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PubMed2005

The cingulate as a catalyst region for global dysfunction: a dynamical modelling paradigm.

The anterior cingulate (AC) often exhibits both structural and functional abnormalities in affective disorders. Neither the cause for this vulnerability nor its effect on behaviour is known. Due to its extensive connectivity, minor output changes from the AC may exert widespread consequences. A causal model describing coupling coefficients (effective connectivity) among several brain regions in healthy subjects performing a memory task inspired our work. This stationary causal analysis provides a theoretical framework for our nonlinear dynamical models. We tested the effects of global and local perturbations upon stability of a systems-level neural network of interconnected brain regions. Interactions between regions, represented by path coefficients, were modelled using connectivity matrices. We found that both characteristic behaviour and response to perturbation differed in networks representing perceptual matching and long-delay conditions. Owing to the highly interconnected character of the networks, activation of a few areas was sufficient to trigger characteristic patterns of behaviour. However, only perturbation of key regions resulted in global dysfunction. Likewise, recovery of function was possible by increasing output from some, but not all, regions. We suggest for this recovery to be context specific, conditional on the task, integrity of other regions and global properties such as neuronal excitability.

Biological Clocks↗
PubMed2005

Afferents and homotypic neighbors regulate horizontal cell morphology, connectivity, and retinal coverage.

Horizontal cells are inhibitory interneurons with laterally oriented dendrites that overlap one another, contacting the pedicles of cone photoreceptors. Because of their regular spacing, the network of horizontal cells provides a uniform coverage of the retinal surface. The developmental processes establishing these network properties are undefined, but cell-intrinsic instructions and interactions with other cells have each been suggested to play a role. Here, we show that the intercellular spacing of horizontal cells is essentially independent of genetic background and is predicted by local density, suggesting that horizontal cell positioning is modulated by proximity to other horizontal cells. Dendritic field area compensates for this variation in intercellular spacing, maintaining constant dendritic coverage between strains. Functional dendritic overlap is achieved anatomically at the level of the pedicles, where horizontal cells interact with one another to establish their connectivity: the number of dendritic terminals contacting a pedicle changes, reciprocally, between neighboring horizontal cells during development based on their relative proximity to each pedicle. Cellular morphology is also shown to be regulated by the afferents themselves: afferent elimination before innervation does not alter dendritic field size nor stratification but compromises dendritic branching and prevents terminal formation. Afferent and homotypic interactions therefore generate the morphology, spacing, and connectivity of horizontal cells underlying their functional coverage of the retina.

Animals↗
PubMed2005

Cellular interactions in lymph node development.

The organized accumulation of lymphocytes is a biological phenomenon used to optimize both homeostatic immune surveillance, as well as chronic responses to pathogenic stimuli. During embryonic development, circulating hemopoietic cells gather at predestined sites throughout the body, where they are subsequently arranged in T and B cell-specific areas characteristic of secondary lymphoid organs. In contrast, the body seems to harbor a limited second set of selected sites that support formation of organized lymphoid aggregates. However, these are only revealed at times of local, chronic inflammation, when so-called tertiary lymphoid structures appear. Once thought of as two distinct phenomena, recent insights suggest that highly similar networks of paracrine interactions regulate the formation of both secondary and tertiary lymphoid structures. This review will focus on these cellular interactions between organizing and inducing cell populations leading to the formation of lymph nodes or organized inflammatory infiltrates.

Animals↗
PubMed1999

Retinal waves are governed by collective network properties.

Propagating neural activity in the developing mammalian retina is required for the normal patterning of retinothalamic connections. This activity exhibits a complex spatiotemporal pattern of initiation, propagation, and termination. Here, we discuss the behavior of a model of the developing retina using a combination of simulation and analytic calculation. Our model produces spatially and temporally restricted waves without requiring inhibition, consistent with the early depolarizing action of neurotransmitters in the retina. We find that highly correlated, temporally regular, and spatially restricted activity occurs over a range of network parameters; this ensures that such spatiotemporal patterns can be produced robustly by immature neural networks in which synaptic transmission by individual neurons may be unreliable. Wider variation of these parameters, however, results in several different regimes of wave behavior. We also present evidence that wave properties are locally determined by a single variable, the fraction of recruitable (i.e., nonrefractory) cells within the dendritic field of a retinal neuron. From this perspective, a given local area's ability to support waves with a wide range of propagation velocities-as observed in experiment-reflects the variability in the local state of excitability of that area. This prediction is supported by whole-cell voltage-clamp recordings, which measure significant wave-to-wave variability in the amount of synaptic input a cell receives when it participates in a wave. This approach to describing the developing retina provides unique insight into how the organization of a neural circuit can lead to the generation of complex correlated activity patterns.

Animals↗
PubMedDate not supplied

[Palisading granuloma of the penis: a variant of subcutaneous granuloma annulare].

INTRODUCTION: Subcutaneous granuloma annulare on the penis has only been reported exceptionally. OBSERVATION: A 41 year-old man presented with four small, asymptomatic nodules on the glans penis. Histological examination of a biopsy revealed a deep palisading granuloma progressing not only around the alcian-blue necrobiosis areas but also around the smooth muscle fibers. The lesion regressed spontaneously after two years of progression. DISCUSSION: Palisading granuloma of the penis appears to be a most particular clinical form of subcutaneous granuloma annulare. It is characterized by small single or multiple nodules localized on the penis. On histological examination, the granuloma is deep and concentrates around the network of smooth muscle fibers of dartoic origin.

Adult↗
PubMed2005

Design of an integrated system for Milwaukee children with developmental disabilities.

Currently, data on children with developmental delays are collected on an as-needed basis and in general are created and maintained locally. In this paper, a comprehensive, user-friendly integrated system design for children age birth to three years with disabilities in Milwaukee County is proposed. After the prototype system is developed and tested as a "proof-of-concept" the product system will be migrated into the Wisconsin Public Health Information Network (WI-PHIN) as a Program Area Module (PAM).

Child, Preschool↗
PubMed1999

Short-term memory in olfactory network dynamics.

Neural assemblies in a number of animal species display self-organized, synchronized oscillations in response to sensory stimuli in a variety of brain areas. In the olfactory system of insects, odour-evoked oscillatory synchronization of antennal lobe projection neurons (PNs) is superimposed on slower and stimulus-specific temporal activity patterns. Hence, each odour activates a specific and dynamic projection neuron assembly whose evolution during a stimulus is locked to the oscillation clock. Here we examine, using locusts, the changes in population dynamics of projection-neuron assemblies over repeated odour stimulations, as would occur when an animal first encounters and then repeatedly samples an odour for identification or localization. We find that the responses of these assemblies rapidly decrease in intensity, while they show a marked increase in spike time precision and inter-neuronal oscillatory coherence. Once established, this enhanced precision in the representation endures for several minutes. This change is stimulus-specific, and depends on events within the antennal lobe circuits, independent of olfactory receptor adaptation: it may thus constitute a form of sensory memory. Our results suggest that this progressive change in olfactory network dynamics serves to converge, over repeated odour samplings, on a more precise and readily classifiable odour representation, using relational information contained across neural assemblies.

Animals↗
PubMed2001

Computerized radiographic mass detection--part II: Decision support by featured database visualization and modular neural networks.

Based on the enhanced segmentation of suspicious mass areas, further development of computer-assisted mass detection may be decomposed into three distinctive machine learning tasks: 1) construction of the featured knowledge database; 2) mapping of the classified and/or unclassified data points in the database; and 3) development of an intelligent user interface. A decision support system may then be constructed as a complementary machine observer that should enhance the radiologists performance in mass detection. We adopt a mathematical feature extraction procedure to construct the featured knowledge database from all the suspicious mass sites localized by the enhanced segmentation. The optimal mapping of the data points is then obtained by learning the generalized normal mixtures and decision boundaries, where a is developed to carry out both soft and hard clustering. A visual explanation of the decision making is further invented as a decision support, based on an interactive visualization hierarchy through the probabilistic principal component projections of the knowledge database and the localized optimal displays of the retrieved raw data. A prototype system is developed and pilot tested to demonstrate the applicability of this framework to mammographic mass detection.

Artificial Intelligence↗
PubMed2001

Cortical networks recruited for time perception: a monkey positron emission tomography (PET) study.

The presence of an "internal clock" in the brain has been assumed to underlie the information processing related to time. This clock plays a critical role in time keeping and time perception, which are closely associated with integrated functions in the brain. To identify the brain areas recruited for time keeping and time perception, we performed positron emission tomography (PET) studies with rhesus monkeys to measure regional cerebral blood flow (rCBF) as an index of neural activity during time discrimination tasks of different durations ranging from 400 to 1500 ms. Changes in rCBF that covaried significantly with the durations of the target being perceived by subjects were found in the dorsolateral prefrontal cortex (DLPFC), the posterior part of the inferior parietal cortex, basal ganglia, and posterior cingulate cortex. Furthermore, a loss of neuronal function in the DLPFC caused by a local application of bicuculline resulted in the selective reduction of performance in time discrimination tasks. The results indicate that a neural network composed of the posterior inferior parietal cortex to the DLPFC plays a crucial role in the temporal monitoring process in time perception.

Animals↗
PubMed2000

Part 9: pediatric basic life support. European Resuscitation Council.

The epidemiology and outcome of pediatric cardiopulmonary arrest and the priorities, techniques, and sequence of pediatric resuscitation assessments and intervention differ from those of adults. Current guidelines have been updated after extensive multinational evidence-based review and discussion over several years. Areas of controversy in current guidelines and recommendations made by consensus are detailed. A large degree of uniformity exists in the current guidelines advocated by the AHA, Council on Latin American Resuscitation, Heart and Stroke Foundation of Canada, European Resuscitation Council, Australian Resuscitation Council, and Resuscitation Council of Southern Africa. Differences are currently based on local and regional preferences, training networks, and customs rather than scientific controversy. Unresolved issues with potential for future universal application are highlighted.

Algorithms↗
PubMedDate not supplied

Biological thermal detection: micromechanical and microthermal properties of biological infrared receptors.

Bioinspired design of biomimetic sensors relies upon the complete understanding of properties and functioning of biological analogues in conjunction with an understanding of their microstructural organization at various length scales. In the spirit of this approach, the microscopic properties of infrared (IR) receptors of snakes with "infrared vision" were studied with scanning thermal microscopy and micromechanical analysis. Low surface thermal conductivity of 0.11 W/(m K) was measured for the IR receptor surfaces as compared to the nonspecific skin areas. This difference in surface thermal conductivity should result in a significant local temperature gradient around the receptor areas. Micromechanical analysis showed that pit organs were more compliant than surrounding skin areas with an elastic modulus close to 40 MPa. In addition, the maximum elastic modulus was detected for the outermost layer with gradually reduced elastic resistance for the interior. The porous microstructure of the underlying tissue combined with the highly branched microfibrillar network (Biomacromolecules 2001, 2, 757) is thought to be responsible for such a combination of biomaterial properties. Considering these biomaterials features, we postulated a possible design of an artificial photothermal detector inspired by the microstructure of natural receptors. This bioinspired design would include a microfabricated cavity filled with an ordered lattice of microspheres with a gradient periodicity from the surface to the interior. Such a "photonic cavity" could provide an opportunity for multiple scattering at wavelength tuned to 8-12 microm as a range of highest sensitivity.

Animals↗
PubMed1998

Reconstruction and display of curvilinear objects from optical section data using 3-D curve fitting algorithms.

Biological objects resembling filaments are often highly elongated while presenting a small cross-sectional area. Examination of such objects requires acquisition of images from regions large enough to contain entire objects, but at sufficiently high resolution to resolve individual filaments. These requirements complicate the application of conventional optical sectioning and volume reconstruction techniques. For example, objective lenses used to acquire images of entire filaments or filament networks may lack sufficient depth (Z) resolution to localize filament cross-sections along the optical axis. Because volume reconstruction techniques consider only the information represented by a single volume element (voxel), views of filament networks reconstructed from images obtained at low Z-resolution will not accurately represent filament morphology. A possible solution to these problems is to simultaneously utilize all available information on the path of an object by fitting 3-D curves through data points localized in 2-D images. Here, we present an application of this approach to the reconstruction of microtubule networks from 2-D optical sections obtained using confocal microscopy, and to synthesized curves which have been distorted using a simple mathematical model of optical sectioning artefacts. Our results demonstrate that this strategy can produce high resolution 3-D views of filamentous objects from a small number of optical sections.

Algorithms↗
PubMed2003

Non-muscle cofilin is a component of tubulobulbar complexes in the testis.

Tubulobulbar complexes are finger-like structures that form at the interface between maturing spermatids and Sertoli cells prior to sperm release and at the interface between two Sertoli cells near the base of the seminiferous epithelium. They originate in areas previously occupied by actin filament-associated intercellular adhesion plaques known as ectoplasmic specializations. Actin filaments also are associated with tubulobulbar complexes where they appear to form a network, rather than the tightly packed bundles found in ectoplasmic specializations. Cofilin, a calcium-independent actin-depolymerizing protein, previously has been identified in the testis, but has not been localized to specific structures in the seminiferous epithelium. To determine if cofilin is found in Sertoli cells and is concentrated at actin-rich structures, we reacted fixed frozen sections of rat testis, fixed fragmented tissue, and blots of seminiferous epithelium with pan-specific and non-muscle cofilin antibodies. In addition, GeneChip microarrays (Affymetrix, Santa Clara, CA) were utilized to determine the abundance of mRNA for all cofilin isoforms in Sertoli cells. Using the monoclonal pan-specific cofilin antibody, we found specific labeling exclusively at tubulobulbar complexes and not at ectoplasmic specializations. On one-dimensional (1D) Western blots this antibody reacted monospecifically with one band, and on 2D blots reacted with two dots, which we interpret as phosphorylated and nonphosphorylated forms of a single cofilin isotype. Messenger RNA for non-muscle cofilin in Sertoli cells is about 8.5-fold higher than for muscle-type cofilin. To confirm that the non-muscle isoform of cofilin is present at tubulobulbar complexes, we used antibodies specific to non-muscle cofilin for immunofluorescent localization. As with the pan-specific antibody, we found that the non-muscle cofilin antibody exclusively labeled tubulobulbar complexes. Results presented here indicate that non-muscle cofilin is concentrated at tubulobulbar complexes. Our results also indicate that cofilin is not concentrated at ectoplasmic specializations.

Actin Cytoskeleton↗
PubMed2002

Epidemics due to imported syphilis in Finland.

BACKGROUND: Russia and other states of the former Soviet Union experienced a huge increase in syphilis beginning in the early 1990s. At first these epidemics were not well known in neighboring countries such as Finland. STUDY DESIGN: In 1995 the incidence of syphilis in Finland doubled to 3.3/100,000 and a local cluster of 18 cases was detected in the city of Tampere. The reasons for this epidemic were analyzed and the occurrence of syphilis was carefully monitored up to 2001. RESULTS: The main reason for the increased incidence in Finland was the import of syphilis from Russia; only a few cases were acquired from Estonia or elsewhere. The source partners of Finnish men who contracted syphilis abroad were mostly sex workers or other casual partners. Mobile prostitution to Finland was not involved in the transmission. Most syphilis cases were found sporadically in southern Finland, in areas where foreign travel is frequent. Secondary transmission in Finland was usually limited to one or two partners. The only isolated cluster was further away and developed due to unawareness of the risk of syphilis by the cases and local healthcare providers. From 1995 onward, syphilis was carefully monitored by national reporting and a special sexually transmitted disease (STD) surveillance network, and the incidence remained at a constant level even though travel to and from Russia more than tripled. Nationwide serologic surveillance in STD and maternity clinics and among blood donors showed no major changes in the prevalence of syphilis. CONCLUSION: An epidemic of syphilis imported mainly by heterosexual men from Russia caused one sporadic cluster in Finland in 1995. Thereafter, general awareness by the public and healthcare providers about the risks of contracting syphilis from abroad, in addition to effective use of national surveillance and notification systems, was needed to protect the country from further spread of syphilis to an endemic infection.

Adult↗
PubMed2003

Auditory comprehension of language in young children: neural networks identified with fMRI.

OBJECTIVE: The organization of neuronal systems that process language in young children is poorly understood. The authors used fMRI to identify brain regions underlying auditory comprehension in healthy young children. METHODS: Fifteen right-handed children (mean age 6.8 years) underwent fMRI at 1.5-T using blood oxygen level dependent echoplanar imaging. They listened to stories with a reverse speech control condition. Group data were analyzed with statistical parametric mapping. Individual subject data were analyzed with a region of interest approach based on t-maps. An asymmetry index (AI = [(L-R)/(L+R)]) was calculated for each region. RESULTS: Group analysis showed significant activation in the left middle temporal gyrus (Brodmann area [BA] 21) and left superior temporal gyrus (BA 22) along the superior temporal sulcus extending back to the angular gyrus (BA 39). Individual maps showed lateralized activation in temporal regions (AI > 0.49 +/- 0.39). There was minimal activation in the frontal lobe. There were no significant correlations between age and regional AI. CONCLUSION: Networks for auditory language processing are regionally localized and lateralized by age 5. These data may provide a means to interpret language fMRI studies performed in preparation for brain surgery, and may be employed to investigate the effect of chronic disease states, such as epilepsy, on language organization during critical periods for plasticity.

Auditory Pathways↗
PubMed1992

Normal anatomy and neurophysiology of the hippocampal formation.

This article reviews the anatomy and neurophysiology of the normal hippocampal formation, with emphasis on the human hippocampus. The hippocampus receives inputs from numerous limbic, cortical, and subcortical areas, primarily via the entorhinal cortex and subiculum. The primary pathway of neural activity entering the hippocampus is from entorhinal cortex via the perforant path to the dentate granule cells, with collaterals to CA1 and CA3 pyramidal cells. Mossy fibers from granule cells excite CA3 pyramidal cells and hilar interneurons. CA3 pyramidal cells excite CA1 pyramidal cells, with local and commissural excitatory collaterals exciting other CA3 pyramidal cells and septum. CA1 pyramidal cells send efferent fibers to subiculum, entorhinal cortex, and several subcortical areas. The principal excitatory synapses are glutamatergic, with two important postsynaptic receptor types, alpha-amino-3-hydroxy-5-methyl-isoxazolepropionic acid and N-methyl-D-aspartate. The primary inhibitory transmitter is gamma-aminobutyric acid (GABA), with two postsynaptic receptor types, GABAA and GABAB. A number of modulatory transmitters and neuropeptides are also present. Inhibitory local synaptic networks in the hippocampus are described. Membrane ion channels in hippocampal neurons, particularly Ca2+ channels and K+ channels, are responsible for the regulation and patterning of neural activity. Long-term potentiation and axon sprouting are two experimental paradigms of neural plasticity presumably involved in hippocampal memory function.

Animals↗
PubMed2003

Impact of hypoosmotic challenges on spongy architecture of the cytoplasm of the giant marine alga Valonia utricularis.

The ultrastructure of the several micrometers thick cytoplasmic layer of the giant marine alga Valonia utricularis displays characteristics which are apparently linked with the capability of this alga to regulate turgor pressure. Transmission and scanning electron microscopy of cells prefixed in different ways, including a protocol that allows prefixation of the alga in a turgescent state, revealed a highly dendritic network of cytoplasmic strands connecting and enveloping the chloroplasts and the nuclei. Innumerable vacuolar entities are embedded in the network, giving the cytoplasm a spongy appearance. Vacuolar perfusion of turgor-pressure-clamped cells with prefixation solution containing tannic acid presented evidence that these vacuolar entities together with the huge central vacuole form a large unstirred continuum. In contrast to the tonoplast, the plasmalemma followed smoothly the lining of the cell wall, even at the numerous cell wall ingrowths. Sucrose, but not polyethylene glycol 6000, induced chloroplast clustering. Acute hypoosmotic treatment (established by reduction of external NaCl or by replacement of part of the external NaCl by equivalent osmotic concentrations of sucrose or polyethylene glycol 6000) resulted in a local relocation of the chloroplasts and cytoplasm towards the central vacuole. This effect did not occur when the relatively low reflection coefficients of these two osmolytes were taken into account. The increase in spacing between the spongy cytoplasm and the plasmalemma by chloroplast relocation (viewed by confocal laser scanning microscopy) was associated with a speckled appearance of the affected surface area under the light microscope. As indicated by electron microscopy, hypoosmotically induced chloroplast relocation resulted from disproportionate swelling of the vacuolar entities located close to the plasmalemma. The cytoskeleton in the cytoplasm and the mucopolysaccharide network in the central vacuole apparently resisted swelling of these compartments. This finding has the important consequence that relevant hydrostatic pressure gradients can be built up throughout the entire multifolded vacuolar space. This gradient could represent the trigger for turgor pressure regulation which is manifested electrically first in the tonoplast.

Chlorophyta↗
PubMed2005

Social capital in settings with a high concentration of road traffic injuries. The case of Cuernavaca, Mexico.

There exists a differential ability within local communities to maintain effective social controls to prevent road traffic injuries (RTIs) in high risks areas. In 2002 we conducted a cross-sectional study in Cuernavaca, Mexico which incorporated 339 adults living in three areas which were characterized by high RTI concentrations. Multivariate analyses demonstrated that even when participants perceived RTIs as a local problem, they expressed no expectations that community members would exert social control through their involvement in local issues and law adherence. The study revealed four key conclusions regarding the association between the low levels of social capital and RTIs: (a) public roads are used solely for transportation, are not viewed as a communal space, and consequently reciprocity is not viewed as a relevant way of controlling behaviors in public places; (b) "strong immediate personal networks" bring about a lack of reciprocity between those sharing the public space which generates uncooperative behavior; (c) high levels of residential instability hinders the identification of common problems; (d) when there exists a low level of civic commitment and a scarcity of social resources directed towards the problem, the possibilities of social control over RTIs are low.

Accidents, Traffic↗