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At least 847 records · Page 47Linked to original sources
PubMed2006

Electrical isolation of pulmonary veins in patients with atrial fibrillation: reduction of fluoroscopy exposure and procedure duration by the use of a non-fluoroscopic navigation system (NavX).

AIMS: The aim of the study was to investigate the feasibility of performing segmental pulmonary vein (PV) isolation guided by the NavX (Endocardial Solutions, St Jude Medical, Inc., St Paul, MN, USA) system without the three-dimensional (3D) geometric reconstruction option and whether the use of NavX system will reduce the radiation exposure and procedure duration. METHODS AND RESULTS: The study included 64 patients with symptomatic paroxysmal or permanent atrial fibrillation, in whom PV isolation was performed using fluoroscopic guidance (n=32) or the NavX system (n=32). Pulmonary vein mapping with a circular mapping catheter allowed the identification and localization of myocardial connections between the PV and the left atrium. PV isolation was performed by radiofrequency ablation of these connections at the atrial aspect of the PV ostium. Primary success rate for isolated PVs did not differ significantly in patients ablated under fluoroscopic guidance vs. those ablated under guidance of NavX system [100/107 PVs (93.5%) vs. 120/124 PV (96.8%; P=n.s.)]. Compared with fluoroscopy guided procedures, NavX-guided procedures showed a significant reduction in the fluoroscopy time (75.8+/-24.5 vs. 38.9+/-19.3 min, P<0.05), total X-ray exposure (93.2+/-51.6 vs. 56.6+/-37.9 Gy cm(2), P=0.03), and total procedural time (237.7+/-65.4 vs. 188.6+/-62.7 min, P=0.01). The mean follow-up was 9.5+/-3.0 months. One patient in each group was lost to follow-up. Seven-day Holter monitoring showed that 23 of 31 patients (74.2%) in the NavX-guided group and 21 of 31 patients (67.7%) in the fluoroscopy-guided group were in sinus rhythm (P=0.57). CONCLUSION: The 3D visualization of the catheters by NavX system allows a rapid and precise visualization of the mapping and ablation catheters at the PV ostia and markedly reduces fluoroscopy time, total X-ray exposure, and procedural duration during PV isolation compared with ablation performed under fluoroscopy guidance.

Aged↗
PubMed1973

Specification of positional information in retinal ganglion cells of Xenopus: assays for analysis of the unspecified state.

The central connections of retinal ganglion cells are retinotopically organized, producing a "map" of the retina on the surface of the optic tectum. Exactly how and when individual ganglion cells develop the position-dependent properties (termed locus specificities) subserving formation of the map is unknown, but the positional information that each ganglion cell will use in this process is specified in the early Xenopus embryo during a critical period at stages 28-32. We report two methods for isolating eye primordia from the axial cues of the animals during this critical period and for then allowing the eyes to form retinotectal connections in a carrier embryo. The results show that, as early as optic vesicle stages 22-23, the eyes already contain orthogonal reference axes, that positional information can be specified with respect to these axes in vitro, and that the specification process itself may only entail a transition from a reversible to an irreversible state.

Animals↗
PubMed2006

A gene-based high-resolution comparative radiation hybrid map as a framework for genome sequence assembly of a bovine chromosome 6 region associated with QTL for growth, body composition, and milk performance traits.

BACKGROUND: A number of different quantitative trait loci (QTL) for various phenotypic traits, including milk production, functional, and conformation traits in dairy cattle as well as growth and body composition traits in meat cattle, have been mapped consistently in the middle region of bovine chromosome 6 (BTA6). Dense genetic and physical maps and, ultimately, a fully annotated genome sequence as well as their mutual connections are required to efficiently identify genes and gene variants responsible for genetic variation of phenotypic traits. A comprehensive high-resolution gene-rich map linking densely spaced bovine markers and genes to the annotated human genome sequence is required as a framework to facilitate this approach for the region on BTA6 carrying the QTL. RESULTS: Therefore, we constructed a high-resolution radiation hybrid (RH) map for the QTL containing chromosomal region of BTA6. This new RH map with a total of 234 loci including 115 genes and ESTs displays a substantial increase in loci density compared to existing physical BTA6 maps. Screening the available bovine genome sequence resources, a total of 73 loci could be assigned to sequence contigs, which were already identified as specific for BTA6. For 43 loci, corresponding sequence contigs, which were not yet placed on the bovine genome assembly, were identified. In addition, the improved potential of this high-resolution RH map for BTA6 with respect to comparative mapping was demonstrated. Mapping a large number of genes on BTA6 and cross-referencing them with map locations in corresponding syntenic multi-species chromosome segments (human, mouse, rat, dog, chicken) achieved a refined accurate alignment of conserved segments and evolutionary breakpoints across the species included. CONCLUSION: The gene-anchored high-resolution RH map (1 locus/300 kb) for the targeted region of BTA6 presented here will provide a valuable platform to guide high-quality assembling and annotation of the currently existing bovine genome sequence draft to establish the final architecture of BTA6. Hence, a sequence-based map will provide a key resource to facilitate prospective continued efforts for the selection and validation of relevant positional and functional candidates underlying QTL for milk production and growth-related traits mapped on BTA6 and on similar chromosomal regions from evolutionary closely related species like sheep and goat. Furthermore, the high-resolution sequence-referenced BTA6 map will enable precise identification of multi-species conserved chromosome segments and evolutionary breakpoints in mammalian phylogenetic studies.

Animals↗
PubMed2002

Aquaglyceroporins: channel proteins with a conserved core, multiple functions, and variable surfaces.

Membrane channels for water and small nonionic solutes are required for osmoregulation in bacteria, plants, and animals. Aquaporin-1, the water channel of human erythrocytes, is the first channel demonstrated to conduct water, by expression in Xenopus oocytes. Phylogenetic analyses reveal the existence of two clusters of subfamilies, the aquaporins (AQPs) and glycerol facilitators (GLPs). Sequence-based structure prediction provided a model comprising six membrane-spanning helices, while sequence analyses suggested strategic residues that are important for structure and function. The surface topography of several AQPs has been mapped by atomic force microscopy, revealing different features that correlate with differences in the loops connecting transmembrane helices. The 3D structures of AQP1 and GlpF have been determined by electron cryomicroscopy. The 3.8-A density map allowed the first atomic model of AQP1 to be built, taking into account data from sequence analyses. This model provides some insight into the permeation of water through a channel that blocks the passage of protons. GIpF has been resolved to 6.9 A, revealing helices that are similar to those of AQP1. Homology modeling shows the channel region of these distant aquaglyceroporins to be similar, as confirmed by the 2.2-A structure of GlpF from X-ray crystallography.

Animals↗
PubMedDate not supplied

Electroanatomical maps of the heart in the athletes.

The CARTO system is a new, non fluoroscopic method for mapping designed of associating a specific intracardiac electrocardiogram with the endocardial location from which it has been recorded. Thus for the first time, the CARTO system allows precise correlation of electrophysiological information with cardiac anatomy. It acquires, through a special catheter, and then displays on its computer screen, the precise three-dimensional electro-anatomical maps of the different cardiac chambers. The maps are constructed by integrating information from recorded intracardiac electro-grams with knowledge of their precise anatomic location within the heart. The method is based on the ability to connect a new locatable catheter with a system for endocardial navigation and mapping.

Adult↗
PubMed2007

Detecting functional nodes in large-scale cortical networks with functional magnetic resonance imaging: a principal component analysis of the human visual system.

This study aimed to demonstrate how a regional variant of principal component analysis (PCA) can be used to delineate the known functional subdivisions of the human visual system. Unlike conventional eigenimage analysis, PCA was carried out as a second-level analysis subsequent to model-based General Linear Model (GLM)-type functional activation mapping. Functional homogeneity of the functional magnetic resonance imaging (fMRI) time series within and between clusters was examined on several levels of the visual network, starting from the level of individual clusters up to the network level comprising two or more distinct visual regions. On each level, the number of significant components was identified and compared with the number of clusters in the data set. Eigenimages were used to examine the regional distribution of the extracted components. It was shown that voxels within individual clusters and voxels located in bilateral homologue visual regions can be represented by a single component, constituting the characteristic functional specialization of the cluster(s). If, however, PCA was applied to time series of voxels located in functionally distinct visual regions, more than one component was observed with each component being dominated by voxels in one of the investigated regions. The model of functional connections derived by PCA was in accordance with the well-known functional anatomy and anatomical connectivity of the visual system. PCA in combination with conventional activation mapping might therefore be used to identify the number of functionally distinct nodes in an fMRI data set in order to generate a model of functional connectivity within a neuroanatomical network.

Adult↗
PubMed2003

Mixed total anomalous pulmonary venous connection: Case report with bilateral venous collectors.

We present a case report of a 3-month-old boy with a mixed total anomalous pulmonary venous connection. The patient had situs solitus, small atrial septal defect, and 2 separate venous collectors. The right pulmonary veins drained through a right-sided venous collector into the coronary sinus. The left-sided pulmonary veins drained through the left-sided venous collector directly into the right superior vena cava. The use of the echocardiogram and Doppler color flow mapping to establish a detailed morphologic analysis, the sites of connection, and the presence of pulmonary venous obstructions as well as the value of this information to facilitate a successful surgical repair are discussed.

Cardiac Surgical Procedures↗
PubMed2005

Electrical stimulation of the cochlear nerve in rats: analysis of c-Fos expression in auditory brainstem nuclei.

We investigated functional activation of central auditory brainstem nuclei in response to direct electrical stimulation of the cochlear nerve using c-Fos immunoreactivity as a marker for functional mapping. The cochlear nerve was stimulated in the cerebellopontine angle of Lewis rats applying biphasic electrical pulses (120-250 muA, 5 Hz) for 30 min. In a control group, bilateral cochlectomy was performed in order to assess the basal expression of c-Fos in the auditory brainstem nuclei. The completeness of cochlear ablations and the response of auditory brainstem nuclei to electrical stimulation were electrophysiologically verified. C-Fos immunohistochemistry was performed using the free floating method. In anaesthetized animals with unilateral electrical stimulation of the cochlear nerve, increased expression of c-Fos was detected in the ipsilateral ventral cochlear nucleus (VCN), in the dorsal cochlear nucleus bilaterally (DCN), in the ipsilateral lateral superior olive (LSO) and in the contralateral inferior colliculus (IC). A bilateral slight increase of c-Fos expression in all subdivisions of the lateral lemniscus (LL) did not reach statistical significance. Contralateral inhibition of the nuclei of the trapezoid body (TB) was observed. Our data show that unilateral electrical stimulation of the cochlear nerve leads to increased expression of c-Fos in most auditory brainstem nuclei, similar to monaural auditory stimulation. They also confirm previous studies suggesting inhibitory connections between the cochlear nuclei. C-Fos immunoreactivity mapping is an efficient tool to detect functional changes following direct electrical stimulation of the cochlear nerve on the cellular level. This could be particularly helpful in studies of differential activation of the central auditory system by experimental cochlear and brainstem implants.

Animals↗
PubMedDate not supplied

[Interaction foci, informational synthesis and mental processes].

Brain organization of mental activity is based on the nervous integration, specialization of functions and combination of rigid and flexible connections. First of them are provided by structural changes in synapses, the second--by a coincidence of rhythmic characteristics and synchronization of the activity. These principles are realized in dynamic structures--interaction foci, revealed in the cortex during the process of mental activity by a method of mapping the intracortical interaction. Interaction foci are the centers of nervous connections. Each group has its appropriate frequency characteristics and is connected with the isorhythmic nervous elements at the periphery. Construction of the interaction focus provides the synthesis of the information coming from the sensory organs and the centers of motivations and that extracted from the memory. Informational synthesis is in the basis of the mental functions, having a rigid nucleus and a system of peripheral connections whose configuration can be changed, stipulating a unique character of experienced psychic feeling. Topography of interaction foci is different at different mental acts, realizing a principle of functional specialization. At perception the projection cortex is the center of integration, at thinking that are the cortical associative zones. Imaginable thinking is predominantly connected with the parieto-temporal, abstract--with the frontal cortical areas. Probably two basic functions of consciousness--integration of the "Self" including voluntary factor and communication-are also separated in space.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1997

Receptive Field Map Development by Anti-Hebbian Learning.

Neurons selective to oriented visual stimuli participate in the early steps of visual signal processes in higher mammals. A highly ordered neural connectivity responds to such a selectivity. The information necessary to establish this connectivity is too large to be contained in a genome. Moreover, neurophysiological experiments show that the alteration of small parts of the developing visual neural system affects the normal development of the whole system. Self-organizing processes able to produce local order from general properties have already been proposed as the driving force of these development stages. In order to model these self-organizing processes we study a two layer neural network based on simple organizational rules such as (1) diffusion of neural signal in the same layer, (2) Hebbian and anti-Hebbian learning, and (3) individual restrictions to the growth of each neuronal connection. We simulate the development of neurons selective to orientation and size organized in a map, underscoring the importance of anti-Hebbian learning for normal neural visual system development. Copyright 1997 Elsevier Science Ltd.

Journal Article↗
PubMed1989

Amino acid sequence of Mirabilis antiviral protein, total synthesis of its gene and expression in Escherichia coli.

We have determined the complete amino acid sequence of Mirabilis antiviral protein (MAP). MAP is composed of 250 amino acids having a combined molecular weight of 27,833 and contains 23 lysine residues and 7 arginine residues. The amino acid sequence of MAP has 24% homology with the Ricin D-A chain. To carry out systematic structure-function studies of MAP, we have accomplished the total synthesis of its gene. We designed a synthetic MAP gene containing 12 unique restriction sites that were on the average 65 base pairs apart. Thirty synthetic oligonucleotides were enzymatically joined to form DNA duplexes. These were strategically synthesized to have EcoRI and HindIII cohesive ends and were cloned in pUC19. Nine blocks of the synthetic fragments were assembled in pUC19 to form the MAP gene consisting of 759 base pairs. The correctness of the connecting reactions was confirmed by step-wise sequencing of each assembled fragment as well as the total gene. When expressed under control of the tac promoter in Escherichia coli, the synthetic gene gave a protein similar to the native MAP. This was confirmed by an enzyme-linked immunosorbent assay and Western blotting analysis.

Amino Acid Sequence↗
PubMed1991

Echocardiographic and color flow Doppler assessment of systemic and pulmonary venous connection and drainage in the neonate with congenital heart disease.

Systemic and pulmonary venous anomalies are frequently encountered either as isolated lesions or as a significant component of a more complex lesion in the newborn infant with congenital heart disease. Two-dimensional echocardiography and Doppler techniques (conventional and color flow) have become the primary diagnostic imaging modality in this setting. Precise pre-operative definition of these variable venous connection and drainage patterns is critical as the required surgical procedure may solely be based on exact understanding of the veins' anatomy and physiology. On the systemic venous site, anomalies of superior and inferior venae cavae, innominate vein, and coronary sinus can be equally well imaged with either echocardiography or angiography. However, on the pulmonary venous site, echocardiography and Doppler techniques including color flow mapping are superior to angiography for precise definition of the connection and drainage sites of the individual pulmonary veins.

Echocardiography, Doppler↗
PubMed1998

Clinical applications of motor evoked potentials.

Magnetic stimulation of brain and spinal roots provides a non-invasive evaluation of nervous propagation as well as of motor cortex excitability in healthy subjects and in patients affected by neurological diseases (i.e. multiple sclerosis, stroke, Parkinson's disease, myelopathies etc.). Motor areas can be reliably mapped and short- and long-term 'plastic' changes of neural connections can be studied and monitored over time. By evaluating excitatory and inhibitory phenomena following transcranial stimuli, the mechanisms of action of different drugs, including antiepileptics, can be studied. Moreover, transcranial stimulation of non-motor brain areas represents a probe for the evaluation of lateralized hemispheric properties connected with higher cortical functions. Recent studies suggest a therapeutic role of repetitive magnetic stimulation in psychiatric disorders.

Animals↗
PubMed1999

The role of visual experience in the cortical topographic map reorganization following retinal lesions.

The mature visual cortex is capable of reorganizing its functional connections in response to retinal injuries. Although this phenomenon is well established, there are a number of unresolved issues. This paper will review some of the more critical aspects of adult plasticity including those based on our most recent findings. Our preliminary data indicate that a large-scale reorganization of cortical maps following retinal injuries may require an increase in synaptic strengths at key cortical sites promoted by long-term, repeated use.

Journal Article↗
PubMed2006

Brain areas involved in medial temporal lobe seizures: a principal component analysis of ictal SPECT data.

The study describes brain areas involved in medial temporal lobe (mTL) seizures of 12 patients. All patients showed so-called oro-alimentary behavior within the first 20 s of clinical seizure manifestation characteristic of mTL seizures. Single photon emission computed tomography (SPECT) images of regional cerebral blood flow (rCBF) were acquired from the patients in ictal and interictal phases and from normal volunteers. Image analysis employed categorical comparisons with statistical parametric mapping and principal component analysis (PCA) to assess functional connectivity. PCA supplemented the findings of the categorical analysis by decomposing the covariance matrix containing images of patients and healthy subjects into distinct component images of independent variance, including areas not identified by the categorical analysis. Two principal components (PCs) discriminated the subject groups: patients with right or left mTL seizures and normal volunteers, indicating distinct neuronal networks implicated by the seizure. Both PCs were correlated with seizure duration, one positively and the other negatively, confirming their physiological significance. The independence of the two PCs yielded a clear clustering of subject groups. The local pattern within the temporal lobe describes critical relay nodes which are the counterpart of oro-alimentary behavior: (1) right mesial temporal zone and ipsilateral anterior insula in right mTL seizures, and (2) temporal poles on both sides that are densely interconnected by the anterior commissure. Regions remote from the temporal lobe may be related to seizure propagation and include positively and negatively loaded areas. These patterns, the covarying areas of the temporal pole and occipito-basal visual association cortices, for example, are related to known anatomic paths.

Adolescent↗
PubMed1997

Coding for auditory space in the nucleus of the brachium of the inferior colliculus in the ferret.

Coding for auditory space in the nucleus of the brachium of the inferior colliculus in the ferret. J. Neurophysiol. 78: 2717-2731, 1997. The nucleus of the brachium of the inferior colliculus (BIN) projects topographically to the deeper layers of the superior colliculus (SC), which contain a two-dimensional map of auditory space. In this study, we have used broadband stimuli presented in the free field to investigate how auditory space is represented in the BIN of the ferret. Response latencies and temporal firing patterns were comparable with those in the SC, and both properties showed some variation with stimulus location. We obtained spatial response profiles at two sound levels (5-15 and 25-35 dB above unit threshold). A large proportion of azimuth profiles (41% in the suprathreshold condition, 80% in the near-threshold condition) presented a single peak, indicating that they were tuned to single regions in space. For some of these units, the preferred speaker position varied considerably with sound level. The remaining units showed predominantly either broad "hemifield" or spatially ambiguous "bilobed" response profiles. At suprathreshold sound levels, the preferred azimuths of the tuned cells were ordered topographically along the rostrocaudal axis of the BIN, although this representation is considerably more scattered than that in the SC. In contrast to the SC, we observed no systematic variation in the distribution of near-threshold best azimuths, which were instead concentrated around the interaural axis in the contralateral hemifield. The azimuth tuning of individual units in the BIN was generally broader at both sound levels than that in the SC. Many units also were tuned for the elevation of the sound source (48% for supra-, 77% for near-threshold stimulation), but there was no evidence for topographic order in the distribution of preferred elevations within the BIN. These results suggest that the BIN sends inputs to the SC that are already selective for sound azimuth and elevation and that show some degree of topographic order for sound azimuth. These inputs then presumably are sharpened and their topography refined by a mechanism that is likely to involve convergence of other inputs and activity-dependent fine tuning of terminal connections, to result in a precise two-dimensional map of auditory space in the SC.

Acoustic Stimulation↗
PubMed2004

Subcortical pathways serving cortical language sites: initial experience with diffusion tensor imaging fiber tracking combined with intraoperative language mapping.

The combination of mapping functional cortical neurons by intraoperative cortical stimulation and axonal architecture by diffusion tensor MRI fiber tracking can be used to delineate the pathways between functional regions. In this study the authors investigated the feasibility of combining these techniques to yield connectivity associated with motor speech and naming. Diffusion tensor MRI fiber tracking provides maps of axonal bundles and was combined with intraoperative mapping of eloquent cortex for a patient undergoing brain tumor surgery. Tracks from eight stimulated sites in the inferior frontal cortex including mouth motor, speech arrest, and anomia were generated from the diffusion tensor MRI data. The regions connected by the fiber tracking were compared to foci from previous functional imaging reports on language tasks. Connections were found between speech arrest, mouth motor, and anomia sites and the SMA proper and cerebral peduncle. The speech arrest and a mouth motor site were also seen to connect to the putamen via the external capsule. This is the first demonstration of delineation of subcortical pathways using diffusion tensor MRI fiber tracking with intraoperative cortical stimulation. The combined techniques may provide improved preservation of eloquent regions during neurological surgery, and may provide access to direct connectivity information between functional regions of the brain.

Adult↗
PubMed2003

Groundwater-surface water interaction in inland New South Wales: a scoping study.

Groundwater and surface water have traditionally been managed separately in New South Wales (NSW). However, where rivers and aquifers are hydraulically connected, groundwater pumping has the potential to deplete streamflow. To highlight the major areas of connection in inland NSW, major streams were overlaid with groundwater depth data and the locations of irrigation bores. A consistent pattern was revealed related to basin geomorphology. The main areas of connection are the mid-sections of the major rivers where alluvial systems are well developed yet still narrow and constricted and groundwater depths are shallow. The mapping was validated and the processes explored by calculating water balances for a connected and disconnected reach in the Murrumbidgee River. These showed that, in highly connected reaches, river losses and/or gains are closely related to groundwater levels.

Agriculture↗