Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Local Area Networks”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources
PubMed1999

Localization of the Wilson's disease protein in human liver.

BACKGROUND & AIMS: Wilson's disease is an autosomal-recessive disorder of copper metabolism that results from the absence or dysfunction of a copper-transporting P-type adenosine triphosphatase that leads to impaired biliary copper excretion and disturbed holoceruloplasmin synthesis. To gain further insight into the role of the Wilson's disease protein in hepatic copper handling, its localization in human liver was investigated. METHODS: By use of a specific antibody, localization of the Wilson's disease protein was studied in liver membrane fractions and liver sections by immunoblotting, immunohistochemistry, and double-label confocal scanning laser microscopy. RESULTS: The 165-kilodalton protein, found by immunoblotting, was most abundant mainly in isolated plasma membrane fractions enriched in canalicular domains. Immunohistochemistry revealed intracellular punctuate staining of hepatocytes in certain regions of the liver, whereas a canalicular membrane staining pattern was observed in other regions. Double-labeling studies showed that in the latter regions the transporter is present mainly in vesicular structures just underneath the canalicular membrane that are positive for markers of the trans-Golgi network. A weak staining of the canalicular membrane, identified by staining for P-glycoprotein, was observed. CONCLUSIONS: These results show that in human liver the Wilson's disease protein is predominantly present in trans-Golgi vesicles in the pericanalicular area, whereas relatively small amounts of the protein appear to localize to the canalicular membrane, consistent with a dual function of the protein in holoceruloplasmin synthesis and biliary copper excretion.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Integration of the Internet into medical education].

The Internet promises dramatic changes in the way we learn and teach, the way we interact as a society. Networked technologies introduce interactivity and multimedia into the educational process. The student of the 21st century will use his/her PC as a learning station, as a tutoring system, as an information provider and as a communication center. Therefore the passive classroom (teacher-centered teaching) will evolve into active studio learning (student-centered learning). This will be achieved by new teaching techniques and standards of quality. The role of the new generation of educators is to create exploratory learning environments that offer a wide range of views on many subject areas and encourage active lifelong learning. This will be achieved by 1) placing courseware on the web where it can be accessed by remote students and by 2) finding and reviewing teaching materials obtained from www for possible integration into the local lecture material. The paper suggests strategies for introducing medical educators to networked teaching.

Education, Medical↗
PubMed2004

Appetite regulatory neuropeptides are expressed in the sheep hypothalamus before birth.

In the adult, a hypothalamic neural network acts to maintain energy balance in response to nutritional feedback from the periphery. Although there is an immediate requirement for this system to be functional at birth, it is unknown whether the components of this central neural network are expressed in the developing brain before birth. We therefore examined in the fetal sheep hypothalamus during late gestation gene expression for leptin receptor (OB-Rb) and neuropeptides that regulate energy balance in the adult. Brains were collected from fetal sheep at 110 days (n = 12) and 140 days of gestation (n = 5) (term = 150 days) and gene expression was detected in all hypothalami using in situ hybridization with radiolabelled riboprobes for OB-Rb, neuropeptide Y (NPY), agouti-related peptide, pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript (CART). All mRNAs were expressed in the arcuate nucleus of fetuses at both time points. Additional sites of mRNA expression were the dorsomedial hypothalamus (DMH) for NPY, the paraventricular nucleus (PVN), ventromedial hypothalamus (VMH) and lateral hypothalamic area for CART, and the DMH, PVN and VMH for OB-Rb. We have therefore demonstrated that adult-like localization of gene expression for OB-Rb and key appetite regulatory neuropeptides is established in the ovine hypothalamus before birth. Thus, the fetus possesses a central appetite regulatory neural network with the potential to respond to changes in nutrient supply, which could impact on energy balance regulation both before and after birth.

Age Factors↗
PubMed1981

Mouse c1q: light and electron microscopic immunohistochemical localization.

The localization of mouse C1q in various mouse tissues was assessed by immunohistochemistry. In all mouse strains examined, C1q was associated with cells in small focal areas of lymph nodes, Peyer's patches, and spleens often near germinal centers. Ultrastructural studies of these foci demonstrated that C1q was present in the endoplasmic reticulum of mononucleated cells that had an extensive cytoplasmic network. Occasionally, small deposits of C1q were observed in the perinuclear space of mononucleated cells that had scanty cytoplasm with few organelles. Extracellular C1q was found at the surface of interdigitating cell processes in these lymphatic foci. In addition to the presence of C1q within lympho-reticular tissues, C1q frequently was detected in renal glomeruli but not in urinary tract epithelium or intestinal epithelium of adult mice; in contrast, C1q was localized in the intestinal epithelium of neonatal mice. C1q was not detected in tissue fibroblasts nor in cultured fibroblasts; however, a subpopulation of mouse adherent peritoneal cells maintained in vitro did contain C1q. The results of these studies provide new information regarding the distribution and, thus, the possible sites of C1q biosynthesis in normal mouse tissues.

Animals↗
PubMed2005

Cross-cultural effect on the brain revisited: universal structures plus writing system variation.

Recognizing printed words requires the mapping of graphic forms, which vary with writing systems, to linguistic forms, which vary with languages. Using a newly developed meta-analytic approach, aggregated Gaussian-estimated sources (AGES; Chein et al. [2002]: Psychol Behav 77:635-639), we examined the neuroimaging results for word reading within and across writing systems and languages. To find commonalities, we compiled 25 studies in English and other Western European languages that use an alphabetic writing system, 9 studies of native Chinese reading, 5 studies of Japanese Kana (syllabic) reading, and 4 studies of Kanji (morpho-syllabic) reading. Using the AGES approach, we created meta-images within each writing system, isolated reliable foci of activation, and compared findings across writing systems and languages. The results suggest that these writing systems utilize a common network of regions in word processing. Writing systems engage largely the same systems in terms of gross cortical regions, but localization within those regions suggests differences across writing systems. In particular, the region known as the visual word form area (VWFA) shows strikingly consistent localization across tasks and across writing systems. This region in the left mid-fusiform gyrus is critical to word recognition across writing systems and languages.

Brain↗
PubMed1994

Model of local connectivity patterns in CA3 and CA1 areas of the hippocampus.

In this study we describe a model of connectivity linking the different neurons in the CA3 and CA1 areas of the young male rat hippocampus. The anatomical and electrophysiological values of the parameters used in the model were selected from the available literature. Each type of synapse was characterized by its spatial location on the dendritic tree, its weight, its probability of activation, and the ionotropic receptors involved. We have shown that the degree of convergence and divergence of inputs is highly dependent upon the type of neuron and its spatial location. The different gradients of connectivity we describe support the lamellar hypothesis from a functional point of view, even if the anatomical patterns seem diffuse. The analysis of the proportion of common afferents to a class of neurons further confirmed this point. It is suggested that the circuitry creates local coherence in terms of processing of information by establishing restricted areas where information is preferentially treated. The functional consequences and limitations of these findings are also discussed. This model is the first step in the development of a network model of the hippocampus with realistic architecture.

Afferent Pathways↗
PubMed1992

Localization of a 82 kDa protein in postsynaptic density and its association with cytoskeletons.

A fraction of synaptic junctional complex (SJC) was prepared from rat synaptosomes and served as antigen material to produce monoclonal antibodies (Mab) for examining the component proteins of the SJC. An antibody, Mab SJ-8, was obtained, which recognized a protein with a molecular weight of 82,000 Da in the SJC preparation by immunoblot analysis. The immunohistochemical localization of the 82 kDa protein was studied with the rat cerebellum. Mab SJ-8 labeled the peripheral areas of the Purkinje and granule cells. Small punctate areas were also stained in the molecular layer with SJ-8. Intracellular localization of the protein was examined with rat brain synaptosomes. Immunoelectron microscopy demonstrated that Mab SJ-8 strongly labeled the postsynaptic density (PSD) and also a fibrous network spreading out of it. However, the antibody did not label the pre- or post-synaptic membrane or the cleft material.

Animals↗
PubMed1998

Functionally distinct NMDA receptors mediate horizontal connectivity within layer 4 of mouse barrel cortex.

In sensory areas of neocortex, thalamocortical afferents project primarily onto the spiny stellate neurons of Layer 4. Anatomical evidence indicates that these cells receive most of their excitatory input from other cortical neurons, including other spiny stellate cells. Although this local network must play an important role in sensory processing, little is known about the properties of the neurons and synapses involved. We have produced a slice preparation of mouse barrel cortex that isolates Layer 4. We report that excitatory interaction between spiny stellate neurons is largely via N-methyl-D-aspartate receptors (NMDARs) and that a given neuron contains more than one type of NMDAR, as distinguished by voltage dependence. Thus, spiny stellate cells act as effective integrators of powerful and persistent NMDAR-mediated recurrent excitation.

2-Amino-5-phosphonovalerate↗
PubMed1996

Use of computer conferencing to allow view box-style teaching sessions with residents at outlying hospitals.

RATIONALE AND OBJECTIVES: Health care reform is placing new pressures on radiology faculty members to use their time more efficiently. We implemented a computer conferencing technique that allows one faculty member to perform a simultaneous view box-style teaching session with residents at local and outlying hospitals. METHODS: The system simultaneously displays digital images on computer screens at the local and outlying hospitals; an on-screen pen allows the instructor or the participants to point to findings on the images. Audio is provided either by a telephone conference call using speakerphones or over the wide-area network using microphones and speakers built into the computers. RESULTS: The technique has been in use for 1 year. A survey of the faculty and residents indicate that computer conferencing is equivalent to traditional face-to-face teaching sessions at the view box. CONCLUSION: Computer conferencing is possible and accepted. The technique is low-cost, using generic computers that are part of the picture archiving and communication system at both hospitals, and relatively inexpensive conferencing software.

Computer Communication Networks↗
PubMed2004

Leptin, leptin receptors and ACTH immunoreactivities are present in the gastrointestinal tract and the neural tube of tadpoles of the newt Triturus.

Leptin, its receptor and ACTH were detected by immunohistochemistry in the gastrointestinal tract and the neural tube of the amphibian urodele, Triturus cristatus carnifex, during development. These molecules were found after hatching of tadpoles, starting from stage 41. In the gastrointestinal tract, cells immunoreactive to leptin and its receptor were first revealed in the stomach, the liver and the gut and then in the pancreas. Both immunoreactives were colocalized in the same cells in some areas. Immunostaining for ACTH appeared at stages 43/45 in the stomach, the gut and the pancreas. In adjacent sections, a few cells immunoreactive to both ACTH and leptin receptor were detected. A few cells were immunoreactive to both insulin and leptin receptor. Immunoreactivities to leptin and its receptor were also found in adjacent sections of the neural tube, often colocalized in the same cell. Moreover, in prosencephalon, mesencephalon, rhomboencephalon and spinal cord, ACTH-immunoreactive cells were detected in the same areas as the leptin receptor immunoreactive cells. These results suggest the existence of a neuroendocrine network in newt tadpoles both at the central level, where it resembles that of mammals, and at the peripheral level, where it may act locally to regulate food intake and metabolism, e.g. yolk digestion.

Adrenocorticotropic Hormone↗
PubMed2004

Theta-modulated feedforward network generates rate and phase coded firing in the entorhino-hippocampal system.

Principal cells of the hippocampus and of its only cortical input region, the entorhinal cortex exhibit place specific activity in the freely moving rat. While entorhinal cells have widely tuned place fields, hippocampal place fields are more localized and determine not only the rate but also the timing of place cell spikes. Several models have successfully attempted to explain this fine tuning making use of intrahippocampal attractor network dynamics provided by the recurrent collaterals of hippocampal area CA3. Recent experimental evidence shows that CA1 place cells preserve their tuning curves even in the absence of input from CA3. We propose a model in which entorhinal and hippocampal pyramidal cell populations are only connected via feedforward connections. Synaptic transmission in our sytem is gated by a class of interneurons inhibiting specifically the entorhino-hippocampal pathway. Theta rhythm modulates the activity of each component. Our results show that rhythmic shunting inhibition endows entorhinal cells with a novel type of temporal code conveyed by the phase jitter of individual spikes. This converts coarsely tuned place-specific activity in the entorhinal cortex to velocity-dependent postsynaptic excitation and, thus, provides hippocampal place cells with an input that has recently been proposed to account for their rate and phase coded firing. Hippocampal place fields are generated through this mechanism and also shown to be robust against variations in the level of tonic inhibition.

Action Potentials↗
PubMed2003

Neural basis for the processes that underlie visually guided and internally guided force control in humans.

Despite an intricate understanding of the neural mechanisms underlying visual and motor systems, it is not completely understood in which brain regions humans transfer visual information into motor commands. Furthermore, in the absence of visual information, the retrieval process for motor memory information remains unclear. We report an investigation where visuomotor and motor memory processes were separated from only visual and only motor activation. Subjects produced precision grip force during a functional MRI (fMRI) study that included four conditions: rest, grip force with visual feedback, grip force without visual feedback, and visual feedback only. Statistical and subtractive logic analyses segregated the functional process maps. There were three important observations. First, along with the well-established parietal and premotor cortical network, the anterior prefrontal cortex, putamen, ventral thalamus, lateral cerebellum, intermediate cerebellum, and the dentate nucleus were directly involved in the visuomotor transformation process. This activation occurred despite controlling for the visual input and motor output. Second, a detailed topographic orientation of visuomotor to motor/sensory activity was mapped for the premotor cortex, parietal cortex, and the cerebellum. Third, the retrieval of motor memory information was isolated in the dorsolateral prefrontal cortex, ventral prefrontal cortex, and anterior cingulate. The motor memory process did not extend to the supplementary motor area (SMA) and the basal ganglia. These findings provide evidence in humans for a model where a distributed network extends over cortical and subcortical regions to control the visuomotor transformation process used during visually guided tasks. In contrast, a localized network in the prefrontal cortex retrieves force output from memory during internally guided actions.

Adult↗
PubMed1995

Reciprocity in marital and social networks: illustration with Indian data.

Three measures of reciprocity, denoted s2, s3, and s4, that are applicable to both simple and weighted networks are considered here. By reciprocity I mean symmetry or mutuality of ties between different vertices of the network. These measures have simple formulas except in some extreme situations and can be used for most networks. Among the three measures, s2 is generally preferred, although the choice in any situation depends on the validity of the assumptions underlying its derivation and its discriminating power. I illustrate how reciprocity in the network of marital exchanges between different surnames and settlements can reveal something about the structure of a population. Reciprocity is higher if the endogamous group is close-knit, is well settled in a smaller geographic area, and has a low surname diversity index. Thus reciprocity is high in the Vadde, somewhat high in the Pattusali, and low in the Yanadi. Although s2, s3, and s4 measure reciprocity in a network as a whole, the local reciprocity index can be used to see how reciprocally a particular vertex is tied to others and can help in the study of the direction of the exchanges. The low local reciprocity indexes of the neighborhood settlements of the Yanadi in some regions indicate that the settlements are involved in one-way marital exchanges with other settlements. The study of reciprocity can be relevant in other contexts also. High reciprocity in a well-settled population was also observed in the social networks of 21 villages with respect to the "help" relation. It was found that reciprocity is highly negatively correlated with the percentage of migrants in the village but does not show high positive or negative correlation with other demographic, socioeconomic, and location characteristics of the villages.

Female↗
PubMed2004

Rat sperm AS-A: subcellular localization in testis and epididymis and surface distribution in epididymal sperm.

In this study, we investigated the subcellular compartmentalization of arylsulfatase-A (AS-A) in the testis and epididymis as well as the surface distribution in rat epididymal sperm. Testicular AS-A was compartmentalized specifically to the area underneath the outer acrosomal membrane of the acrosomal granule and to the dorsal aspect of the sperm acrosome. Epididymal AS-A was synthesized in the endoplasmic reticular (ER) network of principal cells and secreted into epididymal lumen as evident by its reactivity in the apical cytoplasm and vesicles therein underneath stereocilia. In clear cells, AS-A reactivity was found throughout the cytoplasmic machineries involved in endocytosis. Surface distribution of AS-A was initially detectable at the concave ridge as early as in sperm of the initial segment (IS). AS-A was additionally localized to the post-acrosomal region in caput (CP), corpus (CO) and cauda (CD) epididymal sperm. The expression levels of surface AS-A gradually increased during sperm transit from IS to CD epididymidis. These results favored the adsorption of AS-A from epididymal fluid onto the sperm surface, rather than shunting from the acrosome as a consequence of capacitation-associated membrane priming.

Animals↗
PubMed2006

Habitat loss through disruption of constrained dispersal networks.

Large losses of habitat could be caused by land use change that disrupts the dispersal networks used by migratory species. We assessed the relative losses of habitat for diadromous fish (i.e., those migrating between sea and freshwater) due to physical barriers, degradation of migratory passage associated with catchment land use, and site-scale land use characteristics on the West Coast, South Island, New Zealand. Fish occurrence, land use data, and river network models were analyzed in a GIS and subjected to a three-level hierarchical analysis. To identify accessible habitat not restricted by physical barriers, we used the migratory distance and maximum downstream slope encountered to identify accessible sites in least-impacted catchments and applied the results to all catchments within the study area. For two fish species, banded kokopu (Galaxias fasciatus) and koaro (G. brevipinnis), sites modeled as accessible using logistic regression in least-impacted catchments were then used to assess the impacts of catchment-scale deforestation and downstream land uses on habitat loss. Finally, sites not restricted by physical barriers or land-use-related impacts on migratory passage were used to model the effects of local land use. The models indicated that koaro and banded kokopu potentially had access to 28,000 km and 5300 km, respectively, of the 40,600 km of streams within the study area. Impacts due to intensive agricultural land use downstream in catchments affecting migratory passage were predicted to reduce the accessible habitats for koaro and banded kokopu by 55% and 70%, respectively. Local land use further reduced koaro and banded kokopu habitats to 70% and 90%, respectively, of total accessible habitat. Habitat lost through disruption of the dispersal network was disproportionately large because potentially useable habitat was rendered inaccessible.

Animal Migration↗
PubMed2001

Developing principles for health impact assessment.

BACKGROUND: Policies and practice in many sectors affect health. Health impact assessment (HIA) is a way to predict these health impacts, in order to recommend improvements in policies to improve health. There has been debate about appropriate methods for this work. The Scottish Executive funded the Scottish Needs Assessment Programme to conduct two pilot HIAs and from these to develop guidance on HIA. METHODS: Case study 1 compared three possible future scenarios for developing transport in Edinburgh, based on funding levels. It used a literature review, analysis of local data and the knowledge and opinions of key informants. Impacts borne by different population groups.were compared using grids. Case study 2 assessed the health impacts of housing investment in a disadvantaged part of Edinburgh, using published literature, focus groups with community groups and interviews with professionals. RESULTS: Disadvantaged communities bore more detrimental effects from the low transport investment scenario, in the areas of: accidents; pollution; access to amenities, jobs and social contacts; physical activity; and impacts on community networks. The housing investment had greatest impact on residents' mental health, by reducing overcrowding, noise pollution, stigma and fear of crime. CONCLUSION: Although there is no single 'blueprint' for HIA that will be appropriate for all circumstances, key principles to inform future HIA were defined. HIA should be systematic; involve decision-makers and affected communities; take into account local factors; use evidence and methods appropriate to the impacts identified and the importance and scope of the policy; and make practical recommendations.

Adolescent↗
PubMed2000

Working memory of auditory localization.

To investigate brain mechanisms of sound location memory, we studied the distribution of brain activation with functional magnetic resonance imaging (fMRI) in subjects performing an audiospatial n-back task with three memory load levels. Working memory processing of audiospatial information activated areas in the superior, middle and inferior frontal gyri, and in the posterior parietal and middle temporal cortices. In a control experiment, fMRI during audio- and visuospatial 2-back task performances revealed only few differentially activated subregions between the two tasks. These results demonstrate that working memory processing of auditory locations involves a distributed network of brain areas and suggest that mnemonic processing of audio- and visuospatial information is directed along a common neural pathway in the posterior parietal and prefrontal cortices.

Acoustic Stimulation↗
PubMed2000

Improved quantitative structure property relationships for the prediction of dielectric constants for a set of diverse compounds by subsetting of the data set

In a recent publication we explored the development of quantitative structure property relationships for the calculation of dielectric constants, which resulted in a general model for a wide range of compounds. Our current work explores the division of the set of compounds into eight more homogeneous subsets for which local models are developed. The full data set consists of 454 compounds with dielectric constants ranging from 1 to 40. A pool of up to 16 molecular descriptors is calculated for each of the eight data sets. The descriptors include dipole moment, polarizability, counts of elemental types or functional groups, charged partial surface area, and molecular connectivity. All possible 4-16 descriptor models are calculated for each of the eight data sets, and the best models are selected and compared to the results obtained from the best general model for all 454 compounds. Neural networks using the Broyden-Fletcher-Goldfarb-Shanno training algorithm are employed to build the models. The resulting combined mean test set error for the eight local models of 1.31 is significantly better than the mean test set error of 1.85 for the general model.

Journal Article↗