bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of brain activation patterns during covert and overt paced auditory serial addition test tasks
Authors: Forn Cristina , Ventura‐Campos Noelia , Belenguer Antonio , Belloch Vicente , Parcet Maria Antònia , Ávila César 
Published: June 2007

AbstractThe Paced Auditory Serial Addition test (PASAT) is a sensitive task for evaluating cognitive impairment in patients with diffuse brain disorders, such as multiple sclerosis patients. Brain areas involved in this task have been investigated in diverse fMRI studies using different methodologies to control the subjects' responses during scanning. Here, we examined the possible differences between overt and covert responses during the PASAT task in 13 volunteers. Results showed similar activations in parietal and frontal brain areas during both versions of the task. The contrast between the two conditions (overt and covert) indicated that differences in these two methodologies were minimal. Unlike the covert condition, the overt version of the task obtained significant activations in the left superior and inferior frontal gyrus, bilateral occipital cortex, caudate nucleus and cerebellum. As expected, no significant overactivations were observed in the covert when compared with the overt condition. Discussion focuses on the lower cost of using verbal responses to monitor performance during the PASAT task, which might be generalisable to other frontal lobe tasks requiring discrete responses. Hum Brain Mapp, 2008. © 2007 Wiley‐Liss, Inc.
Developmental differences in white matter architecture between boys and girls
Authors: Schmithorst Vincent J. , Holland Scott K. , Dardzinski Bernard J. 
Published: June 2007

AbstractPrevious studies have found developmental differences between males and females in brain structure. During childhood and adolescence, relative white matter volume increases faster in boys than in girls. Sex differences in the development of white matter microstructure were investigated in a cohort of normal children ages 5–18 in a cross‐sectional diffusion tensor imaging (DTI) study. Greater fractional anisotropy (FA) in boys was shown in associative white matter regions (including the frontal lobes), while greater FA in girls was shown in the splenium of the corpus callosum. Greater mean diffusivity (MD) in boys was shown in the corticospinal tract and in frontal white matter in the right hemisphere; greater MD in girls was shown in occipito‐parietal regions and the most superior aspect of the corticospinal tract in the right hemisphere. Significant sex–age interactions on FA and MD were also shown. Girls displayed a greater rate of fiber density increase with age when compared with boys in associative regions (reflected in MD values). However, girls displayed a trend toward increased organization with age (reflected in FA values) only in the right hemisphere, while boys displayed this trend only in the left hemisphere. These results indicate differing developmental trajectories in white matter for boys and girls and the importance of taking sex into account in developmental DTI studies. The results also may have implications for the study of the relationship of brain architecture with intelligence. Hum Brain Mapp, 2008. © 2007 Wiley‐Liss, Inc.
Atorvastatin lowers portal pressure in cirrhotic rats by inhibition of RhoA/Rho-kinase and activation of endothelial nitric oxide synthase
Authors: Trebicka Jonel , Hennenberg Martin , Laleman Wim , Shelest Nataliya , Biecker Erwin , Schepke Michael , Nevens Frederik , Sauerbruch Tilman , Heller Jörg 
Published: June 2007

AbstractIn cirrhosis, increased RhoA/Rho-kinase signaling and decreased nitric oxide (NO) availability contribute to increased intrahepatic resistance and portal hypertension. Hepatic stellate cells (HSCs) regulate intrahepatic resistance. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) inhibit synthesis of isoprenoids, which are necessary for membrane translocation and activation of small GTPases like RhoA and Ras. Activated RhoA leads to Rho-kinase activation and NO synthase inhibition. We therefore investigated the effects of atorvastatin in cirrhotic rats and isolated HSCs. Rats with secondary biliary cirrhosis (bile duct ligation, BDL) were treated with atorvastatin (15 mg/kg per day for 7 days) or remained untreated. Hemodynamic parameters were determinedin vivo(colored microspheres). Intrahepatic resistance was investigated inin situperfused livers. Expression and phosphorylation of proteins were analyzed by RT-PCR and immunoblots. Three-dimensional stress-relaxed collagen lattice contractions of HSCs were performed after incubation with atorvastatin. Atorvastatin reduced portal pressure without affecting mean arterial pressurein vivo. This was associated with a reduction in intrahepatic resistance and reduced responsiveness ofin situ–perfused cirrhotic livers to methoxamine. Furthermore, atorvastatin reduced the contraction of activated HSCs in a 3-dimensional stress-relaxed collagen lattice. In cirrhotic livers, atorvastatin significantly decreased Rho-kinase activity (moesin phosphorylation) without affecting expression of RhoA, Rho-kinase and Ras. In activated HSCs, atorvastatin inhibited the membrane association of RhoA and Ras. Furthermore, in BDL rats, atorvastatin significantly increased hepatic endothelial nitric oxide synthase (eNOS) mRNA and protein levels, phospho-eNOS, nitrite/nitrate, and the activity of the NO effector protein kinase G (PKG).Conclusion:In cirrhotic rats, atorvastatin inhibits hepatic RhoA/Rho-kinase signaling and activates the NO/PKG-pathway. This lowers intrahepatic resistance, resulting in decreased portal pressure. Statins might represent a therapeutic option for portal hypertension in cirrhosis. (HEPATOLOGY 2007;46:242–253.)
Posterior parahippocampal place learning in H.M.
Authors: Bohbot Véronique D. , Corkin Suzanne 
Published: June 2007

AbstractIn a previous experiment with patients who had undergone unilateral temporal thermocoagulation lesions to alleviate intractable epilepsy, we demonstrated that the right parahippocampal cortex was critical for the performance of a spatial memory task (Bohbot et al. (1998) Neuropsychologia 36:1217–1238). Based on this evidence, we predicted that H.M., whose caudal parahippocampal cortex was structurally intact (Corkin et al. (1997) J Neurosci 17:3964–3979), would be able to learn the spatial memory task. This task was designed to be a human analogue of the Morris water maze in that it measured participants' ability to learn the location of a target, which was an invisible weight sensor placed under a carpet (Bohbot et al. (1998) Neuropsychologia 36:1217–1238). H.M. was first tested with the sensor under a small carpet (162 cm × 150 cm). Then, interspersed with the first sensor location, he was tested with the sensor in a second location, covered by a larger carpet (250 cm × 210 cm). He found the second target location in a direct path on only 10% of the trials. In contrast, when tested on the first sensor location, he walked directly toward the center of the testing area in 19/35 trials and from there found the sensor in a direct path on 15 of the 19 trials (80%). The number of direct hits at the first target location was significantly greater than chance (P< 0.0005). An analysis of H.M.'s paths showed that they were characteristic of fast learning, and that he did not rely on egocentric, short‐term, or working memory strategies to learn the task. H.M's ability to locate the sensor is remarkable given his severe amnesia and his inability to explicitly recollect the testing episode. These findings underscore the role of the parahippocampal cortex in spatial memory. © 2007 Wiley‐Liss, Inc.
Cohesiveness of spatial and directional representations recorded from neural ensembles in the anterior thalamus, parasubiculum, medial entorhinal cortex, and hippocampus
Authors: Hargreaves Eric L. , Yoganarasimha D. , Knierim James J. 
Published: June 2007

AbstractAnatomical and physiological evidence suggests that hippocampal place cells derive their spatial firing properties from the medial entorhinal cortex (MEC) and other parahippocampal areas that send spatial and directional input to the MEC. MEC neurons fire in a precise, geometric pattern, forming a hexagonal grid that tessellates the surface of environments. Similar to place cells and head direction cells, the orientation of grid cell firing patterns can be controlled by visual landmarks, but the cells maintain their firing patterns even in the dark. Place cells and head direction cells can also completely decouple from external landmarks in the light, but it is not known whether the MEC and parahippocampal regions exhibit similar properties or are more explicitly tied to external landmarks. We recorded neurons in the MEC, parasubiculum, and CA1 and head direction cells of the anterior thalamus as the rat's internal direction sense was pitted against a salient visual landmark by slowly rotating the rat in a covered bucket while counter‐rotating the visual cue. In different sessions, spatial firing rate maps and head direction tuning curves either rotated their preferred firing locations/directions by the same amount as the bucket rotation or maintained their preferences in the external laboratory framework. In few cases, the firing preferences rotated with the cue card. When cells from different regions were recorded simultaneously, the dominant response in one area almost always matched the response of the other areas. Although dominant responses were consistent throughout the recording regions, CA1 ensembles exhibited a greater degree of response heterogeneity than other regions, which nearly all exhibited internally consistent responses. Thus, the parahippocampal and MEC input to the hippocampus can be controlled by the animal's internal direction sense (presumably reflected in the firing of head direction cells) and become completely decoupled from external sensory input, yet maintain internal coherence with each other and in general with the place cell system of the hippocampus. © 2007 Wiley‐Liss, Inc.
Hippocampal and neocortical interactions during context discrimination: Electrophysiological evidence from the rat
Authors: Mizumori Sheri J.Y. , Smith David M. , Puryear Corey B. 
Published: June 2007

AbstractThere is substantial evidence that hippocampus plays an important role in the processing of contextual information. Its specific role, however, remains unclear. One possibility is that single hippocampal neurons represent context information so that local circuits can construct representations of the current context, and the context that is expected based on past experience. Population codes derived from input by multiple local circuits may then engage match–mismatch algorithms that compare current and expected context information to determine the extent to which an expected context has changed. The results of such match–mismatch comparisons can be used to discriminate contexts. When context changes are detected, efferent messages may be passed on to connected neocortical areas so that informed “decisions” regarding future behavioral and cognitive strategies can be made. Here, a brief review describes evidence that a primary consequence of hippocampal processing is the discrimination of meaningful contexts. Then, the functional significance of neocortical circuits that likely receive hippocampal output messages are described in terms of their contribution to the control of ongoing behavioral and cognitive strategy, especially during active navigation. It is clear from this systems view that studies of spatial navigation continue to provide researchers with an excellent model of hippocampal–neocortical interactions during learning. © 2007 Wiley‐Liss, Inc.
Space and context in the temporal cortex
Authors: Bilkey David K. 
Published: June 2007

AbstractThe hippocampus has a critical role in certain kinds of spatial memory processes. Hippocampal “place” cells, fire selectively when an animal is in a particular location within the environment. It is thought that this activity underlies a representation of the environment that can be used for memory‐based spatial navigation. But how is this representation constructed and how is it “read”? A simple mechanism, based on place field density across an environment, is described that could allow hippocampal representations to be “read” by other brain regions for the purpose of navigation. The possible influence of activity in neighboring brain regions such as the perirhinal cortex, and pre‐ and para‐subiculum on the construction of the hippocampal spatial representation is then discussed. © 2007 Wiley‐Liss, Inc.
An oscillatory interference model of grid cell firing
Authors: Burgess Neil , Barry Caswell , O'Keefe John 
Published: June 2007

AbstractWe expand upon our proposal that the oscillatory interference mechanism proposed for the phase precession effect in place cells underlies the grid‐like firing pattern of dorsomedial entorhinal grid cells (O'Keefe and Burgess (2005) Hippocampus 15:853–866). The original one‐dimensional interference model is generalized to an appropriate two‐dimensional mechanism. Specifically, dendritic subunits of layer II medial entorhinal stellate cells provide multiple linear interference patterns along different directions, with their product determining the firing of the cell. Connection of appropriate speed‐ and direction‐ dependent inputs onto dendritic subunits could result from an unsupervised learning rule which maximizes postsynaptic firing (e.g. competitive learning). These inputs cause the intrinsic oscillation of subunit membrane potential to increase above theta frequency by an amount proportional to the animal's speed of running in the “preferred” direction. The phase difference between this oscillation and a somatic input at theta‐frequency essentially integrates velocity so that the interference of the two oscillations reflects distance traveled in the preferred direction. The overall grid pattern is maintained in environmental location by phase reset of the grid cell by place cells receiving sensory input from the environment, and environmental boundaries in particular. We also outline possible variations on the basic model, including the generation of grid‐like firing via the interaction of multiple cells rather than via multiple dendritic subunits. Predictions of the interference model are given for the frequency composition of EEG power spectra and temporal autocorrelograms of grid cell firing as functions of the speed and direction of running and the novelty of the environment. © 2007 Wiley‐Liss, Inc.
Cingulate cortex projections to the parahippocampal region and hippocampal formation in the rat
Authors: Jones Bethany F. , Witter Menno P. 
Published: June 2007

AbstractIn the present study we aimed to determine the topographical and laminar characteristics of cingulate projections to the parahippocampal region and hippocampal formation in the rat, using the anterograde tracers Phaseolus vulgaris‐leucoagglutinin and biotinylated dextranamine. The results show that all areas of the cingulate cortex project extensively to the parahippocampal region but not to the hippocampal formation. Rostral cingulate areas (infralimbic‐, prelimbic cortices, rostral 1/3 of the dorsal anterior cingulate cortex) primarily project to the perirhinal and lateral entorhinal cortices. Projections from the remaining cingulate areas preferentially target the postrhinal and medial entorhinal cortices as well as the presubiculum and parasubiculum. At a more detailed level the projections show differences in topographical specificities according to their site of origin within the cingulate cortex suggesting the functional contribution of cingulate areas may differ at an individual level. This organization of the cingulate‐parahippocampal projections relates to the overall organization of postulated parallel parahippocampal‐hippocampal processing streams mediated through the lateral and medial entorhinal cortex respectively. The mid‐rostrocaudal part of the dorsal anterior cingulate cortex appears to be connected to both networks as well as to rostral and caudal parts of the cingulate cortex. This region may therefore responsible for integrating information across these specific networks. © 2007 Wiley‐Liss, Inc.
Optimal operation of reservoirs for downstream water quality control using linked simulation optimization
Authors: Dhar Anirban , Datta Bithin 
Published: June 2007

AbstractA methodology is developed for optimal operation of reservoirs to control water quality requirements at downstream locations. The physicochemical processes involved are incorporated using a numerical simulation model. This simulation model is then linked externally with an optimization algorithm. This linked simulation–optimization‐based methodology is used to obtain optimal reservoir operation policy. An elitist genetic algorithm is used as the optimization algorithm. This elitist‐genetic‐algorithm‐based linked simulation–optimization model is capable of evolving short‐term optimal operation strategies for controlling water quality downstream of a reservoir. The performance of the methodology developed is evaluated for an illustrative example problem. Different plausible scenarios of management are considered. The operation policies obtained are tested by simulating the resulting pollutant concentrations downstream of the reservoir. These performance evaluations consider various scenarios of inflow, permissible concentration limits, and a number of management periods. These evaluations establish the potential applicability of the developed methodology for optimal control of water quality downstream of a reservoir. Copyright © 2007 John Wiley & Sons, Ltd.
ADAMTSL3/punctin‐2, a gene frequently mutated in colorectal tumors, is widely expressed in normal and malignant epithelial cells, vascular endothelial cells and other cell types, and its mRNA is reduced in colon cancer
Authors: Koo Bon‐Hun , Hurskainen Tiina , Mielke Katrina , Aung Phyu Phyu , Casey Graham , Autio‐Harmainen Helena , Apte Suneel S. 
Published: June 2007

AbstractADAMTSL3/punctin‐2 is a secreted glycoprotein that resembles the ADAMTS proteases. Recently, identification of frequent ADAMTSL3 mutations in colorectal cancer suggested it might have a regulatory role in cellular homeostasis in colorectal epithelium or in pathways to colorectal malignancy. Here, we used in situ hybridization to validate ADAMTSL3 antibodies for IHC of a variety of normal and malignant tissues, including colon cancer. Quantitative real‐time PCR (RTQ‐PCR) was used to compare mRNA expression levels in colon carcinoma (n = 10) and adjacent normal colon. ADAMTSL3 is expressed in epithelial cells of the colon, fallopian tube, skin, breast, prostate, epididymis, liver, pancreatic islets and bile ducts, as well as by vascular endothelial cells, smooth muscle cells, fibroblasts, cortical and ganglionic neurons and cardiac myocytes. Malignant epithelial cells in colon cancer, as well as breast, prostate, renal and skin tumors expressed ADAMTSL3. Normal colon showed stronger immunostaining of surface than basal crypt epithelium and staining of a variety of cells within the lamina propria and submucosa. Colon carcinomas demonstrated weaker staining in tumor cells than normal colon epithelium and weak stromal staining. RTQ‐PCR comparison of ADAMTSL3 mRNA in colon carcinoma and adjacent normal colon demonstrated a statistically significant reduction in the tumors, possibly reflecting their decreased stromal content and lack of complete differentiation of tumor samples. The major findings of these studies are that ADAMTSL3 is expressed in numerous tissues, suggesting a broader regulatory role than in colorectal epithelium alone, and that colorectal cancer has both structural mutations as well as decreased expression of ADAMTSL3. © 2007 Wiley‐Liss, Inc.
Mammary cancer resistance and precocious mammary differentiation in the WKY rat: Identification of 2 quantitative trait loci
Authors: Lella Virginie , Stieber Daniel , Rivière Michèle , Szpirer Josiane , Szpirer Claude 
Published: June 2007

AbstractThe COP and WKY rat strains are resistant to mammary cancer. It has shown previously that upon chemical carcinogen treatment, COP females exhibit mammary preneoplastic lesions which disappear within a few weeks. We show here that in similar conditions, WKY females do not exhibit any visible preneoplastic lesions. WKY females are characterized by precocious mammary tissue differentiation, including active expression of the beta‐casein gene in young virgin females. This trait might be critical in resistance to mammary carcinogenesis of WKY rats. To test this hypothesis, we took advantage of 2 congenic strains that contain a limited chromosome segment of WKY origin, derived either from chromosome 5 or from chromosome 18, introgressed in the susceptible genetic background (SPRD‐Cu3). Each of these congenic strains has been shown to be partially resistant to chemically induced mammary carcinogenesis (reduction in tumour multiplicity with respect to the susceptible SPRD‐Cu3 rats). We show here that these 2 congenic strains also exhibit precocious mammary differentiation, though to a lower extent than the WKY females. The conclusion of this study is thus 2‐fold: (i) eradication of preneoplastic lesions is not a general phenomenon in mammary cancer resistance; (ii) the same segment of rat chromosomes 5 or 18 that controls mammary cancer resistance also contains a quantitative trait locus imposing precocious mammary differentiation. These 2 traits are thus associated, supporting the hypothesis that there might be a cause‐effect relationship between precocious mammary differentiation and cancer resistance. © 2007 Wiley‐Liss, Inc.
Binding of endostatin to human ovarian cancer cells inhibits cell attachment
Authors: Yokoyama Yumi , Ramakrishnan S. 
Published: June 2007

AbstractEndostatin, a C‐terminal fragment of collagen type XVIII, is one of the well‐characterized endogenous inhibitors of angiogenesis. Endostatin is known to bind integrin α5β1, which is upregulated on tumor endothelium. Most of the ovarian cancer cells express significant amounts of α5β1 integrin, which is important for ovarian cancer cells to attach to the peritoneal wall. Therefore we investigated whether endostatin could directly bind ovarian cancer cells and inhibit tumor cell attachment to extracellular matrix. Binding of endostatin to ovarian cancer cells was characterized by preincubation with function blocking antibodies to integrin subunits. These studies showed that ovarian cancer cell attachment to fibronectin‐coated wells can be inhibited by α5β1 integrin specific antibodies as well as endostatin. Downregulation of integrin α5 and β1 by siRNA abrogated the binding of OVCAR5 and human umbilical vein endothelial cell to endostatin. Although endostatin treatment did not affect ovarian cancer cell migration, treated cells failed to attach mouse peritoneal wall preparations. These studies suggest an extra‐antiangiogenic role for endostatin, which can be used prevent peritoneal attachment and dissemination of ovarian cancer cells. © 2007 Wiley‐Liss, Inc.
An evaluation of the life cycle effects of minimum pensions on retirement behavior
Authors: Jiménez‐Martín Sergi , Sánchez Martín Alfonso R. 
Published: June 2007

AbstractIn this paper we explore the effects of the minimum pension program on welfare and retirement in Spain. This is done with a stylized life cycle model which provides a convenient analytical characterization of optimal behavior. We use data from the Spanish Social Security to estimate the behavioral parameters of the model and then simulate the changes induced by the minimum pension in aggregate retirement patterns. The impact is substantial: there is a threefold increase in retirement at 60 (the age of first entitlement) with respect to the economy without minimum pensions, and total early retirement (before or at 60) is almost 50% larger. Copyright © 2007 John Wiley & Sons, Ltd.