin rubber improves evidently their mechanical properties and causes the two Tg's to become closer.
Graft copolymerization of vinylpyridines onto cellulosic fibres by the ceric ion method. The monomer concentration effect
Authors: Leza M. L. , Casinos I. , Guzmán G. M.
Published: March 2011

The effect of monomer concentration on the graft polymerization of 4‐vinylpyridine (4‐VP) and of 2‐vinylpyridine (2‐VP) on cellulose and on partially carboxymethylated cellulose (PCMC) initiated by cerium ammonium nitrate (CAN) in dilute nitric acid has been examinated. The grafting parameters: grafting efficiency (GE), graft yield (G), graft frequency (GF), and ceric ion consumption ((Ceiv)c)were studied as a function of the monomer concentration. The fraction of poly(4‐vinylpyridine), P(4‐VP), in the graft polymer increased with increasing monomer concentration for both cellulosic substrates. The molecular weight of the grafted P(4‐VP) was obtained viscosimetrically after hydrolyzing away the cellulose backbone. When 2‐VP was grafted on PCMC and on unmodified cotton, the graft yields also increased with monomer concentration, but they were much smaller than in the previous case. Presence of carboxymethyl groups in cellulose enhanced G, GE, Mv, and GF.
Towards a generalization of stereospecific nucleophilic substitution of PVC
Authors: Millán J. , Martínez G. , Mijangos C. , Méndez A. , Gómez‐Elvira J. M. , Gómez‐Daza M.
Published: March 2011

Two series of nucleophilic substitution reactions on PVC using either the same nucleophile but different experimental conditions or various nucleophiles in cyclohexanone (CH) dilute solutions, were performed. The evolution of unreacted iso‐, hetero‐and syndiotactic triads with degree of conversion was followed by 13 C NMR. While the kinetics and yield changed markedly with both the type of nucleophile and the reaction conditions the stereochemical structure of modified polymers proved to depend only on degree of substitution. These results afford further support to a conformational mechanism of substitution, as proposed by earlier works.
Some developments in the study of radical polymerization
Authors: Bevington John C.
Published: March 2011

Studies of initiation by azobis(isobutyronitrile) and benzoyl peroxide are discussed. Consideration is given to initiators containing carbon‐13 or carbon‐14 for end‐group analyses, and also to the applications of radical‐trapping techniques for study of oxygen‐centred radicals. Other topics dealt with are (a) head‐addition of primary radicals to monomers, (b) the formation of end‐groups by primary radical termination and by transfer to initiator, and (c) the involvement of stilbene‐like compounds in initiation.
Galvinoxyl as scavenger in the radical polymerization of styrene initiated by AIBN
Authors: Areizaga J. F. , Guzmán G. M.
Published: March 2011

The initiation of the polymerization of styrene by AIBN has been studied at 59, 8°C and 69, 9°C, using Galvinoxyl as a free radical scavenger, by spectrophotometric means. Rates of 7×10−9 and 2×10−8 mol·1−1 · s−1 have been measured for the scavengeable free radicals formation in the initiation process of the thermal polymerization of pure styrene, respectively. Values of 6×10−6 s−1 and 2, 4×10−5 s−1 have been obtained for the rate constants of production of scavengeable pairs of free radicals (kdf) from AIBN assuming an ideal kinetic scheme.
Template polymerization of N‐vinylimidazole along poly(methacrylic acid)
Authors: van De Grampel H. T. , Tan Y. Y. , Challa G.
Published: March 2011

The radical polymerization of N‐vinylimidazole (VIm) along an atactic poly(methacrylic acid) (PMAA) template in aqueous solution at 50°C was investigated by varying [PMAA]0 from 0 to 0.7 basemol/dm3 at constant [VIm]0 of 0.41 mol/dm3. Rate enhancements were observed only beyond [PMAA]0 of 0.18 basemol/dm3. By studying the initial pH and ηsp/c of the polymerization mixtures and taking account of preferential adsorption of protonated VIm on PMAA, part of which is probably mobile, a mechanism is suggested.
The observation of polymer microstruture by NMR
Authors: Bovey F. A.
Published: March 2011

Nuclear magnetic resonance (NMR) is a method of great importance for the study of most aspects of the structure and behavior of polymers. In this review, I deal with its application to the observation of the detailed structure of polymer chains, particularly those of vinyl and diene polymers and copolymers. This is for the most part accomplished using polymer solutions, but NMR also allows one to observe chain structure and conformation in the solid state by means of magic angle spinning and high power proton decoupling.
Use of small‐angle neutron scattering to investigate the morphology of some polymeric materials
Authors: Hammouda Boualem
Published: March 2011

Small‐angle neutron scattering is a molecular probe to monitor chain conformations in partially deuterated polymers. It can also be used to investigate the morphology of microphase segregated multiphase systems. It offers a means of understanding polymer microstructure, which can then be related to physical properties and sample treatments. This technique is applied here to the problem of macromolecular orientation in polystyrene subject to hot‐stretching as well as to a block copolymer system (50/50 mixture of bisphenol A carbonate and dimethylsiloxane). A general description of the technique as well as specific results are discussed.
Electron spectroscopic imaging studies on polyethylene, chain‐folded and extended‐chain crystals
Authors: Kunz M. , Möller M. , Heinrich U.‐R. , Cantow H.‐J.
Published: March 2011

Discrimination of elastically and inelastically scattered electrons in transmission electron microscopy (TEM) yields electron micrographs with enhanced and specific contrast. Highly resolved micrographs can be obtained in which the contrast reflects the local concentrations of specific elements. In the present work, Electron Spectroscopic Imaging (ESI) by means of a Zeiss EM 902 TEM are reported for a series of differently crystallized polyethylene samples. Excellent contrast can be achieved without staining. The different techniques allow easy verification of the observed morphology.
Characterization of piezoelectric polymers with the aid of NMR
Authors: Chûjô Riichirô
Published: March 2011

Piezoelectric polymers, poly(vinylidene cyanide‐co‐vinyl acetate), poly(vinylidene cyanide‐co‐vinyl benzoate), and related polymers were characterized with the aids of NMR on the following items:

copolymer composition

stereoregularity

conformation

segmental motion.

In a series of the above items, the most significant difference was found in segmental motion between piezoelectric and non‐piezoelectric polymers; larger segmental mobility may be essential for poling process, while smaller mobility is convenient for the maintaining of piezoelectricity after poling.
Study of phase transitions and curie temperature in ferroelectric copolymers of PVF2 using synchrotron radiation techniques
Authors: Cabarcos E. López , Arche A. Gonzalez , Calleja F. J. Baltá , Zachmann H. G.
Published: March 2011

Real time wide angle (WA) and small angle X‐ray scattering (SAXS) data from 70/30 and 80/20 vinylidene fluoride/trifluoroethylene copolymers are reported as a function of temperature during crystallization from the melt. The para‐ferroelectric Curie transition detected from DSC and WAXD experiments in the temperature interval 70–40°C for the 70/30 copolymer and in the range 90–60°C for the 80/20 material are associated to a sudden increase of the integrated SAXS intensity. Comparison of experimental and calculated data based on a sandwich model of crystals alternated by amorphous layers supports the view of a coexistence of para‐ and ferroelectric phases within the crystalline material through the transition range studied.
Thermodynamics of polymer solutions and blends
Authors: Kleintjens L. A. , Koningsveld R.
Published: March 2011

Polymerization reactions are quite often accompanied by liquid‐liquid phase separations. Processing of polymer blends is commonly also based on the phase behaviour of the system; for some applications homogenous blends are to be obtained while for other two‐phase systems are desired. Experimental methods suitable for gaining insight into the thermodynamic behaviour in such viscous systems will be discussed and some relevant measurements, performed by equilibrium methods, will be shown.

Classic thermodynamic equilibrium considerations, based on simple molecular models lead to useful descriptions and predictions of the phase behaviour of partially miscible polymer systems. Depending on the amount of experimental information and on the complexity of the polymeric system, predictions will be more or less quantitative. Solubility parameter and group contribution approaches present the first level, and such predictions indicate whether a system is miscible or not.

The second level of description is given by Flory‐Huggins‐Staverman approaches. These models call for some experimental evidence but permit estimation of the location of miscibility gaps and their dependence on the polymer molar mass. The concentration ranges of the demixed region are usually not well presented by these models.

The quality of the description is improved considerably when the disparity of size and shape between the repeat units of the polymer and solvent constituents are taken into account. On this third level the influence of pressure can be included in the model and reasonable descriptions of the P‐T‐x space can be obtained.

Extensions to copolymer systems are being developed nowadays, but still fail to give quantitative representation of the actual complex phase behaviour of such systems.
Microcalorimetric studies of the complexation between poly(ethylene oxide) and alkaline salts in solution
Authors: Daoust Hubert , Cloutier Bruno
Published: March 2011

A series of microcalorimetric measurements have been done on complex formation between poly(ethylene oxide) (PEO) and some alkaline metal salts in solution at 25°C. Heat of complexation measurements as a function of PEO content were done with a Tian‐Calvet microcalorimeter and heat capacity measurements have been done with a Picker dynamic microcalorimeter. A very weak exothermic interaction between the species has been found for the PEO‐KSCN pair in water indicating that complexation is difficult to obtain due to the important hydration of both solutes. However, a comparatively large exothermic interaction has been observed for the same pair in anhydrous methanol. Exothermic interactions have also been found for PEO‐KI, ‐NaI and ‐LiI systems in methanol with decreasing absolute values for heats of complexation going from KI to LiI. In methanol, heats of complexation pass through a rather flat and broad maximum at PEO/salt molar ratios going from 1:1 to 4:1 for KSCN and KI. For NaI, the maximum appears for a molar ratio of 2:1 and for LiI, this ratio is 4:1. Heat capacity measurements do not indicate any specific feature for any of the systems except in the case of KSCN in methanol. Experimental results are discussed in terms of ion size and of ion solvation.
Preferential and total sorption in the systems methacrylic polymer/toluene + butyl chloride
Authors: Katime Issa A. , Huglin M. B. , Sasía P. M.
Published: March 2011

Viscometric, dialysis equilibrium differential refractometry. densitometric and light scattering measurements have been performed for three different polymethacrylates: poly(methyl methacrylate). poly(butyl methacrylate) and poly(cyclohexyl methacrylate) in toluene/butylchloride binary mixture at 298 K. We have measured the preferential and total sorption to the polymer chain by the solvents, the Mark‐Houwink‐Sakurada parameters and the B interaction parameter. We have drawn conclusions about the liquid‐liquid and polymer‐liquid interactions, trying to explain the influence of the polymer side group in its solution behaviour.
On the miscibility and interchange reactions in bisphenol a polycarbonate/nylon 6 blends
Authors: Eguiazábal José Ignacio , Nazábal Jon
Published: March 2011

The miscibility and the interchange reactions in bisphenol A polycarbonate/nylon 6 blends prepared by melt mixing have been studied by means of the torque‐time relationships, calorimetric analysis and solubility tests. The results indicate that the blends are partially miscible and also the existence of interchange reactions between the polymers when they are melt‐mixed.
Morphologies and regimes of growth of polybutene crystals in phase II
Authors: Monasse Bernard , Haudin Jean Marc
Published: March 2011

The growth rates of two poly(1‐butene) with different molecular weights have been deduced from microscopic observations and the corresponding morphologies have been described. In both polymers two changes in the growth regime are observed and interpreted according to Hoffman's kinetic theory of polymer crystallization. The main nucleation parameters can be determined from the growth regime transitions when the relevant formulations of the kinetic and the transport laws have been selected, taking into account the large range of crystallization temperature.
Crystallization and melt behaviour of poly(vinylidene fluoride) + poly(vinyl alcohol) blends
Authors: Katime Issa A. , Quintana José R. , Cesteros Luis C. , Peleteiro María C.
Published: March 2011

Melting and crystallization behaviour of poly(vinylidene fluoride) (PVF2)/poly(vinyl alcohol) (PVAL) blends have been analyzed. From Hoffman‐Weeks plots we have found that an appreciable melting point depression of PVF2 does not exist. On the other hand, we have found that the presence of PVAL affects the morphological factor γ, which is not constant with the composition of the blend. This factor suggests that the melting behaviour of this system depends on kinetics effects. The kinetics of isothermal crystallization was analyzed by means of the Avrami equation.
Rheological properties of thermotropic polyester‐based gels
Authors: Muñoz M. E. , Gallego F. , Peña J. J. , Santamaría A.
Published: March 2011

Cooling concentrated solutions of the aromatic copolyester poly(ethylene terephthalate‐co‐p‐benzoate)(60 mol‐% p‐benzoate units)in m‐cresol results in gels whose viscoelastic properties are studied in this paper.

The gelation process is monitored in a Couette‐type viscometer. From the gelation temperature an enthalpy of formation of ΔHa = 3 kcal/mol is obtained. Dynamic viscoelastic measurements are also carried out, and the theory of rubber elasticity is applied to a well‐defined temperature and frequency independent modulus.

From the obtained results we suggest that hydrogen bonds between carbonyl groups of the chain backbone and hydroxyl hydrogens of the solvent are responsible for gel formation.
Liquid crystalline solutions of poly(α‐isobutyl‐L‐aspartate)
Authors: Montserrat J. M. , Muñoz‐Guerra S. , Subirana J. A.
Published: March 2011

Poly(α‐isobutyl‐L‐aspartate), abbreviated PAIBLA, is a helical polymer. In this paper we evaluate its potential to form liquid crystals. We have observed highly birefringent solutions in helicogenic solvents as chloroform and dichloromethane. They were further characterized by PMR spectroscopy, and hydrodynamic and optical measurements. From these solutions, solid films were cast which displayed a uniplanar orientation with helical molecules lying parallel to the film surface. We conclude that PAIBLA is capable of forming lyotropic liquid crystals with a cholesteric structure.