WorldWideScience

Sample records for cell firing patterns

  1. Modeling thalamocortical cell: impact of Ca2+ channel distribution and cell geometry on firing pattern

    Directory of Open Access Journals (Sweden)

    Reza Zomorrodi

    2008-12-01

    Full Text Available The influence of calcium channel distribution and geometry of the thalamocortical cell upon its tonic firing and the low threshold spike (LTS generation was studied in a 3-compartment model, which represents soma, proximal and distal dendrites as well as in multi-compartment model using the morphology of a real reconstructed neuron. Using an uniform distribution of Ca2+ channels, we determined the minimal number of low threshold voltage-activated calcium channels and their permeability required for the onset of LTS in response to a hyperpolarizing current pulse. In the 3-compartment model, we found that the channel distribution influences the firing pattern only in the range of 3% below the threshold value of total T-channel density. In the multi-compartmental model, the LTS could be generated by only 64% of unequally distributed T-channels compared to the minimal number of equally distributed T-channels. For a given channel density and injected current, the tonic firing frequency was found to be inversely proportional to the size of the cell. However, when the Ca2+ channel density was elevated in soma or proximal dendrites, then the amplitude of LTS response and burst spike frequencies were determined by the ratio of total to threshold number of T-channels in the cell for a specific geometry.

  2. Modeling Thalamocortical Cell: Impact of Ca2+ Channel Distribution and Cell Geometry on Firing Pattern

    Science.gov (United States)

    Zomorrodi, Reza; Kröger, Helmut; Timofeev, Igor

    2008-01-01

    The influence of calcium channel distribution and geometry of the thalamocortical cell upon its tonic firing and the low threshold spike (LTS) generation was studied in a 3-compartment model, which represents soma, proximal and distal dendrites as well as in multi-compartment model using the morphology of a real reconstructed neuron. Using an uniform distribution of Ca2+ channels, we determined the minimal number of low threshold voltage-activated calcium channels and their permeability required for the onset of LTS in response to a hyperpolarizing current pulse. In the 3-compartment model, we found that the channel distribution influences the firing pattern only in the range of 3% below the threshold value of total T-channel density. In the multi-compartmental model, the LTS could be generated by only 64% of unequally distributed T-channels compared to the minimal number of equally distributed T-channels. For a given channel density and injected current, the tonic firing frequency was found to be inversely proportional to the size of the cell. However, when the Ca2+ channel density was elevated in soma or proximal dendrites, then the amplitude of LTS response and burst spike frequencies were determined by the ratio of total to threshold number of T-channels in the cell for a specific geometry. PMID:19129908

  3. A Simulation-Based Study of Dorsal Cochlear Nucleus Pyramidal Cell Firing Patterns

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Daliri

    2012-02-01

    Full Text Available A two-variable integrate and fire model is presented to study the role of transient outward potassium currents in producing temporal aspects of dorsal cochlear nucleus (DCN pyramidal cells with different profiles namely the chopper, the pauser and the buildup. This conductance based model is a reduced version of KM-LIF model (Meng & Rinzel, 2010 which captures qualitative firing features of a detailed physiological model (Kanold & Manis, 2000.For our development we benefit from transient potassium currents properties i.e.fast activation and slow inactivation to generate long latency before start of firing.We compare our minimal model outputs in response to a hyperpolarizing stimulus fallowed by a depolarizing one with the data of KM-LIF model.The results conform well to the KM-LIF model with lower complexity.

  4. Kv3 channels modulate calcium signals induced by fast firing patterns in the rat retinal ganglion cells.

    Science.gov (United States)

    Kuznetsov, Kirill I; Grygorov, Oleksii O; Maslov, Vitaly Yu; Veselovsky, Nikolay S; Fedulova, Svetlana A

    2012-11-01

    Expression of non-inactivating Kv3.1/Kv3.2 potassium channels determines fast-spiking phenotype of many types of neurones including retinal ganglion cells (RGCs); furthermore Kv3 channels regulate neurotransmitter release from presynaptic terminals. In the present study we investigated how inhibition of Kv3 channel by low TEA concentrations modifies firing properties and Ca2+ influx in the rat RGCs. Experiments were performed on the whole-mount retinal preparations from 4 to 6 weeks old Wistar rats using simultaneous whole cell patch clamp and intracellular Ca2+ measurements in combination with single-cell RT-PCR. In response to 500-ms depolarization step the RGCs demonstrated fast firing tonic behaviour with a mean frequency of spiking 61±5 Hz (n=28). All of the tonic cells tested (n=9) expressed specific mRNA for either Kv3.1 or Kv3.2 or for both channels. Bath applications of TEA (250 μM, 500 μM and 1 mM) modified firing patterns dose-dependently as follows: firing frequency was decreased, mean action potential (AP) half-width increased and mean amplitude of after hyperpolarization was reduced. The amplitude of the Ca2+ signals induced by the cells firing was linearly dependent on number of APs with a mean slope of 7.3±0.9 nM per one AP (n=8). APs widening by TEA increased the slope of the amplitude vs. AP number plots in a dose-dependent manner: 250 μM of TEA increased the mean slope value to 9.5±1.2 nM/AP, 500 μM to 12.4±2.4 nM/AP and 1 mM to 13.2±2.9 nM/AP (n=6). All these parameters, as well as the cells firing properties, were significantly different from controls and from each other except between 500 μM and 1 mM. This is consistent with the pharmacological properties of Kv3.1/Kv3.2 channels: the TEA IC50 is in the range 150-300 μM with almost complete block at 1 mM. This suggests that Kv3.1/Kv3.2 channels underlie the fast firing of the rat RGCs and provide at a given firing frequency 1.8-fold restriction Ca2+ influx, thus protecting the cells

  5. A hydroclimatic model of global fire patterns

    Science.gov (United States)

    Boer, Matthias

    2015-04-01

    Satellite-based earth observation is providing an increasingly accurate picture of global fire patterns. The highest fire activity is observed in seasonally dry (sub-)tropical environments of South America, Africa and Australia, but fires occur with varying frequency, intensity and seasonality in almost all biomes on Earth. The particular combination of these fire characteristics, or fire regime, is known to emerge from the combined influences of climate, vegetation, terrain and land use, but has so far proven difficult to reproduce by global models. Uncertainty about the biophysical drivers and constraints that underlie current global fire patterns is propagated in model predictions of how ecosystems, fire regimes and biogeochemical cycles may respond to projected future climates. Here, I present a hydroclimatic model of global fire patterns that predicts the mean annual burned area fraction (F) of 0.25° x 0.25° grid cells as a function of the climatic water balance. Following Bradstock's four-switch model, long-term fire activity levels were assumed to be controlled by fuel productivity rates and the likelihood that the extant fuel is dry enough to burn. The frequency of ignitions and favourable fire weather were assumed to be non-limiting at long time scales. Fundamentally, fuel productivity and fuel dryness are a function of the local water and energy budgets available for the production and desiccation of plant biomass. The climatic water balance summarizes the simultaneous availability of biologically usable energy and water at a site, and may therefore be expected to explain a significant proportion of global variation in F. To capture the effect of the climatic water balance on fire activity I focused on the upper quantiles of F, i.e. the maximum level of fire activity for a given climatic water balance. Analysing GFED4 data for annual burned area together with gridded climate data, I found that nearly 80% of the global variation in the 0.99 quantile of F

  6. Maturation of firing pattern in chick vestibular nucleus neurons.

    Science.gov (United States)

    Shao, M; Hirsch, J C; Peusner, K D

    2006-08-25

    The principal cells of the chick tangential nucleus are vestibular nucleus neurons participating in the vestibuloocular and vestibulocollic reflexes. In birds and mammals, spontaneous and stimulus-evoked firing of action potentials is essential for vestibular nucleus neurons to generate mature vestibular reflex activity. The emergence of spike-firing pattern and the underlying ion channels were studied in morphologically-identified principal cells using whole-cell patch-clamp recordings from brain slices of late-term embryos (embryonic day 16) and hatchling chickens (hatching day 1 and hatching day 5). Spontaneous spike activity emerged around the perinatal period, since at embryonic day 16 none of the principal cells generated spontaneous action potentials. However, at hatching day 1, 50% of the cells fired spontaneously (range, 3 to 32 spikes/s), which depended on synaptic transmission in most cells. By hatching day 5, 80% of the principal cells could fire action potentials spontaneously (range, 5 to 80 spikes/s), and this activity was independent of synaptic transmission and showed faster kinetics than at hatching day 1. Repetitive firing in response to depolarizing pulses appeared in the principal cells starting around embryonic day 16, when calcium-dependent potassium current modulated both the spontaneous and evoked spike firing activity. Altogether, these in vitro studies showed that during the perinatal period, the principal cells switched from displaying no spontaneous spike activity at resting membrane potential and generating one spike on depolarization to the tonic firing of spontaneous and evoked action potentials.

  7. T-type and L-type Ca2+ conductances define and encode the bimodal firing pattern of vestibulocerebellar unipolar brush cells.

    Science.gov (United States)

    Diana, Marco A; Otsu, Yo; Maton, Gilliane; Collin, Thibault; Chat, Mireille; Dieudonné, Stéphane

    2007-04-04

    Cerebellar unipolar brush cells (UBCs) are glutamatergic interneurons that receive direct input from vestibular afferents in the form of a unique excitatory synapse on their dendritic brush. UBCs constitute independent relay lines for vestibular signals, and their inherent properties most likely determine how vestibular activity is encoded by the cerebellar cortex. We now demonstrate that UBCs are bimodal cells; they can either fire high-frequency bursts of action potentials when stimulated from hyperpolarized potentials or discharge tonically during sustained depolarizations. The two functional states can be triggered by physiological-like activity of the excitatory input and are encoded by distinct Ca2+-signaling systems. By combining complementary strategies, consisting of molecular and electrophysiological analysis and of ultrafast acousto-optical deflector-based two-photon imaging, we unraveled the identity and the subcellular localization of the Ca2+ conductances activating in each mode. Fast inactivating T-type Ca2+ channels produce low-threshold spikes, which trigger the high-frequency bursts and generate powerful Ca2+ transients in the brush and, to a much lesser extent, in the soma. The tonic firing mode is encoded by a signalization system principally composed of L-type channels. Ca2+ influx during tonic firing produces a linear representation of the spike rate of the cell in the form of a widespread and sustained Ca2+ concentration increase and regulates cellular excitability via BK potassium channels. The bimodal firing pattern of UBCs may underlie different coding strategies of the vestibular input by the cerebellum, thus likely increasing the computational power of this structure.

  8. Grid cell firing patterns may arise from feedback interaction between intrinsic rebound spiking and transverse travelling waves with multiple heading angles

    Directory of Open Access Journals (Sweden)

    Michael E Hasselmo

    2014-10-01

    Full Text Available This article presents a model using cellular resonance and rebound properties to model grid cells in medial entorhinal cortex. The model simulates the intrinsic resonance properties of single layer II stellate cells with different frequencies due to the hyperpolarization activated cation current (h current. The stellate cells generate rebound spikes after a delay interval that differs for neurons with different resonance frequency. Stellate cells drive inhibitory interneurons to cause rebound from inhibition in an alternating set of stellate cells that drive interneurons to activate the first set of cells. This allows maintenance of activity with cycle skipping of the spiking of cells that matches recent physiological data on theta cycle skipping. The rebound spiking interacts with subthreshold oscillatory input to stellate cells or interneurons regulated by medial septal input and defined relative to the spatial location coded by neurons. The timing of rebound determines whether the network maintains the activity for the same location or shifts to phases of activity representing a different location. Simulations show that spatial firing patterns similar to grid cells can be generated with a range of different resonance frequencies, indicating how grid cells could be generated with low frequencies present in bats and in mice with knockout of the HCN1 subunit of the h current.

  9. Cross-border firing and injury patterns

    Directory of Open Access Journals (Sweden)

    Nital Gupta

    2016-01-01

    Full Text Available Introduction: Cross-border firing are increasingly being common in the modern era. The injuries resulting from these low intensity conflicts are a source of anxiety among treating physicians and their respective governments. The provisions are required to minimise the suffering of the victims viz. Mode of injuries, mortality patterns, adequacy of treatment at pre-hospital and tertiary care hospital and provisions to decrease morbidity and mortality for the people living in these areas. Materials and Methods: A retrospective study was conducted in GMCH, Jammu who suffered injuries due to cross border firing in the month of October, 2014. 68 patients were reported in the causality wing. All the patients were referred from level 2 trauma centre. There were 51 males and 17 females out of which 5 were children. The cause of injury, involvement of organ system, cause of mortality and morbidity and loopholes in prehospital management were identified. Results: Sharpnel were the most common cause of injury followed by indirect trauma. The common cause of mortality was abdominal and thoracic injuries. There were 4 deaths at hospital 2 of which were brought dead and 2 died during the course of treatment. There were twenty patients with extremity injuries, fourteen with chest trauma, eleven with abdomen including parineal injuries, three with head injuries, eight with ENT injuries, three with eye injuries and nine with splinters in the back out of which two were in the spinal canal. Conclusion: Prehospital stabilisation, early transport, in-transit resuscitation, immediate surgery if required and implementation of triage model and ATLS protocol has been the key to reduce mortality and morbidity.

  10. Dynamics analysis on neural firing patterns by symbolic approach

    Institute of Scientific and Technical Information of China (English)

    Gao Zhi-Ying; Lu Qi-Shao

    2007-01-01

    Neural firing patterns are investigated by using symbolic dynamics. Bifurcation behaviour of the Hindmarsh-Rose (HR) neuronal model is simulated with the external stimuli gradually decreasing, and various firing activities with different topological structures are orderly numbered. Through constructing first-return maps of interspike intervals, all firing patterns are described and identified by symbolic expressions. On the basis of ordering rules of symbolic sequences, the corresponding relation between parameters and firing patterns is established, which will be helpful for encoding neural information. Moreover, using the operation rule of * product, generation mechanisms and intrinsic configurations of periodic patterns can be distinguished in detail. Results show that the symbolic approach is a powerful tool to study neural firing activities. In particular, such a coarse-grained way can be generalized in neural electrophysiological experiments to extract much valuable information from complicated experimental data.

  11. Dynamics, patterns and causes of fires in Northwestern Amazonia.

    Directory of Open Access Journals (Sweden)

    Dolors Armenteras

    Full Text Available According to recent studies, two widespread droughts occurred in the Amazon basin, one during 2005 and one during 2010. The drought increased the prevalence of climate-driven fires over most of the basin. Given the importance of human-atmosphere-vegetation interactions in tropical rainforests, these events have generated concerns over the vulnerability of this area to climate change. This paper focuses on one of the wettest areas of the basin, Northwestern Amazonia, where the interactions between the climate and fires are much weaker and where little is known about the anthropogenic drivers of fires. We have assessed the response of fires to climate over a ten-year period, and analysed the socio-economic and demographic determinants of fire occurrence. The patterns of fires and climate and their linkages in Northwestern Amazonia differ from the enhanced fire response to climate variation observed in the rest of Amazonia. The highest number of recorded fires in Northwestern Amazonia occurred in 2004 and 2007, and this did not coincide with the periods of extreme drought experienced in Amazonia in 2005 and 2010. Rather, during those years, Northwestern Amazonia experienced a relatively small numbers of fire hotspots. We have shown that fire occurrence correlated well with deforestation and was determined by anthropogenic drivers, mainly small-scale agriculture, cattle ranching (i.e., pastures and active agricultural frontiers (including illegal crops. Thus, the particular climatic conditions for air convergence and rainfall created by proximity to the Andes, coupled with the presence of one of the most active colonisation fronts in the region, make this region differently affected by the general drought-induced fire patterns experienced by the rest of the Amazon. Moreover, the results suggest that, even in this wet region, humans are able to modify the frequency of fires and impact these historically well preserved forests.

  12. Dynamics, patterns and causes of fires in Northwestern Amazonia.

    Science.gov (United States)

    Armenteras, Dolors; Retana, Javier

    2012-01-01

    According to recent studies, two widespread droughts occurred in the Amazon basin, one during 2005 and one during 2010. The drought increased the prevalence of climate-driven fires over most of the basin. Given the importance of human-atmosphere-vegetation interactions in tropical rainforests, these events have generated concerns over the vulnerability of this area to climate change. This paper focuses on one of the wettest areas of the basin, Northwestern Amazonia, where the interactions between the climate and fires are much weaker and where little is known about the anthropogenic drivers of fires. We have assessed the response of fires to climate over a ten-year period, and analysed the socio-economic and demographic determinants of fire occurrence. The patterns of fires and climate and their linkages in Northwestern Amazonia differ from the enhanced fire response to climate variation observed in the rest of Amazonia. The highest number of recorded fires in Northwestern Amazonia occurred in 2004 and 2007, and this did not coincide with the periods of extreme drought experienced in Amazonia in 2005 and 2010. Rather, during those years, Northwestern Amazonia experienced a relatively small numbers of fire hotspots. We have shown that fire occurrence correlated well with deforestation and was determined by anthropogenic drivers, mainly small-scale agriculture, cattle ranching (i.e., pastures) and active agricultural frontiers (including illegal crops). Thus, the particular climatic conditions for air convergence and rainfall created by proximity to the Andes, coupled with the presence of one of the most active colonisation fronts in the region, make this region differently affected by the general drought-induced fire patterns experienced by the rest of the Amazon. Moreover, the results suggest that, even in this wet region, humans are able to modify the frequency of fires and impact these historically well preserved forests.

  13. Dynamics, Patterns and Causes of Fires in Northwestern Amazonia

    Science.gov (United States)

    Armenteras, Dolors; Retana, Javier

    2012-01-01

    According to recent studies, two widespread droughts occurred in the Amazon basin, one during 2005 and one during 2010. The drought increased the prevalence of climate-driven fires over most of the basin. Given the importance of human-atmosphere-vegetation interactions in tropical rainforests, these events have generated concerns over the vulnerability of this area to climate change. This paper focuses on one of the wettest areas of the basin, Northwestern Amazonia, where the interactions between the climate and fires are much weaker and where little is known about the anthropogenic drivers of fires. We have assessed the response of fires to climate over a ten-year period, and analysed the socio-economic and demographic determinants of fire occurrence. The patterns of fires and climate and their linkages in Northwestern Amazonia differ from the enhanced fire response to climate variation observed in the rest of Amazonia. The highest number of recorded fires in Northwestern Amazonia occurred in 2004 and 2007, and this did not coincide with the periods of extreme drought experienced in Amazonia in 2005 and 2010. Rather, during those years, Northwestern Amazonia experienced a relatively small numbers of fire hotspots. We have shown that fire occurrence correlated well with deforestation and was determined by anthropogenic drivers, mainly small-scale agriculture, cattle ranching (i.e., pastures) and active agricultural frontiers (including illegal crops). Thus, the particular climatic conditions for air convergence and rainfall created by proximity to the Andes, coupled with the presence of one of the most active colonisation fronts in the region, make this region differently affected by the general drought-induced fire patterns experienced by the rest of the Amazon. Moreover, the results suggest that, even in this wet region, humans are able to modify the frequency of fires and impact these historically well preserved forests. PMID:22523580

  14. Fire Patterns and Drivers of Fires in the West African Tropical Forest

    Science.gov (United States)

    Dwomoh, F. K.; Wimberly, M. C.

    2015-12-01

    The West African tropical forest (referred to as the Upper Guinean forest, UGF), is a global biodiversity hotspot providing vital ecosystem services for the region's socio-economic and environmental wellbeing. It is also one of the most fragmented and human-modified tropical forest ecosystems, with the only remaining large patches of original forests contained in protected areas. However, these remnant forests are susceptible to continued fire-mediated degradation and forest loss due to intense climatic, demographic and land use pressures. We analyzed human and climatic drivers of fire activity in the sub-region to better understand the spatial and temporal patterns of these risks. We utilized MODIS active fire and burned area products to identify fire activity within the sub-region. We measured climatic variability using TRMM rainfall data and derived indicators of human land use from a variety of geospatial datasets. We used a boosted regression trees model to determine the influences of predictor variables on fire activity. Our analyses indicated that the spatial and temporal variability of precipitation is a key driving factor of fire activity in the UGF. Anthropogenic effects on fire activity in the area were evident through the influences of agriculture and low-density populations. These human footprints in the landscape make forests more susceptible to fires through forest fragmentation, degradation, and fire spread from agricultural areas. Forested protected areas within the forest savanna mosaic experienced frequent fires, whereas the more humid forest areas located in the south and south-western portions of the study area had fewer fires as these rainforests tend to offer some buffering against fire encroachment. These results improve characterization of UGF fire regime and expand our understanding of the spatio-temporal dynamics of tropical forest fires in response to human and climatic pressures.

  15. Tonic GABAA conductance bidirectionally controls interneuron firing pattern and synchronization in the CA3 hippocampal network.

    OpenAIRE

    Pavlov, I.; Savtchenko, L P; Song, I.; Koo, J; A. PIMASHKIN; Rusakov, D A; A. SEMYANOV

    2013-01-01

    The spiking output of interneurons is key for rhythm generation in the brain. However, what controls interneuronal firing remains incompletely understood. Here we combine dynamic clamp experiments with neural network simulations to understand how tonic GABAA conductance regulates the firing pattern of CA3 interneurons. In baseline conditions, tonic GABAA depolarizes these cells, thus exerting an excitatory action while also reducing the excitatory postsynaptic potential (EPSP) amplitude throu...

  16. Intrinsic membrane properties determine hippocampal differential firing pattern in vivo in anesthetized rats

    OpenAIRE

    Kowalski, Janina; Gan, Jian; Jonas, Peter; Pernía‐Andrade, Alejandro J.

    2015-01-01

    ABSTRACT The hippocampus plays a key role in learning and memory. Previous studies suggested that the main types of principal neurons, dentate gyrus granule cells (GCs), CA3 pyramidal neurons, and CA1 pyramidal neurons, differ in their activity pattern, with sparse firing in GCs and more frequent firing in CA3 and CA1 pyramidal neurons. It has been assumed but never shown that such different activity may be caused by differential synaptic excitation. To test this hypothesis, we performed high...

  17. Pattern formation and firing synchronization in networks of map neurons

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qingyun [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Duan Zhisheng [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Huang Lin [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Chen Guanrong [Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China); Lu Qishao [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

    2007-10-15

    Patterns and collective phenomena such as firing synchronization are studied in networks of nonhomogeneous oscillatory neurons and mixtures of oscillatory and excitable neurons, with dynamics of each neuron described by a two-dimensional (2D) Rulkov map neuron. It is shown that as the coupling strength is increased, typical patterns emerge spatially, which propagate through the networks in the form of beautiful target waves or parallel ones depending on the size of networks. Furthermore, we investigate the transitions of firing synchronization characterized by the rate of firing when the coupling strength is increased. It is found that there exists an intermediate coupling strength; firing synchronization is minimal simultaneously irrespective of the size of networks. For further increasing the coupling strength, synchronization is enhanced. Since noise is inevitable in real neurons, we also investigate the effects of white noise on firing synchronization for different networks. For the networks of oscillatory neurons, it is shown that firing synchronization decreases when the noise level increases. For the missed networks, firing synchronization is robust under the noise conditions considered in this paper. Results presented in this paper should prove to be valuable for understanding the properties of collective dynamics in real neuronal networks.

  18. Muscular endurance training and motor unit firing patterns during fatigue.

    Science.gov (United States)

    Mettler, Joni A; Griffin, Lisa

    2016-01-01

    With muscular training, the central nervous system may regulate motor unit firing rates to sustain force output and delay fatigue. The aims of this study were to investigate motor unit firing rates and patterns of the adductor pollicis (AdP) muscle in young, able-bodied adults throughout a sustained submaximal isometric fatiguing contraction and postactivation potentiation pre-post 4 weeks of muscular endurance training. Fifteen participants (training group: N = 10; control group: N = 5) performed maximal voluntary contractions (MVCs) and a sustained isometric 20 % MVC fatigue task pre-post training. Single-motor-unit potentials were recorded from the AdP during the fatigue task with intramuscular fine-wire electrodes. Twitch force potentiation was measured during single-pulse electrical stimulation of the ulnar nerve before and after MVCs. The training group endurance trained their AdP muscle at 20 % MVC for 4 weeks. Mean motor unit firing rates were calculated every 5 % of endurance time (ET). ET increased by 45.2 ± 8.7 % (p pattern consisted of an initial slowing followed by an increase in firing rate late in fatigue and remained consistent pre-post training. Potentiation did not change following training. These data suggest that the ability of the neuromuscular system to sustain motor unit firing rate may serve as a mechanism to augment the duration of submaximal muscle performance and delay muscular fatigue.

  19. Tonic GABAA conductance bidirectionally controls interneuron firing pattern and synchronization in the CA3 hippocampal network.

    Science.gov (United States)

    Pavlov, Ivan; Savtchenko, Leonid P; Song, Inseon; Koo, Jaeyeon; Pimashkin, Alexey; Rusakov, Dmitri A; Semyanov, Alexey

    2014-01-07

    The spiking output of interneurons is key for rhythm generation in the brain. However, what controls interneuronal firing remains incompletely understood. Here we combine dynamic clamp experiments with neural network simulations to understand how tonic GABAA conductance regulates the firing pattern of CA3 interneurons. In baseline conditions, tonic GABAA depolarizes these cells, thus exerting an excitatory action while also reducing the excitatory postsynaptic potential (EPSP) amplitude through shunting. As a result, the emergence of weak tonic GABAA conductance transforms the interneuron firing pattern driven by individual EPSPs into a more regular spiking mode determined by the cell intrinsic properties. The increased regularity of spiking parallels stronger synchronization of the local network. With further increases in tonic GABAA conductance the shunting inhibition starts to dominate over excitatory actions and thus moderates interneuronal firing. The remaining spikes tend to follow the timing of suprathreshold EPSPs and thus become less regular again. The latter parallels a weakening in network synchronization. Thus, our observations suggest that tonic GABAA conductance can bidirectionally control brain rhythms through changes in the excitability of interneurons and in the temporal structure of their firing patterns.

  20. Spatial patterns of large natural fires in Sierra Nevada wilderness areas

    Science.gov (United States)

    Collins, B.M.; Kelly, M.; van Wagtendonk, J.W.; Stephens, S.L.

    2007-01-01

    The effects of fire on vegetation vary based on the properties and amount of existing biomass (or fuel) in a forest stand, weather conditions, and topography. Identifying controls over the spatial patterning of fire-induced vegetation change, or fire severity, is critical in understanding fire as a landscape scale process. We use gridded estimates of fire severity, derived from Landsat ETM+ imagery, to identify the biotic and abiotic factors contributing to the observed spatial patterns of fire severity in two large natural fires. Regression tree analysis indicates the importance of weather, topography, and vegetation variables in explaining fire severity patterns between the two fires. Relative humidity explained the highest proportion of total sum of squares throughout the Hoover fire (Yosemite National Park, 2001). The lowest fire severity corresponded with increased relative humidity. For the Williams fire (Sequoia/Kings Canyon National Parks, 2003) dominant vegetation type explains the highest proportion of sum of squares. Dominant vegetation was also important in determining fire severity throughout the Hoover fire. In both fires, forest stands that were dominated by lodgepole pine (Pinus contorta) burned at highest severity, while red fir (Abies magnifica) stands corresponded with the lowest fire severities. There was evidence in both fires that lower wind speed corresponded with higher fire severity, although the highest fire severity in the Williams fire occurred during increased wind speed. Additionally, in the vegetation types that were associated with lower severity, burn severity was lowest when the time since last fire was fewer than 11 and 17 years for the Williams and Hoover fires, respectively. Based on the factors and patterns identified, managers can anticipate the effects of management ignited and naturally ignited fires at the forest stand and the landscape levels. ?? 2007 Springer Science+Business Media, Inc.

  1. Responses from two firing patterns in inferior colliculus neurons to stimulation of the lateral lemniscus dorsal nucleus

    Science.gov (United States)

    Li, Xiao-ting; Wang, Ning-yu; Wang, Yan-jun; Xu, Zhi-qing; Liu, Jin-feng; Bai, Yun-fei; Dai, Jin-sheng; Zhao, Jing-yi

    2016-01-01

    The γ-aminobutyric acid neurons (GABAergic neurons) in the inferior colliculus are classified into various patterns based on their intrinsic electrical properties to a constant current injection. Although this classification is associated with physiological function, the exact role for neurons with various firing patterns in acoustic processing remains poorly understood. In the present study, we analyzed characteristics of inferior colliculus neurons in vitro, and recorded responses to stimulation of the dorsal nucleus of the lateral lemniscus using the whole-cell patch clamp technique. Seven inferior colliculus neurons were tested and were classified into two firing patterns: sustained-regular (n = 4) and sustained-adapting firing patterns (n = 3). The majority of inferior colliculus neurons exhibited slight changes in response to stimulation and bicuculline. The responses of one neuron with a sustained-adapting firing pattern were suppressed after stimulation, but recovered to normal levels following application of the γ-aminobutyric acid receptor antagonist. One neuron with a sustained-regular pattern showed suppressed stimulation responses, which were not affected by bicuculline. Results suggest that GABAergic neurons in the inferior colliculus exhibit sustained-regular or sustained-adapting firing patterns. Additionally, GABAergic projections from the dorsal nucleus of the lateral lemniscus to the inferior colliculus are associated with sound localization. The different neuronal responses of various firing patterns suggest a role in sound localization. A better understanding of these mechanisms and functions will provide better clinical treatment paradigms for hearing deficiencies. PMID:27335563

  2. Responses from two firing patterns in inferior colliculus neurons to stimulation of the lateral lemniscus dorsal nucleus

    Directory of Open Access Journals (Sweden)

    Xiao-ting Li

    2016-01-01

    Full Text Available The γ-aminobutyric acid neurons (GABAergic neurons in the inferior colliculus are classified into various patterns based on their intrinsic electrical properties to a constant current injection. Although this classification is associated with physiological function, the exact role for neurons with various firing patterns in acoustic processing remains poorly understood. In the present study, we analyzed characteristics of inferior colliculus neurons in vitro, and recorded responses to stimulation of the dorsal nucleus of the lateral lemniscus using the whole-cell patch clamp technique. Seven inferior colliculus neurons were tested and were classified into two firing patterns: sustained-regular (n = 4 and sustained-adapting firing patterns (n = 3. The majority of inferior colliculus neurons exhibited slight changes in response to stimulation and bicuculline. The responses of one neuron with a sustained-adapting firing pattern were suppressed after stimulation, but recovered to normal levels following application of the γ-aminobutyric acid receptor antagonist. One neuron with a sustained-regular pattern showed suppressed stimulation responses, which were not affected by bicuculline. Results suggest that GABAergic neurons in the inferior colliculus exhibit sustained-regular or sustained-adapting firing patterns. Additionally, GABAergic projections from the dorsal nucleus of the lateral lemniscus to the inferior colliculus are associated with sound localization. The different neuronal responses of various firing patterns suggest a role in sound localization. A better understanding of these mechanisms and functions will provide better clinical treatment paradigms for hearing deficiencies.

  3. Intrinsic membrane properties determine hippocampal differential firing pattern in vivo in anesthetized rats.

    Science.gov (United States)

    Kowalski, Janina; Gan, Jian; Jonas, Peter; Pernía-Andrade, Alejandro J

    2016-05-01

    The hippocampus plays a key role in learning and memory. Previous studies suggested that the main types of principal neurons, dentate gyrus granule cells (GCs), CA3 pyramidal neurons, and CA1 pyramidal neurons, differ in their activity pattern, with sparse firing in GCs and more frequent firing in CA3 and CA1 pyramidal neurons. It has been assumed but never shown that such different activity may be caused by differential synaptic excitation. To test this hypothesis, we performed high-resolution whole-cell patch-clamp recordings in anesthetized rats in vivo. In contrast to previous in vitro data, both CA3 and CA1 pyramidal neurons fired action potentials spontaneously, with a frequency of ∼3-6 Hz, whereas GCs were silent. Furthermore, both CA3 and CA1 cells primarily fired in bursts. To determine the underlying mechanisms, we quantitatively assessed the frequency of spontaneous excitatory synaptic input, the passive membrane properties, and the active membrane characteristics. Surprisingly, GCs showed comparable synaptic excitation to CA3 and CA1 cells and the highest ratio of excitation versus hyperpolarizing inhibition. Thus, differential synaptic excitation is not responsible for differences in firing. Moreover, the three types of hippocampal neurons markedly differed in their passive properties. While GCs showed the most negative membrane potential, CA3 pyramidal neurons had the highest input resistance and the slowest membrane time constant. The three types of neurons also differed in the active membrane characteristics. GCs showed the highest action potential threshold, but displayed the largest gain of the input-output curves. In conclusion, our results reveal that differential firing of the three main types of hippocampal principal neurons in vivo is not primarily caused by differences in the characteristics of the synaptic input, but by the distinct properties of synaptic integration and input-output transformation.

  4. Normalized burn ratios link fire severity with patterns of avian occurrence

    Science.gov (United States)

    Rose, Eli T.; Simons, Theodore R.; Klein, Rob; McKerrow, Alexa

    2016-01-01

    ContextRemotely sensed differenced normalized burn ratios (DNBR) provide an index of fire severity across the footprint of a fire. We asked whether this index was useful for explaining patterns of bird occurrence within fire adapted xeric pine-oak forests of the southern Appalachian Mountains.ObjectivesWe evaluated the use of DNBR indices for linking ecosystem process with patterns of bird occurrence. We compared field-based and remotely sensed fire severity indices and used each to develop occupancy models for six bird species to identify patterns of bird occurrence following fire.MethodsWe identified and sampled 228 points within fires that recently burned within Great Smoky Mountains National Park. We performed avian point counts and field-assessed fire severity at each bird census point. We also used Landsat™ imagery acquired before and after each fire to quantify fire severity using DNBR. We used non-parametric methods to quantify agreement between fire severity indices, and evaluated single season occupancy models incorporating fire severity summarized at different spatial scales.ResultsAgreement between field-derived and remotely sensed measures of fire severity was influenced by vegetation type. Although occurrence models using field-derived indices of fire severity outperformed those using DNBR, summarizing DNBR at multiple spatial scales provided additional insights into patterns of occurrence associated with different sized patches of high severity fire.ConclusionsDNBR is useful for linking the effects of fire severity to patterns of bird occurrence, and informing how high severity fire shapes patterns of bird species occurrence on the landscape.

  5. Identification of neural firing patterns, frequency and temporal coding mechanisms in individual aortic baroreceptors

    Directory of Open Access Journals (Sweden)

    Huaguang eGu

    2015-08-01

    Full Text Available In rabbit depressor nerve fibers, an on-off firing pattern, period-1 firing, and integer multiple firing with quiescent state were observed as the static pressure level was increased. A bursting pattern with bursts at the systolic phase of blood pressure, continuous firing, and bursting with burst at diastolic phase and quiescent state at systolic phase were observed as the mean level of the dynamic blood pressure was increased. For both static and dynamic pressures, the firing frequency of the first two firing patterns increased and of the last firing pattern decreased due to the quiescent state. If the quiescent state is disregarded, the spike frequency becomes an increasing trend. The instantaneous spike frequency of the systolic phase bursting, continuous firing, and diastolic phase bursting can reflect the temporal process of the systolic phase, whole procedure, and diastolic phase of the dynamic blood pressure signal, respectively. With increasing the static current corresponding to pressure level, the deterministic Hodgkin-Huxley (HH model manifests a process from a resting state first to period-1 firing via a subcritical Hopf bifurcation and then to a resting state via a supercritical Hopf bifurcation, and the firing frequency increases. The on-off firing and integer multiple firing were here identified as noise-induced firing patterns near the subcritical and supercritical Hopf bifurcation points, respectively, using the stochastic HH model. The systolic phase bursting and diastolic phase bursting were identified as pressure-induced firings near the subcritical and supercritical Hopf bifurcation points, respectively, using an HH model with a dynamic signal. The firing, spike frequency, and instantaneous spike frequency observed in the experiment were simulated and explained using HH models. The results illustrate the dynamics of different firing patterns and the frequency and temporal coding mechanisms of aortic baroreceptor.

  6. Global fire activity patterns (1996-2006) and climatic influence: an analysis using the World Fire Atlas

    Science.gov (United States)

    Le Page, Y.; Pereira, J. M. C.; Trigo, R.; da Camara, C.; Oom, D.; Mota, B.

    2008-04-01

    Vegetation fires have been acknowledged as an environmental process of global scale, which affects the chemical composition of the troposphere, and has profound ecological and climatic impacts. However, considerable uncertainty remains, especially concerning intra and inter-annual variability of fire incidence. The main goals of our global-scale study were to characterise spatial-temporal patterns of fire activity, to identify broad geographical areas with similar vegetation fire dynamics, and to analyse the relationship between fire activity and the El Niño-Southern Oscillation. This study relies on 10 years (mid 1996-mid 2006) of screened European Space Agency World Fire Atlas (WFA) data, obtained from Along Track Scanning Radiometer (ATSR) and Advanced ATSR (AATSR) imagery. Empirical Orthogonal Function analysis was used to reduce the dimensionality of the dataset. Regions of homogeneous fire dynamics were identified with cluster analysis, and interpreted based on their eco-climatic characteristics. The impact of 1997-1998 El Niño is clearly dominant over the study period, causing increased fire activity in a variety of regions and ecosystems, with variable timing. Overall, this study provides the first global decadal assessment of spatial-temporal fire variability and confirms the usefulness of the screened WFA for global fire ecoclimatology research.

  7. Somatostatinergic modulation of firing pattern and calcium-activated potassium currents in medium spiny neostriatal neurons.

    Science.gov (United States)

    Galarraga, E; Vilchis, C; Tkatch, T; Salgado, H; Tecuapetla, F; Perez-Rosello, T; Perez-Garci, E; Hernandez-Echeagaray, E; Surmeier, D J; Bargas, J

    2007-05-11

    Somatostatin is synthesized and released by aspiny GABAergic interneurons of the neostriatum, some of them identified as low threshold spike generating neurons (LTS-interneurons). These neurons make synaptic contacts with spiny neostriatal projection neurons. However, very few somatostatin actions on projection neurons have been described. The present work reports that somatostatin modulates the Ca(2+) activated K(+) currents (K(Ca) currents) expressed by projection cells. These actions contribute in designing the firing pattern of the spiny projection neuron; which is the output of the neostriatum. Small conductance (SK) and large conductance (BK) K(Ca) currents represent between 30% and 50% of the sustained outward current in spiny cells. Somatostatin reduces SK-type K(+) currents and at the same time enhances BK-type K(+) currents. This dual effect enhances the fast component of the after hyperpolarizing potential while reducing the slow component. Somatostatin then modifies the firing pattern of spiny neurons which changed from a tonic regular pattern to an interrupted "stuttering"-like pattern. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) tissue expression analysis of dorsal striatal somatostatinergic receptors (SSTR) mRNA revealed that all five SSTR mRNAs are present. However, single cell RT-PCR profiling suggests that the most probable receptor in charge of this modulation is the SSTR2 receptor. Interestingly, aspiny interneurons may exhibit a "stuttering"-like firing pattern. Therefore, somatostatin actions appear to be the entrainment of projection neurons to the rhythms generated by some interneurons. Somatostatin is then capable of modifying the processing and output of the neostriatum.

  8. Post-fire vegetation and fuel development influences fire severity patterns in reburns.

    Science.gov (United States)

    Coppoletta, Michelle; Merriam, Kyle E; Collins, Brandon M

    2016-04-01

    In areas where fire regimes and forest structure have been dramatically altered, there is increasing concern that contemporary fires have the potential to set forests on a positive feedback trajectory with successive reburns, one in which extensive stand-replacing fire could promote more stand-replacing fire. Our study utilized an extensive set of field plots established following four fires that occurred between 2000 and 2010 in the northern Sierra Nevada, California, USA that were subsequently reburned in 2012. The information obtained from these field plots allowed for a unique set of analyses investigating the effect of vegetation, fuels, topography, fire weather, and forest management on reburn severity. We also examined the influence of initial fire severity and time since initial fire on influential predictors of reburn severity. Our results suggest that high- to moderate-severity fire in the initial fires led to an increase in standing snags and shrub vegetation, which in combination with severe fire weather promoted high-severity fire effects in the subsequent reburn. Although fire behavior is largely driven by weather, our study demonstrates that post-fire vegetation composition and structure are also important drivers of reburn severity. In the face of changing climatic regimes and increases in extreme fire weather, these results may provide managers with options to create more fire-resilient ecosystems. In areas where frequent high-severity fire is undesirable, management activities such as thinning, prescribed fire, or managed wildland fire can be used to moderate fire behavior not only prior to initial fires, but also before subsequent reburns.

  9. Enduring Effects of Early Life Stress on Firing Patterns of Hippocampal and Thalamocortical Neurons in Rats: Implications for Limbic Epilepsy.

    Directory of Open Access Journals (Sweden)

    Idrish Ali

    Full Text Available Early life stress results in an enduring vulnerability to kindling-induced epileptogenesis in rats, but the underlying mechanisms are not well understood. Recent studies indicate the involvement of thalamocortical neuronal circuits in the progression of kindling epileptogenesis. Therefore, we sought to determine in vivo the effects of early life stress and amygdala kindling on the firing pattern of hippocampus as well as thalamic and cortical neurons. Eight week old male Wistar rats, previously exposed to maternal separation (MS early life stress or early handling (EH, underwent amygdala kindling (or sham kindling. Once fully kindled, in vivo juxtacellular recordings in hippocampal, thalamic and cortical regions were performed under neuroleptic analgesia. In the thalamic reticular nucleus cells both kindling and MS independently lowered firing frequency and enhanced burst firing. Further, burst firing in the thalamic reticular nucleus was significantly increased in kindled MS rats compared to kindled EH rats (p<0.05. In addition, MS enhanced burst firing of hippocampal pyramidal neurons. Following a stimulation-induced seizure, somatosensory cortical neurons exhibited a more pronounced increase in burst firing in MS rats than in EH rats. These data demonstrate changes in firing patterns in thalamocortical and hippocampal regions resulting from both MS and amygdala kindling, which may reflect cellular changes underlying the enhanced vulnerability to kindling in rats that have been exposed to early life stress.

  10. Phasic firing in vasopressin cells: understanding its functional significance through computational models.

    Directory of Open Access Journals (Sweden)

    Duncan J MacGregor

    Full Text Available Vasopressin neurons, responding to input generated by osmotic pressure, use an intrinsic mechanism to shift from slow irregular firing to a distinct phasic pattern, consisting of long bursts and silences lasting tens of seconds. With increased input, bursts lengthen, eventually shifting to continuous firing. The phasic activity remains asynchronous across the cells and is not reflected in the population output signal. Here we have used a computational vasopressin neuron model to investigate the functional significance of the phasic firing pattern. We generated a concise model of the synaptic input driven spike firing mechanism that gives a close quantitative match to vasopressin neuron spike activity recorded in vivo, tested against endogenous activity and experimental interventions. The integrate-and-fire based model provides a simple physiological explanation of the phasic firing mechanism involving an activity-dependent slow depolarising afterpotential (DAP generated by a calcium-inactivated potassium leak current. This is modulated by the slower, opposing, action of activity-dependent dendritic dynorphin release, which inactivates the DAP, the opposing effects generating successive periods of bursting and silence. Model cells are not spontaneously active, but fire when perturbed by random perturbations mimicking synaptic input. We constructed one population of such phasic neurons, and another population of similar cells but which lacked the ability to fire phasically. We then studied how these two populations differed in the way that they encoded changes in afferent inputs. By comparison with the non-phasic population, the phasic population responds linearly to increases in tonic synaptic input. Non-phasic cells respond to transient elevations in synaptic input in a way that strongly depends on background activity levels, phasic cells in a way that is independent of background levels, and show a similar strong linearization of the response

  11. GluA1 Phosphorylation Alters Evoked Firing Pattern In Vivo

    Directory of Open Access Journals (Sweden)

    Balázs Barkóczi

    2012-01-01

    Full Text Available AMPA and NMDA receptors convey fast synaptic transmission in the CNS. Their relative contribution to synaptic output and phosphorylation state regulate synaptic plasticity. The AMPA receptor subunit GluA1 is central in synaptic plasticity. Phosphorylation of GluA1 regulates channel properties and trafficking. The firing rate averaged over several hundred ms is used to monitor cellular input. However, plasticity requires the timing of spiking within a few ms; therefore, it is important to understand how phosphorylation governs these events. Here, we investigate whether the GluA1 phosphorylation (p-GluA1 alters the spiking patterns of CA1 cells in vivo. The antidepressant Tianeptine was used for inducing p-GluA1, which resulted in enhanced AMPA-evoked spiking. By comparing the spiking patterns of AMPA-evoked activity with matched firing rates, we show that the spike-trains after Tianeptine application show characteristic features, distinguishing from spike-trains triggered by strong AMPA stimulation. The interspike-interval distributions are different between the two groups, suggesting that neuronal output may differ when new inputs are activated compared to increasing the gain of previously activated receptors. Furthermore, we also show that NMDA evokes spiking with different patterns to AMPA spike-trains. These results support the role of the modulation of NMDAR/AMPAR ratio and p-GluA1 in plasticity and temporal coding.

  12. Relationships between dendritic morphology, spatial distribution and firing patterns in rat layer 1 neurons

    Directory of Open Access Journals (Sweden)

    D.V.V. Santos

    2012-12-01

    Full Text Available The cortical layer 1 contains mainly small interneurons, which have traditionally been classified according to their axonal morphology. The dendritic morphology of these cells, however, has received little attention and remains ill defined. Very little is known about how the dendritic morphology and spatial distribution of these cells may relate to functional neuronal properties. We used biocytin labeling and whole cell patch clamp recordings, associated with digital reconstruction and quantitative morphological analysis, to assess correlations between dendritic morphology, spatial distribution and membrane properties of rat layer 1 neurons. A total of 106 cells were recorded, labeled and subjected to morphological analysis. Based on the quantitative patterns of their dendritic arbor, cells were divided into four major morphotypes: horizontal, radial, ascendant, and descendant cells. Descendant cells exhibited a highly distinct spatial distribution in relation to other morphotypes, suggesting that they may have a distinct function in these cortical circuits. A significant difference was also found in the distribution of firing patterns between each morphotype and between the neuronal populations of each sublayer. Passive membrane properties were, however, statistically homogeneous among all subgroups. We speculate that the differences observed in active membrane properties might be related to differences in the synaptic input of specific types of afferent fibers and to differences in the computational roles of each morphotype in layer 1 circuits. Our findings provide new insights into dendritic morphology and neuronal spatial distribution in layer 1 circuits, indicating that variations in these properties may be correlated with distinct physiological functions.

  13. Firing Patterns and Transitions in Coupled Neurons Controlled by a Pacemaker

    Institute of Scientific and Technical Information of China (English)

    LI Mei-Sheng; LU Qi-Shao; DUAN Li-Xia; WANG Qing-Yun

    2008-01-01

    @@ To reveal the dynamics of neuronal networks with pacemakers, the firing patterns and their transitions are investigated in a ring HR neuronal network with gap junctions under the control of a pacemaker. Compared with the situation without pacemaker, the neurons in the network can exhibit various firing patterns as the external current is applied or the coupling strength of pacemaker varies. The results are beneficial for understanding the complex cooperative behaviour of large neural assemblies with pacemaker control.

  14. Tree mortality patterns following prescribed fire for Pinus and Abies across the southwestern United States

    Science.gov (United States)

    van Mantgem, Philip J.; Nesmith, Jonathan C. B.; Keifer, MaryBeth; Brooks, Matthew

    2012-01-01

    The reintroduction of fire to historically fire-prone forests has been repeatedly shown to reduce understory fuels and promote resistance to high severity fire. However, there is concern that prescribed fire may also have unintended consequences, such as high rates of mortality for large trees and fire-tolerant Pinus species. To test this possibility we evaluated mortality patterns for two common genera in the western US, Pinus and Abies, using observations from a national-scale prescribed fire effects monitoring program. Our results show that mortality rates of trees >50 DBH were similar for Pinus (4.6% yr-1) and Abies (4.0% yr-1) 5 years following prescribed fires across seven sites in the southwestern US. In contrast, mortality rates of trees >50 cm DBH differed between Pinus (5.7% yr-1) and Abies (9.0% yr-1). Models of post-fire mortality probabilities suggested statistically significant differences between the genera (after including differences in bark thickness), but accounting for these differences resulted in only small improvements in model classification. Our results do not suggest unusually high post-fire mortality for large trees or for Pinus relative to the other common co-occurring genus, Abies, following prescribed fire in the southwestern US.

  15. Rainfall patterns after fire differentially affect the recruitment of three Mediterranean shrubs

    Science.gov (United States)

    Moreno, J. M.; Zuazua, E.; Pérez, B.; Luna, B.; Velasco, A.; Resco de Dios, V.

    2011-12-01

    In fire-prone environments, the "event-dependent hypothesis" states that plant population changes are driven by the unique set of conditions of a fire (e.g. fire season, climate). Climate variability, in particular changes in rainfall patterns, can be most important for seeder species, since they regenerate after fire from seeds, and for Mediterranean shrublands, given the high yearly variability of rainfall in these ecosystems. Yet, the role of rainfall variability and its interaction with fire characteristics (e.g. fire season) on plant populations has received little attention. Here we investigated the changes in seedling emergence and recruitment of three seeder species (Cistus ladanifer, Erica umbellata and Rosmarinus officinalis) after fires lit during three different years and at two times (early and late) during the fire season. Three plots were burned at each season, for a total of 18 plots burned during the three years. After fire, emerged seedlings were tallied, tagged and monitored during three years (two in the last burning year). Rainfall during the study period was rather variable and, in some years, it was well below average. Postfire seedling emergence varied by a factor of 3 to 12, depending on the species and on the burning year. The bulk of seedling emergence occurred during the first year after fire; seedling recruitment at the end of the study period was tightly correlated with this early emergence. Emergence in Erica and Rosmarinus, but not in Cistus, was correlated with precipitation in the fall and winter immediately after fire, with Erica being the most sensitive to reduced rainfall. Fire season was generally neither an important factor in controlling emergence nor, in particular, recruitment. We discuss how projected changes in rainfall patterns with global warming could alter the balance of species in this shrubland, and could drive some species to near local extinction.

  16. Grazers, browsers, and fire influence the extent and spatial pattern of tree cover in the Serengeti.

    Science.gov (United States)

    Holdo, Ricardo M; Holt, Robert D; Fryxell, John M

    2009-01-01

    Vertebrate herbivores and fire are known to be important drivers of vegetation dynamics in African savannas. It is of particular importance to understand how changes in herbivore population density, especially of elephants, and fire frequency will affect the amount of tree cover in savanna ecosystems, given the critical importance of tree cover for biodiversity, ecosystem function, and human welfare. We developed a spatially realistic simulation model of vegetation, fire, and dominant herbivore dynamics, tailored to the Serengeti ecosystem of east Africa. The model includes key processes such as tree-grass competition, fire, and resource-based density dependence and adaptive movement by herbivores. We used the model to project the ecosystem 100 years into the future from its present state under different fire, browsing (determined by elephant population density), and grazing (with and without wildebeest present) regimes. The model produced the following key results: (1) elephants and fire exert synergistic negative effects on woody cover; when grazers are excluded, the impact of fire and the strength of the elephant-fire interaction increase; (2) at present population densities of 0.15 elephants/km2, the total amount of woody cover is predicted to remain stable in the absence of fire, but the mature tree population is predicted to decline regardless of the fire regime; without grazers present to mitigate the effects of fire, the size structure of the tree population will become dominated by seedlings and mature trees; (3) spatial heterogeneity in tree cover varies unimodally with elephant population density; fire increases heterogeneity in the presence of grazers and decreases it in their absence; (4) the marked rainfall gradient in the Serengeti directly affects the pattern of tree cover in the absence of fire; with fire, the woody cover is determined by the grazing patterns of the migratory wildebeest, which are partly rainfall driven. Our results show that, in

  17. Firing patterns of long-term cultured neuronal network on multi-electrode array

    Institute of Scientific and Technical Information of China (English)

    LI Xiangning; ZHOU Wei; LIU Man; ZENG Shaoqun; LUO Qingming

    2006-01-01

    Spontaneous neuronal activity plays an important role in the development and plasticity of brain. To explore the developmental changes in the firing pattern of the neuronal networks in vitro, the hippocampal neurons were cultured on the multi-microelectrode array dish for over 14 weeks and the spontaneous activity was recorded. The results showed that random firing was observed in the 1st week and transformed into synchronized activity after two weeks, then tightly synchronized activity appeared in week 2 to 7 and finally the activities transformed into the random firing pattern. These results suggested three stages in the long-term development of neuronal network in vitro: the stage for connection, the stage of synchronized activity and the mature stage. Synchronized firing shown by spontaneous activity was an important phenomenon in high density cultured neuronal network and transformed patterns during development.

  18. Learning causes reorganization of neuronal firing patterns to represent related experiences within a hippocampal schema.

    Science.gov (United States)

    McKenzie, Sam; Robinson, Nick T M; Herrera, Lauren; Churchill, Jordana C; Eichenbaum, Howard

    2013-06-19

    According to schema theory as proposed by Piaget and Bartlett, learning involves the assimilation of new memories into networks of preexisting knowledge, as well as alteration of the original networks to accommodate the new information. Recent evidence has shown that rats form a schema of goal locations and that the hippocampus plays an essential role in adding new memories to the spatial schema. Here we examined the nature of hippocampal contributions to schema updating by monitoring firing patterns of multiple CA1 neurons as rats learned new goal locations in an environment in which there already were multiple goals. Before new learning, many neurons that fired on arrival at one goal location also fired at other goals, whereas ensemble activity patterns also distinguished different goal events, thus constituting a neural representation that linked distinct goals within a spatial schema. During new learning, some neurons began to fire as animals approached the new goals. These were primarily the same neurons that fired at original goals, the activity patterns at new goals were similar to those associated with the original goals, and new learning also produced changes in the preexisting goal-related firing patterns. After learning, activity patterns associated with the new and original goals gradually diverged, such that initial generalization was followed by a prolonged period in which new memories became distinguished within the ensemble representation. These findings support the view that consolidation involves assimilation of new memories into preexisting neural networks that accommodate relationships among new and existing memories.

  19. Dense pattern multiple pass cells

    Science.gov (United States)

    Silver, Joel A.; Bomse, David S.

    2010-09-21

    An optical cell and a method of operating an optical cell comprising employing a first mirror comprising a first hole therein at approximately a center of the first mirror and through which laser light enters the cell, employing a second mirror comprising a second hole therein at approximately a center of the second mirror and through which laser light exits the cell, and forming a Lissajous pattern of spots on the mirrors by repeated reflection of laser light entering the cell.

  20. Effect of Herbal Prescriptions in Accordance with Pattern Identification in Acute Cerebral Infarction Patients: Based on Fire-Heat Pattern

    Directory of Open Access Journals (Sweden)

    WooSang Jung

    2015-01-01

    Full Text Available Objectives. This study was conducted to verify the necessity of corresponding prescription to the diagnosed pattern in acute cerebral infarction patients. Methods. We studied cerebral infarction patients hospitalized within 30 days after the ictus. Forty-four clinical indicators, Motricity Index (MI score, Scandinavian Stroke Scale (SSS score, and herbal prescriptions were checked twice, two weeks apart. The probability of each pattern was calculated based on the clinical indicators. Changes in MI score, SSS score, and the probability of fire-heat pattern were compared between the pattern-prescription correspondence group and the noncorrespondence group. Results. Increments of MI score and SSS score in the correspondence group were significantly greater than those of the noncorrespondence group (p=0.003, p=0.001 while the baseline score of the two groups showed no significant difference. Probability of fire-heat pattern decreased significantly in the correspondence group (p=0.013 while the noncorrespondence group showed no significant difference after the treatment. Conclusion. Acute cerebral infarction patients who are diagnosed as fire-heat pattern showed better improvement in dysfunctions caused by the disease when they took the pattern corresponding prescriptions. This study provides evidence for the necessity and usefulness of pattern identification in Traditional Korean Medicine.

  1. Extracellular Ca2+ fluctuations in vivo affect afterhyperpolarization potential and modify firing patterns of neocortical neurons.

    Science.gov (United States)

    Boucetta, Sofiane; Crochet, Sylvain; Chauvette, Sylvain; Seigneur, Josée; Timofeev, Igor

    2013-07-01

    Neocortical neurons can be classified in four major electrophysiological types according to their pattern of discharge: regular-spiking (RS), intrinsically-bursting (IB), fast-rhythmic-bursting (FRB), and fast-spiking (FS). Previously, we have shown that these firing patterns are not fixed and can change as a function of membrane potential and states of vigilance. Other studies have reported that extracellular calcium concentration ([Ca(2+)]o) fluctuates as a function of the phase of the cortical slow oscillation. In the present study we investigated how spontaneous and induced changes in [Ca(2+)]o affect the properties of action potentials (APs) and firing patterns in cortical neurons in vivo. Intracellular recordings were performed in cats anesthetized with ketamine-xylazine during spontaneous [Ca(2+)]o fluctuation and while changing [Ca(2+)]o with reverse microdialysis. When [Ca(2+)]o fluctuated spontaneously according to the phase of the slow oscillation, we found an increase of the firing threshold and a decrease of the afterhyperpolarization (AHP) amplitude during the depolarizing (active, up) phase of the slow oscillation and some neurons also changed their firing pattern as compared with the hyperpolarizing (silent, down) phase. Induced changes in [Ca(2+)]o significantly affected the AP properties in all neurons. The AHP amplitude was increased in high calcium conditions and decreased in low calcium conditions, in particular the earliest components. Modulation of spike AHP resulted in notable modulation of intrinsic firing pattern and some RS neurons revealed burst firing when [Ca(2+)]o was decreased. We also found an increase in AHP amplitude in high [Ca(2+)]o with in vitro preparation. We suggest that during spontaneous network oscillations in vivo, the dynamic changes of firing patterns depend partially on fluctuations of the [Ca(2+)]o.

  2. Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

    Directory of Open Access Journals (Sweden)

    Judit Lecina-Diaz

    Full Text Available Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1 determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together and (2 ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires. The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn

  3. Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

    Science.gov (United States)

    Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

    2014-01-01

    Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

  4. Pattern and process of prescribed fires influence effectiveness at reducing wildfire severity in dry coniferous forests

    Science.gov (United States)

    Arkle, Robert S.; Pilliod, David S.; Welty, Justin L.

    2012-01-01

    We examined the effects of three early season (spring) prescribed fires on burn severity patterns of summer wildfires that occurred 1–3 years post-treatment in a mixed conifer forest in central Idaho. Wildfire and prescribed fire burn severities were estimated as the difference in normalized burn ratio (dNBR) using Landsat imagery. We used GIS derived vegetation, topography, and treatment variables to generate models predicting the wildfire burn severity of 1286–5500 30-m pixels within and around treated areas. We found that wildfire severity was significantly lower in treated areas than in untreated areas and significantly lower than the potential wildfire severity of the treated areas had treatments not been implemented. At the pixel level, wildfire severity was best predicted by an interaction between prescribed fire severity, topographic moisture, heat load, and pre-fire vegetation volume. Prescribed fire severity and vegetation volume were the most influential predictors. Prescribed fire severity, and its influence on wildfire severity, was highest in relatively warm and dry locations, which were able to burn under spring conditions. In contrast, wildfire severity peaked in cooler, more mesic locations that dried later in the summer and supported greater vegetation volume. We found considerable evidence that prescribed fires have landscape-level influences within treatment boundaries; most notable was an interaction between distance from the prescribed fire perimeter and distance from treated patch edges, which explained up to 66% of the variation in wildfire severity. Early season prescribed fires may not directly target the locations most at risk of high severity wildfire, but proximity of these areas to treated patches and the discontinuity of fuels following treatment may influence wildfire severity and explain how even low severity treatments can be effective management tools in fire-prone landscapes.

  5. Detection of Variability of the Motor Unit Action Potential Shape by Means of the Firing Patterns

    DEFF Research Database (Denmark)

    Krarup, Christian; Nikolic, Mile; Dahl, Kristian;

    1997-01-01

    The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed.......The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed....

  6. Synchronised firing patterns in a random network of adaptive exponential integrate-and-fire

    CERN Document Server

    Borges, Fernando da Silva; Lameu, Ewandson Luiz; Bonetti, Robson Conrado; Iarosz, Kelly Cristiane; Caldas, Iberê Luiz; Baptista, Murilo da Silva; Batista, Antonio Marcos

    2016-01-01

    We have studied neuronal synchronisation in a random network of adaptive exponential integrate-and-fire neurons. We study how spiking or bursting synchronous behaviour appears as a function of the coupling strength and the probability of connections, by constructing parameter spaces that identify these synchronous behaviours from measurements of the inter-spike interval and the calculation of the order parameter. Moreover, we verify the robustness of synchronisaton by applying an external perturbation to each neuron. The simulations show that bursting synchronisation is more robust than spike synchronisation.

  7. Fire patterns in the range of the greater sage-grouse, 1984-2013 — Implications for conservation and management

    Science.gov (United States)

    Brooks, Matthew L.; Matchett, John R.; Shinneman, Douglas J.; Coates, Peter S.

    2015-09-10

    Fire ranks among the top three threats to the greater sage-grouse (Centrocercus urophasianus) throughout its range, and among the top two threats in the western part of its range. The national research strategy for this species and the recent U.S. Department of the Interior Secretarial Order 3336 call for science-based threats assessment of fire to inform conservation planning and fire management efforts. The cornerstone of such assessments is a clear understanding of where fires are occurring and what aspects of fire regimes may be shifting outside of their historical range of variation. This report fulfills this need by describing patterns of fire area, fire size, fire rotation, and fire season length and timing from 1984 to 2013 across the range of the greater sage-grouse. This information need is further addressed by evaluating the ecological and management implications of these fire patterns. Analyses are stratified by major vegetation types and the seven greater sage-grouse management zones, delineated regionally as four western and three eastern management zones. Soil temperature and moisture indicators of resilience to fire and resistance to cheatgrass invasion, and the potential for establishment of a grass/fire cycle, are used as unifying concepts in developing fire threat assessments for each analysis strata.

  8. Post-fire spatial patterns of soil nitrogen mineralization and microbial abundance.

    Directory of Open Access Journals (Sweden)

    Erica A H Smithwick

    Full Text Available Stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. However, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. The objectives of this study were to (1 quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2 determine whether microbial variables aid predictions of in situ net nitrogen mineralization rates in recently burned stands. The study was conducted in lodgepole pine (Pinus contorta var. latifolia and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa forest stands that burned during summer 2000 in Greater Yellowstone (Wyoming, USA. Using a fully probabilistic spatial process model and Bayesian kriging, the spatial structure of microbial lipid abundance and fungi-to-bacteria ratios were found to be spatially structured within plots two years following fire (for most plots, autocorrelation range varied from 1.5 to 10.5 m. Congruence of spatial patterns among microbial variables, in situ net N mineralization, and cover variables was evident. Stepwise regression resulted in significant models of in situ net N mineralization and included variables describing fungal and bacterial abundance, although explained variance was low (R²<0.29. Unraveling complex spatial patterns of nutrient cycling and the biotic factors that regulate it remains challenging but is critical for explaining post-fire ecosystem function, especially in Greater Yellowstone, which is projected to experience increased fire frequencies by mid 21(st Century.

  9. Shoulder muscle firing patterns during the windmill softball pitch.

    Science.gov (United States)

    Maffet, M W; Jobe, F W; Pink, M M; Brault, J; Mathiyakom, W

    1997-01-01

    The purpose of this study was to describe the activity of eight shoulder muscles during the windmill fast-pitch softball throw. Ten collegiate female pitchers were analyzed with intramuscular electromyography, high-speed cinematography, and motion analysis. The supraspinatus muscle fired maximally during arm elevation from the 6 to 3 o'clock position phase, centralizing the humeral head within the glenoid. The posterior deltoid and teres minor muscles acted maximally from the 3 to 12 o'clock position phase to continue arm elevation and externally rotate the humerus. The pectoralis major muscle accelerated the arm from the 12 o'clock position to ball release phase. The serratus anterior muscle characteristically acted to position the scapula for optimal glenohumeral congruency, and the subscapularis muscle functioned as an internal rotator and to protect the anterior capsule. Although the windmill softball pitch is overtly different from the baseball pitch, several surprising similarities were revealed. The serratus anterior and pectoralis major muscles work in synchrony and seem to have similar functions in both pitches. Although the infraspinatus and teres minor muscles are both posterior cuff muscles, they are characteristically uncoupled during the 6 to 3 o'clock position phase, with the infraspinatus muscle acting more independently below 90 degrees. Subscapularis muscle activity seems important in dynamic anterior glenohumeral stabilization and as an internal rotator in both the baseball and softball throws.

  10. Changes in firing rate and firing pattern of midbrain dopaminergic neurons after lesioning of the dorsal raphe nucleus by 5,7-drhydroxytryptamine in adult rats

    Institute of Scientific and Technical Information of China (English)

    Wang Shuang; Liu Jian; Wang Tao; Han Lingna; Zhang Qiaojun; Li Qiang

    2008-01-01

    Objective To study the effect of serotonergic efferent projection of the dorsal rophe nucleus (DRN) on the activity of substantia nigro pars compacta (SNc) and ventral tegmenta area (VTA) dopaminergic neurons after lesioning of the DRN by the neurotoxin 5,7-drhydroxytryptamine (5,7-DHT) in rot. Methods The changes in the firing rote and firing pattern of SNc and VTA dopaminergic neurons were observed with extrocellular recording in control and the lesioned rats. Results The results showed that the mean firing rotes of the fast-firing dopaminergic neurons of the SNc in control and the lesioned rots were (5.34±0. 13 ) Hz (n = 23 ) and ( 7.13±0. 49 ) Hz (n=37), respectively. The mean firing rote of the fast-firing dopaminergic neurons of the SNc in the lesioned rats was significantly increased when compared to that of control rots (P<0.01), while the mean firing rote of the slow-firing dopaminergic neurons of the SNc did not change. The mean firing rotes of dopaminergic neurons of the VTA in control and the lesioned rots were (5.27±0. 38)Hz (n=35) and (3.6±0.2)Hz (n=52), respectively. Lesioning of the DRN induced a significant decrease in the mean firing rote of dopaminergic neurons of the VTA. The firing pattern of SNc and VTA dopaminergic neurons changed towards a more bursting or irrgular firing after the lesioning. Conlusion These data suggest that the serotonergic efferent projections of the DRN significantly affect the activity of SNe and VTA dopaminergic neurons.

  11. Cell type-specific tuning of hippocampal interneuron firing during gamma oscillations in vivo.

    Science.gov (United States)

    Tukker, John J; Fuentealba, Pablo; Hartwich, Katja; Somogyi, Peter; Klausberger, Thomas

    2007-08-01

    Cortical gamma oscillations contribute to cognitive processing and are thought to be supported by perisomatic-innervating GABAergic interneurons. We performed extracellular recordings of identified interneurons in the hippocampal CA1 area of anesthetized rats, revealing that the firing patterns of five distinct interneuron types are differentially correlated to spontaneous gamma oscillations. The firing of bistratified cells, which target dendrites of pyramidal cells coaligned with the glutamatergic input from hippocampal area CA3, is strongly phase locked to field gamma oscillations. Parvalbumin-expressing basket, axo-axonic, and cholecystokinin-expressing interneurons exhibit moderate gamma modulation, whereas the spike timing of distal dendrite-innervating oriens-lacunosum moleculare interneurons is not correlated to field gamma oscillations. Cholecystokinin-expressing interneurons fire earliest in the gamma cycle, a finding that is consistent with their suggested function of thresholding individual pyramidal cells. Furthermore, we show that field gamma amplitude correlates with interneuronal spike-timing precision and firing rate. Overall, our recordings suggest that gamma synchronization in vivo is assisted by temporal- and domain-specific GABAergic inputs to pyramidal cells and is initiated in pyramidal cell dendrites in addition to somata and axon initial segments.

  12. Stochastically gating ion channels enable patterned spike firing through activity-dependent modulation of spike probability.

    Directory of Open Access Journals (Sweden)

    Joshua T Dudman

    2009-02-01

    Full Text Available The transformation of synaptic input into patterns of spike output is a fundamental operation that is determined by the particular complement of ion channels that a neuron expresses. Although it is well established that individual ion channel proteins make stochastic transitions between conducting and non-conducting states, most models of synaptic integration are deterministic, and relatively little is known about the functional consequences of interactions between stochastically gating ion channels. Here, we show that a model of stellate neurons from layer II of the medial entorhinal cortex implemented with either stochastic or deterministically gating ion channels can reproduce the resting membrane properties of stellate neurons, but only the stochastic version of the model can fully account for perithreshold membrane potential fluctuations and clustered patterns of spike output that are recorded from stellate neurons during depolarized states. We demonstrate that the stochastic model implements an example of a general mechanism for patterning of neuronal output through activity-dependent changes in the probability of spike firing. Unlike deterministic mechanisms that generate spike patterns through slow changes in the state of model parameters, this general stochastic mechanism does not require retention of information beyond the duration of a single spike and its associated afterhyperpolarization. Instead, clustered patterns of spikes emerge in the stochastic model of stellate neurons as a result of a transient increase in firing probability driven by activation of HCN channels during recovery from the spike afterhyperpolarization. Using this model, we infer conditions in which stochastic ion channel gating may influence firing patterns in vivo and predict consequences of modifications of HCN channel function for in vivo firing patterns.

  13. Patch to landscape patterns in post fire recruitment of a serotinous conifer

    Science.gov (United States)

    Ne'eman, G.; Fotheringham, C.J.; Keeley, J.E.

    1999-01-01

    Obligate seeding species are highly specialized to fire disturbance and many conifers such as cypress, which are adapted to high intensity stand-replacing fires, have canopy seed banks stored in serotinous cones. Resilience of these trees to fire disturbance is a function of disturbance frequency and one focus of this study was to determine the effect of patch age on postfire recruitment. A second focus was to determine the extent to which fire induced a landscape level change in the location of the forest boundary. Prior to a fire in 1994, a large Cupressus sargentii forest was a mosaic landscape of different aged patches of nearly pure cypress bordered by chaparral. Patches less than 60 years of age were relatively dense with roughly one tree every 1-2 m2 but older patches had thinned to one tree every 3-15 m2. Older trees had substantially greater canopy cone crops but the stand level seed bank size was not significantly correlated with stand age. Fire-dependent obligate seeding species are sensitive to fire return interval because of potential changes in the size of seed banks - facing both a potential 'immaturity risk' and a 'senescence risk'. At our site, C. sargentii regeneration was substantial in stands as young as 20 years, suggesting that fire return interval would need to be shorter than this to pose any significant risk. Reduced seedling recruitment in stands nearly 100 years of age may indicate risk from senescence is greater, however, even the lowest density seedling recruitment was many times greater than the density of mature forests - thus this cypress would appear to be resilient to a wide range of fire return intervals. Changes in landscape patterning of forest and chaparral are unlikely except after fire. Factors that inhibit tree establishment within the shrubland, as well as factors that affect shrub establishment within the forest border likely affect the 'permeability' of this ecotone. After the 1994 fire this boundary appeared to be stable

  14. An analysis of motor unit firing pattern during sustained low force contraction in fatigued muscle.

    Science.gov (United States)

    Olsen, H B; Christensen, H; Søgaard, K

    2001-01-01

    In the present study motor unit (MU) firing pattern was analysed during long-term static contraction in order to see if fatigue would induce rotation of activity between different MU. Surface as well as intramuscular EMG were obtained from ten subjects during a sustained hand lift for 5 minutes after performance of a 30% MVC fatiguing contraction of the extensor carpi radialis muscle. A newly developed decomposition program constituted a powerful tool to obtain detailed knowledge of long term activity pattern of MU during low force contractions. Although the muscle was highly fatigued the majority of MU showed a continuous firing pattern after recruitment and no clear incidences of rotation were found for any of the subjects. Therefore, long term, low force contractions, as performed during many occupational work tasks, may involve continuous activation of the low threshold MU and this could have mechanical as well as metabolic implications for these muscle fibers.

  15. Remote Sensing Techniques in Monitoring Post-Fire Effects and Patterns of Forest Recovery in Boreal Forest Regions: A Review

    Directory of Open Access Journals (Sweden)

    Thuan Chu

    2013-12-01

    Full Text Available The frequency and severity of forest fires, coupled with changes in spatial and temporal precipitation and temperature patterns, are likely to severely affect the characteristics of forest and permafrost patterns in boreal eco-regions. Forest fires, however, are also an ecological factor in how forest ecosystems form and function, as they affect the rate and characteristics of tree recruitment. A better understanding of fire regimes and forest recovery patterns in different environmental and climatic conditions will improve the management of sustainable forests by facilitating the process of forest resilience. Remote sensing has been identified as an effective tool for preventing and monitoring forest fires, as well as being a potential tool for understanding how forest ecosystems respond to them. However, a number of challenges remain before remote sensing practitioners will be able to better understand the effects of forest fires and how vegetation responds afterward. This article attempts to provide a comprehensive review of current research with respect to remotely sensed data and methods used to model post-fire effects and forest recovery patterns in boreal forest regions. The review reveals that remote sensing-based monitoring of post-fire effects and forest recovery patterns in boreal forest regions is not only limited by the gaps in both field data and remotely sensed data, but also the complexity of far-northern fire regimes, climatic conditions and environmental conditions. We expect that the integration of different remotely sensed data coupled with field campaigns can provide an important data source to support the monitoring of post-fire effects and forest recovery patterns. Additionally, the variation and stratification of pre- and post-fire vegetation and environmental conditions should be considered to achieve a reasonable, operational model for monitoring post-fire effects and forest patterns in boreal regions.

  16. Firing patterns and complete synchronization of coupled Hindmarsh-Rose neurons

    Institute of Scientific and Technical Information of China (English)

    石霞; 陆启韶

    2005-01-01

    The firing activities of Hindmarsh-Rose (HR) neurons are studied by means of numerical simulation and bifurcation analysis. A single HR neuron exhibits various firing patterns, such as quiescent state, periodic spiking, periodic bursting and chaos, when the external current input is changed. The fast/slow dynamical analysis is applied to explore the dynamical behaviour of the HR model. The complete synchronization of two coupled identical HR neurons with electrical coupling mimicking gap junctions can be realized in certain ranges of the coupling strength, whenever each individual neuron shows quiescency, periodic firing and chaos. The criteria for complete synchronization are analysed theoretically, and the corresponding numericaI simulation is presented as well. The persistence of the interspike intervals bifurcation structure of the coupled HR neuronal system under electrical coupling is also discussed.

  17. Cell patterning with mucin biopolymers

    Science.gov (United States)

    Crouzier, T.; Jang, H.; Ahn, J.; Stocker, R.; Ribbeck, K.

    2014-01-01

    The precise spatial control of cell adhesion to surfaces is an endeavor that has enabled discoveries in cell biology and new possibilities in tissue engineering. The generation of cell-repellent surfaces currently requires advanced chemistry techniques and could be simplified. Here we show that mucins, glycoproteins of high structural and chemical complexity, spontaneously adsorb on hydrophobic substrates to form coatings that prevent the surface adhesion of mammalian epithelial cells, fibroblasts, and myoblasts. These mucin coatings can be patterned with micrometer precision using a microfluidic device, and are stable enough to support myoblast differentiation over seven days. Moreover, our data indicate that the cell-repellent effect is dependent on mucin-associated glycans because their removal results in a loss of effective cell-repulsion. Last, we show that a critical surface density of mucins, which is required to achieve cell-repulsion, is efficiently obtained on hydrophobic surfaces, but not on hydrophilic glass surfaces. However, this limitation can be overcome by coating glass with hydrophobic fluorosilane. We conclude that mucin biopolymers are attractive candidates to control cell adhesion on surfaces. PMID:23980712

  18. The use of satellite data for monitoring temporal and spatial patterns of fire: a comprehensive review

    Science.gov (United States)

    Lasaponara, R.

    2009-04-01

    fire regimes from Earth observation data Global Change Biology vo. 14. doi: 10.1111/j.1365-2486.2008.01585.x 1-15, Chuvieco E., P. Englefield, Alexander P. Trishchenko, Yi Luo Generation of long time series of burn area maps of the boreal forest from NOAA-AVHRR composite data. Remote Sensing of Environment, Volume 112, Issue 5, 15 May 2008, Pages 2381-2396 Chuvieco Emilio 2006, Remote Sensing of Forest Fires: Current limitations and future prospects in Observing Land from Space: Science, Customers and Technology, Advances in Global Change Research Vol. 4 pp 47-51 De Santis A., E. Chuvieco Burn severity estimation from remotely sensed data: Performance of simulation versus empirical models, Remote Sensing of Environment, Volume 108, Issue 4, 29 June 2007, Pages 422-435. De Santis A., E. Chuvieco, Patrick J. Vaughan, Short-term assessment of burn severity using the inversion of PROSPECT and GeoSail models, Remote Sensing of Environment, Volume 113, Issue 1, 15 January 2009, Pages 126-136 García M., E. Chuvieco, H. Nieto, I. Aguado Combining AVHRR and meteorological data for estimating live fuel moisture content Remote Sensing of Environment, Volume 112, Issue 9, 15 September 2008, Pages 3618-3627 Ichoku C., L. Giglio, M. J. Wooster, L. A. Remer Global characterization of biomass-burning patterns using satellite measurements of fire radiative energy. Remote Sensing of Environment, Volume 112, Issue 6, 16 June 2008, Pages 2950-2962. Lasaponara R. and Lanorte, On the capability of satellite VHR QuickBird data for fuel type characterization in fragmented landscape Ecological Modelling Volume 204, Issues 1-2, 24 May 2007, Pages 79-84 Lasaponara R., A. Lanorte, S. Pignatti,2006 Multiscale fuel type mapping in fragmented ecosystems: preliminary results from Hyperspectral MIVIS and Multispectral Landsat TM data, Int. J. Remote Sens., vol. 27 (3) pp. 587-593. Lasaponara R., V. Cuomo, M. F. Macchiato, and T. Simoniello, 2003 .A self-adaptive algorithm based on AVHRR multitemporal

  19. Setting FIRES to Stem Cell Research

    Science.gov (United States)

    Miller, Roxanne Grietz

    2005-01-01

    The goal of this lesson is to present the basic scientific knowledge about stem cells, the promise of stem cell research to medicine, and the ethical considerations and arguments involved. One of the challenges of discussing stem cell research is that the field is constantly evolving and the most current information changes almost daily. Few…

  20. Rootstock-regulated gene expression patterns associated with fire blight resistance in apple

    Directory of Open Access Journals (Sweden)

    Jensen Philip J

    2012-01-01

    Full Text Available Abstract Background Desirable apple varieties are clonally propagated by grafting vegetative scions onto rootstocks. Rootstocks influence many phenotypic traits of the scion, including resistance to pathogens such as Erwinia amylovora, which causes fire blight, the most serious bacterial disease of apple. The purpose of the present study was to quantify rootstock-mediated differences in scion fire blight susceptibility and to identify transcripts in the scion whose expression levels correlated with this response. Results Rootstock influence on scion fire blight resistance was quantified by inoculating three-year old, orchard-grown apple trees, consisting of 'Gala' scions grafted to a range of rootstocks, with E. amylovora. Disease severity was measured by the extent of shoot necrosis over time. 'Gala' scions grafted to G.30 or MM.111 rootstocks showed the lowest rates of necrosis, while 'Gala' on M.27 and B.9 showed the highest rates of necrosis. 'Gala' scions on M.7, S.4 or M.9F56 had intermediate necrosis rates. Using an apple DNA microarray representing 55,230 unique transcripts, gene expression patterns were compared in healthy, un-inoculated, greenhouse-grown 'Gala' scions on the same series of rootstocks. We identified 690 transcripts whose steady-state expression levels correlated with the degree of fire blight susceptibility of the scion/rootstock combinations. Transcripts known to be differentially expressed during E. amylovora infection were disproportionately represented among these transcripts. A second-generation apple microarray representing 26,000 transcripts was developed and was used to test these correlations in an orchard-grown population of trees segregating for fire blight resistance. Of the 690 transcripts originally identified using the first-generation array, 39 had expression levels that correlated with fire blight resistance in the breeding population. Conclusions Rootstocks had significant effects on the fire blight

  1. Changes in firing rate and firing pattern of midbrain dopaminergic neurons after lesioning of the dorsal raphe nucleus by 5,7-drhydroxytryptamine in adult rats

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Objective To study the effect of serotonergic efferent projection of the dorsal raphe nucleus(DRN)on the activity of substantia nigra pars compacta(SNc)and ventral tegmenta area(VTA)dopaminergic neurons after lesioning of the DRN by the neurotoxin 5,7-drhydroxytryptamine(5,7-DHT)in rat.Methods The changes in the firing rate and firing pattern of SNc and VTA dopaminergic neurons were observed with extracellular recording in control and the lesioned rats.Results The results showed that the mean firing rates o...

  2. Optimizing Grid Patterns on Photovoltaic Cells

    Science.gov (United States)

    Burger, D. R.

    1984-01-01

    CELCAL computer program helps in optimizing grid patterns for different photovoltaic cell geometries and metalization processes. Five different powerloss phenomena associated with front-surface metal grid pattern on photovoltaic cells.

  3. Mapping regional patterns of large forest fires in Wildland-Urban Interface areas in Europe.

    Science.gov (United States)

    Modugno, Sirio; Balzter, Heiko; Cole, Beth; Borrelli, Pasquale

    2016-05-01

    Over recent decades, Land Use and Cover Change (LUCC) trends in many regions of Europe have reconfigured the landscape structures around many urban areas. In these areas, the proximity to landscape elements with high forest fuels has increased the fire risk to people and property. These Wildland-Urban Interface areas (WUI) can be defined as landscapes where anthropogenic urban land use and forest fuel mass come into contact. Mapping their extent is needed to prioritize fire risk control and inform local forest fire risk management strategies. This study proposes a method to map the extent and spatial patterns of the European WUI areas at continental scale. Using the European map of WUI areas, the hypothesis is tested that the distance from the nearest WUI area is related to the forest fire probability. Statistical relationships between the distance from the nearest WUI area, and large forest fire incidents from satellite remote sensing were subsequently modelled by logistic regression analysis. The first European scale map of the WUI extent and locations is presented. Country-specific positive and negative relationships of large fires and the proximity to the nearest WUI area are found. A regional-scale analysis shows a strong influence of the WUI zones on large fires in parts of the Mediterranean regions. Results indicate that the probability of large burned surfaces increases with diminishing WUI distance in touristic regions like Sardinia, Provence-Alpes-Côte d'Azur, or in regions with a strong peri-urban component as Catalunya, Comunidad de Madrid, Comunidad Valenciana. For the above regions, probability curves of large burned surfaces show statistical relationships (ROC value > 0.5) inside a 5000 m buffer of the nearest WUI. Wise land management can provide a valuable ecosystem service of fire risk reduction that is currently not explicitly included in ecosystem service valuations. The results re-emphasise the importance of including this ecosystem service

  4. The relationship between landscape patterns and human-caused fire occurrence in Spain

    Energy Technology Data Exchange (ETDEWEB)

    Castafreda-Aumedes, S.; Garcia-Martin, A.; Vega-Garcia, C.

    2013-05-01

    Aim of study: Human settlements and activities have completely modified landscape structure in the Mediterranean region. Vegetation patterns show the interactions between human activities and natural processes on the territory, and allow understanding historical ecological processes and socioeconomic factors. The arrangement of land uses in the rural landscape can be perceived as a proxy for human activities that often lead to the use, and escape, of fire, the most important disturbance in our forest landscapes. In this context, we tried to predict human-caused fire occurrence in a 5-year period by quantifying landscape patterns. Area of study: This study analyses the Spanish territory included in the Iberian Peninsula and Balearic Islands (497,166 km{sup 2}). Material and Methods: We evaluated spatial pattern applying a set of commonly used landscape ecology metrics to landscape windows of 10x10 sq km (4751 units in the UTM grid) overlaid on the Forest Map of Spain, MFE200. Main results: The best logistic regression model obtained included Shannon's Diversity Index, Mean Patch Edge and Mean Shape Index as explicative variables and the global percentage of correct predictions was 66.3 %. Research highlights: Our results suggested that the highest probability of fire occurrence at that time was associated with areas with a greater diversity of land uses and with more compact patches with fewer edges. (Author) 58 refs.

  5. Nonequilibrium calcium dynamics regulate the autonomous firing pattern of rat striatal cholinergic interneurons.

    Science.gov (United States)

    Goldberg, Joshua A; Teagarden, Mark A; Foehring, Robert C; Wilson, Charles J

    2009-07-01

    Striatal cholinergic interneurons discharge rhythmically in two patterns associated with different afterhyperpolarization timescales, each dictated by a different calcium-dependent potassium current. Single spiking depends on a medium-duration afterhyperpolarization (mAHP) generated by rapid SK currents that are associated with N-type calcium channels. Periodic bursting is driven by a delayed and slowly decaying afterhyperpolarization (sAHP) current associated with L-type channels. Using calcium imaging we show that the calcium transients underlying these currents exhibit two corresponding timescales throughout the somatodendritic tree. This result is not consistent with spatial compartmentalization of calcium entering through the two calcium channels and acting on the two potassium currents, or with differences in channel gating kinetics of the calcium dependent potassium currents. Instead, we show that nonequilibrium dynamics of calcium redistribution among cytoplasmic binding sites with different calcium binding kinetics can give rise to multiple timescales within the same cytoplasmic volume. The resulting independence of mAHP and sAHP currents allows cytoplasmic calcium to control two different and incompatible firing patterns (single spiking or bursting and pausing), depending on whether calcium influx is pulsatile or sustained. During irregular firing, calcium entry at both timescales can be detected, suggesting that an interaction between the medium and slow calcium-dependent afterhyperpolarizations may underlie this firing pattern.

  6. The chronotron: a neuron that learns to fire temporally precise spike patterns.

    Directory of Open Access Journals (Sweden)

    Răzvan V Florian

    Full Text Available In many cases, neurons process information carried by the precise timings of spikes. Here we show how neurons can learn to generate specific temporally precise output spikes in response to input patterns of spikes having precise timings, thus processing and memorizing information that is entirely temporally coded, both as input and as output. We introduce two new supervised learning rules for spiking neurons with temporal coding of information (chronotrons, one that provides high memory capacity (E-learning, and one that has a higher biological plausibility (I-learning. With I-learning, the neuron learns to fire the target spike trains through synaptic changes that are proportional to the synaptic currents at the timings of real and target output spikes. We study these learning rules in computer simulations where we train integrate-and-fire neurons. Both learning rules allow neurons to fire at the desired timings, with sub-millisecond precision. We show how chronotrons can learn to classify their inputs, by firing identical, temporally precise spike trains for different inputs belonging to the same class. When the input is noisy, the classification also leads to noise reduction. We compute lower bounds for the memory capacity of chronotrons and explore the influence of various parameters on chronotrons' performance. The chronotrons can model neurons that encode information in the time of the first spike relative to the onset of salient stimuli or neurons in oscillatory networks that encode information in the phases of spikes relative to the background oscillation. Our results show that firing one spike per cycle optimizes memory capacity in neurons encoding information in the phase of firing relative to a background rhythm.

  7. Fire in the vegetation and peatlands of Borneo, 1997-2007: Patterns, Drivers and Emissions

    Science.gov (United States)

    Spessa, A.; Weber, U.; Langner, A.; Siegert, F.; Heil, A.

    2009-04-01

    Fire activity and emissions from biomass burning in the so-called ‘Arc of Deforestation' along the southern Amazonian forest has been shown to be negatively and non-linearly correlated with rainfall variability, and that this correlation is mediated by human land use and land cover change (LULCC) which drives ignitions and promotes fire spread (Cochrane et al. 1999; Cochrane 2003; Aragao et al. 2008). Other studies have established a similar correlation between fires and associated emissions versus rainfall in Borneo, in particular Kalimantan, with ENSO-driven droughts being identified as the main cause of below average rainfall events over the past decade or so (Field & Shen 2008; van der Werf et al 2008). However, while these particular Borneo studies have indicated that the non-linear relationship between fires and rainfall may be caused by LULCC, they have demonstrated this link only at a broad regional scale. Siegert et al (2001) reported a clear link between fires and logging in Borneo, but this study was restricted to east Kalimantan and the period 1997-98, during which devastating El-Nino driven fires occurred there. Further El Nino events have occurred in Borneo in 2002, 2004 and 2006. The link between fires and emissions, rainfall and LULCC across the island of Borneo therefore remains to be examined using available fine resolution data over a multi-year period. Using rainfall and soil data in combination with state-of-the art satellite sensor data (LANDSAT ETM, MODIS, ATSR and AVHRR) to determine burnt area and deforestation patterns over the decade 1997-2007, we show at a pixel working resolution of 0.25 degrees the following: Burning across Borneo (1997-2007) predominated in southern Kalimantan. Fire activity is negatively and non-linearly correlated to rainfall mainly in pixels that have undergone a significant reduction in forest cover between 1997 and 2007, and that the bigger the reduction, the stronger the correlation. Such pixels occur

  8. A simulation study on the effects of dendritic morphology on layer V PFC pyramidal cell firing behavior

    Directory of Open Access Journals (Sweden)

    Maria Psarrou

    2014-03-01

    Full Text Available The majority of neuronal cells found in the cerebral cortex are pyramidal neurons. Their function has been associated with higher cognitive and emotional functions. Pyramidal neurons have a characteristic structure, consisting of a triangular shaped soma whereon descend two extended and complex dendritic trees, and a long bifurcated axon. All the morphological components of the pyramidal neurons exhibit significant variability across different brain areas and layers. Pyramidal cells receive numerous synaptic inputs along their structure, integration of which in space and in time generates local dendritic spikes that shape their firing pattern. In addition, synaptic integration is influenced by voltage-gated and ion channels, which are expressed in a large repertoire by pyramidal neurons. Electrophysiological categories of pyramidal cells can be established, based on the action potential frequency, generated from a fixed somatic stimulus: (1 cells that fire repetitive action potentials (Regular Spiking – RS, (2 cells that fire clusters of 2 – 5 action potentials with short ISIs (Intrinsic Bursting – IB, and (3 cells that fire in repetitive clusters of 2 – 5 action potentials with short ISIs (Repetitive Oscillatory Bursts – ROB. In vitro and in silico scientific studies, correlate the firing patterns of the pyramidal neurons to their morphological features. This study provides a quantitatively analysis via compartmental neuronal modelling of the effects of dendritic morphology and distribution and concentration of ionic mechanisms, along the basal and/or apical dendrites on the firing behavior of a 112-set of layer V rat PFC pyramidal cells. We focus on how particular morphological and passive features of the dendritic trees shape the neuronal firing patterns. Our results suggest that specific morphological parameters (such as total length, volume and branch number can discriminate the cells as RS or IB, regardless of what is the

  9. Striatal fast-spiking interneurons: from firing patterns to postsynaptic impact

    Directory of Open Access Journals (Sweden)

    Andreas eKlaus

    2011-07-01

    Full Text Available In the striatal microcircuit, fast-spiking (FS interneurons have an important role in mediating inhibition onto neighboring medium spiny (MS projection neurons. In this study, we combined computational modeling with in vitro and in vivo electrophysiological measurements to investigate FS cells in terms of their discharge properties and their synaptic efficacies onto MS neurons. In vivo firing of striatal FS interneurons is characterized by a high firing variability. It is not known, however, if this variability results from the input that FS cells receive, or if it is promoted by the stuttering spike behavior of these neurons. Both our model and measurements in vitro show that FS neurons that exhibit random stuttering discharge in response to steady depolarization, do not show the typical stuttering behavior when they receive fluctuating input. Importantly, our model predicts that electrically coupled FS cells show substantial spike synchronization only when they are in the stuttering regime. Therefore, together with the lack of synchronized firing of striatal FS interneurons that has been reported in vivo, these results suggest that neighboring FS neurons are not in the stuttering regime simultaneously and that in vivo FS firing variability is more likely determined by the input fluctuations. Furthermore, the variability in FS firing is translated to variability in the postsynaptic amplitudes in MS neurons due to the strong synaptic depression of the FS-to-MS synapse. Our results support the idea that these synapses operate over a wide range from strongly depressed to almost fully recovered. The strong inhibitory effects that FS cells can impose on their postsynaptic targets, and the fact that the FS-to-MS synapse model showed substantial depression over extended periods of time might indicate the importance of cooperative effects of multiple presynaptic FS interneurons and the precise orchestration of their activity.

  10. An examination of nucleus accumbens cell firing during extinction and reinstatement of water reinforcement behavior in rats.

    Science.gov (United States)

    Hollander, Jonathan A; Ijames, Stephanie G; Roop, Richard G; Carelli, Regina M

    2002-03-08

    Electrophysiological recording procedures were used to examine nucleus accumbens (Acb) cell firing in rats (n = 13) during water reinforcement sessions consisting of three phases. During phase one (maintenance), a lever press resulted in water reinforcement (fixed ratio 1; 0.05 ml/press) paired with an auditory stimulus (0.5 s). Of 128 Acb neurons recorded during maintenance, 40 cells (31%) exhibited one of three types of neuronal firing patterns described previously [J. Neurosci. 14 (12) (1994) 7735-7746; J. Neurosci. 20 (11) (2000) 4255-4266]. Briefly, Acb neurons exhibited increases in firing rate within seconds preceding the reinforced response (type PR) or increases (type RFe) or decreases (type RFi) in activity seconds following response completion. In phase two (extinction), subsequent lever pressing had no programmed consequences (i.e., water reinforcement and the auditory stimulus were not presented). After 30 min of no responding, animals were given water reinforcement/auditory stimulus 'primes' to reestablish lever pressing behavior during the third phase (reinstatement). Results indicated that all types of phasic neurons (PR, RFe and RFi) exhibited an attenuated firing rate during extinction, and in some cases recovery of patterned discharges were observed during reinstatement. No significant changes in cell firing were observed for any cell type during presentation of the stimulus prime used to reestablish operant responding following extinction. These findings are discussed in terms of how Acb neurons process information related to 'natural' reinforcers versus drugs of abuse.

  11. Electrophysiology of regular firing cells in the rat perirhinal cortex.

    Science.gov (United States)

    D'Antuono, M; Biagini, G; Tancredi, V; Avoli, M

    2001-01-01

    The electrophysiological properties of neurons in the rat perirhinal cortex were analyzed with intracellular recordings in an in vitro slice preparation. Cells included in this study (n = 59) had resting membrane potential (RMP) = -73.9 +/- 8.5 mV (mean +/- SD), action potential amplitude = 95.5 +/- 10.4 mV, input resistance = 36.1 +/- v 15.7 M omega, and time constant = 13.9 +/- 3.4 ms. When filled with neurobiotin (n = 27) they displayed a pyramidal shape with an apical dendrite and extensive basal dendritic tree. Injection of intracellular current pulses revealed: 1) a tetrodotoxin (TTX, 1 microM)-sensitive, inward rectification in the depolarizing direction (n = 6), and 2) a time- and voltage-dependent hyperpolarizing sag that was blocked by extracellular Cs+ (3 mM, n = 5) application. Prolonged (up to 3 s) depolarizing pulses made perirhinal cells discharge regular firing of fast action potentials that diminished over time in frequency and reached a steady level (i.e., adapted). Repetitive firing was followed by an afterhyperpolarization that was decreased, along with firing adaptation, by the Ca(2+)-channel blocker Co2+ (2 mM, n = 6). Action potential broadening became evident during repetitive firing. This behavior, which was more pronounced when larger pulses of depolarizing current were injected (and thus when repetitive firing attained higher rates), was markedly decreased by Co2+ application. Subthreshold membrane oscillations at 5-12 Hz became apparent when cells were depolarized by 10-20 mV from RMP, and action potential clusters appeared with further depolarization. Application of glutamatergic and GABAA receptor antagonists (n = 4), CO2+ (n = 6), or Cs+ (n = 5) did not prevent the occurrence of these oscillations that were abolished by TTX (n = 6). Our results show that pyramidal-like neurons in the perirhinal cortex are regular firing cells with electrophysiological features resembling those of other cortical pyramidal elements. The ability to

  12. A spiking network model of cerebellar Purkinje cells and molecular layer interneurons exhibiting irregular firing

    Directory of Open Access Journals (Sweden)

    William eLennon

    2014-12-01

    Full Text Available While the anatomy of the cerebellar microcircuit is well studied, how it implements cerebellar function is not understood. A number of models have been proposed to describe this mechanism but few emphasize the role of the vast network Purkinje cells (PKJs form with the molecular layer interneurons (MLIs – the stellate and basket cells. We propose a model of the MLI-PKJ network composed of simple spiking neurons incorporating the major anatomical and physiological features. In computer simulations, the model reproduces the irregular firing patterns observed in PKJs and MLIs in vitro and a shift toward faster, more regular firing patterns when inhibitory synaptic currents are blocked. In the model, the time between PKJ spikes is shown to be proportional to the amount of feedforward inhibition from an MLI on average. The two key elements of the model are: (1 spontaneously active PKJs and MLIs due to an endogenous depolarizing current, and (2 adherence to known anatomical connectivity along a parasagittal strip of cerebellar cortex. We propose this model to extend previous spiking network models of the cerebellum and for further computational investigation into the role of irregular firing and MLIs in cerebellar learning and function.

  13. Intrinsic properties and mechanisms of spontaneous firing in mouse cerebellar unipolar brush cells.

    Science.gov (United States)

    Russo, Marco J; Mugnaini, Enrico; Martina, Marco

    2007-06-01

    Neuronal firing patterns are determined by the cell's intrinsic electrical and morphological properties and are regulated by synaptic interactions. While the properties of cerebellar neurons have generally been studied in much detail, little is known about the unipolar brush cells (UBCs), a type of glutamatergic interneuron that is enriched in the granular layer of the mammalian vestibulocerebellum and participates in the representation of head orientation in space. Here we show that UBCs can be distinguished from adjacent granule cells on the basis of differences in membrane capacitance, input resistance and response to hyperpolarizing current injection. We also show that UBCs are intrinsically firing neurons. Using action potential clamp experiments and whole-cell recordings we demonstrate that two currents contribute to this property: a persistent TTX-sensitive sodium current and a ruthenium red-sensitive, TRP-like cationic current, both of which are active during interspike intervals and have reversal potentials positive to threshold. Interestingly, although UBCs are also endowed with a large I(h) current, this current is not involved in their intrinsic firing, perhaps because it activates at voltages that are more hyperpolarized than those associated with autonomous activity.

  14. Cancer cells with irons in the fire.

    Science.gov (United States)

    Bystrom, Laura M; Rivella, Stefano

    2015-02-01

    Iron is essential for the growth and proliferation of cells, as well as for many biological processes that are important for the maintenance and survival of the human body. However, excess iron is associated with the development of cancer and other pathological conditions, due in part to the pro-oxidative nature of iron and its damaging effects on DNA. Current studies suggest that iron depletion may be beneficial for patients that have diseases associated with iron overload or other iron metabolism disorders that may increase the risk for cancer. On the other hand, studies suggest that cancer cells are more vulnerable to the effects of iron depletion and oxidative stress in comparison to normal cells. Therefore, cancer patients might benefit from treatments that alter both iron metabolism and oxidative stress. This review highlights the pro-oxidant effects of iron, the relationship between iron and cancer development, the vulnerabilities of the iron-dependent cancer phenotype, and how these characteristics may be exploited to prevent or treat cancer.

  15. Spatial Patterns of Fire Recurrence Using Remote Sensing and GIS in the Brazilian Savanna: Serra do Tombador Nature Reserve, Brazil

    Directory of Open Access Journals (Sweden)

    Gabriel Antunes Daldegan

    2014-10-01

    Full Text Available The Cerrado is the second largest biome in Brazil after the Amazon and is the savanna with the highest biodiversity in the world. Serra Tombador Natural Reserve (STNR is the largest private reserve located in Goiás State, and the fourth largest in the Cerrado biome. The present study aimed to map the burnt areas and to describe the spatial patterns of fire recurrence and its interactions with the classes of land-cover that occurred in STNR and its surroundings in the period between 2001 and 2010. Several Landsat TM images acquired around the months of July, August and September, coinciding with the region’s dry season when fire events intensify, were employed to monitor burnt areas. Fire scars were mapped using the supervised Mahalanobis-distance classifier and further refined using expert visual interpretation. Burnt area patterns were described by spatial landscape metrics. The effects of fire on landscape structure were obtained by comparing results among different land-cover classes, and results summarized in terms of fire history and frequencies. During the years covered by the study, 69% of the areas analyzed had fire events. The year with the largest burnt area was 2004, followed by 2001, 2007 and 2010. Thus, the largest fire events occurred in a 3-year cycle, which is compatible with other areas of the Brazilian savanna. The regions with higher annual probabilities of fire recurrence occur in the buffer zone around the park. The year 2004 also had the highest number of burnt area patches (831. In contrast, the burnt area in 2007 showed the most extensive fires with low number of patches (82. The physiognomies that suffered most fires were the native savanna formations. The study also identified areas where fires are frequently recurrent, highlighting priority areas requiring special attention. Thus, the methodology adopted in this study assists in monitoring and recovery of areas affected by fire over time.

  16. The firing patterns of spinal neurons: in situ patch-clamp recordings reveal a key role for potassium currents.

    Science.gov (United States)

    Winlove, Crawford I P; Roberts, Alan

    2012-10-01

    Neuron firing patterns underpin the detection and processing of stimuli, influence synaptic interactions, and contribute to the function of networks. To understand how intrinsic membrane properties determine firing patterns, we investigated the biophysical basis of single and repetitive firing in spinal neurons of hatchling Xenopus laevis tadpoles, a well-understood vertebrate model; experiments were conducted in situ. Primary sensory Rohon-Beard (RB) neurons fire singly in response to depolarising current, and dorsolateral (DL) interneurons fire repetitively. RB neurons exhibited a large tetrodotoxin-sensitive sodium current; in DL neurons, the sodium current density was significantly lower. High-voltage-activated calcium currents were similar in both neuron types. There was no evidence of persistent sodium currents, low-voltage-activated calcium currents, or hyperpolarisation-activated currents. In RB neurons, the potassium current was dominated by a tetraethylammonium-sensitive slow component (I(Ks) ); a fast component (I(Kf) ), sensitive to 4-aminopyridine, predominated in DL neurons. Sequential current-clamp and voltage-clamp recordings in individual neurons suggest that high densities of I(Ks) prevent repetitive firing; where I(Ks) is small, I(Kf) density determines the frequency of repetitive firing. Intermediate densities of I(Ks) and I(Kf) allow neurons to fire a few additional spikes on strong depolarisation; this property typifies a novel subset of RB neurons, and may activate escape responses. We discuss how this ensemble of currents and firing patterns underpins the operation of the Xenopus locomotor network, and suggest how simple mechanisms might underlie the similar firing patterns seen in the neurons of diverse species.

  17. Impact of Dendritic Size and Dendritic Topology on Burst Firing in Pyramidal Cells

    NARCIS (Netherlands)

    van Elburg, Ronald A. J.; van Ooyen, Arjen

    2010-01-01

    Neurons display a wide range of intrinsic firing patterns. A particularly relevant pattern for neuronal signaling and synaptic plasticity is burst firing, the generation of clusters of action potentials with short interspike intervals. Besides ion-channel composition, dendritic morphology appears to

  18. Bifurcation Scenarios of Neural Firing Patterns across Two Separated Chaotic Regions as Indicated by Theoretical and Biological Experimental Models

    Directory of Open Access Journals (Sweden)

    Huaguang Gu

    2013-01-01

    Full Text Available Nonlinear dynamics can be used to identify relationships between different firing patterns, which play important roles in the information processing. The present study provides novel biological experimental findings regarding complex bifurcation scenarios from period-1 bursting to period-1 spiking with chaotic firing patterns. These bifurcations were found to be similar to those simulated using the Hindmarsh-Rose model across two separated chaotic regions. One chaotic region lay between period-1 and period-2 burstings. This region has not attracted much attention. The other region is a well-known comb-shaped chaotic region, and it appears after period-2 bursting. After period-2 bursting, the chaotic firings lay in a period-adding bifurcation scenario or in a period-doubling bifurcation cascade. The deterministic dynamics of the chaotic firing patterns were identified using a nonlinear prediction method. These results provided details regarding the processes and dynamics of bifurcation containing the chaotic bursting between period-1 and period-2 burstings and other chaotic firing patterns within the comb-shaped chaotic region. They also provided details regarding the relationships between different firing patterns in parameter space.

  19. Control of Spontaneous Firing Patterns by the Selective Coupling of Calcium Currents to Calcium Activated Potassium Currents in Striatal Cholinergic Interneurons

    OpenAIRE

    Goldberg, Joshua A.; Wilson, Charles J.

    2005-01-01

    The spontaneous firing patterns of striatal cholinergic interneurons are sculpted by potassium currents that give rise to prominent afterhyperpolarizations (AHPs): BK currents contribute to action potential (AP) repolarization; SK currents generate an apamin-sensitive medium AHP (mAHP) following each AP; and bursts of APs generate long-lasting slow AHPs (sAHPs) due to apamin-insensitive currents. As all these currents are calcium-dependent, we conducted voltage- and current-clamp whole-cell r...

  20. Laser fired back contact for silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tucci, M. [ENEA Research Center Casaccia via Anguillarese 301, 00123 Roma (Italy)], E-mail: mario.tucci@casaccia.enea.it; Talgorn, E.; Serenelli, L.; Salza, E.; Izzi, M.; Mangiapane, P. [ENEA Research Center Casaccia via Anguillarese 301, 00123 Roma (Italy)

    2008-08-30

    To get high efficiency c-Si solar cells reduction of surface recombination losses and good surface passivation and/or Back Surface Field (BSF) formation are needed. Most industrial solar cells are made covering the back area with screen-printed Al, forming an Al-BSF upon firing step, with a Back Reflectance of 65% and a Back Surface Recombination Velocity (BSRV) of 1000 cm/s on 1 {omega}cm Si wafer. Simulations reveal that PV efficiency can increase up to 18% after improving the BSRV to {<=} 200 cm/s and the BR to > 95%. The aim of this work is to get these goals by a laser fired back contact with low temperature passivation of the remainder of the back. This can be obtained by a double layer of PECVD Amorphous Silicon and Silicon Nitride, on which a spin-on Boron dopant layer is deposited. The structure is completed by 2 {mu}m thick e-beam evaporated Al. The formation of an improved local BSF is obtained using a Nd:YAG pulsed laser, which promotes an Al and B simultaneous diffusion trough the passivation layers. Several cells, using this structure, have been fabricated on different substrates. By fitting procedure of cell Internal Quantum Efficiency we have extracted several parameters as surface recombination velocity, diffusion length and internal reflection that are comparable with the state of art of the cells having effective back surface field.

  1. Causal relationships vs. emergent patterns in the global controls of fire frequency

    Directory of Open Access Journals (Sweden)

    I. Bistinas

    2014-03-01

    Full Text Available Global controls on month-by-month fractional burnt area (2000–2005 were investigated by fitting a generalized linear model to Global Fire Emissions Database data with 11 predictor variables representing vegetation, climate, land use and potential ignition sources. Burnt area is shown to increase with annual net primary production (NPP, number of dry days, maximum temperature, grazing-land area, grass/shrub cover and diurnal temperature range, and to decrease with soil moisture, cropland area and population density. Lightning showed an apparent (weak negative influence, but this disappeared when pure seasonal-cycle effects were taken into account. The model predicts observed geographic and seasonal patterns, and the emergent relationships seen when burnt area is plotted against each variable separately. Unimodal relationships to mean annual temperature and precipitation, population density and gross domestic product (GDP are reproduced too, and thus shown to be secondary consequences of correlations among different controls (e.g. high NPP with high precipitation; low NPP with low population density and GDP. These findings have major implications for the design of global fire models, as several assumptions in current models – most notably, the widely assumed dependence of fire frequency on ignition rates – are evidently incorrect.

  2. Spider trait assembly patterns and resilience under fire-induced vegetation change in South Brazilian grasslands.

    Directory of Open Access Journals (Sweden)

    Luciana R Podgaiski

    Full Text Available Disturbances induce changes on habitat proprieties that may filter organism's functional traits thereby shaping the structure and interactions of many trophic levels. We tested if communities of predators with foraging traits dependent on habitat structure respond to environmental change through cascades affecting the functional traits of plants. We monitored the response of spider and plant communities to fire in South Brazilian Grasslands using pairs of burned and unburned plots. Spiders were determined to the family level and described in feeding behavioral and morphological traits measured on each individual. Life form and morphological traits were recorded for plant species. One month after fire the abundance of vegetation hunters and the mean size of the chelicera increased due to the presence of suitable feeding sites in the regrowing vegetation, but irregular web builders decreased due to the absence of microhabitats and dense foliage into which they build their webs. Six months after fire rosette-form plants with broader leaves increased, creating a favourable habitat for orb web builders which became more abundant, while graminoids and tall plants were reduced, resulting in a decrease of proper shelters and microclimate in soil surface to ground hunters which became less abundant. Hence, fire triggered changes in vegetation structure that lead both to trait-convergence and trait-divergence assembly patterns of spiders along gradients of plant biomass and functional diversity. Spider individuals occurring in more functionally diverse plant communities were more diverse in their traits probably because increased possibility of resource exploitation, following the habitat heterogeneity hypothesis. Finally, as an indication of resilience, after twelve months spider communities did not differ from those of unburned plots. Our findings show that functional traits provide a mechanistic understanding of the response of communities to

  3. A Simulation Study on the Effects of Dendritic Morphology on Layer V Prefontal Pyramidal Cell Firing Behavior

    Directory of Open Access Journals (Sweden)

    Maria ePsarrou

    2014-09-01

    Full Text Available Pyramidal cells, the most abundant neurons in neocortex, exhibit significant structural variability across different brain areas and layers in different species. Moreover, in response to a somatic step current, these cells display a range of firing behaviors, the most common being (1 repetitive action potentials (Regular Spiking - RS, and (2 an initial cluster of 2-5 action potentials with short ISIs followed by single spikes (Intrinsic Bursting - IB. A correlation between firing behavior and dendritic morphology has recently been reported. In this work we use computational modeling to investigate quantitatively the effects of the basal dendritic tree morphology on the firing behavior of 112 three-dimensional reconstructions of layer V PFC rat pyramidal cells. Particularly, we focus on how different morphological (diameter, total length, volume and branch number and passive (Mean Electrotonic Path length features of basal dendritic trees shape somatic firing when the spatial distribution of ionic mechanisms in the basal dendritic trees is uniform or non-uniform. Our results suggest that total length, volume and branch number are the best morphological parameters to discriminate the cells as RS or IB, regardless of the distribution of ionic mechanisms in basal trees. The discriminatory power of total length, volume and branch number remains high in the presence of different apical dendrites. These results suggest that morphological variations in the basal dendritic trees of layer V pyramidal neurons in the PFC influence their firing patterns in a predictive manner and may in turn influence the information processing capabilities of these neurons.

  4. Wood-fired fuel cells in selected buildings

    Science.gov (United States)

    McIlveen-Wright, D. R.; McMullan, J. T.; Guiney, D. J.

    The positive attributes of fuel cells for high efficiency power generation at any scale and of biomass as a renewable energy source which is not intermittent, location-dependent or very difficult to store, suggest that a combined heat and power (CHP) system consisting of a fuel cell integrated with a wood gasifier (FCIWG) may offer a combination for delivering heat and electricity cleanly and efficiently. Phosphoric acid fuel cell (PAFC) systems, fuelled by natural gas, have already been used in a range of CHP applications in urban settings. Some of these applications are examined here using integrated biomass gasification/fuel cell systems in CHP configurations. Five building systems, which have different energy demand profiles, are assessed. These are a hospital, a hotel, a leisure centre, a multi-residential community and a university hall of residence. Heat and electricity use profiles for typical examples of these buildings were obtained and the FCIWG system was scaled to the power demand. The FCIWG system was modelled for two different types of fuel cell, the molten carbonate and the phosphoric acid. In each case an oxygen-fired gasification system is proposed, in order to eliminate the need for a methane reformer. Technical, environmental and economic analyses of each version were made, using the ECLIPSE process simulation package. Since fuel cell lifetimes are not yet precisely known, economics for a range of fuel cell lifetimes have been produced. The wood-fired PAFC system was found to have low electrical efficiency (13-16%), but much of the heat could be recovered, so that the overall efficiency was 64-67%, suitable where high heat/electricity values are required. The wood-fired molten carbonate fuel cell (MCFC) system was found to be quite efficient for electricity generation (24-27%), with an overall energy efficiency of 60-63%. The expected capital costs of both systems would currently make them uncompetitive for general use, but the specific features

  5. Spatial Patterns of Post-Fire Soil Water Repellency in Rangelands

    Science.gov (United States)

    Nelson, N. A.; Pierce, J. L.

    2006-12-01

    Water repellent soils are naturally occurring but can be created or enhanced by wildfires. Post-fire runoff and the occurrence of fire-related floods and debris flows are related to the extent and continuity of water repellent soils. While many studies have positively correlated post-fire soil water repellency with burn severity and ash thickness in forested and chaparral environments, few studies have examined fire-related water repellency in sage-bitterbrush rangelands (but see Pierson et al., 2001). Rangelands, which comprise 40% of the landmass of the United States and nearly 80% of the lands of the western U.S., burn frequently during the summer with burn areas that often exceed 200 km2. The most commonly used method to measure the extent and severity of post-fire soil water repellency is the water drop penetration test (WDPT): other tests include the molarity of ethanol test, infiltration measured with a minidisk infiltrometer, and patterns of water infiltration measured with blue dye. Unlike tests that measure time until infiltration, the blue dye test provides a means of measuring the spatial extent of water repellent soils as well as area quantification of water saturation and locations of subsurface flowpaths. In early July, 2006, fires burned approximately 1.6 km2 of sagebrush and bitterbrush-dominated rangelands in foothills near Boise, Idaho. Initial studies in August 2006 using both water drop penetration time and the blue dye test show that soil water repellency is highly variable in both extent and severity, and that repellency varies with proximity to burned sage or bitterbrush coppice sites. Out of sixty sample sites, slight soil water repellency occurred outside of coppice boundaries on three occasions, each time in an area with grass and within 1 m of a coppice. Not all coppices exhibited soil water repellency, and only 23% of sites within coppice boundaries exhibited moderate to strong water repellency, as measured by WDPT. Use of the blue dye

  6. Dense pattern optical multipass cell

    Science.gov (United States)

    Silver, Joel A [Santa Fe, NM

    2009-01-13

    A multiple pass optical cell and method comprising providing a pair of opposed cylindrical mirrors having curved axes with substantially equal focal lengths, positioning an entrance hole for introducing light into the cell and an exit hole for extracting light from the cell, wherein the entrance hole and exit hole are coextensive or non-coextensive, introducing light into the cell through the entrance hole, and extracting light from the cell through the exit hole.

  7. Magnetic-directed patterning of cell spheroids.

    Science.gov (United States)

    Whatley, Benjamin R; Li, Xiaowei; Zhang, Ning; Wen, Xuejun

    2014-05-01

    We have described an approach to fabricate three-dimensional (3D) cell-based structures using functionalized super paramagnetic iron oxide nanoparticles (SPIONs) as patterning agents to guide the assembly of endothelial cell spheroids into 3D patterns using the magnetic forces generated by a prefabricated magnetic template. SPIONs were first uptaken by endothelial cells before they were assembled into uniform-sized spheroids through a home-made robotic spheroid maker. To guide the magnetic spheroids, a unique magnetic template was fabricated using computer-aided design and cut from a magnetic sheet. The spheroids were then guided to the prefabricated magnetic template through the attractive magnetic forces between the SPIONs inside the endothelial cells and the magnetic template. Fusion of endothelial cell spheroids over time while adhered to the magnetic template allowed for the formation of 3D cell-based structures. Subsequent removal of the prefabricated magnetic template left 3-D endothelial cell sheets, which may be stacked to fabricate complicated 3D multicellular tissue structures. To enhance the cytocompatibility, SPIONs were silica-coated before use. At low concentrations, the SPIONs did not adversely affect cell viability, proliferation, and phenotype stability. Light and confocal microscopy showed that endothelial cell spheroids could be reproducibly created with high uniformity. The endothelial cells were able to remain viable and maintain the 3D structure in vitro. We have proved the concept to use SPIONs as a patterning agent to direct the attachment and self assembly of SPION-loaded endothelial cell spheroids on a prefabricated magnetic template for the formation of 3D cell based structures. A magnetic-directed technique allows quick patterning of cell spheroids in accordance with desirable magnetic patterns, therefore, holding promise for scalable fabrication of complicated 3D multicellular tissue structures. By varying the cell types and the

  8. Differences in Visual-Spatial Input May Underlie Different Compression Properties of Firing Fields for Grid Cell Modules in Medial Entorhinal Cortex.

    Science.gov (United States)

    Raudies, Florian; Hasselmo, Michael E

    2015-11-01

    Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of environmental barriers. This compression or expansion could be selective for individual grid cell modules with particular properties of spatial scaling. We present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual features on the computation of location that drives grid cell firing patterns. These differences could arise from differences in the position of visual features within the visual field. When location was computed from the movement of visual features on the ground plane (optic flow) in the ventral visual field, this resulted in grid cell spatial firing that was not sensitive to barrier location in modules modeled with small spacing between grid cell firing fields. In contrast, when location was computed from static visual features on walls of barriers, i.e. in the more dorsal visual field, this resulted in grid cell spatial firing that compressed or expanded based on the barrier locations in modules modeled with large spacing between grid cell firing fields. This indicates that different grid cell modules might have differential properties for computing location based on visual cues, or the spatial radius of sensitivity to visual cues might differ between modules.

  9. Customized color patterning of photovoltaic cells

    Science.gov (United States)

    Cruz-Campa, Jose Luis; Nielson, Gregory N.; Okandan, Murat; Lentine, Anthony L.; Resnick, Paul J.; Gupta, Vipin P.

    2016-11-15

    Photovoltaic cells and photovoltaic modules, as well as methods of making and using such photovoltaic cells and photovoltaic modules, are disclosed. More particularly, embodiments of the photovoltaic cells selectively reflect visible light to provide the photovoltaic cells with a colorized appearance. Photovoltaic modules combining colorized photovoltaic cells may be used to harvest solar energy while providing a customized appearance, e.g., an image or pattern.

  10. Deterministic patterns in cell motility

    Science.gov (United States)

    Lavi, Ido; Piel, Matthieu; Lennon-Duménil, Ana-Maria; Voituriez, Raphaël; Gov, Nir S.

    2016-12-01

    Cell migration paths are generally described as random walks, associated with both intrinsic and extrinsic noise. However, complex cell locomotion is not merely related to such fluctuations, but is often determined by the underlying machinery. Cell motility is driven mechanically by actin and myosin, two molecular components that generate contractile forces. Other cell functions make use of the same components and, therefore, will compete with the migratory apparatus. Here, we propose a physical model of such a competitive system, namely dendritic cells whose antigen capture function and migratory ability are coupled by myosin II. The model predicts that this coupling gives rise to a dynamic instability, whereby cells switch from persistent migration to unidirectional self-oscillation, through a Hopf bifurcation. Cells can then switch to periodic polarity reversals through a homoclinic bifurcation. These predicted dynamic regimes are characterized by robust features that we identify through in vitro trajectories of dendritic cells over long timescales and distances. We expect that competition for limited resources in other migrating cell types can lead to similar deterministic migration modes.

  11. Adaptation in the visual cortex: influence of membrane trajectory and neuronal firing pattern on slow afterpotentials.

    Directory of Open Access Journals (Sweden)

    Vanessa F Descalzo

    Full Text Available The input/output relationship in primary visual cortex neurons is influenced by the history of the preceding activity. To understand the impact that membrane potential trajectory and firing pattern has on the activation of slow conductances in cortical neurons we compared the afterpotentials that followed responses to different stimuli evoking similar numbers of action potentials. In particular, we compared afterpotentials following the intracellular injection of either square or sinusoidal currents lasting 20 seconds. Both stimuli were intracellular surrogates of different neuronal responses to prolonged visual stimulation. Recordings from 99 neurons in slices of visual cortex revealed that for stimuli evoking an equivalent number of spikes, sinusoidal current injection activated a slow afterhyperpolarization of significantly larger amplitude (8.5 ± 3.3 mV and duration (33 ± 17 s than that evoked by a square pulse (6.4 ± 3.7 mV, 28 ± 17 s; p<0.05. Spike frequency adaptation had a faster time course and was larger during plateau (square pulse than during intermittent (sinusoidal depolarizations. Similar results were obtained in 17 neurons intracellularly recorded from the visual cortex in vivo. The differences in the afterpotentials evoked with both protocols were abolished by removing calcium from the extracellular medium or by application of the L-type calcium channel blocker nifedipine, suggesting that the activation of a calcium-dependent current is at the base of this afterpotential difference. These findings suggest that not only the spikes, but the membrane potential values and firing patterns evoked by a particular stimulation protocol determine the responses to any subsequent incoming input in a time window that spans for tens of seconds to even minutes.

  12. Acute ethanol exposure inhibits silencing of cerebellar Golgi cell firing induced by granule cell axon input

    Directory of Open Access Journals (Sweden)

    Paolo eBotta

    2014-02-01

    Full Text Available Golgi cells (GoCs are specialized interneurons that provide inhibitory input to granule cells in the cerebellar cortex. GoCs are pacemaker neurons that spontaneously fire action potentials, triggering spontaneous inhibitory postsynaptic currents in granule cells and also contributing to the generation tonic GABAA receptor-mediated currents in granule cells. In turn, granule cell axons provide feedback glutamatergic input to GoCs. It has been shown that high frequency stimulation of granule cell axons induces a transient pause in GoC firing in a type 2-metabotropic glutamate receptor (mGluR2-dependent manner. Here, we investigated the effect ethanol on the pause of GoC firing induced by high frequency stimulation of granule cell axons. GoC electrophysiological recordings were performed in parasagittal cerebellar vermis slices from postnatal day 23 to 26 rats. Loose-patch cell-attached recordings revealed that ethanol (40 mM reversibly decreases the pause duration. An antagonist of mGluR2 reduced the pause duration but did not affect the effect of ethanol. Whole-cell voltage-clamp recordings showed that currents evoked by an mGluR2 agonist were not significantly affected by ethanol. Perforated-patch experiments in which hyperpolarizing and depolarizing currents were injected into GoCs demonstrated that there is an inverse relationship between spontaneous firing and pause duration. Slight inhibition of the Na+/K+ pump mimicked the effect of ethanol on pause duration. In conclusion, ethanol reduces the granule cell axon-mediated feedback mechanism by reducing the input responsiveness of GoCs. This would result in a transient increase of GABAA receptor-mediated inhibition of granule cells, limiting information flow at the input stage of the cerebellar cortex.

  13. Caenorhabditis elegans vulval cell fate patterning

    Science.gov (United States)

    Félix, Marie-Anne

    2012-08-01

    The spatial patterning of three cell fates in a row of competent cells is exemplified by vulva development in the nematode Caenorhabditis elegans. The intercellular signaling network that underlies fate specification is well understood, yet quantitative aspects remain to be elucidated. Quantitative models of the network allow us to test the effect of parameter variation on the cell fate pattern output. Among the parameter sets that allow us to reach the wild-type pattern, two general developmental patterning mechanisms of the three fates can be found: sequential inductions and morphogen-based induction, the former being more robust to parameter variation. Experimentally, the vulval cell fate pattern is robust to stochastic and environmental challenges, and minor variants can be detected. The exception is the fate of the anterior cell, P3.p, which is sensitive to stochastic variation and spontaneous mutation, and is also evolving the fastest. Other vulval precursor cell fates can be affected by mutation, yet little natural variation can be found, suggesting stabilizing selection. Despite this fate pattern conservation, different Caenorhabditis species respond differently to perturbations of the system. In the quantitative models, different parameter sets can reconstitute their response to perturbation, suggesting that network variation among Caenorhabditis species may be quantitative. Network rewiring likely occurred at longer evolutionary scales.

  14. Physiological modulators of Kv3.1 channels adjust firing patterns of auditory brain stem neurons.

    Science.gov (United States)

    Brown, Maile R; El-Hassar, Lynda; Zhang, Yalan; Alvaro, Giuseppe; Large, Charles H; Kaczmarek, Leonard K

    2016-07-01

    Many rapidly firing neurons, including those in the medial nucleus of the trapezoid body (MNTB) in the auditory brain stem, express "high threshold" voltage-gated Kv3.1 potassium channels that activate only at positive potentials and are required for stimuli to generate rapid trains of actions potentials. We now describe the actions of two imidazolidinedione derivatives, AUT1 and AUT2, which modulate Kv3.1 channels. Using Chinese hamster ovary cells stably expressing rat Kv3.1 channels, we found that lower concentrations of these compounds shift the voltage of activation of Kv3.1 currents toward negative potentials, increasing currents evoked by depolarization from typical neuronal resting potentials. Single-channel recordings also showed that AUT1 shifted the open probability of Kv3.1 to more negative potentials. Higher concentrations of AUT2 also shifted inactivation to negative potentials. The effects of lower and higher concentrations could be mimicked in numerical simulations by increasing rates of activation and inactivation respectively, with no change in intrinsic voltage dependence. In brain slice recordings of mouse MNTB neurons, both AUT1 and AUT2 modulated firing rate at high rates of stimulation, a result predicted by numerical simulations. Our results suggest that pharmaceutical modulation of Kv3.1 currents represents a novel avenue for manipulation of neuronal excitability and has the potential for therapeutic benefit in the treatment of hearing disorders.

  15. Wildfire and Spatial Patterns in Forests in Northwestern Mexico: The United States Wishes It Had Similar Fire Problems

    Directory of Open Access Journals (Sweden)

    Scott L. Stephens

    2008-12-01

    Full Text Available Knowledge of the ecological effect of wildfire is important to resource managers, especially from forests in which past anthropogenic influences, e.g., fire suppression and timber harvesting, have been limited. Changes to forest structure and regeneration patterns were documented in a relatively unique old-growth Jeffrey pine-mixed conifer forest in northwestern Mexico after a July 2003 wildfire. This forested area has never been harvested and fire suppression did not begin until the 1970s. Fire effects were moderate especially considering that the wildfire occurred at the end of a severe, multi-year (1999-2003 drought. Shrub consumption was an important factor in tree mortality and the dominance of Jeffrey pine increased after fire. The Baja California wildfire enhanced or maintained a patchy forest structure; similar spatial heterogeneity should be included in US forest restoration plans. Most US forest restoration plans include thinning from below to separate tree crowns and attain a narrow range for residual basal area/ha. This essentially produces uniform forest conditions over broad areas that are in strong contrast to the resilient forests in northern Baja California. In addition to producing more spatial heterogeneity in restoration plans of forests that once experienced frequent, low-moderate intensity fire regimes, increased use of US wildfire management options such as wildland fire use as well as appropriate management responses to non-natural ignitions could also be implemented at broader spatial scales to increase the amount of burning in western US forests.

  16. Altered neuronal firing pattern of the basal ganglia nucleus plays a role in levodopa-induced dyskinesia in patients with Parkinson's disease

    Directory of Open Access Journals (Sweden)

    Xiaoyu eLi

    2015-11-01

    Full Text Available Background: Levodopa therapy alleviates the symptoms of Parkinson's disease (PD, but long-term treatment often leads to motor complications such as levodopa-induced dyskinesia (LID. Aim: To explore the neuronal activity in the basal ganglia nuclei in patients with PD and LID. Methods: Thirty patients with idiopathic PD (age, 55.1±11.0 years; disease duration, 8.7±5.6 years were enrolled between August 2006 and August 2013 at the Xuanwu Hospital, Capital Medical University, China. Their Hoehn and Yahr scores ranged from 2 to 4 and their UPDRS III scores were 28.5±5.2. Fifteen of them had severe LID (UPDRS IV scores of 6.7±1.6. Microelectrode recording was performed in the globus pallidus internus (GPi and subthalamic nucleus (STN during pallidotomy (n=12 or STN deep brain stimulation (DBS; bilateral, n=12; unilateral, n=6. The firing patterns and frequencies of various cell types were analyzed by assessing single cell interspike intervals (ISIs and the corresponding coefficient of variation (CV. Results: A total of 295 neurons were identified from the GPi (n=12 and STN (n=18. These included 26 (8.8% highly grouped discharge, 30 (10.2% low frequency firing, 78 (26.4% rapid tonic discharge, 103 (34.9% irregular activity, and 58 (19.7% tremor-related activity. There were significant differences between the two groups (P<0.05 for neurons with irregular firing, highly irregular cluster-like firing, and low-frequency firing. Conclusion: Altered neuronal activity was observed in the basal ganglia nucleus of GPi and STN, and may play important roles in the pathophysiology of PD and LID.

  17. Measuring the firing rate of high-resistance neurons with cell-attached recording.

    Science.gov (United States)

    Alcami, Pepe; Franconville, Romain; Llano, Isabel; Marty, Alain

    2012-02-29

    Cell-attached recording is extensively used to study the firing rate of mammalian neurons, but potential limitations of the method have not been investigated in detail. Here we perform cell-attached recording of molecular layer interneurons in cerebellar slices from rats and mice, and we study how experimental conditions influence the measured firing rate. We find that this rate depends on time in cell-attached mode, on pipette potential, and on pipette ionic composition. In the first minute after sealing, action currents are variable in shape and size, presumably reflecting membrane instability. The firing rate remains approximately constant during the first 4 min after sealing and gradually increases afterward. Making the pipette potential more positive leads to an increase in the firing rate, with a steeper dependence on voltage if the pipette solution contains K(+) as the main cation than if it contains Na(+). Ca(2+) imaging experiments show that establishing a cell-attached recording can result in an increased somatic Ca(2+) concentration, reflecting an increased firing rate linked to an increase in the pipette-cell conductance. Pipette effects on cell firing are traced to a combination of passive electrical coupling, opening of voltage- and Ca(2+)-sensitive K(+) channels (BK channels) after action potentials, and random activation of voltage-insensitive, presumably mechanosensitive, cationic channels. We conclude that, unless experimental conditions are optimized, cell-attached recordings in small neurons may report erroneous firing rates.

  18. Using tree recruitment patterns and fire history to guide restoration of an unlogged ponderosa pine/Douglas-fir landscape in the southern Rocky Mountains after a century of fire suppression

    Science.gov (United States)

    Kaufmann, M.R.; Huckaby, L.S.; Fornwalt, P.J.; Stoker, J.M.; Romme, W.H.

    2003-01-01

    Tree age and fire history were studied in an unlogged ponderosa pine/Douglas-fir (Pinus ponderosa/Pseudotsuga menziesii) landscape in the Colorado Front Range mountains. These data were analysed to understand tree survival during fire and post-fire recruitment patterns after fire, as a basis for understanding the characteristics of, and restoration needs for, an ecologically sustainable landscape. Comparisons of two independent tree age data sets indicated that sampling what subjectively appear to be the five oldest trees in a forest polygon could identify the oldest tree. Comparisons of the ages of the oldest trees in each data set with maps of fire history suggested that delays in establishment of trees, after stand-replacing fire, ranged from a few years to more than a century. These data indicate that variable fire severity, including patches of stand replacement, and variable temporal patterns of tree recruitment into openings after fire were major causes of spatial heterogeneity of patch structure in the landscape. These effects suggest that restoring current dense and homogeneous ponderosa pine forests to an ecologically sustainable and dynamic condition should reflect the roles of fires and variable patterns of tree recruitment in regulating landscape structure.

  19. Fire Resistant Composite Closed Cell Foam and Nonwoven Textiles for Tents and Shelters

    Science.gov (United States)

    2006-01-01

    Shelter Prototype In order to produce sufficient foam, adhesive and coated nonwoven for construction of a small shelter, larger quantities were...AFRL-ML-TY-TR-2006-4571 FIRE RESISTANT COMPOSITE CLOSED CELL FOAM AND NONWOVEN TEXTILES FOR TENTS AND SHELTERS Stephen C. Davis...18 Figure 12. Screening Fire Test of Nonwoven and PVC/NBR Foam Composite

  20. Control of spontaneous firing patterns by the selective coupling of calcium currents to calcium-activated potassium currents in striatal cholinergic interneurons.

    Science.gov (United States)

    Goldberg, Joshua A; Wilson, Charles J

    2005-11-02

    The spontaneous firing patterns of striatal cholinergic interneurons are sculpted by potassium currents that give rise to prominent afterhyperpolarizations (AHPs). Large-conductance calcium-activated potassium (BK) channel currents contribute to action potential (AP) repolarization; small-conductance calcium-activated potassium channel currents generate an apamin-sensitive medium AHP (mAHP) after each AP; and bursts of APs generate long-lasting slow AHPs (sAHPs) attributable to apamin-insensitive currents. Because all these currents are calcium dependent, we conducted voltage- and current-clamp whole-cell recordings while pharmacologically manipulating calcium channels of the plasma membrane and intracellular stores to determine what sources of calcium activate the currents underlying AP repolarization and the AHPs. The Cav2.2 (N-type) blocker omega-conotoxin GVIA (1 microM) was the only blocker that significantly reduced the mAHP, and it induced a transition to rhythmic bursting in one-third of the cells tested. Cav1 (L-type) blockers (10 microM dihydropyridines) were the only ones that significantly reduced the sAHP. When applied to cells induced to burst with apamin, dihydropyridines reduced the sAHPs and abolished bursting. Depletion of intracellular stores with 10 mM caffeine also significantly reduced the sAHP current and reversibly regularized firing. Application of 1 microM omega-conotoxin MVIIC (a Cav2.1/2.2 blocker) broadened APs but had a negligible effect on APs in cells in which BK channels were already blocked by submillimolar tetraethylammonium chloride, indicating that Cav2.1 (Q-type) channels provide the calcium to activate BK channels that repolarize the AP. Thus, calcium currents are selectively coupled to the calcium-dependent potassium currents underlying the AHPs, thereby creating mechanisms for control of the spontaneous firing patterns of these neurons.

  1. Biogeochemistry and plant physiological traits interact to reinforce patterns of post-fire dominance in boreal forests

    Science.gov (United States)

    Shenoy, A.; Kielland, K.; Johnstone, J. F.

    2011-12-01

    Increases in the frequency, extent, and severity of fire in the North American boreal region are projected to continue under a warming climate and are likely to be associated with changes in future vegetation composition. In interior Alaska, fire severity is linked to the relative dominance of deciduous versus coniferous canopy species. Severely burned areas have high levels of deciduous recruitment and subsequent stand dominance, while lightly burned areas exhibit black spruce self-replacement. To elucidate potential mechanisms by which differential fire severity results in differential post-fire vegetation development, we examined changes in soil nitrogen (N) supply (NO3- and NH4+) and in situ 15N uptake by young aspen (Populus tremuloides) and black spruce (Picea mariana) trees growing in lightly and severely burned areas. We hypothesized that (a) soil nitrate supply would be higher in severely burned sites and (b) since conifers have been shown to have a reduced physiological capacity for NO3- uptake, aspen would display greater rates of NO3- uptake than spruce in severely burned sites. Our results suggested that the composition and magnitude of inorganic N supply 14 years after the fire was nearly identical in high-severity and low-severity sites, and nitrate represented nearly 50% of the supply. However, both aspen and spruce took up substantially more NH4+-N than NO3- -N regardless of fire severity. Surprisingly, spruce exhibited only a moderately lower rate of NO3- uptake (μg N/g root-1h-1) than aspen. At the stand level, aspen took up nearly an order-of-magnitude more N per hectare in severely burned sites compared to lightly burned sites, while spruce exhibited the opposite pattern of N uptake with respect to fire severity. Whereas ammonium appeared to be preferred by both species, nitrate represented a larger component of N uptake (based on the NO3-:NH4+ uptake ratio) in aspen (0.7) than in spruce (0.4). We suggest that these species

  2. Photovoltaic cell with nano-patterned substrate

    Science.gov (United States)

    Cruz-Campa, Jose Luis; Zhou, Xiaowang; Zubia, David

    2016-10-18

    A photovoltaic solar cell comprises a nano-patterned substrate layer. A plurality of nano-windows are etched into an intermediate substrate layer to form the nano-patterned substrate layer. The nano-patterned substrate layer is positioned between an n-type semiconductor layer composed of an n-type semiconductor material and a p-type semiconductor layer composed of a p-type semiconductor material. Semiconductor material accumulates in the plurality of nano-windows, causing a plurality of heterojunctions to form between the n-type semiconductor layer and the p-type semiconductor layer.

  3. Regenerating sprouts of axotomized cat muscle afferents express characteristic firing patterns to mechanical stimulation.

    Science.gov (United States)

    Johnson, R D; Munson, J B

    1991-12-01

    1. In cats, we studied the physiological properties of regenerating sprouts of muscle afferent fibers and compared them with sprouts from cutaneous afferent fibers. 2. Muscle nerves to the triceps surae and cutaneous sural nerves were axotomized in the popliteal fossa, and the proximal ends were inserted into nerve cuffs. Six days later, we recorded action potentials from single Groups I and II muscle and mostly Group II cutaneous afferents driven by mechanostimulation of the cuff. 3. Most muscle afferent sprouts (91%) had a regular slowly adapting discharge in response to sustained mechanical displacement of the cuff, particularly to sustained stretch stimuli, whereas most cutaneous afferents (92%) did not. Muscle afferents were more likely to have a spontaneous discharge and afterdischarge. 4. Group II muscle afferent sprouts had lower stretch thresholds and a higher incidence of spontaneous discharge compared with Group I fiber sprouts, whereas Group I fibers had a higher incidence of high-frequency afterdischarge to mechanical stimuli. 5. We conclude that, 6 days after axotomy, regenerating sprouts of muscle afferents, particularly Group II afferents, have become mechanosensitive in the absence of a receptor target and exhibit physiological properties similar to those found when innervating their native muscle but significantly different from sprouts of cutaneous afferents. Expression of these native muscle afferent firing patterns after the inappropriate reinnervation of hairy skin may be due to inherent properties of the muscle afferent fiber.

  4. Cell patterning by laser-assisted bioprinting.

    Science.gov (United States)

    Devillard, Raphaël; Pagès, Emeline; Correa, Manuela Medina; Kériquel, Virginie; Rémy, Murielle; Kalisky, Jérôme; Ali, Muhammad; Guillotin, Bertrand; Guillemot, Fabien

    2014-01-01

    The aim of tissue engineering is to produce functional three-dimensional (3D) tissue substitutes. Regarding native organ and tissue complexity, cell density and cell spatial 3D organization, which influence cell behavior and fate, are key parameters in tissue engineering. Laser-Assisted Bioprinting (LAB) allows one to print cells and liquid materials with a cell- or picoliter-level resolution. Thus, LAB seems to be an emerging and promising technology to fabricate tissue-like structures that have the physiological functionality of their native counterparts. This technology has additional advantages such as automation, reproducibility, and high throughput. It makes LAB compatible with the (industrial) fabrication of 3D constructs of physiologically relevant sizes. Here we present exhaustively the numerous steps that allow printing of viable cells with a well-preserved micrometer pattern. To facilitate the understanding of the whole cell patterning experiment using LAB, it is discussed in two parts: (1) preprocessing: laser set-up, bio-ink cartridge and bio-paper preparation, and pattern design; and (2) processing: bio-ink printing on the bio-paper.

  5. Fire in the Vegetation and Peatlands of Borneo, 1997-2007: Patterns, Drivers and Emissions from Biomass Burning

    Science.gov (United States)

    Spessa, Allan; Weber, Ulrich; Langner, Andreas; Siegert, Florian; Heil, Angelika

    2010-05-01

    The peatland forests of equatorial SE Asia cover over 20 Mha with most located in Indonesia. Indonesian peatlands are globally one of the largest near-surface reserves of terrestrial organic carbon, with peat deposits of up to 20m thick and an estimated carbon storage of 55-61 Gt. The destructive fires in Indonesia during the exceptionally strong drought of late 1997 and early 1998 mark some of the largest peak emissions events in recorded history of global fires. Past studies estimate that about 1Gt of carbon was released to the atmosphere from the Indonesian fires in 1997- equivalent to 14% of the average global annual fossil fuel emissions released during the 1990s. Previous studies have established a non-linear negative correlation between fires and antecedent rainfall in Borneo, with ENSO-driven droughts being identified as the main cause of below-average rainfall events over the past decade or so. However, while these studies suggest that this non-linear relationship is mediated by ignitions associated with land use and land cover change (LULCC), they have not demonstrated it. A clear link between fires and logging in Borneo has been reported, but this work was restricted to eastern Kalimantan and the period 1997-98. The relationship between fires, emissions, rainfall and LULCC across the island of Borneo therefore remains to be examined using available fine resolution data over a multi-year period. Using rainfall data, up-to-date peat maps and state-of-the art satellite sensor data to determine burnt area and deforestation patterns over the decade 1997-2007, we show at a pixel working resolution of 0.25 degrees the following: Burning across Borneo predominated in southern Kalimantan. Fire activity is negatively and non-linearly correlated to rainfall mainly in pixels that have undergone a significant reduction in forest cover, and that the bigger the reduction, the stronger the correlation. Such pixels occur overwhelmingly in southern Kalimantan. These

  6. Accumulation of cytoplasmic calcium, but not apamin-sensitive afterhyperpolarization current, during high frequency firing in rat subthalamic nucleus cells.

    Science.gov (United States)

    Teagarden, Mark; Atherton, Jeremy F; Bevan, Mark D; Wilson, Charles J

    2008-02-01

    The autonomous firing pattern of neurons in the rat subthalamic nucleus (STN) is shaped by action potential afterhyperpolarization currents. One of these is an apamin-sensitive calcium-dependent potassium current (SK). The duration of SK current is usually considered to be limited by the clearance of calcium from the vicinity of the channel. When the cell is driven to fire faster, calcium is expected to accumulate, and this is expected to result in accumulation of calcium-dependent AHP current. We measured the time course of calcium transients in the soma and proximal dendrites of STN neurons during spontaneous firing and their accumulation during driven firing. We compared these to the time course and accumulation of AHP currents using whole-cell and perforated patch recordings. During spontaneous firing, a rise in free cytoplasmic calcium was seen after each action potential, and decayed with a time constant of about 200 ms in the soma, and 80 ms in the dendrites. At rates higher than 10 Hz, calcium transients accumulated as predicted. In addition, there was a slow calcium transient not predicted by summation of action potentials that became more pronounced at high firing frequency. Spike AHP currents were measured in voltage clamp as tail currents after 2 ms voltage pulses that triggered action currents. Apamin-sensitive AHP (SK) current was measured by subtraction of tail currents obtained before and after treatment with apamin. SK current peaked between 10 and 15 ms after an action potential, had a decay time constant of about 30 ms, and showed no accumulation. At frequencies between 5 and 200 spikes s(-1), the maximal SK current remained the same as that evoked by a single action potential. AHP current did not have time to decay between action potentials, so at frequencies above 50 spikes s(-1) the apamin-sensitive current was effectively constant. These results are inconsistent with the view that the decay of SK current is governed by calcium dynamics. They

  7. Cell pattern in adult human corneal endothelium.

    Directory of Open Access Journals (Sweden)

    Carlos H Wörner

    Full Text Available A review of the current data on the cell density of normal adult human endothelial cells was carried out in order to establish some common parameters appearing in the different considered populations. From the analysis of cell growth patterns, it is inferred that the cell aging rate is similar for each of the different considered populations. Also, the morphology, the cell distribution and the tendency to hexagonallity are studied. The results are consistent with the hypothesis that this phenomenon is analogous with cell behavior in other structures such as dry foams and grains in polycrystalline materials. Therefore, its driving force may be controlled by the surface tension and the mobility of the boundaries.

  8. Voronoi cell patterns: Theoretical model and applications

    Science.gov (United States)

    González, Diego Luis; Einstein, T. L.

    2011-11-01

    We use a simple fragmentation model to describe the statistical behavior of the Voronoi cell patterns generated by a homogeneous and isotropic set of points in 1D and in 2D. In particular, we are interested in the distribution of sizes of these Voronoi cells. Our model is completely defined by two probability distributions in 1D and again in 2D, the probability to add a new point inside an existing cell and the probability that this new point is at a particular position relative to the preexisting point inside this cell. In 1D the first distribution depends on a single parameter while the second distribution is defined through a fragmentation kernel; in 2D both distributions depend on a single parameter. The fragmentation kernel and the control parameters are closely related to the physical properties of the specific system under study. We use our model to describe the Voronoi cell patterns of several systems. Specifically, we study the island nucleation with irreversible attachment, the 1D car-parking problem, the formation of second-level administrative divisions, and the pattern formed by the Paris Métro stations.

  9. Evaluation of GLOCK 9 mm Firing Pin Aperture Shear Mark Individuality Based On 1,632 Different Pistols by Traditional Pattern Matching and IBIS Pattern Recognition.

    Science.gov (United States)

    Hamby, James E; Norris, Stephen; Petraco, Nicholas D K

    2016-01-01

    Over a period of 21 years, a number of fired GLOCK cartridge cases have been evaluated. A total of 1632 GLOCK firearms were used to generate a sample of the same size. Our research hypothesis was that no cartridge cases fired from different 9-mm semiautomatic GLOCK pistols would be mistaken as coming from the same gun. Using optical comparison microscopy, two separate experiments were carried out to test this hypothesis. A subsample of 617 test-fired cases were subjected to algorithmic comparison by the Integrated Ballistics Identification System (IBIS). The second experiment subjected the full set of 1632 cases to manual comparisons using traditional pattern matching. None of the cartridge cases were "matched" by either of these two experiments. Using these empirical findings, an established Bayesian probability model was used to estimate the chance that a 9-mm cartridge case, fired from a GLOCK, could be mistaken as coming from the same firearm when in fact it did not (i.e., the random match probability).

  10. Rootstock-regulated gene expression patterns associated with fire blight resistance in apple

    Science.gov (United States)

    Background: Desirable apple varieties are clonally propagated by grafting vegetative scions onto rootstocks. Rootstocks influence many phenotypic traits of the scion, including resistance to pathogens such as Erwinia amylovora, which causes fire blight, the most serious bacterial disease of apple....

  11. Patterning bacterial communities on epithelial cells.

    Directory of Open Access Journals (Sweden)

    Mohammed Dwidar

    Full Text Available Micropatterning of bacteria using aqueous two phase system (ATPS enables the localized culture and formation of physically separated bacterial communities on human epithelial cell sheets. This method was used to compare the effects of Escherichia coli strain MG1655 and an isogenic invasive counterpart that expresses the invasin (inv gene from Yersinia pseudotuberculosis on the underlying epithelial cell layer. Large portions of the cell layer beneath the invasive strain were killed or detached while the non-invasive E. coli had no apparent effect on the epithelial cell layer over a 24 h observation period. In addition, simultaneous testing of the localized effects of three different bacterial species; E. coli MG1655, Shigella boydii KACC 10792 and Pseudomonas sp DSM 50906 on an epithelial cell layer is also demonstrated. The paper further shows the ability to use a bacterial predator, Bdellovibriobacteriovorus HD 100, to selectively remove the E. coli, S. boydii and P. sp communities from this bacteria-patterned epithelial cell layer. Importantly, predation and removal of the P. Sp was critical for maintaining viability of the underlying epithelial cells. Although this paper focuses on a few specific cell types, the technique should be broadly applicable to understand a variety of bacteria-epithelial cell interactions.

  12. Auditory hair cell innervational patterns in lizards.

    Science.gov (United States)

    Miller, M R; Beck, J

    1988-05-22

    The pattern of afferent and efferent innervation of two to four unidirectional (UHC) and two to nine bidirectional (BHC) hair cells of five different types of lizard auditory papillae was determined by reconstruction of serial TEM sections. The species studies were Crotaphytus wislizeni (iguanid), Podarcis (Lacerta) sicula and P. muralis (lacertids), Ameiva ameiva (teiid), Coleonyx variegatus (gekkonid), and Mabuya multifasciata (scincid). The main object was to determine in which species and in which hair cell types the nerve fibers were innervating only one (exclusive innervation), or two or more hair cells (nonexclusive innervation); how many nerve fibers were supplying each hair cell; how many synapses were made by the innervating fibers; and the total number of synapses on each hair cell. In the species studies, efferent innervation was limited to the UHC, and except for the iguanid, C. wislizeni, it was nonexclusive, each fiber supplying two or more hair cells. Afferent innervation varied both with the species and the hair cell types. In Crotaphytus, both the UHC and the BHC were exclusively innervated. In Podarcis and Ameiva, the UHC were innervated exclusively by some fibers but nonexclusively by others (mixed pattern). In Coleonyx, the UHC were exclusively innervated but the BHC were nonexclusively innervated. In Mabuya, both the UHC and BHC were nonexclusively innervated. The number of afferent nerve fibers and the number of afferent synapses were always larger in the UHC than in the BHC. In Ameiva, Podarcis, and Mabuya, groups of bidirectionally oriented hair cells occur in regions of cytologically distinct UHC, and in Ameiva, unidirectionally oriented hair cells occur in cytologically distinct BHC regions.

  13. Global Characterization of Biomass-Burning Patterns using Satellite Measurements of Fire Radiative Energy

    Science.gov (United States)

    Ichoku, Charles; Giglio, Louis; Wooster, Martin J.; Remer, Lorraine A.

    2008-01-01

    Remote sensing is the most practical means of measuring energy release from large open-air biomass burning. Satellite measurement of fire radiative energy (FRE) release rate or power (FRP) enables distinction between fires of different strengths. Based on a 1-km resolution fire data acquired globally by the MODerate-resolution Imaging Spectro-radiometer (MODIS) sensor aboard the Terra and Aqua satellites from 2000 to 2006, instanteaneous FRP values ranged between 0.02 MW and 1866 MW, with global daily means ranging between 20 and 40 MW. Regionally, at the Aqua-MODIS afternoon overpass, the mean FRP values for Alaska, Western US, Western Australia, Quebec and the rest of Canada are significantly higher than these global means, with Quebec having the overall highest value of 85 MW. Analysis of regional mean FRP per unit area of land (FRP flux) shows that a peak fire season in certain regions, fires can be responsible for up to 0.2 W/m(sup 2) at peak time of day. Zambia has the highest regional monthly mean FRP flux of approximately 0.045 W/m(sup 2) at peak time of day and season, while the Middle East has the lowest value of approximately 0.0005 W/m(sup 2). A simple scheme based on FRP has been devised to classify fires into five categories, to facilitate fire rating by strength, similar to earthquakes and hurricanes. The scheme uses MODIS measurements of FRP at 1-km resolution as follows: catagory 1 (less than 100 MW), category 2 (100 to less than 500 MW), category 3 (500 to less than 1000 MW), category 4 (1000 to less than 1500 MW), catagory 5 (greater than or equal to 1500 MW). In most regions of the world, over 90% of fires fall into category 1, while only less than 1% fall into each of categories 3 to 5, although these proportions may differ significantly from day to day and by season. The frequency of occurence of the larger fires is region specific, and could not be explained by ecosystem type alone. Time-series analysis of the propertions of higher category

  14. Medium afterhyperpolarization and firing pattern modulation in interneurons of stratum radiatum in the CA3 hippocampal region.

    Science.gov (United States)

    Savić, N; Pedarzani, P; Sciancalepore, M

    2001-05-01

    Stratum (st.) radiatum interneurons represent a heterogeneous class of hippocampal cells with as yet poorly characterized physiological properties. Intracellular staining with biocytin, in situ hybridization, and patch-clamp recording have been combined to investigate the morphological and electrophysiological properties of these cells in the CA3 hippocampal region in young rats [postnatal days 10 to 21 (P10-21)]. Labeled cells presented a heterogeneous morphology with various soma shapes, often found multipolar, and dendritic arborizations confined to st. radiatum. The passive membrane properties of these st. radiatum interneurons showed instead no significant differences between P10 and P21. Low resting potential, high-input resistance, and short time constants characterized CA3 st. radiatum interneurons, which were silent at rest. Action potentials, elicited by brief current pulses, were lower and shorter than in pyramidal cells and followed by a Ca(2+)-dependent medium-duration afterhyperpolarizing potential (mAHP). Prolonged depolarizing current injection generated trains of action potentials that fired at constant frequency after a slight accommodation. The maximum steady-state firing rate was 31 +/- 4 (SD) Hz. Hyperpolarizing current pulses revealed a prominent inward rectification characterized by a "sag," followed by a depolarizing rebound that triggered action potentials. Sag and anodal brake excitation were blocked by Cs(+), suggesting that they were mediated by a hyperpolarization-activated cation conductance (I(h)). In the presence of tetrodotoxin and tetraethylammonium, biphasic tail currents were elicited in voltage clamp after a depolarizing step inducing Ca(2+) influx. Tail currents presented a fast Ca(2+)-activated and apamin-sensitive component (I(AHP)) and were further reduced by carbachol. The presence of I(AHP) was consistent with the high expression level of the apamin-sensitive SK2 subunit transcript in CA3 st. radiatum interneurons as

  15. Experience-dependent firing rate remapping generates directional selectivity in hippocampal place cells

    Directory of Open Access Journals (Sweden)

    Zaneta eNavratilova

    2012-02-01

    Full Text Available When rodents engage in irregular foraging in an open field environment, hippocampal principal cells exhibit place-specific firing that is statistically independent of the direction of traverse through the place field. When the path is restricted to a track, however, in-field rates differ substantially in opposite directions. Frequently, the representations of the track in the two directions are essentially orthogonal. We show that this directionally selective firing is not hard-wired, but develops through experience-dependent plasticity. During the rats’ first pass in each direction, place fields were highly directionally symmetric, whereas over subsequent laps, the firing rates in the two directions gradually but substantially diverged. We conclude that, even on a restricted track, place cell firing is initially determined by allocentric position, and only later, the within-field firing rates change in response to differential sensory information or behavioral cues in the two directions. In agreement with previous data, place fields near local cues, such as textures on the track, developed less directionality than place fields on a uniform part of the track, possibly because the local cues reduced the net difference in sensory input at a given point. Directionality also developed in an open environment without physical restriction of the animal’s path, when rats learned to run along a specified path. In this case, directionality developed later than on the running track, only after the rats began to run in a stereotyped manner. Although the average population firing rates exhibited little if any change over laps in either direction, the direction-specific firing rates in a given place field were up- or down-regulated with about equal probability and magnitude, which was independent in the two directions, suggesting some form of competitive mechanism (e.g., LTP/LTD acting coherently on the set of synapses conveying external information to

  16. Quantum walks on graphs representing the firing patterns of a quantum neural network

    Science.gov (United States)

    Schuld, Maria; Sinayskiy, Ilya; Petruccione, Francesco

    2014-03-01

    Quantum walks have been shown to be fruitful tools in analyzing the dynamic properties of quantum systems. This article proposes using quantum walks as an approach to quantum neural networks (QNNs). QNNs replace binary McCulloch-Pitts neurons with a qubit in order to use the advantages of quantum computing in neural networks. A quantum walk on the firing states of such a QNN is supposed to simulate the central properties of the dynamics of classical neural networks, such as associative memory. It is shown that a biased discrete Hadamard walk derived from the updating process of a biological neuron does not lead to a unitary walk. However, a stochastic quantum walk between the global firing states of a QNN can be constructed, and it is shown that it contains the feature of associative memory. The quantum contribution to the walk accounts for a modest speedup in some regimes.

  17. The specific features and pattern of febrile infection-related epilepsy syndrome (FIRES in children

    Directory of Open Access Journals (Sweden)

    L. V. Shalkevich

    2014-01-01

    Full Text Available The paper considers the etiology, pathogenesis, clinical presentations, diagnosis and treatment in children with febrile infection-related epilepsy syndrome (FIRES and the aspects of identifying this disease as an individual nosological entity. It details a study of the possible etiological factors of FIRES, such as metabolic, genetic, and immunological disorders, aseptic inflammatory processes, as well as a search for a certain infectious agent by inoculations of different biological environments of the body and by polymerase chain reaction; the diagnostic characteristics of FIRES at the present stage, including the use of electroencephalography, positron emission tomography, and magnetic resonance imaging; different approaches to drug therapy for FIRES at the onset stages of its clinical manifestations, protracted status epilepticus, and drugresistant epilepsy. The issues of the predictable outcome of this disease, including survival and the probability of further development of epilepsy and maintenance of cognitive functions, are also viewed. Diagnostic criteria for the syndrome, such as age at its onset 3 to 15 years in previously healthy children; acute onset as fever to develop high-frequency focal seizures several days later; the absence of the identified disease pathogen detected by the examinations of cerebrospinal fluid, serum, and other environments of the body; the development of drug-resistant epilepsy and severe permanent cognitive and motor deficits after the completion of an acute period in most cases are presented. The paper is clinically exemplified by the authors’ observation of an 11-year-old boy who meets the above criteria for the syndrome, but has a relatively favorable course, without developing severe drug-resistant epilepsy.

  18. Patterned Poly(dopamine) Films for Enhanced Cell Adhesion.

    Science.gov (United States)

    Chen, Xi; Cortez-Jugo, Christina; Choi, Gwan H; Björnmalm, Mattias; Dai, Yunlu; Yoo, Pil J; Caruso, Frank

    2017-01-18

    Engineered materials that promote cell adhesion and cell growth are important in tissue engineering and regenerative medicine. In this work, we produced poly(dopamine) (PDA) films with engineered patterns for improved cell adhesion. The patterned films were synthesized via the polymerization of dopamine at the air-water interface of a floating bed of spherical particles. Subsequent dissolution of the particles yielded free-standing PDA films with tunable geometrical patterns. Our results show that these patterned PDA films significantly enhance the adhesion of both cancer cells and stem cells, thus showing promise as substrates for cell attachment for various biomedical applications.

  19. Detecting Determinism in Firing Activities of Retinal Ganglion Cells during Response to Complex Stimuli

    Institute of Scientific and Technical Information of China (English)

    CAI Chao-Feng; ZHANG Ying-Ying; LIU Xue; LIANG Pei-Ji; ZHANG Pu-Ming

    2008-01-01

    Complex stimuli are used to probe the response properties of the chicken's retinal ganglion cells (GCs). Thecorrelation dimension method and the nonlinear forecasting method are applied to detect the determinism in the firing activities of the retinal GCs during response to complex stimuli.The inter-spike interval (ISI) series and the first difference of the ISI (DISI) series are analysed.Two conclusions are drawn.Firstly,the first difference operation of the ISI series makes it comparatively easier for determinism detection in the firing activities of retinal GCs.Secondly,the nonlinear forecasting method is more efficient and reliable than the correlation dimension method for determinism detection.

  20. A Versatile Method of Patterning Proteins and Cells.

    Science.gov (United States)

    Shrirao, Anil B; Kung, Frank H; Yip, Derek; Firestein, Bonnie L; Cho, Cheul H; Townes-Anderson, Ellen

    2017-02-26

    Substrate and cell patterning techniques are widely used in cell biology to study cell-to-cell and cell-to-substrate interactions. Conventional patterning techniques work well only with simple shapes, small areas and selected bio-materials. This article describes a method to distribute cell suspensions as well as substrate solutions into complex, long, closed (dead-end) polydimethylsiloxane (PDMS) microchannels using negative pressure. This method enables researchers to pattern multiple substrates including fibronectin, collagen, antibodies (Sal-1), poly-D-lysine (PDL), and laminin. Patterning of substrates allows one to indirectly pattern a variety of cells. We have tested C2C12 myoblasts, the PC12 neuronal cell line, embryonic rat cortical neurons, and amphibian retinal neurons. In addition, we demonstrate that this technique can directly pattern fibroblasts in microfluidic channels via brief application of a low vacuum on cell suspensions. The low vacuum does not significantly decrease cell viability as shown by cell viability assays. Modifications are discussed for application of the method to different cell and substrate types. This technique allows researchers to pattern cells and proteins in specific patterns without the need for exotic materials or equipment and can be done in any laboratory with a vacuum.

  1. Synchronized Firings in Retinal Ganglion Cells in Response to Natural Stimulation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ying-Ying; XIAO Lei; LIU Wen-Zhong; GONG Hai-Qing; LIANG Pei-Ji

    2011-01-01

    The response of synchronously firing groups of population retinal ganglion cells (RGCs) to natural movies (NMs)and pseudo-random white-noise checker-board flickering (CB, as control) are investigated using an informationtheoretic algorithm.The main results are: (1) the population RGCs tend to fire in synchrony far more frequently than expected by chance during both NM and CB stimulation; (2) more synchronous groups could be formed and each group contains more neurons under NM than CB stimulation; (3) the individual neurons also participate in more groups and have more distinct partners in NM than CB stimulation.All these results suggest that the synchronized firings in RGCs are more extensive and diverse, which may account for more effective information processing in representing the natural visual environment.%@@ The response of synchronously firing groups of population retinal ganglion cells (RGCs) to natural movies (NMs) and pseudo-random white-noise checker-board flickering (CB, as control) are investigated using an information-theoretic algorithm.The main results are: (1) the population RGCs tend to fire in synchrony far more frequently than expected by chance during both NM and CB stimulation; (2) more synchronous groups could be formed and each group contains more neurons under NM than CB stimulation; (3) the individual neurons also participate in more groups and have more distinct partners in NM than CB stimulation.All these results suggest that the synchronized firings in RGCs are more extensive and diverse, which may account for more effective information processing in representing the natural visual environment.

  2. Estimation of key parameters in adaptive neuron model according to firing patterns based on improved particle swarm optimization algorithm

    Science.gov (United States)

    Yuan, Chunhua; Wang, Jiang; Yi, Guosheng

    2017-03-01

    Estimation of ion channel parameters is crucial to spike initiation of neurons. The biophysical neuron models have numerous ion channel parameters, but only a few of them play key roles in the firing patterns of the models. So we choose three parameters featuring the adaptation in the Ermentrout neuron model to be estimated. However, the traditional particle swarm optimization (PSO) algorithm is still easy to fall into local optimum and has the premature convergence phenomenon in the study of some problems. In this paper, we propose an improved method that uses a concave function and dynamic logistic chaotic mapping mixed to adjust the inertia weights of the fitness value, effectively improve the global convergence ability of the algorithm. The perfect predicting firing trajectories of the rebuilt model using the estimated parameters prove that only estimating a few important ion channel parameters can establish the model well and the proposed algorithm is effective. Estimations using two classic PSO algorithms are also compared to the improved PSO to verify that the algorithm proposed in this paper can avoid local optimum and quickly converge to the optimal value. The results provide important theoretical foundations for building biologically realistic neuron models.

  3. Quantifying erosion and deposition patterns using airborne LiDAR following the 2012 High Park Fire and 2013 Colorado Flood

    Science.gov (United States)

    Brogan, D. J.; Nelson, P. A.; MacDonald, L. H.

    2015-12-01

    Quantifying and predicting geomorphic change over large spatial scales is increasingly feasible and of growing interest as repeat high resolution topography becomes available. We began detailed field studies of channel geomorphic change using RTK-GPS in two 15 km2 watersheds following the 2012 High Park Fire; the watersheds were then subjected to a several-hundred year flood in September 2013. During this time a series of airborne LiDAR datasets were collected, and the objectives of this study were to: 1) determine and compare the spatial variability in channel and valley erosion and deposition over time from the LiDAR; and 2) determine if the observed changes can be predicted from channel and valley bottom characteristics. Data quality issues in the initial LiDAR required us to rotate and translate flight lines in order to co-register ground-classified point clouds between successive datasets; uncertainty was then estimated using our RTK-GPS field measurements. Topographic changes were calculated using the Multiscale Model to Model Cloud Comparison (M3C2) algorithm. Results indicate that the 2013 flood mobilized much more sediment than was mobilized due to the fire alone; unfortunately the uncertainty in differencing is still frequently greater than the observed changes, especially within transfer reaches. Valley expansion and constriction are major controls on spatial patterns of erosion and deposition, suggesting that topographic metrics such as longitudinal distributions of channel slope and valley confinement may provide quasi-physically based estimates of sediment deposition and delivery potential.

  4. Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques

    Science.gov (United States)

    The combination of gas chromatography and pattern recognition (GC/PR) analysis is a powerful tool for investigating complicated biological problems. Clustering, mapping, discriminant development, etc. are necessary to analyze realistically large chromatographic data sets and to seek meaningful relat...

  5. Evaluation of the oscillatory interference model of grid cell firing through analysis and measured period variance of some biological oscillators.

    Directory of Open Access Journals (Sweden)

    Eric A Zilli

    2009-11-01

    Full Text Available Models of the hexagonally arrayed spatial activity pattern of grid cell firing in the literature generally fall into two main categories: continuous attractor models or oscillatory interference models. Burak and Fiete (2009, PLoS Comput Biol recently examined noise in two continuous attractor models, but did not consider oscillatory interference models in detail. Here we analyze an oscillatory interference model to examine the effects of noise on its stability and spatial firing properties. We show analytically that the square of the drift in encoded position due to noise is proportional to time and inversely proportional to the number of oscillators. We also show there is a relatively fixed breakdown point, independent of many parameters of the model, past which noise overwhelms the spatial signal. Based on this result, we show that a pair of oscillators are expected to maintain a stable grid for approximately t = 5mu(3/(4pisigma(2 seconds where mu is the mean period of an oscillator in seconds and sigma(2 its variance in seconds(2. We apply this criterion to recordings of individual persistent spiking neurons in postsubiculum (dorsal presubiculum and layers III and V of entorhinal cortex, to subthreshold membrane potential oscillation recordings in layer II stellate cells of medial entorhinal cortex and to values from the literature regarding medial septum theta bursting cells. All oscillators examined have expected stability times far below those seen in experimental recordings of grid cells, suggesting the examined biological oscillators are unfit as a substrate for current implementations of oscillatory interference models. However, oscillatory interference models can tolerate small amounts of noise, suggesting the utility of circuit level effects which might reduce oscillator variability. Further implications for grid cell models are discussed.

  6. Evaluation of the oscillatory interference model of grid cell firing through analysis and measured period variance of some biological oscillators.

    Science.gov (United States)

    Zilli, Eric A; Yoshida, Motoharu; Tahvildari, Babak; Giocomo, Lisa M; Hasselmo, Michael E

    2009-11-01

    Models of the hexagonally arrayed spatial activity pattern of grid cell firing in the literature generally fall into two main categories: continuous attractor models or oscillatory interference models. Burak and Fiete (2009, PLoS Comput Biol) recently examined noise in two continuous attractor models, but did not consider oscillatory interference models in detail. Here we analyze an oscillatory interference model to examine the effects of noise on its stability and spatial firing properties. We show analytically that the square of the drift in encoded position due to noise is proportional to time and inversely proportional to the number of oscillators. We also show there is a relatively fixed breakdown point, independent of many parameters of the model, past which noise overwhelms the spatial signal. Based on this result, we show that a pair of oscillators are expected to maintain a stable grid for approximately t = 5mu(3)/(4pisigma)(2) seconds where mu is the mean period of an oscillator in seconds and sigma(2) its variance in seconds(2). We apply this criterion to recordings of individual persistent spiking neurons in postsubiculum (dorsal presubiculum) and layers III and V of entorhinal cortex, to subthreshold membrane potential oscillation recordings in layer II stellate cells of medial entorhinal cortex and to values from the literature regarding medial septum theta bursting cells. All oscillators examined have expected stability times far below those seen in experimental recordings of grid cells, suggesting the examined biological oscillators are unfit as a substrate for current implementations of oscillatory interference models. However, oscillatory interference models can tolerate small amounts of noise, suggesting the utility of circuit level effects which might reduce oscillator variability. Further implications for grid cell models are discussed.

  7. Reliability of spike and burst firing in thalamocortical relay cells

    NARCIS (Netherlands)

    Zeldenrust, F.; Chameau, P.J.P.; Wadman, W.J.

    2013-01-01

    The reliability and precision of the timing of spikes in a spike train is an important aspect of neuronal coding. We investigated reliability in thalamocortical relay (TCR) cells in the acute slice and also in a Morris-Lecar model with several extensions. A frozen Gaussian noise current, superimpose

  8. Nonequilibrium Calcium Dynamics Regulate the Autonomous Firing Pattern of Rat Striatal Cholinergic Interneurons

    OpenAIRE

    Goldberg, Joshua A.; Teagarden, Mark A.; Foehring, Robert C.; Wilson, Charles J.

    2009-01-01

    Striatal cholinergic interneurons discharge rhythmically in two patterns associated with different afterhyperpolarization timescales, each dictated by a different calcium-dependent potassium current. Single spiking depends on a medium-duration afterhyperpolarization (mAHP) generated by rapid SK currents that are associated with N-type calcium channels. Periodic bursting is driven by a delayed and slowly decaying afterhyperpolarization (sAHP) current associated with L-type channels. Using calc...

  9. Midline thalamic paraventricular nucleus neurons display diurnal variation in resting membrane potentials, conductances, and firing patterns in vitro

    Science.gov (United States)

    Kolaj, Miloslav; Zhang, Li; Rønnekleiv, Oline K.

    2012-01-01

    Neurons in the rodent midline thalamic paraventricular nucleus (PVT) receive inputs from brain stem and hypothalamic sites known to participate in sleep-wake and circadian rhythms. To evaluate possible diurnal changes in their excitability, we used patch-clamp techniques to record and examine the properties of neurons in anterior PVT (aPVT) in coronal rat brain slices prepared at zeitgeber time (ZT) 2–6 vs. ZT 14–18 and recorded at ZT 8.4 ± 0.2 (day) vs. ZT 21.2 ± 0.2 (night), the subjective quiet vs. aroused states, respectively. Compared with neurons recorded during the day, neurons from the night period were significantly more depolarized and exhibited a lower membrane conductance that in part reflected loss of a potassium-mediated conductance. Furthermore, these neurons were also significantly more active, with tonic and burst firing patterns. Neurons from each ZT period were assessed for amplitudes of two conductances known to contribute to bursting behavior, i.e., low-threshold-activated Ca2+ currents (IT) and hyperpolarization-activated cation currents (Ih). Data revealed that amplitudes of both IT and Ih were significantly larger during the night period. In addition, biopsy samples from the night period revealed a significant increase in mRNA for Cav3.1 and Cav3.3 low-threshold Ca2+ channel subtypes. Neurons recorded from the night period also displayed a comparative enhancement in spontaneous bursting at membrane potentials of approximately −60 mV and in burst firing consequent to hyperpolarization-induced low-threshold currents and depolarization-induced current pulses. These novel in vitro observations reveal that midline thalamic neurons undergo diurnal changes in their IT, Ih, and undefined potassium conductances. The underlying mechanisms remain to be characterized. PMID:22219029

  10. EFFECT OF ANGIOTENSIN Ⅱ RECEPTOR SUBTYPE Ⅰ ON THE FIRING RATE IN CATECHOLAMINERGIC TUMOR CELLS

    Institute of Scientific and Technical Information of China (English)

    Du Jianqing(杜剑青); Sun Chengwen(孙成文); Tang Jingshi (唐敬师); Colin Sumners; Mohan K Raizada

    2003-01-01

    Objective To study the action of brain angiotensin Ⅱ(Ang Ⅱ) receptors and underlying intracellular mechanism in the catecholaminergic system(CATH) Methods Action potentials (APs) of the primary co-cultured catecholaminergic tumor (CATH.a) cells were recorded with the whole-cell patch clamp configuration in current clamp mode. Expression of Ang Ⅱ receptors subtypes (AT1 and AT2) was detected by RT-PCR technique. Results The differentiated CATH.a cells represented a neuron-like characterization. All CATH.a cells expressed mRNA encoding both Ang Ⅱ AT1 and AT2 receptor subtypes. Ang Ⅱ increased the firing rate in the CATH.a cells, which was inhibited completely by addition administration of the AT1 but not AT2 receptor antagonist, and partially by using the inhibitors of signal molecules, U73122 (10 μmol*L-1), or KN-93 (10 μmol*L-1), or calphostin C (10 μmol*L-1). Conclusion Ang Ⅱ increases firing rate in CATH.a cells via AT1 receptor. The CATH.a cells expressing functional AT1 and AT2 receptor subtypes may be of general utility for the study of the Ang Ⅱ receptor-induced modulation of brain catecholaminergic system.

  11. Prefrontal cell firing in male rats during approach towards sexually receptive female: interactions with cocaine.

    Science.gov (United States)

    Febo, Marcelo

    2011-04-01

    The medial prefrontal cortex (mPFC) plays a role in anticipation of rewards and goal orientation, properties that are influenced by cocaine administration. Single-unit firing was measured in the mPFC of seven male rats during the expression of approach responses toward a sexually receptive female. Nose-poking in male rats was used as a measure of approach behavior during the following periods: a baseline, first exposure to a female, a second baseline 2 h later and a second exposure to female 10 min after cocaine (15 mg kg⁻¹ i.p.). Two types of excitatory responses were identified. First, a subset of cells (23%) showed increased firing activity during nose-poke behavior upon presentation of the female, but not before. Another subset of cells (12%) showed increased firing in the presence of the female only after cocaine was administered. The present results provide preliminary evidence for neurons in the mPFC that are involved in sexually motivated approach behavior and that are modulated by cocaine.

  12. Endothelial cell motility, coordination and pattern formation during vasculogenesis.

    Science.gov (United States)

    Czirok, Andras

    2013-01-01

    How vascular networks assemble is a fundamental problem of developmental biology that also has medical importance. To explain the organizational principles behind vascular patterning, we must understand how can tissue level structures be controlled through cell behavior patterns like motility and adhesion that, in turn, are determined by biochemical signal transduction processes? We discuss the various ideas that have been proposed as mechanisms for vascular network assembly: cell motility guided by extracellular matrix alignment (contact guidance), chemotaxis guided by paracrine and autocrine morphogens, and multicellular sprouting guided by cell-cell contacts. All of these processes yield emergent patterns, thus endothelial cells can form an interconnected structure autonomously, without guidance from an external pre-pattern.

  13. Neural coordination can be enhanced by occasional interruption of normal firing patterns: a self-optimizing spiking neural network model.

    Science.gov (United States)

    Woodward, Alexander; Froese, Tom; Ikegami, Takashi

    2015-02-01

    The state space of a conventional Hopfield network typically exhibits many different attractors of which only a small subset satisfies constraints between neurons in a globally optimal fashion. It has recently been demonstrated that combining Hebbian learning with occasional alterations of normal neural states avoids this problem by means of self-organized enlargement of the best basins of attraction. However, so far it is not clear to what extent this process of self-optimization is also operative in real brains. Here we demonstrate that it can be transferred to more biologically plausible neural networks by implementing a self-optimizing spiking neural network model. In addition, by using this spiking neural network to emulate a Hopfield network with Hebbian learning, we attempt to make a connection between rate-based and temporal coding based neural systems. Although further work is required to make this model more realistic, it already suggests that the efficacy of the self-optimizing process is independent from the simplifying assumptions of a conventional Hopfield network. We also discuss natural and cultural processes that could be responsible for occasional alteration of neural firing patterns in actual brains.

  14. Influence of atmospheric rivers on vegetation productivity and fire patterns in the southwestern U.S.

    Science.gov (United States)

    Albano, Christine M.; Dettinger, Michael; Soulard, Christopher E.

    2017-01-01

    In the southwestern U.S., the meteorological phenomenon known as atmospheric rivers (ARs) has gained increasing attention due to its strong connections to floods, snowpacks, and water supplies in the West Coast states. Relatively less is known about the ecological implications of ARs, particularly in the interior Southwest, where AR storms are less common. To address this gap, we compared a chronology of AR landfalls on the west coast between 1989 and 2011 and between 25°N and 42.5°N to annual metrics of the normalized difference vegetation index (NDVI; an indicator of vegetation productivity) and daily resolution precipitation data to assess influences of AR-fed winter precipitation on vegetation productivity across the southwestern U.S. We mapped correlations between winter AR precipitation during landfalling ARs and (1) annual maximum NDVI and (2) area burned by large wildfires summarized by ecoregion during the same year as the landfalls and during the following year. Interannual variations of AR precipitation strongly influenced both NDVI and area burned by wildfire in some dryland ecoregions. The influence of ARs on dryland vegetation varied significantly depending on the latitude of landfall, with those ARs making landfall below 35°N latitude more strongly influencing these systems, and with effects observed as far as 1300 km from the landfall location. As climatologists' understanding of the synoptic patterns associated with the occurrence of ARs continues to evolve, an increased understanding of how AR landfalls, in aggregate, influence vegetation productivity and associated wildfire activity in dryland ecosystems may provide opportunities to better predict ecological responses to climate and climate change.

  15. Scaffold-independent Patterning of Cells using Magnetic Nanoparticles

    Science.gov (United States)

    Ghosh, Suvojit; Biswas, Moanaro; Elankumaran, Subbiah; Puri, Ishwar

    2013-03-01

    Spatial patterning of cells in vitro relies on direct contact of cells on to solid surfaces. Scaffold independent patterning of cells has never been achieved so far. Patterning of cells has wide applications including stem cell biology, tissue architecture and regenerative medicine besides fundamental biology. Magnetized cells in a suspension can be manipulated using an externally applied magnetic field enabling directed patterning. We magnetized mammalian cells by internalization of superparamagnetic nanoparticles coated with bovine serum albumin (BSA). A magnetic field is then used to arrange cells in a desired pattern on a substrate or in suspension. The control strategy is derived from the self-assembly of magnetic colloids in a liquid considering magnetostatic interactions. The range of achievable structural features promise novel experimental methods investigating the influence of tissue shape and size on cell population dynamics wherein Fickian diffusion of autocrine growth signals are known to play a significant role. By eliminating the need for a scaffold, intercellular adhesion mechanics and the effects of temporally regulated signals can be investigated. The findings can be applied to novel tissue engineering methods.

  16. Firing patterns of maternal rat prelimbic neurons during spontaneous contact with pups.

    Science.gov (United States)

    Febo, Marcelo

    2012-08-01

    Extracellular single unit activity was recorded from medial prefrontal cortex (mPFC) of postpartum dams over the course of 3 days while they engaged in spontaneous pup-directed behaviors and non-specific exploratory behavior. Out of 109 units identified over the course of the experiment, 15 units were observed to be pup-responsive and 15 increased their discharge rates non-specifically while not attending to pups. An association between neuronal activity and typical maternal behaviors (e.g., retrieval, pup-grooming, nursing) was not observed. Instead, brief bouts of snout contact with pups were accompanied by phasic increases and decreases in spike rates. The observed pup contact responsive cells might play a role in processing of sensory feedback from pups or the transmission of modulatory output to other subcortical maternal brain areas.

  17. Systematic regional variations in Purkinje cell spiking patterns.

    Directory of Open Access Journals (Sweden)

    Jianqiang Xiao

    Full Text Available In contrast to the uniform anatomy of the cerebellar cortex, molecular and physiological studies indicate that significant differences exist between cortical regions, suggesting that the spiking activity of Purkinje cells (PCs in different regions could also show distinct characteristics. To investigate this possibility we obtained extracellular recordings from PCs in different zebrin bands in crus IIa and vermis lobules VIII and IX in anesthetized rats in order to compare PC firing characteristics between zebrin positive (Z+ and negative (Z- bands. In addition, we analyzed recordings from PCs in the A2 and C1 zones of several lobules in the posterior lobe, which largely contain Z+ and Z- PCs, respectively. In both datasets significant differences in simple spike (SS activity were observed between cortical regions. Specifically, Z- and C1 PCs had higher SS firing rates than Z+ and A2 PCs, respectively. The irregularity of SS firing (as assessed by measures of interspike interval distribution was greater in Z+ bands in both absolute and relative terms. The results regarding systematic variations in complex spike (CS activity were less consistent, suggesting that while real differences can exist, they may be sensitive to other factors than the cortical location of the PC. However, differences in the interactions between SSs and CSs, including the post-CS pause in SSs and post-pause modulation of SSs, were also consistently observed between bands. Similar, though less strong trends were observed in the zonal recordings. These systematic variations in spontaneous firing characteristics of PCs between zebrin bands in vivo, raises the possibility that fundamental differences in information encoding exist between cerebellar cortical regions.

  18. Changes in Parthenogenetic Imprinting Patterns during Reprogramming by Cell Fusion.

    Directory of Open Access Journals (Sweden)

    Hyun Sik Jang

    Full Text Available Differentiated somatic cells can be reprogrammed into the pluripotent state by cell-cell fusion. In the pluripotent state, reprogrammed cells may then self-renew and differentiate into all three germ layers. Fusion-induced reprogramming also epigenetically modifies the somatic cell genome through DNA demethylation, X chromosome reactivation, and histone modification. In this study, we investigated whether fusion with embryonic stem cells (ESCs also reprograms genomic imprinting patterns in somatic cells. In particular, we examined imprinting changes in parthenogenetic neural stem cells fused with biparental ESCs, as well as in biparental neural stem cells fused with parthenogenetic ESCs. The resulting hybrid cells expressed the pluripotency markers Oct4 and Nanog. In addition, methylation of several imprinted genes except Peg3 was comparable between hybrid cells and ESCs. This finding indicates that reprogramming by cell fusion does not necessarily reverse the status of all imprinted genes to the state of pluripotent fusion partner.

  19. Impact and Recovery Pattern of a Spring Fire on a Pacific Coast Marsh - Observations and Implications for Endangered Species

    Science.gov (United States)

    Brown, L. N.; Willis, K. S.; Ambrose, R. F.; MacDonald, G. M.

    2015-12-01

    The flammability of California coastal marsh vegetation is highest in winter and spring when dominant high marsh plants such as Sarcocornia pacifica are dormant. With climate change the number of cool-season fires are increasing in the state, and marsh systems are becoming more vulnerable to fire disturbance. Very little information exists in peer-reviewed or grey literature on the presence of fire in Pacific Coast tidal marshes. In 1993, the Green Meadows fire in Ventura County, California burned a small portion of tidally influenced Sarcocornia­-dominated marsh at Point Mugu. After the May 2013 Springs Fire burned a similar portion of the salt marsh vegetation, we conducted a two-year vegetation recovery survey using transects of surface vegetation plots and MODIS derived NDVI remote sensing monitoring. Recovery during the first year was limited. Sixteen months into the recovery period, percent plant coverage reached an average of approximately 60% for all plots in the burned area, as opposed to an average of 100% in control plots, and remained at that level for the duration of the study. NDVI did not approach near pre-fire conditions until 19 months after the fire. While recovery may have been influenced by California's current extreme drought conditions, the recurrence of fire and rate of recovery raise many important questions as to the role of fire in Pacific coast tidal marshes. For example, the lack of Salicornia cover over more than an entire breeding season would be detrimental to protected species such as Rallus obsoletus. Fire adds new vulnerabilities on critical tidal marsh habitat already taxed by the threat of sea-level rise, coastal squeeze and invasive species.

  20. Cell cycles and proliferation patterns in Haematococcus pluvialis

    Science.gov (United States)

    Zhang, Chunhui; Liu, Jianguo; Zhang, Litao

    2016-09-01

    Most studies on Haematococcus pluvialis have been focused on cell growth and astaxanthin accumulation; far less attention has been paid to cell cycles and proliferation patterns. The purpose of this study was to clarify cell cycles and proliferation patterns in H. pluvialis microscopically using a camera and video recorder system. The complicated life history of H. pluvialis can be divided into two stages: the motile stage and the non-motile stage. All the cells can be classified into forms as follows: motile cell, non-motile cell, zoospore and aplanospore. The main cell proliferation, both in the motile phase and non-motile phase in H. pluvialis, is by asexual reproduction. Under normal growth conditions, a motile cell usually produces two, sometimes four, and exceptionally eight zoospores. Under unfavorable conditions, the motile cell loses its flagella and transforms into a non-motile cell, and the non-motile cell usually produces 2, 4 or 8 aplanospores, and occasionally 20-32 aplanospores, which further develop into non-motile cells. Under suitable conditions, the non-motile cell is also able to release zoospores. The larger non-motile cells produce more than 16 zoospores, and the smaller ones produce 4 or 8 zoospores. Vegetative reproduction is by direct cell division in the motile phase and by occasional cell budding in the non-motile phase. There is, as yet, no convincing direct evidence for sexual reproduction.

  1. Heterogeneous differentiation patterns of individual CD8+ T cells.

    Science.gov (United States)

    Gerlach, Carmen; Rohr, Jan C; Perié, Leïla; van Rooij, Nienke; van Heijst, Jeroen W J; Velds, Arno; Urbanus, Jos; Naik, Shalin H; Jacobs, Heinz; Beltman, Joost B; de Boer, Rob J; Schumacher, Ton N M

    2013-05-03

    Upon infection, antigen-specific CD8(+) T lymphocyte responses display a highly reproducible pattern of expansion and contraction that is thought to reflect a uniform behavior of individual cells. We tracked the progeny of individual mouse CD8(+) T cells by in vivo lineage tracing and demonstrated that, even for T cells bearing identical T cell receptors, both clonal expansion and differentiation patterns are heterogeneous. As a consequence, individual naïve T lymphocytes contributed differentially to short- and long-term protection, as revealed by participation of their progeny during primary versus recall infections. The discordance in fate of individual naïve T cells argues against asymmetric division as a singular driver of CD8(+) T cell heterogeneity and demonstrates that reproducibility of CD8(+) T cell responses is achieved through population averaging.

  2. Alteration of the discharge pattern of rat diencephalic neurones with scrotal skin temperature.

    Science.gov (United States)

    Taylor, D C; Gayton, R J

    1986-12-03

    Neuronal responses to different scrotal skin temperatures were examined in the hypothalamus of anaesthetised male rats. Mean firing rate and interspike intervals were calculated on-line by microcomputers. Two types of response were observed when the scrotal skin was warmed: an abrupt change in mean firing rate coupled with a change in firing pattern, or a change of pattern unaccompanied by any change in mean rate. These results suggest that hypothalamic cells can convey information independently of their mean firing rate.

  3. Century-scale patterns and trends of global pyrogenic carbon emissions and fire influences on terrestrial carbon balance

    Science.gov (United States)

    Yang, Jia; Tian, Hanqin; Tao, Bo; Ren, Wei; Lu, Chaoqun; Pan, Shufen; Wang, Yuhang; Liu, Yongqiang

    2015-09-01

    Fires have consumed a large amount of terrestrial organic carbon and significantly influenced terrestrial ecosystems and the physical climate system over the past century. Although biomass burning has been widely investigated at a global level in recent decades via satellite observations, less work has been conducted to examine the century-scale changes in global fire regimes and fire influences on the terrestrial carbon balance. In this study, we investigated global pyrogenic carbon emissions and fire influences on the terrestrial carbon fluxes from 1901 to 2010 by using a process-based land ecosystem model. Our results show a significant declining trend in global pyrogenic carbon emissions between the early 20th century and the mid-1980s but a significant upward trend between the mid-1980s and the 2000s as a result of more frequent fires in ecosystems with high carbon storage, such as peatlands and tropical forests. Over the past 110 years, average pyrogenic carbon emissions were estimated to be 2.43 Pg C yr-1 (1 Pg = 1015 g), and global average combustion rate (defined as carbon emissions per unit area burned) was 537.85 g C m-2 burned area. Due to the impacts of fires, the net primary productivity and carbon sink of global terrestrial ecosystems were reduced by 4.14 Pg C yr-1 and 0.57 Pg C yr-1, respectively. Our study suggests that special attention should be paid to fire activities in the peatlands and tropical forests in the future. Practical management strategies, such as minimizing forest logging and reducing the rate of cropland expansion in the humid regions, are in need to reduce fire risk and mitigate fire-induced greenhouse gases emissions.

  4. Comparison of the Hazard Mapping System (HMS) fire product to ground-based fire records in Georgia, USA

    Science.gov (United States)

    Hu, Xuefei; Yu, Chao; Tian, Di; Ruminski, Mark; Robertson, Kevin; Waller, Lance A.; Liu, Yang

    2016-03-01

    Biomass burning has a significant and adverse impact on air quality, climate change, and various ecosystems. The Hazard Mapping System (HMS) detects fires using data from multiple satellite sensors in order to maximize its fire detection rate. However, to date, the detection rate of the HMS fire product for small fires has not been well studied, especially using ground-based fire records. This paper utilizes the 2011 fire information compiled from ground observations and burn authorizations in Georgia to assess the comprehensiveness of the HMS active fire product. The results show that detection rates of the hybrid HMS increase substantially by integrating multiple satellite instruments. The detection rate increases dramatically from 3% to 80% with an increase in fire size from less than 0.02 km2 to larger than 2 km2, resulting in detection of approximately 12% of all recorded fires which represent approximately 57% of the total area burned. The spatial pattern of detection rates reveals that grid cells with high detection rates are generally located in areas where large fires occur frequently. The seasonal analysis shows that overall detection rates in winter and spring (12% and 13%, respectively) are higher than those in summer and fall (3% and 6%, respectively), mainly because of higher percentages of large fires (>0.19 km2) that occurred in winter and spring. The land cover analysis shows that detection rates are 2-7 percentage points higher in land cover types that are prone to large fires such as forestland and shrub land.

  5. Topology optimization of front metallization patterns for solar cells

    NARCIS (Netherlands)

    Gupta, D.K.; Langelaar, M.; Barink, M.; Keulen, F. van

    2015-01-01

    This paper presents the application of topology optimization (TO) for designing the front electrode patterns for solar cells. Improving the front electrode design is one of the approaches to improve the performance of the solar cells. It serves to produce the voltage distribution for the front surfa

  6. Myocardial Cell Pattern on Piezoelectric Nanofiber Mats for Energy Harvesting

    Science.gov (United States)

    Liu, X.; Wang, X.; Zhao, H.; Du, Y.

    2014-11-01

    The paper presents in vitro contractile myocardial cell pattern on piezoelectric nanofiber mats with applications in energy harvesting. The cell-based energy harvester consists of myocardial cell sheet and a PDMS substrate with a PVDF nanofiber mat on. Experimentally, cultured on specifically distributed nanofiber mats, neonatal rat ventricular cardiomyocytes are characterized with the related morphology and contraction. Previously, we have come up with the concept of energy harvesting from heart beating using piezoelectric material. A bio-hybrid energy harvester combined living cardiomyocytes, PDMS polymer substrate and piezoelectric PVDF film with the electrical output of peak current 87.5nA and peak voltage 92.3mV. However, the thickness of the cardiomyocyte cultured on a two-dimensional substrate is much less than that of the piezoelectric film. The Micro Contact Printing (μCP) method used in cell pattern on the PDMS thin film has tough requirement for the film surface. As such, in this paper we fabricated nanofiber-constructed PDMS thin film to realize cell pattern due to PVDF nanofibers with better piezoelectricity and microstructures of nanofiber mats guiding cell distribution. Living cardiomyocytes patterned on those distributed piezoelectric nanofibers with the result of the same distribution as the nanofiber pattern.

  7. Distinct Pattern of Human Vδ1 T Cells Recognizing MICA

    Institute of Scientific and Technical Information of China (English)

    Jianqiang Li; Lianxian Cui; Wei He

    2005-01-01

    γδ T cells represent one unique recognition pattern, the limited recognition, which distinguishes from the specific recognition for αβ T cells and pattern recognition for macrophages. Vδ1 γδ T cell is the major subset of human γδT cells, which predominates in mucosal tissue including the intestinal epithelia. Presently, a few antigens that human Vδ1TCR can recognize have been identified. Among them, MHC class Ⅰ chain-related molecules A (MICA)have been studied most intensively. Besides Vδ1TCR, MICA is also the ligand of NKG2D, a C-type lectin-like activating immunoreceptor. In human, only Vδ1 cells can simultaneously express both types of receptors of MICA while NK cells, αβ T cells and other subsets of γδ T cells likewise express NKG2D. Although the precise mechanisms are still enigmatic, this distinct pattern of Vδ1 cells recognizing MICA predicts unique biological significance of Vδ1 cells in immune defense. Recent years, some progresses have been made in this issue. In this review we summarize the related reports and put forward some novel views based on our group's studies.

  8. The Classification of HEp-2 Cell Patterns Using Fractal Descriptor.

    Science.gov (United States)

    Xu, Rudan; Sun, Yuanyuan; Yang, Zhihao; Song, Bo; Hu, Xiaopeng

    2015-07-01

    Indirect immunofluorescence (IIF) with HEp-2 cells is considered as a powerful, sensitive and comprehensive technique for analyzing antinuclear autoantibodies (ANAs). The automatic classification of the HEp-2 cell images from IIF has played an important role in diagnosis. Fractal dimension can be used on the analysis of image representing and also on the property quantification like texture complexity and spatial occupation. In this study, we apply the fractal theory in the application of HEp-2 cell staining pattern classification, utilizing fractal descriptor firstly in the HEp-2 cell pattern classification with the help of morphological descriptor and pixel difference descriptor. The method is applied to the data set of MIVIA and uses the support vector machine (SVM) classifier. Experimental results show that the fractal descriptor combining with morphological descriptor and pixel difference descriptor makes the precisions of six patterns more stable, all above 50%, achieving 67.17% overall accuracy at best with relatively simple feature vectors.

  9. Low temperature co-fired ceramic packaging of CMOS capacitive sensor chip towards cell viability monitoring

    Directory of Open Access Journals (Sweden)

    Niina Halonen

    2016-11-01

    Full Text Available Cell viability monitoring is an important part of biosafety evaluation for the detection of toxic effects on cells caused by nanomaterials, preferably by label-free, noninvasive, fast, and cost effective methods. These requirements can be met by monitoring cell viability with a capacitance-sensing integrated circuit (IC microchip. The capacitance provides a measurement of the surface attachment of adherent cells as an indication of their health status. However, the moist, warm, and corrosive biological environment requires reliable packaging of the sensor chip. In this work, a second generation of low temperature co-fired ceramic (LTCC technology was combined with flip-chip bonding to provide a durable package compatible with cell culture. The LTCC-packaged sensor chip was integrated with a printed circuit board, data acquisition device, and measurement-controlling software. The packaged sensor chip functioned well in the presence of cell medium and cells, with output voltages depending on the medium above the capacitors. Moreover, the manufacturing of microfluidic channels in the LTCC package was demonstrated.

  10. Plasma-Sprayed Titanium Patterns for Enhancing Early Cell Responses

    Science.gov (United States)

    Shi, Yunqi; Xie, Youtao; Pan, Houhua; Zheng, Xuebin; Huang, Liping; Ji, Fang; Li, Kai

    2016-06-01

    Titanium coating has been widely used as a biocompatible metal in biomedical applications. However, the early cell responses and long-term fixation of titanium implants are not satisfied. To obviate these defects, in this paper, micro-post arrays with various widths (150-1000 μm) and intervals (100-300 μm) were fabricated on the titanium substrate by template-assisted plasma spraying technology. In vitro cell culture experiments showed that MC3T3-E1 cells exhibited significantly higher osteogenic differentiation as well as slightly improved adhesion and proliferation on the micro-patterned coatings compared with the traditional one. The cell number on the pattern with 1000 µm width reached 130% after 6 days of incubation, and the expressions of osteopontin (OPN) as well as osteocalcin (OC) were doubled. No obvious difference was found in cell adhesion on various size patterns. The present micro-patterned coatings proposed a new modification method for the traditional plasma spraying technology to enhance the early cell responses and convenience for the bone in-growth.

  11. Development of Spatial Distribution Patterns by Biofilm Cells

    DEFF Research Database (Denmark)

    Haagensen, Janus Anders Juul; Hansen, Susse Kirkelund; Bak Christensen, Bjarke

    2015-01-01

    Confined spatial patterns of microbial distribution are prevalent in nature, such as in microbial mats, soil communities, and water stream biofilms. The symbiotic two-species consortium of Pseudomonas putida and Acinetobacter sp. C6, originally isolated from a creosote-polluted aquifer, has evolved...... a distinct spatial organization in the laboratory that is characterized by an increased fitness and productivity. In this consortium, P. putida is reliant on microcolonies formed by Acinetobacter sp. C6 — to which it attaches. Here we describe the processes that lead to the microcolony......-pattern by Acinetobacter sp. C6. Ecological spatial pattern analyses revealed that the microcolonies were not entirely randomly distributed, and instead arranged in a uniform pattern. Detailed time-lapse confocal microscopy at the single cell level demonstrated that the spatial pattern was the result of an intriguing self...

  12. Cell Patterning for Liver Tissue Engineering via Dielectrophoretic Mechanisms

    Directory of Open Access Journals (Sweden)

    Wan Nurlina Wan Yahya

    2014-07-01

    Full Text Available Liver transplantation is the most common treatment for patients with end-stage liver failure. However, liver transplantation is greatly limited by a shortage of donors. Liver tissue engineering may offer an alternative by providing an implantable engineered liver. Currently, diverse types of engineering approaches for in vitro liver cell culture are available, including scaffold-based methods, microfluidic platforms, and micropatterning techniques. Active cell patterning via dielectrophoretic (DEP force showed some advantages over other methods, including high speed, ease of handling, high precision and being label-free. This article summarizes liver function and regenerative mechanisms for better understanding in developing engineered liver. We then review recent advances in liver tissue engineering techniques and focus on DEP-based cell patterning, including microelectrode design and patterning configuration.

  13. Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction.

    Science.gov (United States)

    Watanabe, Kohei; Holobar, Aleš; Kouzaki, Motoki; Ogawa, Madoka; Akima, Hiroshi; Moritani, Toshio

    2016-06-01

    Age-related changes in motor unit activation properties remain unclear for locomotor muscles such as quadriceps muscles, although these muscles are preferentially atrophied with aging and play important roles in daily living movements. The present study investigated and compared detailed motor unit firing characteristics for the vastus lateralis muscle during isometric contraction at low to moderate force levels in the elderly and young. Fourteen healthy elderly men and 15 healthy young men performed isometric ramp-up contraction to 70 % of the maximal voluntary contractions (MVC) during knee extension. Multichannel surface electromyograms were recorded from the vastus lateralis muscle using a two-dimensional grid of 64 electrodes and decomposed with the convolution kernel compensation technique to extract individual motor units. Motor unit firing rates in the young were significantly higher (~+29.7 %) than in the elderly (p  0.05). Firing rates at 60 % of the MVC force level for the motor units recruited at MVC were significantly correlated with MVC force in the elderly (r = 0.885, p  0.05). These results suggest that the motor unit firing rate in the vastus lateralis muscle is affected by aging and muscle strength in the elderly and/or age-related strength loss is related to motor unit firing/recruitment properties.

  14. Physical and chemical analysis of lithium-ion battery cell-to-cell failure events inside custom fire chamber

    Science.gov (United States)

    Spinner, Neil S.; Field, Christopher R.; Hammond, Mark H.; Williams, Bradley A.; Myers, Kristina M.; Lubrano, Adam L.; Rose-Pehrsson, Susan L.; Tuttle, Steven G.

    2015-04-01

    A 5-cubic meter decompression chamber was re-purposed as a fire test chamber to conduct failure and abuse experiments on lithium-ion batteries. Various modifications were performed to enable remote control and monitoring of chamber functions, along with collection of data from instrumentation during tests including high speed and infrared cameras, a Fourier transform infrared spectrometer, real-time gas analyzers, and compact reconfigurable input and output devices. Single- and multi-cell packages of LiCoO2 chemistry 18650 lithium-ion batteries were constructed and data was obtained and analyzed for abuse and failure tests. Surrogate 18650 cells were designed and fabricated for multi-cell packages that mimicked the thermal behavior of real cells without using any active components, enabling internal temperature monitoring of cells adjacent to the active cell undergoing failure. Heat propagation and video recordings before, during, and after energetic failure events revealed a high degree of heterogeneity; some batteries exhibited short burst of sparks while others experienced a longer, sustained flame during failure. Carbon monoxide, carbon dioxide, methane, dimethyl carbonate, and ethylene carbonate were detected via gas analysis, and the presence of these species was consistent throughout all failure events. These results highlight the inherent danger in large format lithium-ion battery packs with regards to cell-to-cell failure, and illustrate the need for effective safety features.

  15. Generation of Viable Cell and Biomaterial Patterns by Laser Transfer

    Science.gov (United States)

    Ringeisen, Bradley

    2001-03-01

    In order to fabricate and interface biological systems for next generation applications such as biosensors, protein recognition microarrays, and engineered tissues, it is imperative to have a method of accurately and rapidly depositing different active biomaterials in patterns or layered structures. Ideally, the biomaterial structures would also be compatible with many different substrates including technologically relevant platforms such as electronic circuits or various detection devices. We have developed a novel laser-based technique, termed matrix assisted pulsed laser evaporation direct write (MAPLE DW), that is able to direct write patterns and three-dimensional structures of numerous biologically active species ranging from proteins and antibodies to living cells. Specifically, we have shown that MAPLE DW is capable of forming mesoscopic patterns of living prokaryotic cells (E. coli bacteria), living mammalian cells (Chinese hamster ovaries), active proteins (biotinylated bovine serum albumin, horse radish peroxidase), and antibodies specific to a variety of classes of cancer related proteins including intracellular and extracellular matrix proteins, signaling proteins, cell cycle proteins, growth factors, and growth factor receptors. In addition, patterns of viable cells and active biomolecules were deposited on different substrates including metals, semiconductors, nutrient agar, and functionalized glass slides. We will present an explanation of the laser-based transfer mechanism as well as results from our recent efforts to fabricate protein recognition microarrays and tissue-based microfluidic networks.

  16. Multiscale patterned transplantable stem cell patches for bone tissue regeneration.

    Science.gov (United States)

    Kim, Jangho; Bae, Won-Gyu; Choung, Han-Wool; Lim, Ki Taek; Seonwoo, Hoon; Jeong, Hoon Eui; Suh, Khap-Yang; Jeon, Noo Li; Choung, Pill-Hoon; Chung, Jong Hoon

    2014-11-01

    Stem cell-based therapy has been proposed as an enabling alternative not only for the treatment of diseases but also for the regeneration of tissues beyond complex surgical treatments or tissue transplantation. In this study, we approached a conceptual platform that can integrate stem cells into a multiscale patterned substrate for bone regeneration. Inspired by human bone tissue, we developed hierarchically micro- and nanopatterned transplantable patches as synthetic extracellular matrices by employing capillary force lithography in combination with a surface micro-wrinkling method using a poly(lactic-co-glycolic acid) (PLGA) polymer. The multiscale patterned PLGA patches were highly flexible and showed higher tissue adhesion to the underlying tissue than did the single nanopatterned patches. In response to the anisotropically multiscale patterned topography, the adhesion and differentiation of human mesenchymal stem cells (hMSCs) were sensitively controlled. Furthermore, the stem cell patch composed of hMSCs and transplantable PLGA substrate promoted bone regeneration in vivo when both the micro- and nanotopography of the substrate surfaces were synergistically combined. Thus, our study concludes that multiscale patterned transplantable stem cell patches may have a great potential for bone regeneration as well as for various regenerative medicine approaches.

  17. Fires in Amazonia

    Science.gov (United States)

    Aragão, Luiz E. O. C.; Anderson, Liana O.; Lima, André; Arai, Egidio

    2016-11-01

    Fire has been used since the first humans arrived in Amazonia; however, it has recently become a widely used instrument for large-scale forest clearance. Patterns of fire incidence in the region have been exacerbated by recent drought events. Understanding temporal and spatial fire patterns as well as their consequences for forest structure, species composition, and the carbon cycle is critical for minimising global change impacts on Amazonian ecosystems and people. In this chapter, we provide an overview of the state of our knowledge on the spatial and temporal patterns of fire incidence in Amazonia, depicting the historical fire usage in the region, their relationship with land use and land cover, and their responses to climate seasonality and droughts. We subsequently focus on the impacts of fire, by quantifying the extent of burnt forests during major droughts and describing the main impacts on forest structure, composition, and carbon stocks. Finally, we present an overview of modelling initiatives for forecasting fire incidence in the region. We conclude by providing a comprehensive view of the processes that influence fire occurrence, potential feedbacks, and impacts in Amazonia. We also highlight how key areas within fire ecology must be improved for a better understanding of the long-term effect of fire on the Amazon forest 'biome'.

  18. Immunohistochemical patterns of follicular dendritic cell meshwork and Ki-67 in small B-cell lymphomas

    Institute of Scientific and Technical Information of China (English)

    时云飞

    2013-01-01

    Objective To identify the immunohistochemical patterns of follicular dendritic cell(FDC)meshwork and Ki-67labeling index in small B-cell lymphomas(SBLs) and their significance in differential diagnosis.Methods

  19. Cell cycling and patterned cell proliferation in the wing primordium of Drosophila.

    OpenAIRE

    1996-01-01

    The pattern of cell proliferation in the Drosophila imaginal wing primordium is spatially and temporally heterogeneous. Direct visualization of cells in S, G2, and mitosis phases of the cell cycle reveals several features invariant throughout development. The fraction of cells in the disc in the different cell cycle stages is constant, the majority remaining in G1. Cells in the different phases of the cell cycle mainly appear in small synchronic clusters that are nonclonally derived but resul...

  20. Fire in the Earth system.

    Science.gov (United States)

    Bowman, David M J S; Balch, Jennifer K; Artaxo, Paulo; Bond, William J; Carlson, Jean M; Cochrane, Mark A; D'Antonio, Carla M; Defries, Ruth S; Doyle, John C; Harrison, Sandy P; Johnston, Fay H; Keeley, Jon E; Krawchuk, Meg A; Kull, Christian A; Marston, J Brad; Moritz, Max A; Prentice, I Colin; Roos, Christopher I; Scott, Andrew C; Swetnam, Thomas W; van der Werf, Guido R; Pyne, Stephen J

    2009-04-24

    Fire is a worldwide phenomenon that appears in the geological record soon after the appearance of terrestrial plants. Fire influences global ecosystem patterns and processes, including vegetation distribution and structure, the carbon cycle, and climate. Although humans and fire have always coexisted, our capacity to manage fire remains imperfect and may become more difficult in the future as climate change alters fire regimes. This risk is difficult to assess, however, because fires are still poorly represented in global models. Here, we discuss some of the most important issues involved in developing a better understanding of the role of fire in the Earth system.

  1. Discovering urban activity patterns in cell phone data

    OpenAIRE

    Widhalm, Peter; Yang, Yingxiang; Ulm, Michael; Athavale, Shounak; Gonzalez, Marta C.

    2015-01-01

    Massive and passive data such as cell phone traces provide samples of the whereabouts and movements of individuals. These are a potential source of information for models of daily activities in a city. The main challenge is that phone traces have low spatial precision and are sparsely sampled in time, which requires a precise set of techniques for mining hidden valuable information they contain. Here we propose a method to reveal activity patterns that emerge from cell phone data by analyzing...

  2. Expressional patterns of chaperones in ten human tumor cell lines

    Directory of Open Access Journals (Sweden)

    Slavc Irene

    2004-12-01

    Full Text Available Abstract Background Chaperones (CH play an important role in tumor biology but no systematic work on expressional patterns has been reported so far. The aim of the study was therefore to present an analytical method for the concomitant determination of several CH in human tumor cell lines, to generate expressional patterns in the individual cell lines and to search for tumor and non-tumor cell line specific CH expression. Human tumor cell lines of neuroblastoma, colorectal and adenocarcinoma of the ovary, osteosarcoma, rhabdomyosarcoma, malignant melanoma, lung, cervical and breast cancer, promyelocytic leukaemia were homogenised, proteins were separated on two-dimensional gel electrophoresis with in-gel digestion of proteins and MALDI-TOF/TOF analysis was carried out for the identification of CH. Results A series of CH was identified including the main CH groups as HSP90/HATPas_C, HSP70, Cpn60_TCP1, DnaJ, Thioredoxin, TPR, Pro_isomerase, HSP20, ERP29_C, KE2, Prefoldin, DUF704, BAG, GrpE and DcpS. Conclusions The ten individual tumor cell lines showed different expression patterns, which are important for the design of CH studies in tumor cell lines. The results can serve as a reference map and form the basis of a concomitant determination of CH by a protein chemical rather than an immunochemical method, independent of antibody availability or specificity.

  3. A Review of Fire Interactions and Mass Fires

    Directory of Open Access Journals (Sweden)

    Mark A. Finney

    2011-01-01

    Full Text Available The character of a wildland fire can change dramatically in the presence of another nearby fire. Understanding and predicting the changes in behavior due to fire-fire interactions cannot only be life-saving to those on the ground, but also be used to better control a prescribed fire to meet objectives. In discontinuous fuel types, such interactions may elicit fire spread where none otherwise existed. Fire-fire interactions occur naturally when spot fires start ahead of the main fire and when separate fire events converge in one location. Interactions can be created intentionally during prescribed fires by using spatial ignition patterns. Mass fires are among the most extreme examples of interactive behavior. This paper presents a review of the detailed effects of fire-fire interaction in terms of merging or coalescence criteria, burning rates, flame dimensions, flame temperature, indraft velocity, pulsation, and convection column dynamics. Though relevant in many situations, these changes in fire behavior have yet to be included in any operational-fire models or decision support systems.

  4. Fire Perimeters

    Data.gov (United States)

    California Department of Resources — The Fire Perimeters data consists of CDF fires 300 acres and greater in size and USFS fires 10 acres and greater throughout California from 1950 to 2003. Some fires...

  5. Fire History

    Data.gov (United States)

    California Department of Resources — The Fire Perimeters data consists of CDF fires 300 acres and greater in size and USFS fires 10 acres and greater throughout California from 1950 to 2002. Some fires...

  6. Development of Spatial Distribution Patterns by Biofilm Cells.

    Science.gov (United States)

    Haagensen, Janus A J; Hansen, Susse K; Christensen, Bjarke B; Pamp, Sünje J; Molin, Søren

    2015-09-01

    Confined spatial patterns of microbial distribution are prevalent in nature, such as in microbial mats, soil communities, and water stream biofilms. The symbiotic two-species consortium of Pseudomonas putida and Acinetobacter sp. strain C6, originally isolated from a creosote-polluted aquifer, has evolved a distinct spatial organization in the laboratory that is characterized by an increased fitness and productivity. In this consortium, P. putida is reliant on microcolonies formed by Acinetobacter sp. C6, to which it attaches. Here we describe the processes that lead to the microcolony pattern by Acinetobacter sp. C6. Ecological spatial pattern analyses revealed that the microcolonies were not entirely randomly distributed and instead were arranged in a uniform pattern. Detailed time-lapse confocal microscopy at the single-cell level demonstrated that the spatial pattern was the result of an intriguing self-organization: small multicellular clusters moved along the surface to fuse with one another to form microcolonies. This active distribution capability was dependent on environmental factors (carbon source and oxygen) and historical contingency (formation of phenotypic variants). The findings of this study are discussed in the context of species distribution patterns observed in macroecology, and we summarize observations about the processes involved in coadaptation between P. putida and Acinetobacter sp. C6. Our results contribute to an understanding of spatial species distribution patterns as they are observed in nature, as well as the ecology of engineered communities that have the potential for enhanced and sustainable bioprocessing capacity.

  7. Oxygen-glucose deprivation increases firing of unipolar brush cells and enhances spontaneous EPSCs in Purkinje cells in the vestibulo-cerebellum.

    Science.gov (United States)

    Takayasu, Yukihiro; Shino, Masato; Nikkuni, Osamu; Yoshida, Yukari; Furuya, Nobuhiko; Chikamatsu, Kazuaki

    2016-05-01

    Unipolar brush cells (UBCs) are excitatory interneurons in the granular layer of the cerebellar cortex, which are predominantly distributed in the vestibulo-cerebellar region. The unique firing properties and synaptic connections of UBCs may underlie lobular heterogeneity of excitability in the granular layer and the susceptibility to ischemia-induced excitotoxicity. In this study, we investigated the effects of oxygen-glucose deprivation (OGD) on the firing properties of UBCs and granule cells and spontaneous excitatory postsynaptic currents (sEPSCs) of Purkinje cells using whole-cell recordings. Short-term OGD induced increases in spontaneous firing of UBCs by causing membrane depolarization via the activation of NMDA receptors. UBC firing indirectly affected Purkinje cells by altering parallel fiber inputs of a subset granule cells, resulting in a marked increase in sEPSCs in Purkinje cells in vestibulo-cerebellar lobules IX-X, but not in lobules IV-VI, which have fewer UBCs. Similarly, the frequency and amplitude of sEPSCs in Purkinje cells were significantly greater in lobules IX-X than in IV-VI, even in control conditions. These results reveal that UBCs play key roles in regulating local excitability in the granular layer, resulting in lobular heterogeneity in the susceptibility to ischemic insult in the cerebellum.

  8. Efficiency Gain For Bi-Facial Multi-Crystalline Solar Cell With Uncapped Al2O3 And Local Firing-Through Al-BSF

    Energy Technology Data Exchange (ETDEWEB)

    Cesar, I.; Manshanden, P.; Janssen, G.; Weeber, A.W. [ECN Solar Energy, P.O. Box 1, 1755 ZG Petten (Netherlands); Granneman, E.; Siarheyeva, O. [Levitech BV, Versterkerstraat 10, 1322 AP Almere (Netherlands)

    2013-06-15

    The p-type bi-facial cell concept, p-PASHA (Passivated on all sides H- pattern), is developed at ECN and employs an uncapped AlOx passivation layer on the rear through which a screen printed H-pattern of aluminium contacts is fired. Here we report a net gain in cell efficiency of 0.2% absolute for the p-PASHA cell vs. industrial reference with the addition of a clean and an ALD step. Even higher gains up to 0.5% abs. are expected after optimization of the cell design and process. Apart from the efficiency gain, the bi-facial cell concept allows for 50-80% reduction in Al paste consumption, the use of thinner wafers, and consists of less processing steps compared to prevalent PERC concepts. The Al2O3 dielectric layer is deposited in the Levitrack, an industrial-type system for high-throughput Atomic Layer Deposition (ALD) developed by Levitech. The efficiency gain is obtained on multi-crystalline wafers, at a rear metal fraction of 40%. Localized IQE mapping, cross-sectional SEM investigation, resistance measurements and 2D simulation relate the efficiency improvement compared to our conventional process to better eutectic and BSF formation at the Al contact edges.

  9. Pattern matching based active optical sorting of colloids/cells

    Science.gov (United States)

    Verma, R. S.; Dasgupta, R.; Ahlawat, S.; Kumar, N.; Uppal, A.; Gupta, P. K.

    2013-08-01

    We report active optical sorting of colloids/cells by employing a cross correlation based pattern matching technique for selection of the desired objects and thereafter sorting using dynamically controllable holographic optical traps. The problem of possible collision between the different sets of objects during sorting was avoided by raising one set of particles to a different plane. We also present the results obtained on using this approach for some representative applications such as sorting of silica particles of two different sizes, of closely packed colloids and of white blood cells and red blood cells from a mixture of the two.

  10. Herbaceous species diversity patterns across various treatments of herbivory and fire along the sodic zone of the Nkuhlu exclosures, Kruger National Park

    Directory of Open Access Journals (Sweden)

    Helga van Coller

    2013-02-01

    Full Text Available Understanding relationships between large herbivores and plant species diversity in dynamic riparian zones is critical to biodiversity conservation. The Nkuhlu exclosures in the Kruger National Park (KNP provided opportunity to investigate spatial heterogeneity patterns within riparian zones, as well as how these patterns are affected by fire and herbivory. A monitoring project was initiated to answer questions about the dynamics of the herbaceous layer and was aimed at determining, (1 whether there exists meaningful variance in herbaceous plant species richness and diversity across different treatments in the ecologically sensitive sodic zone and (2 whether an increase in herbaceous biomass, an artefact of herbivory and fire exclusion, suppresses herbaceous plant species diversity and richness. Herbaceous vegetation was sampled in two 1 m2 circular sub-plots in the eastern and western corners of 81 fixed plots. The biomass of each plot was estimated with a disc pasture meter (DPM diagonally with the plot. DPM-readings were converted to kg/ha, according to the latest conversions for the Lowveld Savanna. Species richness and biomass showed significant variance across treatments, whereas no significant variation in herbaceous species diversity was perceived. Combined treatment of fire absence and herbivore presence contributed to higher forb species richness in the sodic zone. Biomass is significantly higher in fully fenced areas where herbivores are excluded, as opposed to the open and partially fenced areas. Although no significant variation was recorded for diversity across treatments, lowest diversity was recorded in the absence of all herbivores, especially in combination with fire treatment. Therefore herbivores are essential in sustaining herbaceous plant species richness in the sodic zone, whilst no significant results were found with regard to their effect on species diversity. Although statistically non-significant, fire seems to

  11. Effects of habitat characteristics and interspecific interactions on co-occurrence patterns of saproxylic beetles breeding in tree boles after forest fire: null model analyses.

    Science.gov (United States)

    Azeria, Ermias T; Ibarzabal, Jacques; Hébert, Christian

    2012-04-01

    It is often suggested that habitat attributes and interspecific interactions can cause non-random species co-occurrence patterns, but quantifying their contributions can be difficult. Null models that systematically exclude and include habitat effects can give information on the contribution of these factors to community assembly. In the boreal forest, saproxylic beetles are known to be attracted to recently burned forests where they breed in dead and dying trees. We examined whether species co-occurrences of saproxylic beetles that develop in, and emerge from, boles of recently burned trees show non-random patterns. We also estimated the extent to which both the post-fire habitat attributes and interspecific interactions among beetles contribute to such patterns. We sampled tree boles encompassing key attributes (tree species, tree size/dbh and burn severity) that are thought to characterize species-habitat associations of saproxylic beetles, a proposition that we tested using indicator species analysis. Two null models with no habitat constraints ("unconstrained") indicated that a total of 29.4% of the species pairs tested had significant co-occurrence patterns. Habitat-constrained null models indicated that most of the detected species aggregations (72%) and segregations (59%) can be explained by shared and distinct species-habitat relationships, respectively. The assembly pattern was also driven by interspecific interactions, of which some were modulated by habitat; for example, predator and prey species tended to co-occur in large-sized trees (a proxy of available bark/wood food resource primarily for the prey). In addition, some species segregation suggesting antagonistic, competitive, or prey-predator interactions were evident after accounting for the species' affinities for the same tree species. Overall, our results suggest that an intimate link between habitat and interspecific interactions can have important roles for community assembly of saproxylic

  12. High resolution imaging of surface patterns of single bacterial cells

    Energy Technology Data Exchange (ETDEWEB)

    Greif, Dominik; Wesner, Daniel [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany); Regtmeier, Jan, E-mail: jan.regtmeier@physik.uni-bielefeld.de [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany); Anselmetti, Dario [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany)

    2010-09-15

    We systematically studied the origin of surface patterns observed on single Sinorhizobium meliloti bacterial cells by comparing the complementary techniques atomic force microscopy (AFM) and scanning electron microscopy (SEM). Conditions ranged from living bacteria in liquid to fixed bacteria in high vacuum. Stepwise, we applied different sample modifications (fixation, drying, metal coating, etc.) and characterized the observed surface patterns. A detailed analysis revealed that the surface structure with wrinkled protrusions in SEM images were not generated de novo but most likely evolved from similar and naturally present structures on the surface of living bacteria. The influence of osmotic stress to the surface structure of living cells was evaluated and also the contribution of exopolysaccharide and lipopolysaccharide (LPS) by imaging two mutant strains of the bacterium under native conditions. AFM images of living bacteria in culture medium exhibited surface structures of the size of single proteins emphasizing the usefulness of AFM for high resolution cell imaging.

  13. Regional differences in lectin binding patterns of vestibular hair cells

    Science.gov (United States)

    Baird, Richard A.; Schuff, N. R.; Bancroft, J.

    1994-01-01

    Surface glycoconjugates of hair cells and supporting cells in the vestibular endorgans of the bullfrog were identified using biotinylated lectins with different carbohydrate specificities. Lectin binding in hair cells was consistent with the presence of glucose and mannose (CON A), galactose (RCA-I), N-acetylgalactosamine (VVA), but not fucose (UEA-I) residues. Hair cells in the bullfrog sacculus, unlike those in the utriculus and semicircular canals, did not stain for N-acetylglucosamine (WGA) or N-acetylgalactosamine (VVA). By contrast, WGA and, to a lesser extent, VVA, differentially stained utricular and semicircular canal hair cells, labeling hair cells located in peripheral, but not central, regions. In mammals, WGA uniformly labeled Type 1 hair cells while labeling, as in the bullfrog, Type 2 hair cells only in peripheral regions. These regional variations were retained after enzymatic digestion. We conclude that vestibular hair cells differ in their surface glycoconjugates and that differences in lectin binding patterns can be used to identify hair cell types and to infer the epithelial origin of isolated vestibular hair cells.

  14. Floristic patterns and disturbance history in karri ( Eucalyptus diversicolor: Myrtaceae) forest, south-western Australia: 2. Origin, growth form and fire response

    Science.gov (United States)

    Wardell-Johnson, Grant W.; Williams, M. R.; Mellican, A. E.; Annells, A.

    2007-03-01

    We examined the influence of disturbance history on the floristic composition of a single community type in karri forest, south-western Australia. Cover-abundance of 224 plant species and six disturbance and site-based environmental variables were recorded in 91, 20 m × 20 m quadrats. Numerical taxonomic and correlation approaches were used to relate these and 10 plant species-group variables based on origin, growth form and fire response. Ordination revealed no discernable pattern of sites based on floristic composition. However, all 10 species-group variables were significantly correlated with the ordination axes. Species richness within these groups varied with category and with respect to many of the disturbance and site variables. We encountered low diversity of vascular plants at the community level and limited diversity of growth forms. Thus most species were herbs (62.1%) or shrubs (30.3%), and there were no epiphytes and few species of trees or climbers. Although many introduced species were recorded (18.3% of all taxa), virtually all (83%) were herbs that demonstrated little persistence in the community, and there was limited evidence of transformer species. Time-since-fire (and other disturbance) influenced species richness more than the number of recent past fires because of a high proportion of ephemerals associated with the immediate post-fire period. Long-lived shrubs with soil stored seed dominate numerically, and in understorey biomass in comparison with neighboring vegetation types because of their greater flexibility of response following irregular, but intense disturbance events. However, interactions between nutrient status, regeneration mechanisms and community composition may be worthy of further investigation.

  15. Patterning cells on optically transparent indium tin oxide electrodes.

    Science.gov (United States)

    Shah, Sunny; Revzin, Alexander

    2007-01-01

    The ability to exercise precise spatial and temporal control over cell-surface interactions is an important prerequisite to the assembly of multi-cellular constructs serving as in vitro mimics of native tissues. In this study, photolithography and wet etching techniques were used to fabricate individually addressable indium tin oxide (ITO) electrodes on glass substrates. The glass substrates containing ITO microelectrodes were modified with poly(ethylene glycol) (PEG) silane to make them protein and cell resistive. Presence of insulating PEG molecules on the electrode surface was verified by cyclic voltammetry employing potassium ferricyanide as a redox reporter molecule. Importantly, the application of reductive potential caused desorption of the PEG layer, resulting in regeneration of the conductive electrode surface and appearance of typical ferricyanide redox peaks. Application of reductive potential also corresponded to switching of ITO electrode properties from cell non-adhesive to cell-adhesive. Electrochemical stripping of PEG-silane layer from ITO microelectrodes allowed for cell adhesion to take place in a spatially defined fashion, with cellular patterns corresponding closely to electrode patterns. Micropatterning of several cell types was demonstrated on these substrates. In the future, the control of the biointerfacial properties afforded by this method will allow to engineer cellular microenvironments through the assembly of three or more cell types into a precise geometric configuration on an optically transparent substrate.

  16. Microstructural investigations of materials for low temperature co-fired ceramic (LTCC) based fuel cell using small angle neutron scattering

    Science.gov (United States)

    Mohamed, A. A.; Ahmad, M. H.; Ibrahim, A.; Azman, A.; Alias, R.; Ambak, Z.; Shapee, S.; Putra, E. G.; Patriati, A.; Sharom, M. A.; Yazid, H.; Mamat, M. R.; Karim, J. A.; Idris, F. M.; Yazid, K.; Zin, M. R.

    2013-06-01

    The concept and the realization fuel cell based on LTCC technology require the investigations of fired LTCC microstructures. The majority of the works involved using small angle neutron scattering studies on the microstructural of LTCC ceramic tape and development of neutron tomography for future tool to visualize channels inside the fired tape. Most SANS characterization were carried out at Smarter SANS instrument at BATAN, Indonesia. Standard sample for resolving tens of micron of object size were measured using simple neutron tomography setup utilizing monochromatic SANS beam at Malaysian Nuclear Agency. The initial microstructural findings indicates that organic additives shape the final microstructural of LTCC after firing with the glassy material possibly fill the space left by the burned organic additives. The tomography results showed that 40 micron size object can be differentiated. The conductor deposited on LTCC is preliminary investigated which will later be used as support for catalyst.

  17. Role of calcium conductance in firing behavior of retinal ganglion cells

    Institute of Scientific and Technical Information of China (English)

    Dan Wang; Qingli Qiao; Nan Xie

    2011-01-01

    Fohlmeister-Coleman-Miller model of retinal ganglion cells consists of five ion channels; these are sodium channels, calcium channels, and 3 types of potassium channels. An increasing number of studies have investigated sodium channels, voltage-gated potassium channels, and delayed rectifier potassium channels. However, little is known about calcium channels, and in particular the dynamics and computational models of calcium ions. Retinal prostheses have been designed to assist with sight recovery for the blind, and in the present study, the effects of calcium ions in retinal ganglion cell models were analyzed with regard to calcium channel potential and calcium-activated potassium potential. Using MATLAB software, calcium conductance and calcium current from the Fohlmeister-Coleman-Miller model, under clamped voltages, were numerically computed using backward Euler methods. Subsequently, the Fohlmeister-Coleman-Miller model was simulated with the absence of calcium-current (lc,) or calcium-activated potassium current (IK, ca). The model was also analyzed according to the phase plane method.The relationship curve between peak calcium current and clamped potentials revealed an inverted bell shape, and the calcium-activated potassium current increased the frequency of firing and the peak of membrane potential. Results suggested that calcium ion concentrations play an important role in controlling the peak and the magnitude of peak membrane voltage in retinal ganglion cells.

  18. Low-power laser-based carbon monoxide sensor for fire and post-fire detection using a compact Herriott multipass cell

    Science.gov (United States)

    Thomazy, David; So, Stephen; Kosterev, Anatoliy; Lewicki, Rafal; Dong, Lei; Sani, Ardalan A.; Tittel, Frank K.

    2010-01-01

    With the anticipated retirement of Space Shuttles in the next few years, the re-supplying of short-lifetime sensors on the International Space Station (ISS) will be logistically more difficult. Carbon Monoxide (CO) is a well-known combustion product and its absence in a fire and post-fire environment is a reliable indicator for mission specialists that the air quality is at a safe to breathe level. We report on the development and performance of a prototype compact CO sensor, based on the PHOTONS platform [1], developed for the ISS based on tunable diode laser absorption spectroscopy (TDLAS). A CO absorption line at ~4285 cm-1 is targeted using a distributed-feedback (DFB) laser diode operating at room temperature. A custom designed Herriott multipass cell 16cm long, with an effective path length of 3.7 m is employed. Mechanical, optical and electronics systems are integrated into a compact package of dimensions measuring 12.4"x 3.4"x 5". Power consumption is less than 1 W, enabling prolonged battery life. A detection limit of 3 ppm is achieved when performing 40 second long temperature scans. A recent initial test at NASA-JSC was successful. Future improvements include the reduction of the sampling volume, scan time and an improved CO minimum detection limit.

  19. Spatially patterned matrix elasticity directs stem cell fate

    Science.gov (United States)

    Yang, Chun; DelRio, Frank W.; Ma, Hao; Killaars, Anouk R.; Basta, Lena P.; Kyburz, Kyle A.; Anseth, Kristi S.

    2016-08-01

    There is a growing appreciation for the functional role of matrix mechanics in regulating stem cell self-renewal and differentiation processes. However, it is largely unknown how subcellular, spatial mechanical variations in the local extracellular environment mediate intracellular signal transduction and direct cell fate. Here, the effect of spatial distribution, magnitude, and organization of subcellular matrix mechanical properties on human mesenchymal stem cell (hMSCs) function was investigated. Exploiting a photodegradation reaction, a hydrogel cell culture substrate was fabricated with regions of spatially varied and distinct mechanical properties, which were subsequently mapped and quantified by atomic force microscopy (AFM). The variations in the underlying matrix mechanics were found to regulate cellular adhesion and transcriptional events. Highly spread, elongated morphologies and higher Yes-associated protein (YAP) activation were observed in hMSCs seeded on hydrogels with higher concentrations of stiff regions in a dose-dependent manner. However, when the spatial organization of the mechanically stiff regions was altered from a regular to randomized pattern, lower levels of YAP activation with smaller and more rounded cell morphologies were induced in hMSCs. We infer from these results that irregular, disorganized variations in matrix mechanics, compared with regular patterns, appear to disrupt actin organization, and lead to different cell fates; this was verified by observations of lower alkaline phosphatase (ALP) activity and higher expression of CD105, a stem cell marker, in hMSCs in random versus regular patterns of mechanical properties. Collectively, this material platform has allowed innovative experiments to elucidate a novel spatial mechanical dosing mechanism that correlates to both the magnitude and organization of spatial stiffness.

  20. Voronoi Cell Patterns: theoretical model and application to submonolayer growth

    Science.gov (United States)

    González, Diego Luis; Einstein, T. L.

    2012-02-01

    We use a simple fragmentation model to describe the statistical behavior of the Voronoi cell patterns generated by a homogeneous and isotropic set of points in 1D and in 2D. In particular, we are interested in the distribution of sizes of these Voronoi cells. Our model is completely defined by two probability distributions in 1D and again in 2D, the probability to add a new point inside an existing cell and the probability that this new point is at a particular position relative to the preexisting point inside this cell. In 1D the first distribution depends on a single parameter while the second distribution is defined through a fragmentation kernel; in 2D both distributions depend on a single parameter. The fragmentation kernel and the control parameters are closely related to the physical properties of the specific system under study. We apply our model to describe the Voronoi cell patterns of island nucleation for critical island sizes i=0,1,2,3. Experimental results for the Voronoi cells of InAs/GaAs quantum dots are also described by our model.

  1. Tuning cell adhesion by direct nanostructuring silicon into cell repulsive/adhesive patterns

    Energy Technology Data Exchange (ETDEWEB)

    Premnath, Priyatha, E-mail: priyatha.premnath@ryerson.ca [Micro/Nanofabrication Laboratory, Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3 (Canada); Tavangar, Amirhossein, E-mail: atavanga@ryerson.ca [Micro/Nanofabrication Laboratory, Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3 (Canada); Tan, Bo, E-mail: tanbo@ryerson.ca [Nanocharacterization Laboratory, Department of Aerospace Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3 (Canada); Venkatakrishnan, Krishnan, E-mail: venkat@ryerson.ca [Micro/Nanofabrication Laboratory, Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3 (Canada)

    2015-09-10

    Developing platforms that allow tuning cell functionality through incorporating physical, chemical, or mechanical cues onto the material surfaces is one of the key challenges in research in the field of biomaterials. In this respect, various approaches have been proposed and numerous structures have been developed on a variety of materials. Most of these approaches, however, demand a multistep process or post-chemical treatment. Therefore, a simple approach would be desirable to develop bio-functionalized platforms for effectively modulating cell adhesion and consequently programming cell functionality without requiring any chemical or biological surface treatment. This study introduces a versatile yet simple laser approach to structure silicon (Si) chips into cytophobic/cytophilic patterns in order to modulate cell adhesion and proliferation. These patterns are fabricated on platforms through direct laser processing of Si substrates, which renders a desired computer-generated configuration into patterns. We investigate the morphology, chemistry, and wettability of the platform surfaces. Subsequently, we study the functionality of the fabricated platforms on modulating cervical cancer cells (HeLa) behaviour. The results from in vitro studies suggest that the nanostructures efficiently repel HeLa cells and drive them to migrate onto untreated sites. The study of the morphology of the cells reveals that cells evade the cytophobic area by bending and changing direction. Additionally, cell patterning, cell directionality, cell channelling, and cell trapping are achieved by developing different platforms with specific patterns. The flexibility and controllability of this approach to effectively structure Si substrates to cell-repulsive and cell-adhesive patterns offer perceptible outlook for developing bio-functionalized platforms for a variety of biomedical devices. Moreover, this approach could pave the way for developing anti-cancer platforms that selectively repel

  2. Deposition and alignment of cells on laser-patterned quartz

    Energy Technology Data Exchange (ETDEWEB)

    George, Sajan D., E-mail: sajan.george@manipal.edu [Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); Ladiwala, Uma, E-mail: brainwave@cbs.ac.in [UM-DAE Centre for Excellence in Basic Sciences, Kalina Campus, Mumbai 400 098 (India); Thomas, John; Bankapur, Aseefhali; Chidangil, Santhosh [Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); Mathur, Deepak [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India)

    2014-06-01

    Linear grooves have been laser-written on quartz surfaces using ultrashort (50 fs) pulses of 800 nm light. Measurements of water contact angle indicate that laser patterning makes the quartz surface more hydrophilic. Fibroblast cells were cultured on such laser-written surfaces; they were observed to align preferentially along the direction of the laser written grooves (width ∼2 μm. Raman spectroscopy results indicate that there are no chemical changes induced in the surface upon our laser writing. Most unexpectedly, there are also no chemical changes induced in the cells that are spatially aligned along the laser-written grooves. Atomic force microscopy measurements confirm that our laser-writing induces dramatic enhancement of surface roughness along the grooves, and the cells appear to respond to this. Thus, cell alignment seems to be in response to physical cues rather than chemical signals.

  3. Innate immune pattern recognition: a cell biological perspective.

    Science.gov (United States)

    Brubaker, Sky W; Bonham, Kevin S; Zanoni, Ivan; Kagan, Jonathan C

    2015-01-01

    Receptors of the innate immune system detect conserved determinants of microbial and viral origin. Activation of these receptors initiates signaling events that culminate in an effective immune response. Recently, the view that innate immune signaling events rely on and operate within a complex cellular infrastructure has become an important framework for understanding the regulation of innate immunity. Compartmentalization within this infrastructure provides the cell with the ability to assign spatial information to microbial detection and regulate immune responses. Several cell biological processes play a role in the regulation of innate signaling responses; at the same time, innate signaling can engage cellular processes as a form of defense or to promote immunological memory. In this review, we highlight these aspects of cell biology in pattern-recognition receptor signaling by focusing on signals that originate from the cell surface, from endosomal compartments, and from within the cytosol.

  4. Dopamine modulates two potassium currents and inhibits the intrinsic firing properties of an identified motor neuron in a central pattern generator network.

    Science.gov (United States)

    Kloppenburg, P; Levini, R M; Harris-Warrick, R M

    1999-01-01

    The two pyloric dilator (PD) neurons are components [along with the anterior burster (AB) neuron] of the pacemaker group of the pyloric network in the stomatogastric ganglion of the spiny lobster Panulirus interruptus. Dopamine (DA) modifies the motor pattern generated by the pyloric network, in part by exciting or inhibiting different neurons. DA inhibits the PD neuron by hyperpolarizing it and reducing its rate of firing action potentials, which leads to a phase delay of PD relative to the electrically coupled AB and a reduction in the pyloric cycle frequency. In synaptically isolated PD neurons, DA slows the rate of recovery to spike after hyperpolarization. The latency from a hyperpolarizing prestep to the first action potential is increased, and the action potential frequency as well as the total number of action potentials are decreased. When a brief (1 s) puff of DA is applied to a synaptically isolated, voltage-clamped PD neuron, a small voltage-dependent outward current is evoked, accompanied by an increase in membrane conductance. These responses are occluded by the combined presence of the potassium channel blockers 4-aminopyridine and tetraethylammonium. In voltage-clamped PD neurons, DA enhances the maximal conductance of a voltage-sensitive transient potassium current (IA) and shifts its Vact to more negative potentials without affecting its Vinact. This enlarges the "window current" between the voltage activation and inactivation curves, increasing the tonically active IA near the resting potential and causing the cell to hyperpolarize. Thus DA's effect is to enhance both the transient and resting K+ currents by modulating the same channels. In addition, DA enhances the amplitude of a calcium-dependent potassium current (IO(Ca)), but has no effect on a sustained potassium current (IK(V)). These results suggest that DA hyperpolarizes and phase delays the activity of the PD neurons at least in part by modulating their intrinsic postinhibitory recovery

  5. Shavenbaby couples patterning to epidermal cell shape control.

    Directory of Open Access Journals (Sweden)

    Hélène Chanut-Delalande

    2006-09-01

    Full Text Available It is well established that developmental programs act during embryogenesis to determine animal morphogenesis. How these developmental cues produce specific cell shape during morphogenesis, however, has remained elusive. We addressed this question by studying the morphological differentiation of the Drosophila epidermis, governed by a well-known circuit of regulators leading to a stereotyped pattern of smooth cells and cells forming actin-rich extensions (trichomes. It was shown that the transcription factor Shavenbaby plays a pivotal role in the formation of trichomes and underlies all examined cases of the evolutionary diversification of their pattern. To gain insight into the mechanisms of morphological differentiation, we sought to identify shavenbaby's downstream targets. We show here that Shavenbaby controls epidermal cell shape, through the transcriptional activation of different classes of cellular effectors, directly contributing to the organization of actin filaments, regulation of the extracellular matrix, and modification of the cuticle. Individual inactivation of shavenbaby's targets produces distinct trichome defects and only their simultaneous inactivation prevent trichome formation. Our data show that shavenbaby governs an evolutionarily conserved developmental module consisting of a set of genes collectively responsible for trichome formation, shedding new light on molecular mechanisms acting during morphogenesis and the way they can influence evolution of animal forms.

  6. Firing patterns and functional roles of different classes of spinal afferents in rectal nerves during colonic migrating motor complexes in mouse colon.

    Science.gov (United States)

    Zagorodnyuk, Vladimir P; Kyloh, Melinda; Brookes, Simon J; Nicholas, Sarah J; Spencer, Nick J

    2012-08-01

    The functional role of the different classes of visceral afferents that innervate the large intestine is poorly understood. Recent evidence suggests that low-threshold, wide-dynamic-range rectal afferents play an important role in the detection and transmission of visceral pain induced by noxious colorectal distension in mice. However, it is not clear which classes of spinal afferents are activated during naturally occurring colonic motor patterns or during intense contractions of the gut smooth muscle. We developed an in vitro colorectum preparation to test how the major classes of rectal afferents are activated during spontaneous colonic migrating motor complex (CMMC) or pharmacologically induced contraction. During CMMCs, circular muscle contractions increased firing in low-threshold, wide-dynamic-range muscular afferents and muscular-mucosal afferents, which generated a mean firing rate of 1.53 ± 0.23 Hz (n = 8) under isotonic conditions and 2.52 ± 0.36 Hz (n = 17) under isometric conditions. These low-threshold rectal afferents were reliably activated by low levels of circumferential stretch induced by increases in length (1-2 mm) or load (1-3 g). In a small proportion of cases (5 of 34 units), some low-threshold muscular and muscular-mucosal afferents decreased their firing rate during the peak of the CMMC contractions. High-threshold afferents were never activated during spontaneous CMMC contractions or tonic contractions induced by bethanechol (100 μM). High-threshold rectal afferents were only activated by intense levels of circumferential stretch (10-20 g). These results show that, in the rectal nerves of mice, low-threshold, wide-dynamic-range muscular and muscular-mucosal afferents are excited during contraction of the circular muscle that occurs during spontaneous CMMCs. No activation of high-threshold rectal afferents was detected during CMMCs or intense contractile activity in naïve mouse colorectum.

  7. Developmental patterning of glutamatergic synapses onto retinal ganglion cells

    Directory of Open Access Journals (Sweden)

    Schubert Timm

    2008-03-01

    Full Text Available Abstract Background Neurons receive excitatory synaptic inputs that are distributed across their dendritic arbors at densities and with spatial patterns that influence their output. How specific synaptic distributions are attained during development is not well understood. The distribution of glutamatergic inputs across the dendritic arbors of mammalian retinal ganglion cells (RGCs has long been correlated to the spatial receptive field profiles of these neurons. Thus, determining how glutamatergic inputs are patterned onto RGC dendritic arbors during development could provide insight into the cellular mechanisms that shape their functional receptive fields. Results We transfected developing and mature mouse RGCs with plasmids encoding fluorescent proteins that label their dendrites and glutamatergic postsynaptic sites. We found that as dendritic density (dendritic length per unit area of dendritic field decreases with maturation, the density of synapses along the dendrites increases. These changes appear coordinated such that RGCs attain the mature average density of postsynaptic sites per unit area (areal density by the time synaptic function emerges. Furthermore, stereotypic centro-peripheral gradients in the areal density of synapses across the arbor of RGCs are established at an early developmental stage. Conclusion The spatial pattern of glutamatergic inputs onto RGCs arises early in synaptogenesis despite ensuing reorganization of dendritic structure. We raise the possibility that these early patterns of synaptic distributions may arise from constraints placed on the number of contacts presynaptic neurons are able to make with the RGCs.

  8. Laser-based patterning for transfected cell microarrays

    Energy Technology Data Exchange (ETDEWEB)

    Hook, Andrew L; Creasey, Rhiannon; Voelcker, Nicolas H [Flinders University, GPO Box 2100, Bedford Park, SA 5042 (Australia); Hayes, Jason P [MiniFAB, 1 Dalmore Drive, Caribbean Park, Scoresby VIC 3179 (Australia); Thissen, Helmut, E-mail: Nico.Voelcker@flinders.edu.a [CSIRO Molecular and Health Technologies, Bayview Avenue, Clayton VIC 3168 (Australia)

    2009-12-15

    The spatial control over biomolecule- and cell-surface interactions is of great interest to a broad range of biomedical applications, including sensors, implantable devices and cell microarrays. Microarrays in particular require precise spatial control and the formation of patterns with microscale features. Here, we have developed an approach specifically designed for transfected cell microarray (TCM) applications that allows microscale spatial control over the location of both DNA and cells on highly doped p-type silicon substrates. This was achieved by surface modification, involving plasma polymerization of allylamine, grafting of poly(ethylene glycol) and subsequent excimer laser ablation. DNA could be delivered in a spatially defined manner using ink-jet printing. In addition, electroporation was investigated as an approach to transfect attached cells with adsorbed DNA and good transfection efficiencies of approximately 20% were observed. The ability of the microstructured surfaces to spatially direct both DNA adsorption and cell attachment was demonstrated in a functional TCM, making this system an exciting platform for chip-based functional genomics.

  9. Global Splicing Pattern Reversion during Somatic Cell Reprogramming

    Directory of Open Access Journals (Sweden)

    Sho Ohta

    2013-10-01

    Full Text Available Alternative splicing generates multiple transcripts from a single gene, and cell-type-specific splicing profiles are important for the properties and functions of the cells. Recently, somatic cells have been shown to undergo dedifferentiation after the forced expression of transcription factors. However, it remains unclear whether somatic cell splicing is reorganized during reprogramming. Here, by combining deep sequencing with high-throughput absolute qRT-PCR, we show that somatic splicing profiles revert to pluripotent ones during reprogramming. Remarkably, the splicing pattern in pluripotent stem cells resembles that in testes, and the regulatory regions have specific characteristics in length and sequence. Furthermore, our siRNA screen has identified RNA-binding proteins that regulate splicing events in iPSCs. We have then demonstrated that two of the RNA-binding proteins, U2af1 and Srsf3, play a role in somatic cell reprogramming. Our results indicate that the drastic alteration in splicing represents part of the molecular network involved in the reprogramming process.

  10. Chitosan and polycaprolactone membranes patterned via electrospinning: effect of underlying chemistry and pattern characteristics on epithelial/fibroblastic cell behavior.

    Science.gov (United States)

    Simşek, Murat; Capkın, Merve; Karakeçili, Ayşe; Gümüşderelioğlu, Menemşe

    2012-12-01

    Electrospinning was used as an effective route to pattern chitosan (CS) and polycaprolactone (PCL) membranes with submicron fibers having different chemical structure (PCL or PCL/collagen) and physical characteristics (size: between ≈200 and 550 nm; randomly oriented or aligned form). While the PCL fibers with diameters in the same range (≈200 nm) were patterned on both of CS and PCL membranes to evaluate the influence of the underlying membrane chemistry, only CS membranes were patterned with PCL fibers having different sizes simply by changing the electrospinning conditions to investigate the effects of pattern characteristics. Furthermore, collagen was added to the PCL fiber structure to change the chemical composition of the fibers in a cell-attractive way. Two cell lines with different morphologies, fibroblastic MC3T3-E1 preosteoblasts and epithelial Madine Darby Bovine Kidney (MDBK) cells, were cultured on the patterned membranes. The observation of cellular behavior in terms of cell morphology and F-actin synthesis was realized by scanning electron microscopy and confocal microscopy analysis during the first 12 h of culture period. The viability of cells was controlled by MTT assay through 96 h of cell culture. The cell culture studies indicated that the leading aspect for the morphology change on patterned membranes was the fiber orientation. The aligned topography controlled the morphology of cells both on CS and PCL membranes. In the presence of collagen in the fiber structure, F-actin filament synthesis increased for MC3T3-E1 and MDBK cell lines.

  11. A process-based fire parameterization of intermediate complexity in a Dynamic Global Vegetation Model

    Science.gov (United States)

    Li, F.; Zeng, X. D.; Levis, S.

    2012-07-01

    A process-based fire parameterization of intermediate complexity has been developed for global simulations in the framework of a Dynamic Global Vegetation Model (DGVM) in an Earth System Model (ESM). Burned area in a grid cell is estimated by the product of fire counts and average burned area of a fire. The scheme comprises three parts: fire occurrence, fire spread, and fire impact. In the fire occurrence part, fire counts rather than fire occurrence probability are calculated in order to capture the observed high burned area fraction in areas of high fire frequency and realize parameter calibration based on MODIS fire counts product. In the fire spread part, post-fire region of a fire is assumed to be elliptical in shape. Mathematical properties of ellipses and some mathematical derivations are applied to improve the equation and assumptions of an existing fire spread parameterization. In the fire impact part, trace gas and aerosol emissions due to biomass burning are estimated, which offers an interface with atmospheric chemistry and aerosol models in ESMs. In addition, flexible time-step length makes the new fire parameterization easily applied to various DGVMs. Global performance of the new fire parameterization is assessed by using an improved version of the Community Land Model version 3 with the Dynamic Global Vegetation Model (CLM-DGVM). Simulations are compared against the latest satellite-based Global Fire Emission Database version 3 (GFED3) for 1997-2004. Results show that simulated global totals and spatial patterns of burned area and fire carbon emissions, regional totals and spreads of burned area, global annual burned area fractions for various vegetation types, and interannual variability of burned area are reasonable, and closer to GFED3 than CLM-DGVM simulations with the commonly used Glob-FIRM fire parameterization and the old fire module of CLM-DGVM. Furthermore, average error of simulated trace gas and aerosol emissions due to biomass burning

  12. A process-based fire parameterization of intermediate complexity in a Dynamic Global Vegetation Model

    Directory of Open Access Journals (Sweden)

    F. Li

    2012-07-01

    Full Text Available A process-based fire parameterization of intermediate complexity has been developed for global simulations in the framework of a Dynamic Global Vegetation Model (DGVM in an Earth System Model (ESM. Burned area in a grid cell is estimated by the product of fire counts and average burned area of a fire. The scheme comprises three parts: fire occurrence, fire spread, and fire impact. In the fire occurrence part, fire counts rather than fire occurrence probability are calculated in order to capture the observed high burned area fraction in areas of high fire frequency and realize parameter calibration based on MODIS fire counts product. In the fire spread part, post-fire region of a fire is assumed to be elliptical in shape. Mathematical properties of ellipses and some mathematical derivations are applied to improve the equation and assumptions of an existing fire spread parameterization. In the fire impact part, trace gas and aerosol emissions due to biomass burning are estimated, which offers an interface with atmospheric chemistry and aerosol models in ESMs. In addition, flexible time-step length makes the new fire parameterization easily applied to various DGVMs.

    Global performance of the new fire parameterization is assessed by using an improved version of the Community Land Model version 3 with the Dynamic Global Vegetation Model (CLM-DGVM. Simulations are compared against the latest satellite-based Global Fire Emission Database version 3 (GFED3 for 1997–2004. Results show that simulated global totals and spatial patterns of burned area and fire carbon emissions, regional totals and spreads of burned area, global annual burned area fractions for various vegetation types, and interannual variability of burned area are reasonable, and closer to GFED3 than CLM-DGVM simulations with the commonly used Glob-FIRM fire parameterization and the old fire module of CLM-DGVM. Furthermore, average error of simulated trace gas and aerosol

  13. The Glycoprofile Patterns of Endothelial Cells in Usual Interstitial Pneumonia

    Directory of Open Access Journals (Sweden)

    A Barkhordari

    2014-09-01

    Full Text Available [THIS ARTICLE HAS BEEN RETRACTED FOR DUPLICATE PUBLICATION] Background: The pathological classification of cryptogenic fibrosing alveolitis has been a matter of debate and controversy for histopathologists.Objective: To identify and specify the glycotypes of capillary endothelial cells in usual interstitial pneumonia (UIP compared to those found in normal tissue.Methods: Sections of formalin-fixed, paraffin-embedded blocks from 16 cases of UIP were studied by lectin histochemistry with a panel of 27 biotinylated lectins and an avidin-peroxidase revealing system.Results: High expression of several classes of glycan was seen de novo in capillary endothelial cells from patients with UIP including small complex and bi/tri-antennary bisected complex N-linked sequences bolund by Concanavalin A and erythro-phytohemagglutinin, respectively, GalNAca1 residues bound by Helix pomatia and Maclura pomifera agglutinins, and L-fucosylated derivatives of type II glycan chains recognized by Ulex europaeus agglutinin-I. Glycans bound by agglutinins from Lycopersicon esculentum (β1,4GlcNAc and Wisteria floribunda (GalNAc as well as GlcNAc oligomers bound by Phytolacca americana and succinylated Wheat Germ agglutinin were also seen in the capillary endothelial cells of UIP. In contrast, L-fucosylated derivatives of type I glycan chains were absent in cells from cases of UIP when Anguilla anguilla agglutinin was applied, unlike the situation in normal tissue.Conclusion: These results may indicate existence of two distinct populations of endothelial cell in UIP with markedly different patterns of glycosylation, reflecting a pattern of differentiation and angiogenesis, which is not detectable morphologically.

  14. Patterns of expression of cell wall related genes in sugarcane

    Directory of Open Access Journals (Sweden)

    Lima D.U.

    2001-01-01

    Full Text Available Our search for genes related to cell wall metabolism in the sugarcane expressed sequence tag (SUCEST database (http://sucest.lbi.dcc.unicamp.br resulted in 3,283 reads (1% of the total reads which were grouped into 459 clusters (potential genes with an average of 7.1 reads per cluster. To more clearly display our correlation coefficients, we constructed surface maps which we used to investigate the relationship between cell wall genes and the sugarcane tissues libraries from which they came. The only significant correlations that we found between cell wall genes and/or their expression within particular libraries were neutral or synergetic. Genes related to cellulose biosynthesis were from the CesA family, and were found to be the most abundant cell wall related genes in the SUCEST database. We found that the highest number of CesA reads came from the root and stem libraries. The genes with the greatest number of reads were those involved in cell wall hydrolases (e.g. beta-1,3-glucanases, xyloglucan endo-beta-transglycosylase, beta-glucosidase and endo-beta-mannanase. Correlation analyses by surface mapping revealed that the expression of genes related to biosynthesis seems to be associated with the hydrolysis of hemicelluloses, pectin hydrolases being mainly associated with xyloglucan hydrolases. The patterns of cell wall related gene expression in sugarcane based on the number of reads per cluster reflected quite well the expected physiological characteristics of the tissues. This is the first work to provide a general view on plant cell wall metabolism through the expression of related genes in almost all the tissues of a plant at the same time. For example, developing flowers behaved similarly to both meristematic tissues and leaf-root transition zone tissues. Besides providing a basis for future research on the mechanisms of plant development which involve the cell wall, our findings will provide valuable tools for plant engineering in the

  15. Advanced Manufacturing Technologies (AMT): Additive Manufactured Hot Fire Planning and Testing in GRC Cell 32 Project

    Data.gov (United States)

    National Aeronautics and Space Administration — GRC and AR have identified the following roles and responsibilities necessary to accomplish the hot fire objective of this task.  AR will be responsible for...

  16. Pyro-electrification of polymer membranes for cell patterning

    Science.gov (United States)

    Rega, R.; Gennari, O.; Mecozzia, L.; Grilli, S.; Pagliarulo, V.; Ferraro, P.

    2016-05-01

    In the recent years, much attention has been devoted to the possibility of charging polymer-based materials, due to their potential in developing large-scale and inexpensive flexible thin-film technology. The availability of localized electrostatic fields is in of great interest for a huge amount of applications such as distribution of biomolecules and cells from the liquid phase. Here we report a voltage-free pyro-electrification (PE) process able to induce permanent dipoles into polymer layers; the lithium niobate (LN) crystal is the key component that plays the multi-purpose role of sustaining, heating and poling the polymer layer that is then peeled-off easily in order to have a free-standing charged membrane. The results show the fascinating application for the living cell patterning. It well known that cell behaviour is affected by chemical and topographical cues of substrate. In fact, polymers, such as polystyrene (PS) and poly(methyl methacrylate) (PMMA), are naturally cytophobic and require specific functionalization treatments in order to promote cell adhesion. Through our proposal technique, it's possible to obtain spontaneous organization and a driven growth of SH-SY5Y cells that is solely dictated by the nature of the charge polymer surface, opening, in this way, the innovative chance to manipulate and transfer biological samples on a free-standing polymer layer [1].

  17. Improved Computational Model of Grid Cells Based on Column Structure

    Institute of Scientific and Technical Information of China (English)

    Yang Zhou; Dewei Wu; Weilong Li; Jia Du

    2016-01-01

    To simulate the firing pattern of biological grid cells, this paper presents an improved computational model of grid cells based on column structure. In this model, the displacement along different directions is processed by modulus operation, and the obtained remainder is associated with firing rate of grid cell. Compared with the original model, the improved parts include that: the base of modulus operation is changed, and the firing rate in firing field is encoded by Gaussian⁃like function. Simulation validates that the firing pattern generated by the improved computational model is more consistent with biological characteristic than original model. Besides, the firing pattern is badly influenced by the cumulative positioning error, but the computational model can also generate the regularly hexagonal firing pattern when the real⁃time positioning results are modified.

  18. Patterning of cell assemblies regulated by adhesion receptors of the cadherin superfamily.

    OpenAIRE

    2000-01-01

    During morphogenesis, cell-cell association patterns are dynamically altered. We are interested in how cell adhesion molecules can regulate the patterning of cellular assemblies. Cadherins, a group of cell-cell adhesion receptors, are crucial for the organized assembly of many cell types, but they also regulate dynamic aspects of cell association. For example, during neural crest emigration from the neural tube, the cadherin subtypes expressed by crest cells are switched from one subtype to a...

  19. Patterning methods for polymers in cell and tissue engineering.

    Science.gov (United States)

    Kim, Hong Nam; Kang, Do-Hyun; Kim, Min Sung; Jiao, Alex; Kim, Deok-Ho; Suh, Kahp-Yang

    2012-06-01

    Polymers provide a versatile platform for mimicking various aspects of physiological extracellular matrix properties such as chemical composition, rigidity, and topography for use in cell and tissue engineering applications. In this review, we provide a brief overview of patterning methods of various polymers with a particular focus on biocompatibility and processability. The materials highlighted here are widely used polymers including thermally curable polydimethyl siloxane, ultraviolet-curable polyurethane acrylate and polyethylene glycol, thermo-sensitive poly(N-isopropylacrylamide) and thermoplastic and conductive polymers. We also discuss how micro- and nanofabricated polymeric substrates of tunable elastic modulus can be used to engineer cell and tissue structure and function. Such synergistic effect of topography and rigidity of polymers may be able to contribute to constructing more physiologically relevant microenvironment.

  20. Liquid Crystal Pre-Patterning for Cell Division

    Science.gov (United States)

    Hill, Nicholas; Mottram, Nigel; Lydon, John

    2005-11-01

    We are examining the hypothesis that the overall geometry of mitosis is determined by liquid-crystal pre-patterning of the cytoplasm. The identification of mitosis with liquid crystalline (LX) phases is at least 50 years old but no attempt has been made to propose a detailed theory, presumably because of the difficulties in applying a theory of liquid crystals (LCs) in a 3D geometry. In this work, we use a mathematical model (Q-tensor theory) of a nematic LC for the cytoplasm of the cell and solve this numerically to show that the geometry of the prophase and metaphase can be explained using LX phases. The pre-patterning for the spindle is regarded as a bipolar LX assembly with the centrosomes acting as LC poles (centres of LX defects). The centrosomes and the nuclear envelope are both treated as bodies submerged in the LC medium between two spherical shells (the nuclear and cell membranes). The geometries considered are novel and 3D.

  1. External serial connection without layer patterning for organic solar cells

    Science.gov (United States)

    Wong, Ying Qian; Wong, Hin Yong; Tan, Ching Seong; Meng, Hsin-Fei

    2016-12-01

    This paper proposes a novel alternative to conventional internal serial connection, where precise patterning and scribing of organic layers can be eliminated. Adjacent cells can be made nearer for better space-utilization and higher voltages per unit area. Also, blade coating is proposed as the fabrication method as it has low material wastage (less than 5%), easily scalable to large area, has high film uniformity and has high throughput due to its roll-to-roll potential. This paper demonstrates 3-cells large area (12.98 cm2) external serial connection organic solar cells (OSCs) using the material poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and 2,6-Bis(trimethyltin)-4, 8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo [1,2-b:4,5-b']dithiophene:6,6-phenyl C71-butyric acid methyl ester (PBDTTT-CT:PC71BM) respectively. The power conversion efficiencies (PCEs) of the resulting 3-cells modules are 2.0% and 4.1% respectively.

  2. Therapeutic concentrations of varenicline in the presence of nicotine increase action potential firing in human adrenal chromaffin cells.

    Science.gov (United States)

    Hone, Arik J; Michael McIntosh, J; Rueda-Ruzafa, Lola; Passas, Juan; de Castro-Guerín, Cristina; Blázquez, Jesús; González-Enguita, Carmen; Albillos, Almudena

    2017-01-01

    Varenicline is a nicotinic acetylcholine receptor (nAChR) agonist used to treat nicotine addiction, but a live debate persists concerning its mechanism of action in reducing nicotine consumption. Although initially reported as α4β2 selective, varenicline was subsequently shown to activate other nAChR subtypes implicated in nicotine addiction including α3β4. However, it remains unclear whether activation of α3β4 nAChRs by therapeutically relevant concentrations of varenicline is sufficient to affect the behavior of cells that express this subtype. We used patch-clamp electrophysiology to assess the effects of varenicline on native α3β4* nAChRs (asterisk denotes the possible presence of other subunits) expressed in human adrenal chromaffin cells and compared its effects to those of nicotine. Varenicline and nicotine activated α3β4* nAChRs with EC50 values of 1.8 (1.2-2.7) μM and 19.4 (11.1-33.9) μM, respectively. Stimulation of adrenal chromaffin cells with 10 ms pulses of 300 μM acetylcholine (ACh) in current-clamp mode evoked sodium channel-dependent action potentials (APs). Under these conditions, perfusion of 50 or 100 nM varenicline showed very little effect on AP firing compared to control conditions (ACh stimulation alone), but at higher concentrations (250 nM) varenicline increased the number of APs fired up to 436 ± 150%. These results demonstrate that therapeutic concentrations of varenicline are unlikely to alter AP firing in chromaffin cells. In contrast, nicotine showed no effect on AP firing at any of the concentrations tested (50, 100, 250, and 500 nM). However, perfusion of 50 nM nicotine simultaneously with 100 nM varenicline increased AP firing by 290 ± 104% indicating that exposure to varenicline and nicotine concurrently may alter cellular behavior such as excitability and neurotransmitter release.

  3. Computational cell model based on autonomous cell movement regulated by cell-cell signalling successfully recapitulates the "inside and outside" pattern of cell sorting

    Directory of Open Access Journals (Sweden)

    Ajioka Itsuki

    2007-09-01

    Full Text Available Abstract Background Development of multicellular organisms proceeds from a single fertilized egg as the combined effect of countless numbers of cellular interactions among highly dynamic cells. Since at least a reminiscent pattern of morphogenesis can be recapitulated in a reproducible manner in reaggregation cultures of dissociated embryonic cells, which is known as cell sorting, the cells themselves must possess some autonomous cell behaviors that assure specific and reproducible self-organization. Understanding of this self-organized dynamics of heterogeneous cell population seems to require some novel approaches so that the approaches bridge a gap between molecular events and morphogenesis in developmental and cell biology. A conceptual cell model in a computer may answer that purpose. We constructed a dynamical cell model based on autonomous cell behaviors, including cell shape, growth, division, adhesion, transformation, and motility as well as cell-cell signaling. The model gives some insights about what cellular behaviors make an appropriate global pattern of the cell population. Results We applied the model to "inside and outside" pattern of cell-sorting, in which two different embryonic cell types within a randomly mixed aggregate are sorted so that one cell type tends to gather in the central region of the aggregate and the other cell type surrounds the first cell type. Our model can modify the above cell behaviors by varying parameters related to them. We explored various parameter sets with which the "inside and outside" pattern could be achieved. The simulation results suggested that direction of cell movement responding to its neighborhood and the cell's mobility are important for this specific rearrangement. Conclusion We constructed an in silico cell model that mimics autonomous cell behaviors and applied it to cell sorting, which is a simple and appropriate phenomenon exhibiting self-organization of cell population. The model

  4. Analysis of Architectural Building Design Influences on Fire Spread in Densely Urban Settlement using Cellular Automata

    Science.gov (United States)

    Tambunan, L.; Salamah, H.; Asriana, N.

    2017-03-01

    This study aims to determine the influence of architectural design on the risk of fire spread in densely urban settlement area. Cellular Automata (CA) is used to analyse the fire spread pattern, speed, and the extent of damage. Four cells represent buildings, streets, and fields characteristic in the simulated area, as well as their flammability level and fire spread capabilities. Two fire scenarios are used to model the spread of fire: (1) fire origin in a building with concrete and wood material majority, and (2) fire origin in building with wood material majority. Building shape, building distance, road width, and total area of wall openings are considered constant, while wind is ignored. The result shows that fire spread faster in the building area with wood majority than with concrete majority. Significant amount of combustible building material, absence of distance between buildings, narrow streets and limited fields are factors which influence fire spread speed and pattern as well as extent of damage when fire occurs in the densely urban settlement area.

  5. Spatial pattern of cell geometry and cell-division orientation in zebrafish lens epithelium

    Directory of Open Access Journals (Sweden)

    Toshiaki Mochizuki

    2014-09-01

    Full Text Available Cell proliferation is a key regulator of tissue morphogenesis. We examined cell proliferation and cell division in zebrafish lens epithelium by visualizing cell-cycle phases and nuclear positions, using fluorescent-labeled geminin and histone proteins. Proliferation was low in the anterior region of lens epithelium and higher in the marginal zone anterior to the equator, suggesting that the proliferation zone, called the germinative zone, is formed in zebrafish lens. Interestingly, cell-division orientation was biased longitudinally in the anterior region, shifted from longitudinal to circumferential along the anterior–posterior axis of lens sphere, and was biased circumferentially in the peripheral region. These data suggest that cell-division orientation is spatially regulated in zebrafish lens epithelium. The Hertwig rule indicates that cells tend to divide along their long axes. Orientation of long axes and cell division were biased similarly in zebrafish lens epithelium, suggesting that cell geometry correlates with cell-division orientation. A cell adhesion molecule, E-cadherin, is expressed in lens epithelium. In a zebrafish e-cadherin mutant, the long axes and cell-division orientation were shifted more longitudinally. These data suggest that E-cadherin is required for the spatial pattern of cell geometry and cell-division orientation in zebrafish lens epithelium.

  6. Spiral Phyllotaxis Pattern in an Animal Cell: A Fluid- Driven Mechanism for Red Cell Echinocytosis and Programmed Cell Death

    OpenAIRE

    Lofthouse, J. T.

    2004-01-01

    This paper demonstrates that the pattern of lipid spiculesthat emerge on the surface of red blood cells in the classic 'Discocyte to Echinocyte' shape change is a generative spiral, and presents a qualitative, fluid- driven mechanism for their production, compatible with the work of Douady and Couder. Implications for the dynamics of cell growth, plant cell phyllotaxy, programmed cell death and gravity sensitivity are explained in terms of a new qualitative model of cellular fluid dynamics.

  7. Patterned Au/poly(dimethylsiloxane) substrate fabricated by chemical plating coupled with electrochemical etching for cell patterning.

    Science.gov (United States)

    Bai, Hai-Jing; Shao, Min-Ling; Gou, Hong-Lei; Xu, Jing-Juan; Chen, Hong-Yuan

    2009-09-01

    In this paper, we present a novel approach for preparing patterned Au/poly(dimethylsiloxane) (PDMS) substrate. Chemical gold plating instead of conventional metal evaporation or sputtering was introduced to achieve a homogeneous gold layer on native PDMS for the first time, which possesses low-cost and simple operation. An electrochemical oxidation reaction accompanied by the coordination of gold and chloride anion was then exploited to etch gold across the region covered by electrolyte. On the basis of such an electrochemical etching, heterogeneous Au/PDMS substrate which has a gold "island" pattern or PDMS dots pattern was fabricated. Hydrogen bubbles which were generated in the etching process due to water electrolysis were used to produce a safe region under the Pt auxiliary electrode. The safe region would protect gold film from etching and lead to the formation of the gold "island" pattern. In virtue of a PDMS stencil with holes array, gold could be etched from the exposed region and take on the PDMS dots pattern which was selected to for protein and cell patterning. This patterned Au/PDMS substrate is very convenient to construct cytophobic and cytophilic regions. Self-assembled surface modification of (1-mercaptoundec-11-yl)hexa(ethylene glycol) on gold and adsorption of fibronectin on PDMS are suitable for effective protein and cell patterning. This patterned Au/PDMS substrate would be a potentially versatile platform for fabricating biosensing arrays.

  8. Lateral inhibition-induced pattern formation controlled by the size and geometry of the cell.

    Science.gov (United States)

    Seirin Lee, Sungrim

    2016-09-01

    Pattern formation in development biology is one of the fundamental processes by which cells change their functions. It is based on the communication of cells via intra- and intercellular dynamics of biochemicals. Thus, the cell is directly involved in biochemical interactions. However, many theoretical approaches describing biochemical pattern formation have usually neglected the cell's role or have simplified the subcellular process without considering cellular aspects despite the cell being the environment where biochemicals interact. On the other hand, recent experimental observations suggest that a change in the physical conditions of cell-to-cell contact can result in a change in cell fate and tissue patterning in a lateral inhibition system. Here we develop a mathematical model by which biochemical dynamics can be directly observed with explicitly expressed cell structure and geometry in higher dimensions, and reconsider pattern formation by lateral inhibition of the Notch-Delta signaling pathway. We explore how the physical characteristic of cell, such as cell geometry or size, influences the biochemical pattern formation in a multi-cellular system. Our results suggest that a property based on cell geometry can be a novel mechanism for symmetry breaking inducing cell asymmetry. We show that cell volume can critically influence cell fate determination and pattern formation at the tissue level, and the surface area of the cell-to-cell contact can directly affect the spatial range of patterning.

  9. Recurrence patterns of bladder transitional cell carcinoma after radical cystectomy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bohyun; Choi, Hyuck Jae; Kim, Mi-hyun; Cho, Kyung-Sik [Dept. of Radiology, Asan Medical Center, Univ. of Ulsan, Seoul (Korea, Republic of); E-mail: choihj@amc.seoul.kr

    2012-10-15

    Background Multidetector computed tomography (MDCT) is widely accepted as an effective imaging modality in monitoring for bladder cancer recurrence after radical cystectomy. Elucidating the pattern of bladder cancer recurrence on CT can increase the diagnostic accuracy. Purpose To evaluate the recurrence patterns of transitional cell carcinoma of the bladder and the factors associated with cancer recurrence. Material and Methods One hundred and forty-nine consecutive patients (mean age, 66.55 years; range, 32-86 years) who underwent preoperative contrast-enhanced CT and radical cystectomy were included in this study. The presence, site, and time of tumor recurrence were recorded retrospectively by two radiologists in a consensus fashion. The association of tumor recurrence and tumor factors (T stage, lymph node metastasis, nuclear grade, and tumor diameter) were also evaluated using multiple logistic regression analysis and Kaplan-Meier statistics. Results Tumor recurrence occurred in 60 patients (40.3%) with a mean time of 14 months (range, 1-64 months). The sites of recurrence included the operation site (n = 20), lymph node (n = 20), bone (n = 11), liver (n = 6), lung (n = 5), upper urinary tract (n = 4), colon (n = 3), adrenal gland (n = 2), peritoneum (n = 1), abdominal wall (n = 1), psoas muscle (n = 1), and penile skin (n = 1). Tumor recurrence was found to be associated with advanced T stage (P = 0.002) and lymph node metastasis (P < 0.001). Conclusion Transitional cell carcinomas of the bladder recur more frequently at the operation site and lymph node, and T-stage and lymph node metastasis are closely associated with tumor recurrence.

  10. Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration

    Directory of Open Access Journals (Sweden)

    Jean-Michel Bourget

    2016-01-01

    Full Text Available Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro. Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs. The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors.

  11. Patterning of Endothelial Cells and Mesenchymal Stem Cells by Laser-Assisted Bioprinting to Study Cell Migration

    Science.gov (United States)

    Medina, Manuela; Rémy, Murielle; Thébaud, Noélie Brunehilde; Bareille, Reine; Chassande, Olivier; Amédée, Joëlle; Catros, Sylvain

    2016-01-01

    Tissue engineering of large organs is currently limited by the lack of potent vascularization in vitro. Tissue-engineered bone grafts can be prevascularized in vitro using endothelial cells (ECs). The microvascular network architecture could be controlled by printing ECs following a specific pattern. Using laser-assisted bioprinting, we investigated the effect of distance between printed cell islets and the influence of coprinted mesenchymal cells on migration. When printed alone, ECs spread out evenly on the collagen hydrogel, regardless of the distance between cell islets. However, when printed in coculture with mesenchymal cells by laser-assisted bioprinting, they remained in the printed area. Therefore, the presence of mesenchymal cell is mandatory in order to create a pattern that will be conserved over time. This work describes an interesting approach to study cell migration that could be reproduced to study the effect of trophic factors. PMID:27833916

  12. Vacuum-assisted fluid flow in microchannels to pattern substrates and cells.

    Science.gov (United States)

    Shrirao, Anil B; Kung, Frank H; Yip, Derek; Cho, Cheul H; Townes-Anderson, Ellen

    2014-09-01

    Substrate and cell patterning are widely used techniques in cell biology to study cell-to-cell and cell-substrate interactions. Conventional patterning techniques work well only with simple shapes, small areas and selected bio-materials. This paper describes a method to distribute cell suspensions as well as substrate solutions into complex, long, closed (dead-end) polydimethylsiloxane (PDMS) microchannels using negative pressure. Our method builds upon a previous vacuum-assisted method used for micromolding (Jeon et al 1999 Adv. Mater 11 946) and successfully patterned collagen-I, fibronectin and Sal-1 substrates on glass and polystyrene surfaces, filling microchannels with lengths up to 120 mm and covering areas up to 13 × 10 mm(2). Vacuum-patterned substrates were subsequently used to culture mammalian PC12 and fibroblast cells and amphibian neurons. Cells were also patterned directly by injecting cell suspensions into microchannels using vacuum. Fibroblast and neuronal cells patterned using vacuum showed normal growth and minimal cell death indicating no adverse effects of vacuum on cells. Our method fills reversibly sealed PDMS microchannels. This enables the user to remove the PDMS microchannel cast and access the patterned biomaterial or cells for further experimental purposes. Overall, this is a straightforward technique that has broad applicability for cell biology.

  13. Alterations in the growth and adhesion pattern of Vero cells induced by nutritional stress conditions.

    Science.gov (United States)

    Genari, S C; Gomes, L; Wada, M L

    1998-01-01

    The pattern of growth, adhesion and protein synthesis in Vero cells submitted to nutritional stress conditions was investigated. The control cells presented a characteristic pattern, with monolayer growth, while the stressed cells presented multilayered growth, with aggregate or spheroid formation which detached on the flask surface and continued their growth in another region. In the soft agar assay, with reduced amount of nutrients, only the stressed cells presented growth, indicating physical and nutritional independence. A 44-kDa protein was observed in stressed cells and was absent in non-stressed cells. The adhesion index and fibronectin synthesis and distribution were altered in stressed cells. After confluence, control cells presented fibronectin accumulation in lateral cell-cell contact regions, while this fibronectin accumulation pattern was not observed in stressed cells. These alterations may be responsible for the multilayered growth and decreased adhesion index observed in stressed cells which were transformed by nutritional stress conditions.

  14. US Fire Administration Fire Statistics

    Data.gov (United States)

    Department of Homeland Security — The U.S. Fire Administration collects data from a variety of sources to provide information and analyses on the status and scope of the fire problem in the United...

  15. Circadian- and Light-Dependent Regulation of Resting Membrane Potential and Spontaneous Action Potential Firing of Drosophila Circadian Pacemaker Neurons

    OpenAIRE

    Sheeba, Vasu; Gu, Huaiyu; Sharma, Vijay K.; O'Dowd, Diane K.; Holmes, Todd C

    2007-01-01

    The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly ...

  16. Investigating the association between weather conditions, calendar events and socio-economic patterns with trends in fire incidence: an Australian case study

    Science.gov (United States)

    Corcoran, Jonathan; Higgs, Gary; Rohde, David; Chhetri, Prem

    2011-06-01

    Fires in urban areas can cause significant economic, physical and psychological damage. Despite this, there has been a comparative lack of research into the spatial and temporal analysis of fire incidence in urban contexts. In this paper, we redress this gap through an exploration of the association of fire incidence to weather, calendar events and socio-economic characteristics in South-East Queensland, Australia using innovative technique termed the quad plot. Analysing trends in five fire incident types, including malicious false alarms (hoax calls), residential buildings, secondary (outdoor), vehicle and suspicious fires, results suggest that risk associated with all is greatly increased during school holidays and during long weekends. For all fire types the lowest risk of incidence was found to occur between one and six a.m. It was also found that there was a higher fire incidence in socially disadvantaged neighbourhoods and there was some evidence to suggest that there may be a compounding impact of high temperatures in such areas. We suggest that these findings may be used to guide the operations of fire services through spatial and temporal targeting to better utilise finite resources, help mitigate risk and reduce casualties.

  17. Ecological Impacts of the Cerro Grande Fire: Predicting Elk Movement and Distribution Patterns in Response to Vegetative Recovery through Simulation Modeling October 2005

    Energy Technology Data Exchange (ETDEWEB)

    Rupp, Susan P. [Texas Tech Univ., Lubbock, TX (United States)

    2005-10-01

    In May 2000, the Cerro Grande Fire burned approximately 17,200 ha in north-central New Mexico as the result of an escaped prescribed burn initiated by Bandelier National Monument. The interaction of large-scale fires, vegetation, and elk is an important management issue, but few studies have addressed the ecological implications of vegetative succession and landscape heterogeneity on ungulate populations following large-scale disturbance events. Primary objectives of this research were to identify elk movement pathways on local and landscape scales, to determine environmental factors that influence elk movement, and to evaluate movement and distribution patterns in relation to spatial and temporal aspects of the Cerro Grande Fire. Data collection and assimilation reflect the collaborative efforts of National Park Service, U.S. Forest Service, and Department of Energy (Los Alamos National Laboratory) personnel. Geographic positioning system (GPS) collars were used to track 54 elk over a period of 3+ years and locational data were incorporated into a multi-layered geographic information system (GIS) for analysis. Preliminary tests of GPS collar accuracy indicated a strong effect of 2D fixes on position acquisition rates (PARs) depending on time of day and season of year. Slope, aspect, elevation, and land cover type affected dilution of precision (DOP) values for both 2D and 3D fixes, although significant relationships varied from positive to negative making it difficult to delineate the mechanism behind significant responses. Two-dimensional fixes accounted for 34% of all successfully acquired locations and may affect results in which those data were used. Overall position acquisition rate was 93.3% and mean DOP values were consistently in the range of 4.0 to 6.0 leading to the conclusion collar accuracy was acceptable for modeling purposes. SAVANNA, a spatially explicit, process-oriented ecosystem model, was used to simulate successional dynamics. Inputs to the

  18. PECVD-ONO: A New Deposited Firing Stable Rear Surface Passivation Layer System for Crystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    M. Hofmann

    2008-01-01

    Full Text Available A novel plasma-enhanced chemical vapour deposited (PECVD stack layer system consisting of a-SiOx:H, a-SiNx:H, and a-SiOx:H is presented for silicon solar cell rear side passivation. Surface recombination velocities below 60 cm/s (after firing and below 30 cm/s (after forming gas anneal were achieved. Solar cell precursors without front and rear metallisation showed implied open-circuit voltages Voc values extracted from quasi-steady-state photoconductance (QSSPC measurements above 680 mV. Fully finished solar cells with up to 20.0% energy conversion efficiency are presented. A fit of the cell's internal quantum efficiency using software tool PC1D and a comparison to a full-area aluminium-back surface field (Al-BSF and thermal SiO2 is shown. PECVD-ONO was found to be clearly superior to Al-BSF. A separation of recombination at the metallised and the passivated area at the solar cell's rear is presented using the equations of Fischer and Kray. Nuclear reaction analysis (NRA has been used to evaluate the hydrogen depth profile of the passivation layer system at different stages.

  19. Developmental heterogeneity in DNA packaging patterns influences T-cell activation and transmigration.

    Directory of Open Access Journals (Sweden)

    Soumya Gupta

    Full Text Available Cellular differentiation programs are accompanied by large-scale changes in nuclear organization and gene expression. In this context, accompanying transitions in chromatin assembly that facilitates changes in gene expression and cell behavior in a developmental system are poorly understood. Here, we address this gap and map structural changes in chromatin organization during murine T-cell development, to describe an unusual heterogeneity in chromatin organization and associated functional correlates in T-cell lineage. Confocal imaging of DNA assembly in cells isolated from bone marrow, thymus and spleen reveal the emergence of heterogeneous patterns in DNA organization in mature T-cells following their exit from the thymus. The central DNA pattern dominated in immature precursor cells in the thymus whereas both central and peripheral DNA patterns were observed in naïve and memory cells in circulation. Naïve T-cells with central DNA patterns exhibited higher mechanical pliability in response to compressive loads in vitro and transmigration assays in vivo, and demonstrated accelerated expression of activation-induced marker CD69. T-cell activation was characterized by marked redistribution of DNA assembly to a central DNA pattern and increased nuclear size. Notably, heterogeneity in DNA patterns recovered in cells induced into quiescence in culture, suggesting an internal regulatory mechanism for chromatin reorganization. Taken together, our results uncover an important component of plasticity in nuclear organization, reflected in chromatin assembly, during T-cell development, differentiation and transmigration.

  20. Fire and climate in Mongolia (1532-2010 Common Era)

    Science.gov (United States)

    Hessl, Amy E.; Brown, Peter; Byambasuren, Oyunsanaa; Cockrell, Shawn; Leland, Caroline; Cook, Ed; Nachin, Baatarbileg; Pederson, Neil; Saladyga, Thomas; Suran, Byambagerel

    2016-06-01

    Recent increases in wildland fire, warming temperatures, and land use change have coincided in many forested regions, making it difficult to parse causes of elevated fire activity. Here we use 20 multicentury fire scar chronologies (464 fire scar samples) from Mongolia to evaluate the role of climate forcing of fire in the context of livestock grazing and minimal fire suppression. We observe no change in fire return intervals post-1900; however, since the 1500s, periods of drought are coincident with more fire and shorter fire return intervals. We observe same year and some antecedent year effects of drought on fire, a pattern typical of semiarid forests elsewhere. During the instrumental period, drought remains an important driver of fire; however, limited fire activity in recent decades may be due to the coincidence of drought and intensive grazing that have synergized to reduce fuel continuity and fire spread.

  1. Pigment cell interactions and differential xanthophore recruitment underlying zebrafish stripe reiteration and Danio pattern evolution.

    Science.gov (United States)

    Patterson, Larissa B; Bain, Emily J; Parichy, David M

    2014-11-06

    Fishes have diverse pigment patterns, yet mechanisms of pattern evolution remain poorly understood. In zebrafish, Danio rerio, pigment-cell autonomous interactions generate dark stripes of melanophores that alternate with light interstripes of xanthophores and iridophores. Here, we identify mechanisms underlying the evolution of a uniform pattern in D. albolineatus in which all three pigment cell classes are intermingled. We show that in this species xanthophores differentiate precociously over a wider area, and that cis regulatory evolution has increased expression of xanthogenic Colony Stimulating Factor-1 (Csf1). Expressing Csf1 similarly in D. rerio has cascading effects, driving the intermingling of all three pigment cell classes and resulting in the loss of stripes, as in D. albolineatus. Our results identify novel mechanisms of pattern development and illustrate how pattern diversity can be generated when a core network of pigment-cell autonomous interactions is coupled with changes in pigment cell differentiation.

  2. Embryonic control of epidermal cell patterning in the root and hypocotyl of Arabidopsis.

    Science.gov (United States)

    Lin, Y; Schiefelbein, J

    2001-10-01

    A position-dependent pattern of epidermal cell types is produced during the development of the Arabidopsis seedling root and hypocotyl. To understand the origin and regulation of this patterning mechanism, we have examined the embryonic expression of the GLABRA2 (GL2) gene, which encodes a cell-type-specific transcription factor. Using in situ RNA hybridization and a sensitive GL2::GFP reporter, we discovered that a position-dependent pattern of GL2 expression is established within protodermal cells at the heart stage and is maintained throughout the remainder of embryogenesis. In addition, we show that an exceptional GL2 expression character and epidermal cell pattern arises during development of the root-hypocotyl junction, which represents an anatomical transition zone. Furthermore, we find that two of the genes regulating seedling epidermal patterning, TRANSPARENT TESTA GLABRA (TTG) and WEREWOLF (WER), also control the embryonic GL2 pattern, whereas the CAPRICE (CPC) and GL2 genes are not required to establish this pattern. These results indicate that position-dependent patterning of epidermal cell types begins at an early stage of embryogenesis, before formation of the apical meristems and shortly after the cellular anatomy of the protoderm and outer ground tissue layer is established. Thus, epidermal cell specification in the Arabidopsis seedling relies on the embryonic establishment of a patterning mechanism that is perpetuated postembryonically.

  3. Interaction of RECQ4 and MCM10 is important for efficient DNA replication origin firing in human cells

    DEFF Research Database (Denmark)

    Kliszczak, Maciej; Sedlackova, Hana; Pitchai, Ganesha P;

    2015-01-01

    DNA replication is a highly coordinated process that is initiated at multiple replication origins in eukaryotes. These origins are bound by the origin recognition complex (ORC), which subsequently recruits the Mcm2-7 replicative helicase in a Cdt1/Cdc6-dependent manner. In budding yeast, two...... essential replication factors, Sld2 and Mcm10, are then important for the activation of replication origins. In humans, the putative Sld2 homolog, RECQ4, interacts with MCM10. Here, we have identified two mutants of human RECQ4 that are deficient in binding to MCM10. We show that these RECQ4 variants...... are able to complement the lethality of an avian cell RECQ4 deletion mutant, indicating that the essential function of RECQ4 in vertebrates is unlikely to require binding to MCM10. Nevertheless, we show that the RECQ4-MCM10 interaction is important for efficient replication origin firing....

  4. Temporal properties of pattern adaptation of relay cells in the lateral geniculate nucleus of cats

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The temporal properties of pattern adaptation of relay cells induced by repeated sinusoidal drifting grating were investigated in the dorsal lateral geniculate nucleus (dLGN) of cats. The results showed that the response amplitude declined and the response latency prolonged when relay cells were pattern-adapted in dLGN, like the similar fmdings in visual cortex. However, in contrast to the result in cortex,the response phase of relay cells advanced. This implies that an inhibition with relatively long latency may participate in the pattern adaptation of dLGN cells and the adaptation in dLGN may be via a mechanism different from that of visual cortex.``

  5. Determination of the Operating Envelope for a Direct Fired Fuel Cell Turbine Hybrid Using Hardware Based Simulation

    Energy Technology Data Exchange (ETDEWEB)

    David Tucker; Eric Liese; Randall Gemmen

    2009-02-10

    The operating range of a direct fired solid oxide fuel cell gas turbine (SOFC/GT) hybrid with bypass control of cathode airflow was determined using a hardware-based simulation facility designed and built by the U.S. Department of Energy, National Energy Technology Laboratory (NETL). Three methods of cathode airflow management using bypass valves in a hybrid power system were evaluated over the maximum range of operation. The cathode air flow was varied independently over the full range of operation of each bypass valve. Each operating point was taken at a steady state condition and was matched to the thermal, pressure and flow output of a corresponding fuel cell operation condition. Turbine electric load was also varied so that the maximum range of fuel cell operation could be studied, and a preliminary operating map could be made. Results are presented to show operating envelopes in terms of cathode air flow, fuel cell and turbine load, and compressor surge margin to be substantial.

  6. Fabrication and evaluation of the thin NiFe supported solid oxide fuel cell by co-firing method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyeong Hyun; Kim, Haekyoung [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Park, Young Min [Fuel Cell Project, Research Institute of Industrial Science and Technology, Pohang 790-330 (Korea, Republic of)

    2010-12-15

    Metal supported solid oxide fuel cells (SOFCs) are one of the most promising candidates for power plants as well as portable applications due to their good mechanical and thermal properties. In this study, the thin NiFe supported SOFC, which consisted of thin metal support (NiFe, {proportional_to}70 {mu}m), anode functional layer (Ni-YSZ, {proportional_to}30 {mu}m), electrolyte (YSZ, {proportional_to}15 {mu}m), and cathode (LSCF, {proportional_to}30 {mu}m), was fabricated through tape casting and co-firing method. The cell showed 1.05-1.1 V of open circuit voltage and 1.4 W cm{sup -2} of maximum power density at 800 C with the ohmic resistance (R{sub ohm}) of 0.12 {omega} cm{sup 2} and the polarization resistance (R{sub p}) of 0.38 {omega} cm{sup 2}. The high performance and the successful measurement of thin metal supported cell showed the possibility for mobile applications through the large area cell fabrications. (author)

  7. Clear cell renal cell carcinoma with hemangioblastoma-like features: A recently described pattern with unusual immunohistochemical profile

    Directory of Open Access Journals (Sweden)

    Sankalp Sancheti

    2015-01-01

    Full Text Available The diagnosis of clear cell renal cell carcinoma may sometimes pose challenges because of the presence of uncharacteristic morphology, varied immunophenotypic patterns and due to lack of molecular or genetic determinants. More often, the morphological variations can be easily overlooked in routine practice and a more common diagnosis is usually put forward. Solid, acinar and alveolar are the common patterns described in the literature. We report a recently described pattern of clear cell renal cell carcinoma which has hemangioblastoma-like morphology and an unusual immunoprofile. In our case, the tumor showed a diffuse hemangioblastoma-like pattern and diffuse positivity for Alpha-inhibin on immunohistochemistry. A thorough literature search, extensive sampling and an expanded immunohistochemistry panel revealed a clear cell renal cell carcinoma component. Presence of renal vein thrombosis and focal necrosis were other helpful features in discerning the malignant nature of tumor.

  8. Aircraft Mishap Fire Pattern Investigations

    Science.gov (United States)

    1985-08-01

    state. In practice, a TNT heat of detonation of 1100 cal/g or 2,000 Btu/lb. is considered more realistic for air blast situations (Ref. 19). Note that... of detonation of 1100 cal./&. Temperature Limits of Flammability - Extreme limits of temperature within Whicb saturated fuel vapor-air mixtures are...greater than the sum of their individual actions. TNT Equivalent - Energy release of a system expressed as an equivalent mas of TNT with an assumed heat

  9. Proceedings of the joint contractors meeting: FE/EE Advanced Turbine Systems conference FE fuel cells and coal-fired heat engines conference

    Energy Technology Data Exchange (ETDEWEB)

    Geiling, D.W. [ed.

    1993-08-01

    The joint contractors meeting: FE/EE Advanced Turbine Systems conference FEE fuel cells and coal-fired heat engines conference; was sponsored by the US Department of Energy Office of Fossil Energy and held at the Morgantown Energy Technology Center, P.O. Box 880, Morgantown, West Virginia 26507-0880, August 3--5, 1993. Individual papers have been entered separately.

  10. Body sodium overload modulates the firing rate and fos immunoreactivity of serotonergic cells of dorsal raphe nucleus.

    Directory of Open Access Journals (Sweden)

    Andrea Godino

    Full Text Available In order to determine whether serotonergic (5HT dorsal raphe nucleus (DRN cells are involved in body sodium status regulation, the effect of a s.c. infusion of either 2 M or 0.15 M NaCl on 5HT DRN neuron firing was studied using single unit extracellular recordings. In separate groups of 2 M and 0.15 M NaCl-infused rats, water intake, oxytocin (OT plasma concentration, urine and plasma sodium and protein concentrations were also measured. Also, to determine the involvement of particular brain nuclei and neurochemical systems in body sodium overload (SO, animals from both groups were perfused for brain immunohistochemical detection of Fos, Fos-OT and Fos-5HT expression. SO produced a significant increase in serotonergic DRN neuron firing rate compared to baseline and 0.15 M NaCl-infused rats. As expected, 2 M NaCl s.c. infusion also induced a significant increase of water intake, diuresis and natriuresis, plasma sodium concentration and osmolality, even though plasma volume did not increase as indicated by changes in plasma protein concentration. The distribution of neurons along the forebrain and brainstem expressing Fos after SO showed the participation of the lamina terminalis, extended amygdala, supraoptic and paraventricular hypothalamic nuclei in the neural network that controls osmoregulatory responses. Both Fos-OT immunoreactive and plasma OT concentration increased after s.c. hypertonic sodium infusion. Finally, matching the "in vivo" electrophysiological study, SO doubled the number of Fos-5HT immunolabeled cells within the DRN. In summary, the results characterize the behavioral, renal and endocrine responses after body sodium overload without volume expansion and specify the cerebral nuclei that participate at different CNS levels in the control of these responses. The electrophysiological approach also allows us to determine in an "in vivo" model that DRN 5HT neurons increase their firing frequency during an increase in systemic

  11. Performance improvement of anode-supported electrolytes for planar solid oxide fuel cells via a tape-casting/lamination/co-firing technique

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hae-Gu; Moon, Hwan; Park, Sung-Chul; Lee, Jong-Jin; Yoon, Daeil; Hyun, Sang-Hoon [School of Advanced Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea); Kim, Do-Heyoung [Research Institute of Industrial Science and Technology, Kyuongpook 790-600 (Korea)

    2010-05-01

    Recently, solid oxide fuel cells (SOFCs) have attracted considerable attention because of their low emissions, high-energy conversion efficiency, and flexible usage of various fuels. One of the key problems of applying flat-type SOFCs to large-scale power generation is that unit cells of large area and with a high degree of flatness cannot be manufactured satisfactorily. In this study, the effects of tape-casting, laminating, and co-firing conditions on the flatness of anode-supported electrolyte unit cells have been investigated to improve the cell performance of unit cells. The cells are composed of a Ni-yttria-stabilized zirconia (YSZ) anode, a Ni-YSZ anode functional layer (AFL), a YSZ electrolyte, and a lanthanum strontium manganate (LSM)-YSZ cathode. The flatness of the anode-supported electrolyte is optimized by controlling the firing schedule, the lamination method, and the applied load during firing. A 5 cm x 5 cm (active area 4 cm x 4 cm) unit cell having a reasonable flatness of 55 {mu}m/5 cm shows a higher power output of 11.4 W as compared with 7.7 W a unit cell with a flatness of 200 {mu}m/5 cm, when operating at 800 C with humidified hydrogen fuel. (author)

  12. Patterning of cell assemblies regulated by adhesion receptors of the cadherin superfamily.

    Science.gov (United States)

    Takeichi, M; Nakagawa, S; Aono, S; Usui, T; Uemura, T

    2000-07-29

    During morphogenesis, cell-cell association patterns are dynamically altered. We are interested in how cell adhesion molecules can regulate the patterning of cellular assemblies. Cadherins, a group of cell-cell adhesion receptors, are crucial for the organized assembly of many cell types, but they also regulate dynamic aspects of cell association. For example, during neural crest emigration from the neural tube, the cadherin subtypes expressed by crest cells are switched from one subtype to another. Artificial perturbation of this switch results in blocking of their escape from the neural tube. Intracellular modulations of cadherin activity also seem to play a role in regulation of cell adhesion. We identified p120ctn as a regulator of cadherin function in carcinoma cells. With such regulators, cells may make a choice as to whether they should maintain stable cell contacts or disrupt their association. Finally, we found another type of cadherin-mediated cell patterning: Flamingo, a seven-pass transmembrane cadherin, regulates planar cell polarity in Drosophila imaginal discs. Thus, the cadherin superfamily receptors control the patterning of cell assemblies through a variety of mechanisms.

  13. Adhesive-tape soft lithography for patterning mammalian cells: application to wound-healing assays.

    Science.gov (United States)

    Shrirao, Anil B; Hussain, Ali; Cho, Cheul H; Perez-Castillejos, Raquel

    2012-09-13

    This paper introduces a benchtop method for patterning mammalian cells-i.e., for culturing cells at specific locations-on planar substrates. Compared with standard cell culture techniques, which do not allow the control of what areas of a monolayer are populated by one type of cell or another, techniques of cell patterning open new routes to cell biology. Researchers interested in cell patterning, however, are often times hindered by limited access to photolithographic capabilities. This paper shows how cells can be patterned easily with sub-millimeter precision using a non-photolithographic technique that is based on the use of office adhesive tape and poly(dimethylsiloxane) (PDMS). This method is fast (~4 h to go from a layout to have the cells patterned in the shape of such layout) and only requires materials and tools readily available in a conventional biomedical laboratory. A wound-healing assay is presented here that illustrates the potential of the technique (which we call tape-based soft lithography) for patterning mammalian cells and studying biologically significant questions such as collective cellular migration.

  14. Optimal shapes and stresses of adherent cells on patterned substrates

    CERN Document Server

    Banerjee, Shiladitya; Marchetti, M Cristina

    2013-01-01

    We investigate a continuum mechanical model for an adherent cell on two dimensional adhesive micropatterned substrates. The cell is modeled as an isotropic and homogeneous elastic material subject to uniform internal contractile stresses. The build-up of tension from cortical actin bundles at the cell periphery is incorporated by introducing an energy cost for bending of the cell boundary, resulting to a resistance to changes in local curvature. Integrin-based adhesions are modeled as harmonic springs, that pin the cell to adhesive patches of a predefined geometry. Using Monte Carlo simulations and analytical techniques we investigate the competing effects of bulk contractility and cortical bending rigidity in regulating cell shapes on non-adherent regions. We show that the crossover from convex to concave cell edges is controlled by the interplay between contractile stresses and boundary bending rigidity. In particular, the cell boundary becomes concave beyond a critical value of the contractile stress that ...

  15. Linking Cellular Mechanisms to Behavior: Entorhinal Persistent Spiking and Membrane Potential Oscillations May Underlie Path Integration, Grid Cell Firing, and Episodic Memory

    Directory of Open Access Journals (Sweden)

    Michael E. Hasselmo

    2008-01-01

    Full Text Available The entorhinal cortex plays an important role in spatial memory and episodic memory functions. These functions may result from cellular mechanisms for integration of the afferent input to entorhinal cortex. This article reviews physiological data on persistent spiking and membrane potential oscillations in entorhinal cortex then presents models showing how both these cellular mechanisms could contribute to properties observed during unit recording, including grid cell firing, and how they could underlie behavioural functions including path integration. The interaction of oscillations and persistent firing could contribute to encoding and retrieval of trajectories through space and time as a mechanism relevant to episodic memory.

  16. Enhanced conversion efficiency in nanocrystalline solar cells using optically functional patterns

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yang Doo; Park, Sang Jun [Department of Materials and Science Engineering, Korea University, 5-1 Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Jang, Eunseok [Photovoltaic Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Oh, Kyoung Suk [KIER-UNIST Advanced Center for Energy, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Cho, Jun-Sik, E-mail: jscho@kier.re.kr [Photovoltaic Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Lee, Heon, E-mail: heonlee@korea.ac.kr [Department of Materials and Science Engineering, Korea University, 5-1 Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of)

    2015-07-31

    The lower conversion efficiency of nanocrystalline silicon (nc-Si:H) solar cells is a result of its lower photon absorption capability of nc-Si:H. To increase photon absorption of nc-Si:H, the Ag substrates were fabricated with optically functional patterns. Two types of patterns, with random and regular structures, were formed by direct imprint technology. Owing to these optically functional patterns, the scattering of reflected light at the surface of the patterned Ag was enhanced and the optical path became longer. Thus, a greater amount of photons was absorbed by the nc-Si:H layer. Compared to flat Ag (without a surface pattern), the light absorption value of the nc-Si:H layer with a random structure pattern was increased at wavelengths ranging from 600 to 1100 nm. In the case of the regular patterned Ag, the light absorption value of the nc-Si:H layer was higher than the flat Ag at 300 to 1100 nm. Subsequently, nc-Si:H solar cells constructed on the optically functional pattern exhibit a 15.7% higher J{sub sc} value and a 19.5% higher overall conversion efficiency, compared to an identical solar cell on flat Ag. - Highlights: • Optically functional patterns were fabricated by direct printing technique. • The light absorption of solar cells was increased by the patterned Ag substrate. • Current density of solar cells on patterned Ag increased by approximately 15.7%. • The efficiency of solar cells on patterned Ag increased by 19.5%.

  17. Modelling the spreading of large-scale wildland fires

    CERN Document Server

    Drissi, Mohamed

    2014-01-01

    The objective of the present study is twofold. First, the last developments and validation results of a hybrid model designed to simulate fire patterns in heterogeneous landscapes are presented. The model combines the features of a stochastic small-world network model with those of a deterministic semi-physical model of the interaction between burning and non-burning cells that strongly depends on local conditions of wind, topography, and vegetation. Radiation and convection from the flaming zone, and radiative heat loss to the ambient are considered in the preheating process of unburned cells. Second, the model is applied to an Australian grassland fire experiment as well as to a real fire that took place in Corsica in 2009. Predictions compare favorably to experiments in terms of rate of spread, area and shape of the burn. Finally, the sensitivity of the model outcomes (here the rate of spread) to six input parameters is studied using a two-level full factorial design.

  18. Synaptic kainate receptors in interplay with INaP shift the sparse firing of dentate granule cells to a sustained rhythmic mode in temporal lobe epilepsy.

    Science.gov (United States)

    Artinian, Julien; Peret, Angélique; Marti, Geoffrey; Epsztein, Jérôme; Crépel, Valérie

    2011-07-27

    Dentate granule cells, at the gate of the hippocampus, use coincidence detection of synaptic inputs to code afferent information under a sparse firing regime. In both human patients and animal models of temporal lobe epilepsy, mossy fibers sprout to form an aberrant glutamatergic network between dentate granule cells. These new synapses operate via long-lasting kainate receptor-mediated events, which are not present in the naive condition. Here, we report that in chronic epileptic rat, aberrant kainate receptors in interplay with the persistent sodium current dramatically expand the temporal window for synaptic integration. This introduces a multiplicative gain change in the input-output operation of dentate granule cells. As a result, their sparse firing is switched to an abnormal sustained and rhythmic mode. We conclude that synaptic kainate receptors dramatically alter the fundamental coding properties of dentate granule cells in temporal lobe epilepsy.

  19. On fire

    DEFF Research Database (Denmark)

    Hansen, Helle Rabøl

    The title of this paper: “On fire”, refers to two (maybe three) aspects: firstly as a metaphor of having engagement in a community of practice according to Lave & Wenger (1991), and secondly it refers to the concrete element “fire” in the work of the fire fighters – and thirdly fire as a signifier...

  20. Fire Power

    Science.gov (United States)

    Denker, Deb; West, Lee

    2009-01-01

    For education administrators, campus fires are not only a distressing loss, but also a stark reminder that a campus faces risks that require special vigilance. In many ways, campuses resemble small communities, with areas for living, working and relaxing. A residence hall fire may raise the specter of careless youth, often with the complication of…

  1. Hyperpolarization induces a long-term increase in the spontaneous firing rate of cerebellar Golgi cells

    OpenAIRE

    Hull, Court; Chu, YunXiang; Thanawala, Monica; Regehr, Wade G.

    2013-01-01

    Golgi cells (GoCs) are inhibitory interneurons that influence the cerebellar cortical response to sensory input by regulating the excitability of the granule cell layer. While GoC inhibition is essential for normal motor coordination, little is known about the circuit dynamics that govern the activity of these cells. In particular, while GoC spontaneous spiking influences the extent of inhibition and gain throughout the granule cell layer, it is not known whether this spontaneous activity can...

  2. Improved conversion efficiency of amorphous Si solar cells using a mesoporous ZnO pattern

    Science.gov (United States)

    Go, Bit-Na; Kim, Yang Doo; suk Oh, Kyoung; Kim, Chaehyun; Choi, Hak-Jong; Lee, Heon

    2014-09-01

    To provide a front transparent electrode for use in highly efficient hydrogenated amorphous silicon (a-Si:H) thin-film solar cells, porous flat layer and micro-patterns of zinc oxide (ZnO) nanoparticle (NP) layers were prepared through ultraviolet nanoimprint lithography (UV-NIL) and deposited on Al-doped ZnO (AZO) layers. Through this, it was found that a porous micro-pattern of ZnO NPs dispersed in resin can optimize the light-trapping pattern, with the efficiency of solar cells based on patterned or flat mesoporous ZnO layers increased by 27% and 12%, respectively.

  3. Development of Spatial Distribution Patterns by Biofilm Cells

    DEFF Research Database (Denmark)

    Haagensen, Janus Anders Juul; Hansen, Susse Kirkelund; Bak Christensen, Bjarke;

    2015-01-01

    in the context of species distribution patterns observed in macroecology, and we summarize observations about the processes involved in co-adaptation between P. putida and Acinetobacter sp. C6. Our results contribute to an understanding of spatial species distribution patterns as they are observed in nature......Confined spatial patterns of microbial distribution are prevalent in nature, such as in microbial mats, soil communities, and water stream biofilms. The symbiotic two-species consortium of Pseudomonas putida and Acinetobacter sp. C6, originally isolated from a creosote-polluted aquifer, has evolved...... a distinct spatial organization in the laboratory that is characterized by an increased fitness and productivity. In this consortium, P. putida is reliant on microcolonies formed by Acinetobacter sp. C6 — to which it attaches. Here we describe the processes that lead to the microcolony...

  4. Protein micro patterned lattices to probe a fundamental lengthscale involved in cell adhesion

    CERN Document Server

    Guillou, Herve; Chaussy, Jacques; Block, Marc R

    2009-01-01

    Cell adhesion, a fundamental process of cell biology is involved in the embryo development and in numerous pathologies especially those related to cancers. We constrained cells to adhere on extracellular matrix proteins patterned in a micro lattices. The actin cytoskeleton is particularly sensitive to this constraint and reproducibly self organizes in simple geometrical patterns. Such highly organized cells are functional and proliferate. We performed statistical analysis of spread cells morphologies and discuss the existence of a fundamental lengthscale associated with active processes required for spreading.

  5. A feedback mechanism controlling SCRAMBLED receptor accumulation and cell-type pattern in Arabidopsis.

    Science.gov (United States)

    Kwak, Su-Hwan; Schiefelbein, John

    2008-12-23

    Cellular pattern formation in the root epidermis of Arabidopsis occurs in a position-dependent manner, generating root-hair (H) cells contacting two underlying cortical cells and nonhair (N) cells contacting one cortical cell. SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase (LRR-RLK), mediates this process through its effect on a downstream transcription factor regulatory network. After perception of a positional cue, the SCM signaling pathway is proposed to preferentially repress WEREWOLF (WER) transcription factor expression in H cells and thereby bias the outcome of mutual lateral inhibition acting between H and N cells. However, the molecular mechanism responsible for this preferential SCM signaling is unknown. Here, we analyze the distribution of the SCM receptor and the biological effect of altering its accumulation pattern. We find that SCM expression and accumulation in the epidermal cell layer is necessary and sufficient to direct the cell-type pattern. Further, SCM preferentially accumulates in H cells, and this accumulation pattern is dependent on the downstream transcription factors. Thus, SCM participates in an autoregulatory feedback loop, enabling cells engaged in SCM signaling to maintain high levels of SCM receptor, which provides a simple mechanism for reinforcing a bias in receptor-mediated signaling to ensure robust pattern formation.

  6. JACKDAW controls epidermal patterning in the Arabidopsis root meristem through a non-cell-autonomous mechanism.

    Science.gov (United States)

    Hassan, Hala; Scheres, Ben; Blilou, Ikram

    2010-05-01

    In Arabidopsis, specification of the hair and non-hair epidermal cell types is position dependent, in that hair cells arise over clefts in the underlying cortical cell layer. Epidermal patterning is determined by a network of transcriptional regulators that respond to an as yet unknown cue from underlying tissues. Previously, we showed that JACKDAW (JKD), a zinc finger protein, localizes in the quiescent centre and the ground tissue, and regulates tissue boundaries and asymmetric cell division by delimiting SHORT-ROOT movement. Here, we provide evidence that JKD controls position-dependent signals that regulate epidermal-cell-type patterning. JKD is required for appropriately patterned expression of the epidermal cell fate regulators GLABRA2, CAPRICE and WEREWOLF. Genetic interaction studies indicate that JKD operates upstream of the epidermal patterning network in a SCRAMBLED (SCM)-dependent fashion after embryogenesis, but acts independent of SCM in embryogenesis. Tissue-specific induction experiments indicate non-cell-autonomous action of JKD from the underlying cortex cell layer to specify epidermal cell fate. Our findings are consistent with a model where JKD induces a signal in every cortex cell that is more abundant in the hair cell position owing to the larger surface contact of cells located over a cleft.

  7. Evaluation of deriving fire cycle of forested landscape based on time-since-fire distribution

    Institute of Scientific and Technical Information of China (English)

    ZHANG Quan-fa; Kurt S. Pregitzer; JIANG Ming-xi; CHEN Wen-jun

    2006-01-01

    Estimation of fire cycle has been conducted by using the negative exponential function as an approximation of time-since-fire distribution of a landscape assumed .to be homogeneous with respect to fire spread processes. The authors imposed predefined fire cycles on a virtual landscape of 100 cell ×100 cell, and obtained a mosaic composing of patches with different stand ages (i.e. time since fire). Graphical and statistical methods (Van Wagner 1978; Reed et al. 1998) were employed to derive fire cycle from the virtual landscape. By comparing the predefined and the derived fire cycles, the two methods and tested the effects of sample size and hazard of burning (i.e., stand's susceptibility to fire in relation to its stand age) were evaluated on fire cycle deviation. The simulation results indicated a minimum sample size of 10 times of the annual burnt area would be required for partitioning time-since-fire distribution into homogeneous epochs indicating temporal change in fire cycle. Statistically, there was significant difference among the imposed and the derived fire cycle, regardless of sample sizes with or without consideration of hazard of burning. Both methods underestimated the more recent fire cycle without significant difference between them. The results imply that deviation of fire cycle based on time-since-fire distribution warrants cautious interpretation, especially when a landscape is spatially partitioned into small units and temporal changes in fire cycle are involved.

  8. Auxin Acts through MONOPTEROS to Regulate Plant Cell Polarity and Pattern Phyllotaxis.

    Science.gov (United States)

    Bhatia, Neha; Bozorg, Behruz; Larsson, André; Ohno, Carolyn; Jönsson, Henrik; Heisler, Marcus G

    2016-12-05

    The periodic formation of plant organs such as leaves and flowers gives rise to intricate patterns that have fascinated biologists and mathematicians alike for hundreds of years [1]. The plant hormone auxin plays a central role in establishing these patterns by promoting organ formation at sites where it accumulates due to its polar, cell-to-cell transport [2-6]. Although experimental evidence as well as modeling suggest that feedback from auxin to its transport direction may help specify phyllotactic patterns [7-12], the nature of this feedback remains unclear [13]. Here we reveal that polarization of the auxin efflux carrier PIN-FORMED 1 (PIN1) is regulated by the auxin response transcription factor MONOPTEROS (MP) [14]. We find that in the shoot, cell polarity patterns follow MP expression, which in turn follows auxin distribution patterns. By perturbing MP activity both globally and locally, we show that localized MP activity is necessary for the generation of polarity convergence patterns and that localized MP expression is sufficient to instruct PIN1 polarity directions non-cell autonomously, toward MP-expressing cells. By expressing MP in the epidermis of mp mutants, we further show that although MP activity in a single-cell layer is sufficient to promote polarity convergence patterns, MP in sub-epidermal tissues helps anchor these polarity patterns to the underlying cells. Overall, our findings reveal a patterning module in plants that determines organ position by orienting transport of the hormone auxin toward cells with high levels of MP-mediated auxin signaling. We propose that this feedback process acts broadly to generate periodic plant architectures.

  9. 6-羟多巴胺毁损的帕金森病模型大鼠脚桥核神经元放电频率和放电形式的变化%Increase of firing rate with changes in firing pattern of neurons of the pedunculopontine nucleus in 6-hydrodopamine lesioned rats

    Institute of Scientific and Technical Information of China (English)

    王勇; 张巧俊; 刘健; 冯洁; 褚玉霞; 高蕊; 刘娅萍

    2005-01-01

    Objective To explore the change in the firing rate and firing pattern of pedunculopontine nucleus (PPN)neurons in 6-hydrodopamine (6-OHDA) unilaterally lesiond rats. Methods Electrophysiological recordings of PPN neurons were done in normal rats and 6-OHDA lesiond rats with standard single unit glass microelectrode method in vivo. Results The firing rate of PPN neurons in normal rats and 6-OHDA lesiond rats were (9.0 ± 0.8 ) Hz [ (0.5-25.2) Hz, n = 56 ] and ( 16. 1 ± 1.6) Hz [ (1.2-49.7) Hz, n= 57), respectively. The firing rate of 6-OHDA lesioned rats was significantly increased when compared to control rats (P < 0. 001 ). Concerning the firing pattern, 68% (38/56) of the neurons recorded discharged regularly, 27% (15/56) exhibited an irregular pattern and 5% (3/56) discharged in bursts in normal rats. In 6-OHDA lesioned rats, 39% (22/57) discharged regularly, 47% (27/57) exhibited an irregular pattern and 14% (8/57) in bursts. The number of PPN neurons in 6-OHDA lesioned rats fired irregularly was significantly higher than in control rats ( P < 0.05). Conclusion The firing rate and the percentage of the irregularly firing neuron in PPN of 6-OHDA lesioned rats increased significantly, which may be contributed to the pathophysiological changes of Parkinson's disease.%目的观察6-羟多巴胺毁损的帕金森病(Parkinson's disease,PD)模型大鼠脚桥核(pedunculopontine nucleus,PPN)神经元放电频率和放电形式的变化.方法采用在体玻璃微电极细胞外记录法,记录正常对照组和PD模型组大鼠PPN神经元的电活动.结果对照组和PD组大鼠PPN神经元的放电频率分别为(9.0±0.8)Hz[(0.5-25.2)Hz,n=56]和(16.1±1.6)Hz[(1.2-49.7)Hz,n=57],PD组大鼠的放电频率显著高于对照组(P<0.001).在对照组大鼠脚桥核,68%(38/56)的神经元呈现规则放电,27%(15/56)呈现不规则放电,5%(3/56)为爆发式放电;在PD组大鼠脚桥核,具有规则、不规则和爆发式放电的神经元比例分别为39

  10. Cell patterning on polylactic acid through surface-tethered oligonucleotides.

    Science.gov (United States)

    Matsui, Toshiki; Arima, Yusuke; Takemoto, Naohiro; Iwata, Hiroo

    2015-02-01

    Polylactic acid (PLA) is a candidate material to prepare scaffolds for 3-D tissue regeneration. However, cells do not adhere or proliferate well on the surface of PLA because it is hydrophobic. We report a simple and rapid method for inducing cell adhesion to PLA through DNA hybridization. Single-stranded DNA (ssDNA) conjugated to poly(ethylene glycol) (PEG) and to a terminal phospholipid (ssDNA-PEG-lipid) was used for cell surface modification. Through DNA hybridization, modified cells were able to attach to PLA surfaces modified with complementary sequence (ssDNA'). Different cell types can be attached to PLA fibers and films in a spatially controlled manner by using ssDNAs with different sequences. In addition, they proliferate well in a culture medium supplemented with fetal bovine serum. The coexisting modes of cell adhesion through DNA hybridization and natural cytoskeletal adhesion machinery revealed no serious effects on cell growth. The combination of a 3-D scaffold made of PLA and cell immobilization on the PLA scaffold through DNA hybridization will be useful for the preparation of 3-D tissue and organs.

  11. Epidermal Patterning Genes Impose Non-cell Autonomous Cell Size Determination and have Additional Roles in Root Meristem Size Control

    Institute of Scientific and Technical Information of China (English)

    Christian L?fke; Kai Dünser; Jürgen Kleine-Vehn

    2013-01-01

    The regulation of cellular growth is of vital importance for embryonic and postembryonic patterning. Growth regulation in the epidermis has importance for organ growth rates in roots and shoots, proposing epidermal cells as an interesting model for cellular growth regulation. Here we assessed whether the root epidermis is a suitable model system to address cell size determination. In Arabidopsis thaliana L., root epidermal cells are regularly spaced in neighbouring tricho-(root hair) and atrichoblast (non-hair) cells, showing already distinct cell size regulation in the root meristem. We determined cell sizes in the root meristem and at the onset of cellular elongation, revealing that not only division rates but also cellular shape is distinct in tricho-and atrichoblasts. Intriguingly, epidermal-patterning mutants, failing to define differential vacuolization in neighbouring epidermal cell files, also display non-differential growth. Using these epidermal-patterning mutants, we show that polarized growth behaviour of epidermal tricho-and atrichoblast is interdependent, suggesting non-cell autonomous signals to integrate tissue expansion. Besides the interweaved cell-type-dependent growth mechanism, we reveal an additional role for epidermal patterning genes in root meristem size and organ growth regulation. We conclude that epidermal cells represent a suitable model system to study cell size determination and interdependent tissue growth.

  12. 钠电流对皮层中间神经元放电模式影响%Na+ Current to Extend the Influence of Firing Patterns in Interneurons

    Institute of Scientific and Technical Information of China (English)

    周青青; 熊冬生; 刘深泉; 汪雷

    2011-01-01

    Objective: The firing patterns of inhibitory Interneurons in the neocortex are researched in this paper. Methods: Through FS mode, the numerical analysis on the firing patterns of among inhibitory neurons in the neocortex as well as the transformation among the patterns was made according to the change of parameters in Na ion. Hi addition, various kinds of period bifurcation phenomenon were displayed by ISIs. Results and Conclusions: The analysis results showed that there were apparent period doubling bifurcation and period adverse doubling bifurcation following the change of parameters in Na ion. Furthermore, after period doubling bifurcation and period adverse doubling bifurcation, the firing patterns returned to 1 period firing pattern. From the three-dimensional figures of gate variable of Na, with the increasing of &, different bifurcation figures had the characteristics of similarity and time delay.%目的:通过分析FS模型来探索皮层抑制性中间神经元放电的规律.方法:数值分析钠离子通道参数改变的情况下,皮层中间神经元的发放模式以及不同发放模式之间的转移,并通过峰峰间距(InterSpike Intervals,ISIs)序列展示了不同发放模式转移过程中出现的各种周期分岔现象.结果与结论:随着钠通道参数的改变,出现了明显的倍周期分岔和逆倍周期分岔现象,并且最终发放模型从分岔模式回归到周期1簇的放电模式.从钠通道门变量m的三维分岔图得出,随着gd的增加,不同分岔图之间出现相似性,具有延缓特性.

  13. Collective motion of cells mediates segregation and pattern formation in co-cultures.

    Directory of Open Access Journals (Sweden)

    Elod Méhes

    Full Text Available Pattern formation by segregation of cell types is an important process during embryonic development. We show that an experimentally yet unexplored mechanism based on collective motility of segregating cells enhances the effects of known pattern formation mechanisms such as differential adhesion, mechanochemical interactions or cell migration directed by morphogens. To study in vitro cell segregation we use time-lapse videomicroscopy and quantitative analysis of the main features of the motion of individual cells or groups. Our observations have been extensive, typically involving the investigation of the development of patterns containing up to 200,000 cells. By either comparing keratocyte types with different collective motility characteristics or increasing cells' directional persistence by the inhibition of Rac1 GTP-ase we demonstrate that enhanced collective cell motility results in faster cell segregation leading to the formation of more extensive patterns. The growth of the characteristic scale of patterns generally follows an algebraic scaling law with exponent values up to 0.74 in the presence of collective motion, compared to significantly smaller exponents in case of diffusive motion.

  14. Biased inheritance of the protein PatN frees vegetative cells to initiate patterned heterocyst differentiation.

    Science.gov (United States)

    Risser, Douglas D; Wong, Francis C Y; Meeks, John C

    2012-09-18

    Heterocysts, cells specialized for nitrogen fixation in certain filamentous cyanobacteria, appear singly in a nonrandom spacing pattern along the chain of vegetative cells. A two-stage, biased initiation and competitive resolution model has been proposed to explain the establishment of this spacing pattern. There is substantial evidence that competitive resolution of a subset of cells initiating differentiation occurs by interactions between a self-enhancing activator protein, HetR, and a diffusible pentapeptide inhibitor PatS-5 (RGSGR). Results presented here show that the absence of a unique membrane protein, PatN, in Nostoc punctiforme strain ATCC 29133 leads to a threefold increase in heterocyst frequency and a fourfold decrease in the vegetative cell interval between heterocysts. A PatN-GFP translational fusion shows a pattern of biased inheritance in daughter vegetative cells of ammonium-grown cultures. Inactivation of another heterocyst patterning gene, patA, is epistatic to inactivation of patN, and transcription of patA increases in a patN-deletion strain, implying that patN may function by modulating levels of patA. The presence of PatN is hypothesized to decrease the competency of a vegetative cell to initiate heterocyst differentiation, and the cellular concentration of PatN is dependent on cell division that results in cells transiently depleted of PatN. We suggest that biased inheritance of cell-fate determinants is a phylogenetic domain-spanning paradigm in the development of biological patterns.

  15. Patterning processes in aggregates of Hydra cells visualized with the monoclonal antibody, TS19.

    Science.gov (United States)

    Sato, M; Bode, H R; Sawada, Y

    1990-10-01

    The monoclonal antibody, TS19, (Heimfeld et al., 1985), labels the apical surface of ectodermal epithelial cells of tentacles and lower peduncles in Hydra. To investigate the patterning process in a tissue whose original pattern was completely destroyed, the TS19 staining pattern was examined in developing aggregates of Hydra cells. Two types of aggregates were prepared. G-aggregates were made from tissue of the gastric portion of animals and RG-aggregates from gastric tissue allowed to regenerate for 24 hr before making aggregates. G-aggregates were initially TS19-negative, and later dim and uniformly TS19-positive. Thereafter, TS19 staining broke up into brightly stained and unstained regions. The brightly staining regions developed into head or foot structures. The TS19 pattern in RG-aggregates developed differently. Since the initial aggregates contained cells of regenerating tips, they started with TS19-positive cells as well as TS19-negative cells. The numbers of brightly staining TS19-positive cells increased with time. Some patches of these cells developed into head or foot structures, while others did not. These results and a simulation using a reaction-diffusion model suggest that the changes in activation levels affected the temporal changes in the pattern of TS19 staining, and that the de novo pattern formation in hydra can be explained in terms of a process involving activation and inhibition properties.

  16. Developmentally regulated epitopes of cell surface arabinogalactan proteins and their relation to root tissue pattern formation.

    Science.gov (United States)

    Knox, J P; Linstead, P J; Peart, J; Cooper, C; Roberts, K

    1991-11-01

    Two polymorphic forms of an extracellular arabinogalactan protein (AGP1 and AGP2), obtained from the conditioned media of two carrot suspension-cultured cell lines, have been identified in terms of binding of the anti-plasma membrane antibodies JIM4 and MAC207. AGP1 and AGP2 have been used as immunogens to generate further anti-AGP monoclonal antibodies. JIM14 identified an epitope carried by AGP2 and also by glycoproteins of low molecular weight localized to the plant cell wall. In addition, further antibodies (JIM13 and JIM15) identified carbohydrate epitopes of the AGPs that also occur on plasma membrane glycoproteins and are expressed by patterns of cells that reflect cell position at the carrot root apex. Indirect immunofluorescence microscopy indicated that JIM13 recognized the surface of cells forming the epidermis and cells marking the region and axis of the future xylem. JIM15 recognized a pattern of cells directly complementary to the JIM13 pattern. The panel of anti-AGP monoclonal antibodies now available indicates groups of cells within the root meristem that may reflect an early pre-pattern of the tissues of the mature root structure and suggests extensive modulation of cell surface AGPs during cell development and the positioning of cells within the apex.

  17. Patterned carbon nanotubes as a new three-dimensional scaffold for mesenchymal stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Bitirim, Verda Ceylan [Department of Molecular Biology and Genetics, Bilkent University, 06800, Ankara (Turkey); Kucukayan-Dogu, Gokce [Institute of Engineering and Science, Material Science and Nanotechnology Graduate Program, Bilkent University, 06800, Ankara (Turkey); Bengu, Erman [Department of Chemistry, Bilkent University, 06800, Ankara (Turkey); Akcali, Kamil Can, E-mail: akcali@fen.bilkent.edu.tr [Department of Molecular Biology and Genetics, Bilkent University, 06800, Ankara (Turkey); Bilgen, Bilkent University Genetics and Biotechnology Research Center, 06800, Ankara (Turkey)

    2013-07-01

    We investigated the cellular adhesive features of mesenchymal stem cells (MSC) on non-coated and collagen coated patterned and vertically aligned carbon nanotube (CNT) structures mimicking the natural extra cellular matrix (ECM). Patterning was achieved using the elasto-capillary induced by water treatment on the CNT arrays. After confirmation with specific markers both at transcript and protein levels, MSCs from different passages were seeded on either collagen coated or non-coated patterned CNTs. Adhesion and growth of MSCs on the patterned CNT arrays were examined using scanning electron microscopy image analysis and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-tetrazolium bromide (MTT) assays. The highest MSC count was observed on the non-coated patterned CNTs at passage zero, while decreasing numbers of MSCs were found at the later passages. Similarly, MTT assay results also revealed a decrease in the viability of the MSCs for the later passages. Overall, the cell count and viability experiments indicated that MSCs were able to better attach to non-coated patterned CNTs compared to those coated with collagen. Therefore, the patterned CNT surfaces can be potentially used as a scaffold mimicking the ECM environment for MSC growth which presents an alternative approach to MSC-based transplantation therapy applications. - Highlights: • Synthesized vertically aligned CNTs were patterned to be used as scaffold. • The growth of mesenchymal stem cells was achieved on the patterned CNTs. • The cell number was counted higher on the patterned CNTs than collagen coated CNTs. • The MTT assay results revealed the cell viability on the patterned CNTs.

  18. A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells.

    Science.gov (United States)

    Higaki, Takumi; Kutsuna, Natsumaro; Akita, Kae; Takigawa-Imamura, Hisako; Yoshimura, Kenji; Miura, Takashi

    2016-04-01

    Plant leaf epidermal cells exhibit a jigsaw puzzle-like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.

  19. Influence of wavelength on laser doping and laser-fired contact processes for c-Si solar cells

    Science.gov (United States)

    Molpeceres, Carlos; Sánchez-Aniorte, María. Isabel; Morales, Miguel; Muñoz, David; Martín, Isidro; Ortega, Pablo; Colina, Mónica; Voz, Cristóbal; Alcubilla, Ramón

    2012-10-01

    This work investigates the influence of the laser wavelength on laser doping (LD) and laser-fired contact (LFC) formation in solar cell structures. We compare the results obtained using the three first harmonics (corresponding to wavelengths of 1064 nm, 532 nm and 355 nm) of fully commercial solid state laser sources with pulse width in the ns range. The discussion is based on the impact on the morphology and electrical characteristics of test structures. In the case of LFC the study includes the influence of different passivation layers and the assessment of the process quality through electrical resistance measurements of an aluminium single LFC point for the different wavelengths. Values for the normalized LFC resistance far below 1.0 mΩcm2 have been obtained, with better results at shorter wavelengths. To assess the influence of the laser wavelength on LD we have created n+ regions into p-type c-Si wafers, using a dry LD approach to define punctual emitters. J-V characteristics show exponential trends at mid-injection for a broad parametric window in all wavelengths, with local ideality factors well below 1.5. In both processes the best results have been obtained using green (532 nm) and, specially, UV (355 nm). This indicates that to minimize the thermal damage in the material is a clear requisite to obtain the best electrical performance, thus indicating that UV laser shows better potential to be used in high efficiency solar cells.

  20. Cell fate patterning during C. elegans vulval development

    OpenAIRE

    Hill, Russell J.; Sternberg, Paul W.

    1993-01-01

    Precursor cells of the vulva of the C. elegans hermaphrodite choose between two vulval cell fates (1° and 2°) and a non-vulval epidermal fate (3°) in response to three intercellular signals. An inductive signal produced by the anchor cell induces the vulval precursors to assume the 1° and 2° vulval fates. This inductive signal is an EGF-like growth factor encoded by the gene lin-3. An inhibitory signal mediated by lin-15, and which may originate from the surrounding epidermis, prevents the vu...

  1. Innate recognition of apoptotic cells: novel apoptotic cell-associated molecular patterns revealed by crossreactivity of anti-LPS antibodies.

    Science.gov (United States)

    Tennant, I; Pound, J D; Marr, L A; Willems, J J L P; Petrova, S; Ford, C A; Paterson, M; Devitt, A; Gregory, C D

    2013-05-01

    Cells dying by apoptosis are normally cleared by phagocytes through mechanisms that can suppress inflammation and immunity. Molecules of the innate immune system, the pattern recognition receptors (PRRs), are able to interact not only with conserved structures on microbes (pathogen-associated molecular patterns, PAMPs) but also with ligands displayed by apoptotic cells. We reasoned that PRRs might therefore interact with structures on apoptotic cells - apoptotic cell-associated molecular patterns (ACAMPs) - that are analogous to PAMPs. Here we show that certain monoclonal antibodies raised against the prototypic PAMP, lipopolysaccharide (LPS), can crossreact with apoptotic cells. We demonstrate that one such antibody interacts with a constitutively expressed intracellular protein, laminin-binding protein, which translocates to the cell surface during apoptosis and can interact with cells expressing the prototypic PRR, mCD14 as well as with CD14-negative cells. Anti-LPS cross reactive epitopes on apoptotic cells colocalised with annexin V- and C1q-binding sites on vesicular regions of apoptotic cell surfaces and were released associated with apoptotic cell-derived microvesicles (MVs). These results confirm that apoptotic cells and microbes can interact with the immune system through common elements and suggest that anti-PAMP antibodies could be used strategically to characterise novel ACAMPs associated not only with apoptotic cells but also with derived MVs.

  2. Bragg reflector and laser fired back contact in a-Si:H/c-Si heterostructure solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Tucci, M. [ENEA, Research Center Casaccia, via Anguillarese 301, S. Maria di Galeria 00123, Rome (Italy)], E-mail: mario.tucci@casaccia.enea.it; Serenelli, L.; Salza, E.; Pirozzi, L. [ENEA, Research Center Casaccia, via Anguillarese 301, S. Maria di Galeria 00123, Rome (Italy); De Cesare, G.; Caputo, D.; Ceccarelli, M. [Department of Electronic Engineering, University ' Sapienza' , via Eudossiana 18 00184, Rome (Italy)

    2009-03-15

    The amorphous/crystalline silicon (a-Si/c-Si) heterostructure has recently attracted new interest due to higher open circuit voltage V{sub oc} and low temperature fabrication processes. By reducing the wafer thickness all these characteristics become a necessity, together with the requirement of a back reflecting mirror, to obtain an effective optical confinement. To this aim dielectric mirrors can be adopted in the rear side of the solar cells, together with a local process of laser fired back Al contact. Taking advantage of a-Si/SiN{sub x} passivation properties of c-Si surface a Bragg reflector configuration can be formed on the rear side of the c-Si wafer by Plasma Enhanced Chemical Vapor Deposition (PECVD) alternating several couples of a-Si/SiN{sub x} and choosing their thicknesses to maximize the reflectance inward the c-Si wafer in the NIR spectrum. In this work we have adopted this mirror on the rear side of an n-a-Si/i-a-Si/p-c-Si heterostructure solar cell to obtain a full low temperature process. The cell back contact has been ensured by an Al diffusion into the c-Si wafer promoted by Nd-YAG pulsed laser. The front cell contact has been enhanced by chromium silicide CrSi formation on top of the n-a-Si layer and ITO deposition followed by an Ag grid. A V{sub oc} of 681 mV and 94% of IQE at 1000 nm have been reached.

  3. PERIODIC STREAM LINES IN THE THREE-DIMENSIONAL SQUARE CELL PATTERN

    Institute of Scientific and Technical Information of China (English)

    李继彬; 段晚锁

    2001-01-01

    By using the theory of the generalized perturbed Hamiltonian systems, it is shown that there exist periodic stream lines in the three-dimensional square cell pattern of Rayleigh-Benard convection. The result means that our method enables this three dimensional flow pattern to be described in an unambiguous manner, and some experimental results of other authors can be explained.

  4. Expression Patterns of Cancer-Testis Antigens in Human Embryonic Stem Cells and Their Cell Derivatives Indicate Lineage Tracks

    OpenAIRE

    Nadya Lifantseva; Anna Koltsova; Tatyana Krylova; Tatyana Yakovleva; Galina Poljanskaya; Olga Gordeeva

    2011-01-01

    Pluripotent stem cells can differentiate into various lineages but undergo genetic and epigenetic changes during long-term cultivation and, therefore, require regular monitoring. The expression patterns of cancer-testis antigens (CTAs) MAGE-A2, -A3, -A4, -A6, -A8, -B2, and GAGE were examined in undifferentiated human embryonic stem (hES) cells, their differentiated derivatives, teratocarcinoma (hEC) cells, and cancer cell lines of neuroectodermal and mesodermal origin. Undifferentiated hES ce...

  5. Creating two-dimensional patterned substrates for protein and cell confinement.

    Science.gov (United States)

    Johnson, Dawn M; LaFranzo, Natalie A; Maurer, Joshua A

    2011-01-01

    Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.(1) While microcontact printing can be employed to directly print a large number of molecules, including proteins,(2) DNA,(3) and silanes,(4) the formation of self-assembled monolayers (SAMs) from long chain alkane thiols on gold provides a simple way to confine proteins and cells to specific patterns containing adhesive and resistant regions. This confinement can be used to control cell morphology and is useful for examining a variety of questions in protein and cell biology. Here, we describe a general method for the creation of well-defined protein patterns for cellular studies.(5) This process involves three steps: the production of a patterned master using photolithography, the creation of a PDMS stamp, and microcontact printing of a gold-coated substrate. Once patterned, these cell culture substrates are capable of confining proteins and/or cells (primary cells or cell lines) to the pattern. The use of self-assembled monolayer chemistry allows for precise control over the patterned protein/cell adhesive regions and non-adhesive regions; this cannot be achieved using direct protein stamping. Hexadecanethiol, the long chain alkane thiol used in the microcontact printing step, produces a hydrophobic surface that readily adsorbs protein from solution. The glycol-terminated thiol, used for backfilling the non-printed regions of the substrate, creates a monolayer that is resistant to protein adsorption and therefore cell growth.(6) These thiol monomers produce highly structured monolayers that precisely define regions of the substrate that can support protein adsorption and cell growth. As a result, these substrates are useful for a wide variety of applications from the study of intercellular behavior(7) to the creation of microelectronics.(8) While other types of monolayer chemistry have been used for cell culture studies, including work from

  6. Fire Safety

    Science.gov (United States)

    ... Turn off Animations Turn on Animations Our Sponsors Log in | Register Menu Log in | Register Home Our Sponsors Ages & Stages Ages & ... permit escape. If you live in an apartment building, never use an elevator during a fire. Use ...

  7. A review of sediment budget imbalances along Fire Island, New York: Can nearshore geologic framework and patterns of shoreline change explain the deficit?

    Science.gov (United States)

    Hapke, Cheryl J.; Lentz, Erika E.; Gayes, Paul T.; McCoy, Clayton A.; Henderson, Rachel E.; Schwab, William C.; Williams, S. Jeffress

    2010-01-01

    Sediment budget analyses conducted for annual to decadal timescales report variable magnitudes of littoral transport along the south shore of Long Island, New York. It is well documented that the primary transport component is directed alongshore from east to west, but relatively little information has been reported concerning the directions or magnitudes of cross-shore components. Our review of budget calculations for the Fire Island coastal compartment (between Moriches and Fire Island Inlets) indicates an average deficit of 217,700 m3/y. Updrift shoreline erosion, redistribution of nourishment fills, and reworking of inner-shelf deposits have been proposed as the potential sources of additional sediment needed to rectify budget residuals. Each of these sources is probably relevant over various spatial and temporal scales, but previous studies of sediment texture and provenance, inner-shelf geologic mapping, and beach profile comparison indicate that reworking of inner-shelf deposits is the source most likely to resolve budget discrepancies over the broadest scales. This suggests that an onshore component of sediment transport is likely more important along Fire Island than previously thought. Our discussion focuses on relations between geomorphology, inner-shelf geologic framework, and historic shoreline change along Fire Island and the potential pathways by which reworked, inner-shelf sediments are likely transported toward the shoreline.

  8. The influence of a water current on the larval deposition pattern of females of a diverging fire salamander population (Salamandra salamandra)

    NARCIS (Netherlands)

    Krause, E.T.; Caspers, B.A.

    2015-01-01

    Fire salamanders are amphibians that exhibit a highly specific reproductive mode termed ovo-viviparity. The eggs develop inside their mothers, and the females give birth to fully developed larvae. The larvae in our study area cluster in two distinct genetic groups that can be linked directly to the

  9. Fire safety

    Energy Technology Data Exchange (ETDEWEB)

    Keski-Rahkonen, O.; Bjoerkman, J.; Hostikka, S.; Mangs, J. [VTT Building Technology, Espoo (Finland); Huhtanen, R. [VTT Energy, Espoo (Finland); Palmen, H.; Salminen, A.; Turtola, A. [VTT Automation, Espoo (Finland)

    1998-07-01

    According to experience and probabilistic risk assessments, fires present a significant hazard in a nuclear power plant. Fires may be initial events for accidents or affect safety systems planned to prevent accidents and to mitigate their consequences. The project consists of theoretical work, experiments and simulations aiming to increase the fire safety at nuclear power plants. The project has four target areas: (1) to produce validated models for numerical simulation programmes, (2) to produce new information on the behavior of equipment in case of fire, (3) to study applicability of new active fire protecting systems in nuclear power plants, and (4) to obtain quantitative knowledge of ignitions induced by important electric devices in nuclear power plants. These topics have been solved mainly experimentally, but modelling at different level is used to interpret experimental data, and to allow easy generalisation and engineering use of the obtained data. Numerical fire simulation has concentrated in comparison of CFD modelling of room fires, and fire spreading on cables on experimental data. So far the success has been good to fair. A simple analytical and numerical model has been developed for fire effluents spreading beyond the room of origin in mechanically strongly ventilated compartments. For behaviour of equipment in fire several full scale and scaled down calorimetric experiments were carried out on electronic cabinets, as well as on horizontal and vertical cable trays. These were carried out to supply material for CFD numerical simulation code validation. Several analytical models were developed and validated against obtained experimental results to allow quick calculations for PSA estimates as well as inter- and extrapolations to slightly different objects. Response times of different commercial fire detectors were determined for different types of smoke, especially emanating from smoldering and flaming cables to facilitate selection of proper detector

  10. Micro-pattern formation of extracellular matrix (ECM) layers by atmospheric-pressure plasmas and cell culture on the patterned ECMs

    Science.gov (United States)

    Ando, Ayumi; Asano, Toshifumi; Urisu, Tsuneo; Hamaguchi, Satoshi

    2011-12-01

    A new patterning technique for the extracellular matrix (ECM) deposited on a Si substrate was developed with the use of a low-frequency atmospheric-pressure plasma and a metal stencil mask. The development of such a patterning technique for cell arrangement is a crucial step for the development of future cell chips. In this study, optimal process conditions for ECM patterning over the size of a typical single chip (about 1 cm2) were achieved and the obtained ECM patterns were directly observed by fluorescence labelling. It was also demonstrated that HEK293 cells (human embryo kidney cells) attach to and proliferate on the ECM layer patterned by this technique, arranging themselves on the Si substrate in the mask pattern.

  11. Influence of the pattern shape on the photonic efficiency of front-side periodically patterned ultrathin crystalline silicon solar cells

    CERN Document Server

    Herman, Aline; Depauw, Valerie; Daif, Ounsi El; Deparis, Olivier

    2012-01-01

    Patterning the front side of an ultra-thin crystalline silicon (c Si) solar cell helps keeping the energy conversion efficiency high by compensating for the light absorption losses. A super-Gaussian mathematical expression was used in order to encompass a large variety of nanopattern shapes and to study their influence on the photonic performance. We prove that the enhancement in the maximum achievable photo-current is due to both impedance matching condition at short wavelengths and to the wave nature of light at longer wavelengths. We show that the optimal mathematical shape and parameters of the pattern depend on the c Si thickness. An optimal shape comes with a broad optimal parameter zone where fabricating errors would have much less influence on the efficiency. We prove that cylinders are not the best suited shape. To compare our model with a real slab, we fabricated a nanopatterned c Si slab via Nano Imprint Lithography.

  12. Light-Addressable Electrodeposition of Magnetically-Guided Cells Encapsulated in Alginate Hydrogels for Three-Dimensional Cell Patterning

    Directory of Open Access Journals (Sweden)

    Shih-Hao Huang

    2014-11-01

    Full Text Available This paper describes a light-addressable electrolytic system used to perform an electrodeposition of magnetically-guided cells encapsulated in alginate hydrogels using a digital micromirror device (DMD for three-dimensional cell patterning. In this system, the magnetically-labeled cells were first manipulated into a specific arrangement by changing the orientation of the magnetic field, and then a patterned light illumination was projected onto a photoconductive substrate serving as a photo-anode to cause gelation of calcium alginate through sol-gel transition. By controlling the illumination pattern on the DMD, we first successfully produced cell-encapsulated multilayer alginate hydrogels with different shapes and sizes in each layer via performing multiplexed micropatterning. By combining the magnetically-labeled cells, light-addressable electrodeposition, and orientation of the magnetic fields, we have successfully demonstrated to fabricate two layers of the cell-encapsulated alginate hydrogels, where cells in each layer can be manipulated into cross-directional arrangements that mimic natural tissue. Our proposed method provides a programmable method for the spatiotemporally controllable assembly of cell populations into three-dimensional cell patterning and could have a wide range of biological applications in tissue engineering, toxicology, and drug discovery.

  13. A survey of cellulose microfibril patterns in dividing, expanding, and differentiating cells of Arabidopsis thaliana.

    Science.gov (United States)

    Fujita, Miki; Wasteneys, Geoffrey O

    2014-05-01

    Cellulose microfibrils are critical for plant cell specialization and function. Recent advances in live cell imaging of fluorescently tagged cellulose synthases to track cellulose synthesis have greatly advanced our understanding of cellulose biosynthesis. Nevertheless, cellulose deposition patterns remain poorly described in many cell types, including those in the process of division or differentiation. In this study, we used field emission scanning electron microscopy analysis of cryo-planed tissues to determine the arrangement of cellulose microfibrils in various faces of cells undergoing cytokinesis or specialized development, including cell types in which cellulose cannot be imaged by conventional approaches. In dividing cells, we detected microfibrillar meshworks in the cell plates, consistent with the concentration at the cell plate of cellulose synthase complexes, as detected by fluorescently tagged CesA6. We also observed a loss of parallel cellulose microfibril orientation in walls of the mother cell during cytokinesis, which corresponded with the loss of fluorescently tagged cellulose synthase complexes from these surfaces. In recently formed guard cells, microfibrils were randomly organized and only formed a highly ordered circumferential pattern after pore formation. In pit fields, cellulose microfibrils were arranged in circular patterns around plasmodesmata. Microfibrils were random in most cotyledon cells except the epidermis and were parallel to the growth axis in trichomes. Deposition of cellulose microfibrils was spatially delineated in metaxylem and protoxylem cells of the inflorescence stem, supporting recent studies on microtubule exclusion mechanisms.

  14. Distinguishing Pattern Formation Phenotypes: Applying Minkowski Functionals to Cell Biology Systems

    Science.gov (United States)

    Rericha, Erin; Guven, Can; Parent, Carole; Losert, Wolfgang

    2011-03-01

    Spatial Clustering of proteins within cells or cells themselves frequently occur in cell biology systems. However quantifying the underlying order and determining the regulators of these cluster patterns have proved difficult due to the inherent high noise levels in the systems. For instance the patterns formed by wild type and cyclic-AMP regulatory mutant Dictyostelium cells are visually distinctive, yet the large error bars in measurements of the fractal number, area, Euler number, eccentricity, and wavelength making it difficult to quantitatively distinguish between the patterns. We apply a spatial analysis technique based on Minkowski functionals and develop metrics which clearly separate wild type and mutant cell lines into distinct categories. Having such a metric facilitated the development of a computational model for cellular aggregation and its regulators. Supported by NIH-NGHS Nanotechnology (R01GM085574) and the Burroughs Wellcome Fund.

  15. DNA methyltransferase 1 and DNA methylation patterning contribute to germinal center B-cell differentiation

    DEFF Research Database (Denmark)

    Shaknovich, Rita; Cerchietti, Leandro; Tsikitas, Lucas;

    2011-01-01

    The phenotype of germinal center (GC) B cells includes the unique ability to tolerate rapid proliferation and the mutagenic actions of activation induced cytosine deaminase (AICDA). Given the importance of epigenetic patterning in determining cellular phenotypes, we examined DNA methylation and t......, the GC B cells of Dnmt1 hypomorphic animals showed evidence of increased DNA damage, suggesting dual roles for DNMT1 in DNA methylation and double strand DNA break repair.......The phenotype of germinal center (GC) B cells includes the unique ability to tolerate rapid proliferation and the mutagenic actions of activation induced cytosine deaminase (AICDA). Given the importance of epigenetic patterning in determining cellular phenotypes, we examined DNA methylation...... and the role of DNA methyltransferases in the formation of GCs. DNA methylation profiling revealed a marked shift in DNA methylation patterning in GC B cells versus resting/naive B cells. This shift included significant differential methylation of 235 genes, with concordant inverse changes in gene expression...

  16. 基于GIS的景观格局对云南省森林火灾的影响%Effect of Landscape Pattern on Forest Fires in Yunnan Province Based on GIS

    Institute of Scientific and Technical Information of China (English)

    张晨; 牛树奎; 陈锋; 邵潇; 王欢

    2016-01-01

    灾蔓延有抑制作用;2)在(0,1]hm2森林火灾中,香农多样性指数、景观丰度和蔓延性指数对火灾面积的影响程度依次降低;在(50,100]hm2森林火灾中,蔓延性指数、香农多样性指数和斑块数量对火灾面积影响程度依次降低,以上排序可通过Bootstrap显著性检验;3)香农多样性指数、斑块数量和斑块密度的相关系数随着火灾等级(面积扩大)提高向更高的负相关转化,对森林火灾面积的抑制作用逐渐增加。相反,蔓延性指数的相关系数随着火灾等级提高逐渐向正相关发展,对森林火灾面积变化起到促进作用。以上景观指数对100 hm2以上的森林火灾面积变化的影响程度最为明显。%Objective]In this study,the influences of landscape pattern on forest fires in Yunnan Province were studied. The landscape index was calculated and the correlation analysis was conducted to examine the influences of different land use types on forest fires,as well as the influence strength of the increasing fire burned area. This study aimed to lay a theoretical foundation for future in-depth study on the impact of forest landscape on forest fires. [Method]Forest fires were classified based on the Forest Protection Regulations combined with the actual situation in the study area in Yunnan Province. The remote sensing images were pretreated and reclassified,and the land use classification diagram of Yunnan Province was granted. The ArcGIS grid method was used to grid and seven kinds of landscape indexes were chosen[number of plaques ( NP ) ,mean patch size ( MPS ) ,patch density ( PD ) ,contagion index ( CONTAG ) ,patch richness( PR ) ,patch richness density ( PRD ) ,Shannon ’s diversity index ( SHDI) ] and calculated. The correlation analysis and the Bootstrap method were applied to study the relationship between forest fires and the landscape index, furthermore to investigate the influence of landscape pattern on forest fires.[Result]A total of 1

  17. Systematic variation in gene expression patterns in human cancer cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Douglas T.; Scherf, Uwe; Eisen, Michael B.; Perou, Charles M.; Rees, Christian; Spellman, Paul; Iyer, Vishwanath; Jeffrey, Stefanie S.; Van de Rijn, Matt; Waltham, Mark; Pergamenschikov, Alexander; Lee, Jeffrey C.F.; Lashkari, Deval; Shalon, Dari; Myers, Timothy G.; Weinstein, John N.; Botstein, David; Brown, Patrick O.

    2000-01-01

    We used cDNA micro arrays to explore the variation in expression of approximately 8,000 unique genes among the 60 cell lines used in the National Cancer Institute s screen for anti-cancer drugs. Classification of the cell lines based solely on the observed patterns of gene expression revealed a correspondence to the ostensible origins of the tumors from which the cell lines were derived. The consistent relationship between the gene expression patterns and the tissue of origin allowed us to recognize outliers whose previous classification appeared incorrect. Specific features of the gene expression patterns appeared to be related to physiological properties of the cell lines, such as their doubling time in culture, drug metabolism or the interferon response. Comparison of gene expression patterns in the cell lines to those observed in normal breast tissue or in breast tumor specimens revealed features of the expression patterns in the tumors that had recognizable counterparts in specific cell lines, reflecting the tumor, stromal and inflammatory components of the tumor tissue. These results provided a novel molecular characterization of this important group of human cell lines and their relationships to tumors in vivo.

  18. Gelatin-based laser direct-write technique for the precise spatial patterning of cells.

    Science.gov (United States)

    Schiele, Nathan R; Chrisey, Douglas B; Corr, David T

    2011-03-01

    Laser direct-writing provides a method to pattern living cells in vitro, to study various cell-cell interactions, and to build cellular constructs. However, the materials typically used may limit its long-term application. By utilizing gelatin coatings on the print ribbon and growth surface, we developed a new approach for laser cell printing that overcomes the limitations of Matrigel™. Gelatin is free of growth factors and extraneous matrix components that may interfere with cellular processes under investigation. Gelatin-based laser direct-write was able to successfully pattern human dermal fibroblasts with high post-transfer viability (91% ± 3%) and no observed double-strand DNA damage. As seen with atomic force microscopy, gelatin offers a unique benefit in that it is present temporarily to allow cell transfer, but melts and is removed with incubation to reveal the desired application-specific growth surface. This provides unobstructed cellular growth after printing. Monitoring cell location after transfer, we show that melting and removal of gelatin does not affect cellular placement; cells maintained registry within 5.6 ± 2.5 μm to the initial pattern. This study demonstrates the effectiveness of gelatin in laser direct-writing to create spatially precise cell patterns with the potential for applications in tissue engineering, stem cell, and cancer research.

  19. Patterns of efficiency and degradation of composite polymer solar cells

    NARCIS (Netherlands)

    Jeranko, T; Tributsch, H; Sariciftci, NS; Hummelen, JC

    2004-01-01

    Bulk-heterojunction plastic solar cells (PSC) produced from a conjugated polymer, poly(2-methoxy-5-(3',7'-dimethyloctyl-oxy)-1,4-phenylenevinylene) (MDMO-PPV), and a methanofullerene [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) were investigated using photocurrent imaging techniques to determi

  20. The isolation of spatial patterning modes in a mathematical model of juxtacrine cell signalling.

    Science.gov (United States)

    O'Dea, R D; King, J R

    2013-06-01

    Juxtacrine signalling mechanisms are known to be crucial in tissue and organ development, leading to spatial patterns in gene expression. We investigate the patterning behaviour of a discrete model of juxtacrine cell signalling due to Owen & Sherratt (1998, Mathematical modelling of juxtacrine cell signalling. Math. Biosci., 153, 125-150) in which ligand molecules, unoccupied receptors and bound ligand-receptor complexes are modelled. Feedback between the ligand and receptor production and the level of bound receptors is incorporated. By isolating two parameters associated with the feedback strength and employing numerical simulation, linear stability and bifurcation analysis, the pattern-forming behaviour of the model is analysed under regimes corresponding to lateral inhibition and induction. Linear analysis of this model fails to capture the patterning behaviour exhibited in numerical simulations. Via bifurcation analysis, we show that since the majority of periodic patterns fold subcritically from the homogeneous steady state, a wide variety of stable patterns exists at a given parameter set, providing an explanation for this failure. The dominant pattern is isolated via numerical simulation. Additionally, by sampling patterns of non-integer wavelength on a discrete mesh, we highlight a disparity between the continuous and discrete representations of signalling mechanisms: in the continuous case, patterns of arbitrary wavelength are possible, while sampling such patterns on a discrete mesh leads to longer wavelength harmonics being selected where the wavelength is rational; in the irrational case, the resulting aperiodic patterns exhibit 'local periodicity', being constructed from distorted stable shorter wavelength patterns. This feature is consistent with experimentally observed patterns, which typically display approximate short-range periodicity with defects.

  1. An interplay of migratory and division forces as a generic mechanism for stem cell patterns

    CERN Document Server

    Hannezo, Edouard; Joanny, Jean-François

    2015-01-01

    In many adult tissues, stem cells and differentiated cells are not homogeneously distributed : stem cells are arranged in periodic "niches", and differentiated cells are constantly produced and migrate out of these niches. In this article, we provide a general theoretical framework to study mixtures of dividing and actively migrating particles, which we apply to biological tissues. We show in particular that the interplay between the stresses arising from active cell migration and stem cell division give rise to robust stem cell patterns. The instability of the tissue leads to spatial patterns which are either steady or oscillating in time. The wavelength of the instability has an order of magnitude consistent with the biological observations. We also discuss the implications of these results for future in vitro and in vivo experiments.

  2. Patterned three-dimensional encapsulation of embryonic stem cells using dielectrophoresis and stereolithography.

    Science.gov (United States)

    Bajaj, Piyush; Marchwiany, Daniel; Duarte, Carlos; Bashir, Rashid

    2013-03-01

    Controlling the assembly of cells in three dimensions is very important for engineering functional tissues, drug screening, probing cell-cell/cell-matrix interactions, and studying the emergent behavior of cellular systems. Although the current methods of cell encapsulation in hydrogels can distribute them in three dimensions, these methods typically lack spatial control of multi-cellular organization and do not allow for the possibility of cell-cell contacts as seen for the native tissue. Here, we report the integration of dielectrophoresis (DEP) with stereolithography (SL) apparatus for the spatial patterning of cells on custom made gold micro-electrodes. Afterwards, they are encapsulated in poly (ethylene glycol) diacrylate (PEGDA) hydrogels of different stiffnesses. This technique can mimic the in vivo microscale tissue architecture, where the cells have a high degree of three dimensional (3D) spatial control. As a proof of concept, we show the patterning and encapsulation of mouse embryonic stem cells (mESCs) and C2C12 skeletal muscle myoblasts. mESCs show high viability in both the DEP (91.79% ± 1.4%) and the no DEP (94.27% ± 0.5%) hydrogel samples. Furthermore, we also show the patterning of mouse embryoid bodies (mEBs) and C2C12 spheroids in the hydrogels, and verify their viability. This robust and flexible in vitro platform can enable various applications in stem cell differentiation and tissue engineering by mimicking elements of the native 3D in vivo cellular micro-environment.

  3. 46 CFR 108.423 - Fire hydrants and associated equipment.

    Science.gov (United States)

    2010-10-01

    ... alley with no assigned space for stowage of combustibles, each spray pattern of water must be from one... horizontal. (d) Each fire hydrant must have at least one spanner and at least one fire hose rack or reel....

  4. Patterning Cells on Optically Transparent Indium Tin Oxide Electrodes

    OpenAIRE

    Shah, Sunny; Revzin, Alexander

    2007-01-01

    The ability to exercise precise spatial and temporal control over cell-surface interactions is an important prerequisite to the assembly of multi-cellular constructs serving as in vitro mimics of native tissues. In this study, photolithography and wet etching techniques were used to fabricate individually addressable indium tin oxide (ITO) electrodes on glass substrates. The glass substrates containing ITO microelectrodes were modified with poly(ethylene glycol) (PEG) silane to make them pr...

  5. Topology optimization: An effective method for designing front metallization patterns of solar cells

    NARCIS (Netherlands)

    Gupta, D.K.; Langelaar, M.; Barink, M.; Keulen, F. van

    2014-01-01

    Optimal front electrode design is one of the approaches to improve the performance of solar cells. This work introduces the application of topology optimization (TO) to design complex front metallization patterns for solar cells. TO optimizes the distribution of electrode material on the front surfa

  6. Combined Cell Culture-Biosensing Platform Using Vertically Aligned Patterned Peptide Nanofibers for Cellular Studies

    DEFF Research Database (Denmark)

    Taskin, Mehmet B.; Sasso, Luigi; Dimaki, Maria

    2013-01-01

    This Article presents the development of a combined cell culture–biosensing platform using vertically aligned self-assembled peptide nanofibers. Peptide nanofibers were patterned on a microchip containing gold microelectrodes to provide the cells with a 3D environment enabling them to grow...

  7. Cell-fate specification in the epidermis: a common patterning mechanism in the root and shoot.

    Science.gov (United States)

    Schiefelbein, John

    2003-02-01

    The specification of epidermal hairs in Arabidopsis provides a useful model for the study of pattern formation in plants. Although the distributions of hair cells in the root and shoot appear quite different, recent studies show that pattern formation in each relies on a common cassette of transcriptional regulators. During development in each organ, neighboring cells compete to express regulators that specify the primary cell fate (including WEREWOLF [WER]/GLABRA1 [GL1], GL3/bHLH, TRANSPARENT TESTA GLABRA [TTG], and GL2), as well as those that prevent their neighbors from adopting this fate (including CAPRICE [CPC] and TRIPTYCHON [TRY]). The basic mechanism of lateral inhibition with feedback that has been uncovered by recent studies provides a conceptual framework for understanding how patterns of cell fate in general may be specified during plant development.

  8. Reconstitution of a Patterned Neural Tube from Single Mouse Embryonic Stem Cells.

    Science.gov (United States)

    Ishihara, Keisuke; Ranga, Adrian; Lutolf, Matthias P; Tanaka, Elly M; Meinhardt, Andrea

    2017-01-01

    The recapitulation of tissue development and patterning in three-dimensional (3D) culture is an important dimension of stem cell research. Here, we describe a 3D culture protocol in which single mouse ES cells embedded in Matrigel under neural induction conditions clonally form a lumen containing, oval-shaped epithelial structure within 3 days. By Day 7 an apicobasally polarized neuroepithelium with uniformly dorsal cell identity forms. Treatment with retinoic acid at Day 2 results in posteriorization and self-organization of dorsal-ventral neural tube patterning. Neural tube organoid growth is also supported by pure laminin gels as well as poly(ethylene glycol) (PEG)-based artificial extracellular matrix hydrogels, which can be fine-tuned for key microenvironment characteristics. The rapid generation of a simple, patterned tissue in well-defined culture conditions makes the neural tube organoid a tractable model for studying neural stem cell self-organization.

  9. Control of programmed cell death by distinct electrical activity patterns.

    Science.gov (United States)

    Golbs, Antje; Nimmervoll, Birgit; Sun, Jyh-Jang; Sava, Irina E; Luhmann, Heiko J

    2011-05-01

    Electrical activity and sufficient supply with survival factors play a major role in the control of apoptosis in the developing cortex. Coherent high-frequency neuronal activity, which efficiently releases neurotrophins, is essential for the survival of immature neurons. We studied the influence of neuronal activity on apoptosis in the developing cortex. Dissociated cultures of the newborn mouse cerebral cortex were grown on multielectrode arrays to determine the activity patterns that promote neuronal survival. Cultures were transfected with a plasmid coding for a caspase-3-sensitive fluorescent protein allowing real-time analysis of caspase-3-dependent apoptosis in individual neurons. Elevated extracellular potassium concentrations (5 and 8 mM), application of 4-aminopyridine or the γ-aminobutyric acid-A receptor antagonist Gabazine induced a shift in the frequency distribution of activity toward high-frequency bursts. Under these conditions, a reduction or delay in caspase-3 activation and an overall increase in neuronal survival could be observed. This effect was dependent on the activity of phosphatidylinositol-3 kinase, as blockade of this enzyme abolished the survival-promoting effect of high extracellular potassium concentrations. Our data indicate that increased network activity can prevent apoptosis in developing cortical neurons.

  10. Origins of adult pigmentation: diversity in pigment stem cell lineages and implications for pattern evolution.

    Science.gov (United States)

    Parichy, David M; Spiewak, Jessica E

    2015-01-01

    Teleosts comprise about half of all vertebrate species and exhibit an extraordinary diversity of adult pigment patterns that function in shoaling, camouflage, and mate choice and have played important roles in speciation. Here, we review studies that have identified several distinct neural crest lineages, with distinct genetic requirements, that give rise to adult pigment cells in fishes. These lineages include post-embryonic, peripheral nerve-associated stem cells that generate black melanophores and iridescent iridophores, cells derived directly from embryonic neural crest cells that generate yellow-orange xanthophores, and bipotent stem cells that generate both melanophores and xanthophores. This complexity in adult chromatophore lineages has implications for our understanding of adult traits, melanoma, and the evolutionary diversification of pigment cell lineages and patterns.

  11. Engineered antifouling microtopographies: surface pattern effects on cell distribution.

    Science.gov (United States)

    Decker, Joseph T; Sheats, Julian T; Brennan, Anthony B

    2014-12-23

    Microtopography has been observed to lead to altered attachment behavior for marine fouling organisms; however, quantification of this phenomenon is lacking in the scientific literature. Here, we present quantitative measurement of the disruption of normal attachment behavior of the fouling algae Ulva linza by antifouling microtopographies. The distribution of the diatom Navicula incerta was shown to be unaffected by the presence of topography. The radial distribution function was calculated for both individual zoospores and cells as well as aggregates of zoospores from attachment data for a variety topographic configurations and at a number of different attachment densities. Additionally, the screening distance and maximum values were mapped according to the location of zoospore aggregates within a single unit cell. We found that engineered topographies decreased the distance between spore aggregates compared to that for a smooth control surface; however, the distributions for individual spores were unchanged. We also found that the local attachment site geometry affected the screening distance for aggregates of zoospores, with certain geometries decreasing screening distance and others having no measurable effect. The distribution mapping techniques developed and explored in this article have yielded important insight into the design parameters for antifouling microtopographies that can be implemented in the next generation of antifouling surfaces.

  12. Examining the lateral displacement of HL60 cells rolling on asymmetric P-selectin patterns.

    Science.gov (United States)

    Lee, Chia-Hua; Bose, Suman; Van Vliet, Krystyn J; Karp, Jeffrey M; Karnik, Rohit

    2011-01-01

    The lateral displacement of cells orthogonal to a flow stream by rolling on asymmetrical receptor patterns presents a new opportunity for the label-free separation and analysis of cells. Understanding the nature of cell rolling trajectories on such substrates is necessary to the engineering of substrates and the design of devices for cell separation and analysis. Here, we investigate the statistical nature of cell rolling and the effect of pattern geometry and flow shear stress on cell rolling trajectories using micrometer-scale patterns of biomolecular receptors with well-defined edges. Leukemic myeloid HL60 cells expressing the PSGL-1 ligand were allowed to flow across a field of patterned lines fabricated using microcontact printing and functionalized with the P-selectin receptor, leveraging both the specific adhesion of this ligand-receptor pair and the asymmetry of the receptor pattern inclination angle with respect to the fluid shear flow direction (α = 5, 10, 15, and 20°). The effects of the fluid shear stress magnitude (τ = 0.5, 1, 1.5, and 2.0 dyn/cm(2)), α, and P-selectin incubation concentration were quantified in terms of the rolling velocity and edge tracking length. Rolling cells tracked along the inclined edges of the patterned lines before detaching and reattaching on another line. The detachment of rolling cells after tracking along the edge was consistent with a Poisson process of history-independent interactions. Increasing the edge inclination angle decreased the edge tracking length in an exponential manner, contrary to the shear stress magnitude and P-selectin incubation concentration, which did not have a significant effect. On the basis of these experimental data, we constructed an empirical model that predicted the occurrence of the maximum lateral displacement at an edge angle of 7.5°. We also used these findings to construct a Monte Carlo simulation for the prediction of rolling trajectories of HL60 cells on P-selectin-patterned

  13. Muscarinic signaling influences the patterning and phenotype of cholinergic amacrine cells in the developing chick retina

    Directory of Open Access Journals (Sweden)

    Fischer Andy J

    2008-02-01

    Full Text Available Abstract Background Many studies in the vertebrate retina have characterized the differentiation of amacrine cells as a homogenous class of neurons, but little is known about the genes and factors that regulate the development of distinct types of amacrine cells. Accordingly, the purpose of this study was to characterize the development of the cholinergic amacrine cells and identify factors that influence their development. Cholinergic amacrine cells in the embryonic chick retina were identified by using antibodies to choline acetyltransferase (ChAT. Results We found that as ChAT-immunoreactive cells differentiate they expressed the homeodomain transcription factors Pax6 and Islet1, and the cell-cycle inhibitor p27kip1. As differentiation proceeds, type-II cholinergic cells, displaced to the ganglion cell layer, transiently expressed high levels of cellular retinoic acid binding protein (CRABP and neurofilament, while type-I cells in the inner nuclear layer did not. Although there is a 1:1 ratio of type-I to type-II cells in vivo, in dissociated cell cultures the type-I cells (ChAT-positive and CRABP-negative out-numbered the type-II cells (ChAT and CRABP-positive cells by 2:1. The relative abundance of type-I to type-II cells was not influenced by Sonic Hedgehog (Shh, but was affected by compounds that act at muscarinic acetylcholine receptors. In addition, the abundance and mosaic patterning of type-II cholinergic amacrine cells is disrupted by interfering with muscarinic signaling. Conclusion We conclude that: (1 during development type-I and type-II cholinergic amacrine cells are not homotypic, (2 the phenotypic differences between these subtypes of cells is controlled by the local microenvironment, and (3 appropriate levels of muscarinic signaling between the cholinergic amacrine cells are required for proper mosaic patterning.

  14. Nanoscale Patterning of Antigen on Silicon Substrate to Examine Mast Cell Activation

    Science.gov (United States)

    2002-04-01

    Examine Mast Cell Activation DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE...Materials Research Society N4.3 Nanoscale Patterning of Antigen on Silicon Substrate to Examine Mast Cell Activation Reid N. Orth", Min Wu2 , Theodore G...nanometer scale to spatially control the stimulation of specific immunoreceptors on RBL mast cells . This work was motivated by previous research to

  15. Computational model-informed design and bioprinting of cell-patterned constructs for bone tissue engineering.

    Science.gov (United States)

    Carlier, Aurélie; Skvortsov, Gözde Akdeniz; Hafezi, Forough; Ferraris, Eleonora; Patterson, Jennifer; Koç, Bahattin; Van Oosterwyck, Hans

    2016-05-17

    Three-dimensional (3D) bioprinting is a rapidly advancing tissue engineering technology that holds great promise for the regeneration of several tissues, including bone. However, to generate a successful 3D bone tissue engineering construct, additional complexities should be taken into account such as nutrient and oxygen delivery, which is often insufficient after implantation in large bone defects. We propose that a well-designed tissue engineering construct, that is, an implant with a specific spatial pattern of cells in a matrix, will improve the healing outcome. By using a computational model of bone regeneration we show that particular cell patterns in tissue engineering constructs are able to enhance bone regeneration compared to uniform ones. We successfully bioprinted one of the most promising cell-gradient patterns by using cell-laden hydrogels with varying cell densities and observed a high cell viability for three days following the bioprinting process. In summary, we present a novel strategy for the biofabrication of bone tissue engineering constructs by designing cell-gradient patterns based on a computational model of bone regeneration, and successfully bioprinting the chosen design. This integrated approach may increase the success rate of implanted tissue engineering constructs for critical size bone defects and also can find a wider application in the biofabrication of other types of tissue engineering constructs.

  16. Social observation enhances cross-environment activation of hippocampal place cell patterns.

    Science.gov (United States)

    Mou, Xiang; Ji, Daoyun

    2016-10-03

    Humans and animals frequently learn through observing or interacting with others. The local enhancement theory proposes that presence of social subjects in an environment facilitates other subjects' understanding of the environment. To explore the neural basis of this theory, we examined hippocampal place cells, which represent spatial information, in rats as they stayed in a small box while a demonstrator rat running on a separate, nearby linear track, and as they ran on the same track themselves. We found that place cell firing sequences during self-running on the track also appeared in the box. This cross-environment activation occurred even prior to any self-running experience on the track and was absent without a demonstrator. Our data thus suggest that social observation can facilitate the observer's spatial representation of an environment without actual self-exploration. This finding may contribute to neural mechanisms of local enhancement.

  17. Modulating patterned adhesion and repulsion of HEK 293 cells on microengineered parylene-C/SiO(2) substrates.

    Science.gov (United States)

    Hughes, M A; Bunting, A S; Cameron, K; Murray, A F; Shipston, M J

    2013-02-01

    This article describes high resolution patterning of HEK 293 cells on a construct of micropatterned parylene-C and silicon dioxide. Photolithographic patterning of parylene-C on silicon dioxide is an established and consistent process. Activation of patterns by immersion in serum has previously enabled patterning of murine hippocampal neurons and glia, as well as the human hNT cell line. Adapting this protocol we now illustrate high resolution patterning of the HEK 293 cell line. We explore hypotheses that patterning is mediated by transmembrane integrin interactions with differentially absorbed serum proteins, and also by etching the surface substrate with piranha solution. Using rationalized protein activation solutions in place of serum, we show that cell patterning can be modulated or even inverted. These cell-patterning findings assist our wider goal of engineering and interfacing functional neuronal networks via a silicon semiconductor platform.

  18. CHARACTERIZATION OF LACTATE DEHYDROGENASE ISOZYME PATTERN AND MORPHOLOGY OF THREE MARINE FISH CELL LINES

    Institute of Scientific and Technical Information of China (English)

    郭华荣; 张士璀; 李红岩; 童裳亮; 相建海

    2002-01-01

    Three continuous marine fish cell lines of FG (i. e., Hounder Gill) from flounder (Paralichthys olivaceus) gill, SPH (i. e. , Sea Perch Heart) from sea perch (Lateolabrax japonicus) heart and RSBF (i.e., Red Sea Bream Fin) from red sea bream (Pagrosomus major) fin, were characterized by lactate dehydrogenase (LDH) isozyme and morphological analysis. The LDH isozyme patterns of these three cell lines and their corresponding tissues of origin were investigated and compared. The results showed: (1) No difference was found in the LDH isozyme patterns of FG and flounder gill tissue. However, the LDH isozyme patterns of SPH and RSBF were significantly different from their corresponding tissues of origin; (2) LDH isozyme patterns of FG, SPH and RSBF were markedly different from each other and could serve as genetic markers for species identification and detection of cross contamination. Morphological change analysis of these three cell lines in comparison to their original tissues indicated that FG cells still appeared epithelioid without morphological transformation. However, morphological changes were found in SPH and RSBF compared to their original tissues. Therefore, the cellular morphology was still plastic in the relatively stable culture conditions, and it was possible that change of LDH patterns wasrelated to morphological changes of fish cells in vitro.

  19. CHARACTERIZATION OF LACTATE DEHYDROGENASE ISOZYME PATTERN AND MORPHOLOGY OF THREE MARINE FISH CELL LINES

    Institute of Scientific and Technical Information of China (English)

    郭华荣; 张士璀; 李红岩; 童裳亮; 相建海

    2002-01-01

    Three continuous marine fish cell lines of FG (i.e. , Flounder Gill) from flounder (Paralichthys olivaceus) gill, SPH (i.e., Sea Perch Heart) fro m sea perch (Lateolabrax japonicus) heart and RSBF (i.e., Red Sea Bream Fin) from red se a bream (Pagrosomus major) fin, were characterized by lactate dehydrogenase (LDH) is ozyme and morphological analysis. The LDH isozyme patterns of these three cell lines and their corresponding tissues of origin were investigated and compared. The results sho wed: (1) No difference was found in the LDH isozyme patterns of FG and flounder gill tissue. However, the LDH isozyme patterns of SPH and RSBF were significantly different from their cor responding tissues of origin; (2) LDH isozyme patterns of FG, SPH and RSBF were markedly di fferent from each other and could serve as genetic markers for species identification and de tection of cross contamination. Morphological change analysis of these three cell lines in compa rison to their original tissues indicated that FG cells still appeared epithelioid without mor phological transformation. However, morphological changes were found in SPH and RSBF compa red to their original tissues. Therefore, the cellular morphology was still plastic in the relatively stable culture conditions, and it was possible that change of LDH patterns was related to morphological changes of fish cells in vitro.

  20. A general principle governs vision-dependent dendritic patterning of retinal ganglion cells.

    Science.gov (United States)

    Xu, Hong-Ping; Sun, Jin Hao; Tian, Ning

    2014-10-15

    Dendritic arbors of retinal ganglion cells (RGCs) collect information over a certain area of the visual scene. The coverage territory and the arbor density of dendrites determine what fraction of the visual field is sampled by a single cell and at what resolution. However, it is not clear whether visual stimulation is required for the establishment of branching patterns of RGCs, and whether a general principle directs the dendritic patterning of diverse RGCs. By analyzing the geometric structures of RGC dendrites, we found that dendritic arbors of RGCs underwent a substantial spatial rearrangement after eye-opening. Light deprivation blocked both the dendritic growth and the branch patterning, suggesting that visual stimulation is required for the acquisition of specific branching patterns of RGCs. We further showed that vision-dependent dendritic growth and arbor refinement occurred mainly in the middle portion of the dendritic tree. This nonproportional growth and selective refinement suggest that the late-stage dendritic development of RGCs is not a passive stretching with the growth of eyes, but rather an active process of selective growth/elimination of dendritic arbors of RGCs driven by visual activity. Finally, our data showed that there was a power law relationship between the coverage territory and dendritic arbor density of RGCs on a cell-by-cell basis. RGCs were systematically less dense when they cover larger territories regardless of their cell type, retinal location, or developmental stage. These results suggest that a general structural design principle directs the vision-dependent patterning of RGC dendrites.

  1. Analysis of chlorophyll fluorescence reveals stage specific patterns of chloroplast-containing cells during Arabidopsis embryogenesis.

    Science.gov (United States)

    Tejos, Ricardo I; Mercado, Ana V; Meisel, Lee A

    2010-01-01

    The basic body plan of a plant is established early in embryogenesis when cells differentiate, giving rise to the apical and basal regions of the embryo. Using chlorophyll fluorescence as a marker for chloroplasts, we have detected specific patterns of chloroplast-containing cells at specific stages of embryogenesis. Non-randomly distributed chloroplast-containing cells are seen as early as the globular stage of embryogenesis in Arabidopsis. In the heart stage of embryogenesis, chloroplast containing cells are detected in epidermal cells as well as a central region of the heart stage embryo, forming a triangular septum of chloroplast-containing cells that divides the embryo into three equal sectors. Torpedo stage embryos have chloroplast-containing epidermal cells and a central band of chloroplast-containing cells in the cortex layer, just below the shoot apical meristem. In the walking-stick stage of embryogenesis, chloroplasts are present in the epidermal, cortex and endodermal cells. The chloroplasts appear reduced or absent from the provascular and columella cells of walking-stick stage embryos. These results suggest that there is a tight regulation of plastid differentiation during embryogenesis that generates specific patterns of chloroplast-containing cells in specific cell layers at specific stages of embryogenesis.

  2. Fire Research Enclosure

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Simulates submarine fires, enclosed aircraft fires, and fires in enclosures at shore facilities .DESCRIPTION: FIRE I is a pressurizable, 324 cu m(11,400 cu...

  3. Fire Research Enclosure

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Simulates submarine fires, enclosed aircraft fires, and fires in enclosures at shore facilities . DESCRIPTION: FIRE I is a pressurizable, 324 cu m(11,400...

  4. Pattern formation in a cell based auxin transport model with numerical bifurcation analysis

    CERN Document Server

    Draelants, Delphine; Beemster, Gerrit T S; Vanroose, Wim

    2012-01-01

    Transport models of growth hormones can be used to reproduce the hormone accumulations that occur in plant organs. Mostly, these accumulation patterns are calculated using time step methods, even though only the resulting steady state patterns of the model are of interest. We examine the steady state solutions of the hormone transport model of Smith et al (2006) for a one-dimensional row of plant cells. We search for the steady state solutions as a function of three of the model parameters by using numerical continuation methods and bifurcation analysis. These methods are more adequate for solving steady state problems than time step methods. We discuss a trivial solution where the concentrations of hormones are equal in all cells and examine its stability region. We identify two generic bifurcation scenarios through which the trivial solution loses its stability. The trivial solution becomes either a steady state pattern with regular spaced peaks or a pattern where the concentration is periodic in time.

  5. Host-induced bacterial cell wall decomposition mediates pattern-triggered immunity in Arabidopsis.

    Science.gov (United States)

    Liu, Xiaokun; Grabherr, Heini M; Willmann, Roland; Kolb, Dagmar; Brunner, Frédéric; Bertsche, Ute; Kühner, Daniel; Franz-Wachtel, Mirita; Amin, Bushra; Felix, Georg; Ongena, Marc; Nürnberger, Thorsten; Gust, Andrea A

    2014-06-23

    Peptidoglycans (PGNs) are immunogenic bacterial surface patterns that trigger immune activation in metazoans and plants. It is generally unknown how complex bacterial structures such as PGNs are perceived by plant pattern recognition receptors (PRRs) and whether host hydrolytic activities facilitate decomposition of bacterial matrices and generation of soluble PRR ligands. Here we show that Arabidopsis thaliana, upon bacterial infection or exposure to microbial patterns, produces a metazoan lysozyme-like hydrolase (lysozyme 1, LYS1). LYS1 activity releases soluble PGN fragments from insoluble bacterial cell walls and cleavage products are able to trigger responses typically associated with plant immunity. Importantly, LYS1 mutant genotypes exhibit super-susceptibility to bacterial infections similar to that observed on PGN receptor mutants. We propose that plants employ hydrolytic activities for the decomposition of complex bacterial structures, and that soluble pattern generation might aid PRR-mediated immune activation in cell layers adjacent to infection sites.

  6. Sickle cell anemia in Brazil: personal, medical and endodontic patterns

    Directory of Open Access Journals (Sweden)

    Shirlene Barbosa Pimentel FERREIRA

    2016-01-01

    Full Text Available Abstract Sickle cell anemia (SCA is the most prevalent genetic disease worldwide. Recurrent vaso-occlusive infarcts predispose SCA patients to infections, which are the primary causes of morbidly and mortality. This study aimed to evaluate the relationship between SCA and endodontic diseases. Personal information, medical data (hematological indices, virologic testing, blood transfusions, medications received, splenectomy and information on the need for endodontic treatment were obtained from SCA patients who were registered and followed up by the Fundação Hemominas, Minas Gerais, Brazil.These data were compared with the need for root canal treatment in SCA patients. One hundred eight patients comprised the studied population, and the rate of the need for endodontic therapy was 10.2%. Among the medical data, a significant difference was observed for eosinophil (p = 0.045 counts and atypical lymphocyte counts (p = 0.036 when the groups (with and without the need for endodontic treatment were compared. Statistical relevance was observed when comparing the patients with and without the need for root canal therapy concerned eosinophil counts and atypical lymphocyte counts. The differences in statistical medical data, observed between the groups suggest that both parameters are naturally connected to the stimulation of the immune system that can occur in the presence of root canal infections and that can be harmful to SCA individuals.

  7. Series Resistance Analysis of Passivated Emitter Rear Contact Cells Patterned Using Inkjet Printing

    Directory of Open Access Journals (Sweden)

    Martha A. T. Lenio

    2012-01-01

    Full Text Available For higher-efficiency solar cell structures, such as the Passivated Emitter Rear Contact (PERC cells, to be fabricated in a manufacturing environment, potentially low-cost techniques such as inkjet printing and metal plating are desirable. A common problem that is experienced when fabricating PERC cells is low fill factors due to high series resistance. This paper identifies and attempts to quantify sources of series resistance in inkjet-patterned PERC cells that employ electroless or light-induced nickel-plating techniques followed by copper light-induced plating. Photoluminescence imaging is used to determine locations of series resistance losses in these inkjet-patterned and plated PERC cells.

  8. Nanoimprint-Transfer-Patterned Solids Enhance Light Absorption in Colloidal Quantum Dot Solar Cells.

    Science.gov (United States)

    Kim, Younghoon; Bicanic, Kristopher; Tan, Hairen; Ouellette, Olivier; Sutherland, Brandon R; García de Arquer, F Pelayo; Jo, Jea Woong; Liu, Mengxia; Sun, Bin; Liu, Min; Hoogland, Sjoerd; Sargent, Edward H

    2017-03-16

    Colloidal quantum dot (CQD) materials are of interest in thin-film solar cells due to their size-tunable bandgap and low-cost solution-processing. However, CQD solar cells suffer from inefficient charge extraction over the film thicknesses required for complete absorption of solar light. Here we show a new strategy to enhance light absorption in CQD solar cells by nanostructuring the CQD film itself at the back interface. We use two-dimensional finite-difference time-domain (FDTD) simulations to study quantitatively the light absorption enhancement in nanostructured back interfaces in CQD solar cells. We implement this experimentally by demonstrating a nanoimprint-transfer-patterning (NTP) process for the fabrication of nanostructured CQD solids with highly ordered patterns. We show that this approach enables a boost in the power conversion efficiency in CQD solar cells primarily due to an increase in short-circuit current density as a result of enhanced absorption through light-trapping.

  9. Pathogen-Associated Molecular Patterns Induced Crosstalk between Dendritic Cells, T Helper Cells, and Natural Killer Helper Cells Can Improve Dendritic Cell Vaccination.

    Science.gov (United States)

    Oth, Tammy; Vanderlocht, Joris; Van Elssen, Catharina H M J; Bos, Gerard M J; Germeraad, Wilfred T V

    2016-01-01

    A coordinated cellular interplay is of crucial importance in both host defense against pathogens and malignantly transformed cells. The various interactions of Dendritic Cells (DC), Natural Killer (NK) cells, and T helper (Th) cells can be influenced by a variety of pathogen-associated molecular patterns (PAMPs) and will lead to enhanced CD8(+) effector T cell responses. Specific Pattern Recognition Receptor (PRR) triggering during maturation enables DC to enhance Th1 as well as NK helper cell responses. This effect is correlated with the amount of IL-12p70 released by DC. Activated NK cells are able to amplify the proinflammatory cytokine profile of DC via the release of IFN-γ. The knowledge on how PAMP recognition can modulate the DC is of importance for the design and definition of appropriate therapeutic cancer vaccines. In this review we will discuss the potential role of specific PAMP-matured DC in optimizing therapeutic DC-based vaccines, as some of these DC are efficiently activating Th1, NK cells, and cytotoxic T cells. Moreover, to optimize these vaccines, also the inhibitory effects of tumor-derived suppressive factors, for example, on the NK-DC crosstalk, should be taken into account. Finally, the suppressive role of the tumor microenvironment in vaccination efficacy and some proposals to overcome this by using combination therapies will be described.

  10. Co-culture of vascular endothelial cells and smooth muscle cells by hyaluronic acid micro-pattern on titanium surface

    Science.gov (United States)

    Li, Jingan; Li, Guicai; Zhang, Kun; Liao, Yuzhen; Yang, Ping; Maitz, Manfred F.; Huang, Nan

    2013-05-01

    Micro-patterning as an effective bio-modification technique is increasingly used in the development of biomaterials with superior mechanical and biological properties. However, as of now, little is known about the simultaneous regulation of endothelial cells (EC) and smooth muscle cells (SMC) by cardiovascular implants. In this study, a co-culture system of EC and SMC was built on titanium surface by the high molecular weight hyaluronic acid (HMW-HA) micro-pattern. Firstly, the micro-pattern sample with a geometry of 25 μm wide HMW-HA ridges, and 25 μm alkali-activated Ti grooves was prepared by microtransfer molding (μTM) for regulating SMC morphology. Secondly, hyaluronidase was used to decompose high molecular weight hyaluronic acid into low molecular weight hyaluronic acid which could promote EC adhesion. Finally, the morphology of the adherent EC was elongated by the SMC micro-pattern. The surface morphology of the patterned Ti was imaged by SEM. The existence of high molecular weight hyaluronic acid on the modified Ti surface was demonstrated by FTIR. The SMC micro-pattern and EC/SMC co-culture system were characterized by immunofluorescence microscopy. The nitric oxide release test and cell retention calculation were used to evaluate EC function on inhibiting hyperplasia and cell shedding, respectively. The results indicate that EC in EC/SMC co-culture system displayed a higher NO release and cell retention compared with EC cultured alone. It can be suggested that the EC/SMC co-culture system possessed superiority to EC cultured alone in inhibiting hyperplasia and cell shedding at least in a short time of 24 h.

  11. 3D reconstitution of the patterned neural tube from embryonic stem cells.

    Science.gov (United States)

    Meinhardt, Andrea; Eberle, Dominic; Tazaki, Akira; Ranga, Adrian; Niesche, Marco; Wilsch-Bräuninger, Michaela; Stec, Agnieszka; Schackert, Gabriele; Lutolf, Matthias; Tanaka, Elly M

    2014-12-09

    Inducing organogenesis in 3D culture is an important aspect of stem cell research. Anterior neural structures have been produced from large embryonic stem cell (ESC) aggregates, but the steps involved in patterning such complex structures have been ill defined, as embryoid bodies typically contained many cell types. Here we show that single mouse ESCs directly embedded in Matrigel or defined synthetic matrices under neural induction conditions can clonally form neuroepithelial cysts containing a single lumen in 3D. Untreated cysts were uniformly dorsal and could be ventralized to floor plate (FP). Retinoic acid posteriorized cysts to cervical levels and induced localize FP formation yielding full patterning along the dorsal/ventral (DV) axis. Correct spatial organization of motor neurons, interneurons, and dorsal interneurons along the DV axis was observed. This system serves as a valuable tool for studying morphogen action in 3D and as a source of patterned spinal cord tissue.

  12. Cell pattern in the Arabidopsis root epidermis determined by lateral inhibition with feedback.

    Science.gov (United States)

    Lee, Myeong Min; Schiefelbein, John

    2002-03-01

    In the root epidermis of Arabidopsis, hair and nonhair cell types are specified in a distinct position-dependent pattern. Here, we show that transcriptional feedback loops between the WEREWOLF (WER), CAPRICE (CPC), and GLABRA2 (GL2) genes help to establish this pattern. Positional cues bias the expression of the WER MYB gene, leading to the induction of CPC and GL2 in cells located in a particular position (N) and adoption of the nonhair fate. The truncated MYB encoded by CPC mediates a lateral inhibition mechanism to negatively regulate WER, GL2, and its own gene in the alternative position (H) to induce the hair fate. These results provide a molecular genetic framework for understanding the determination of a cell-type pattern in plants.

  13. The evolutionary context of root epidermis cell patterning in grasses (Poaceae).

    Science.gov (United States)

    Marzec, Marek; Melzer, Michael; Szarejko, Iwona

    2014-01-01

    In the last century, the mechanism for establishing the root epidermal pattern in grasses was proposed as a differentiating trait that can be used in taxonomic studies and as a useful tool to indicate the relationships between genera. However, knowledge about root hair differentiation in monocots is still scarce. During the last few years, this process has been studied intensively, mainly based on genetics and histological studies. A histological analysis of the root epidermis pattern composed from root hairs (trichoblasts) and non-root hair cells (atrichoblasts), as well as observations of the mechanism of the establishment of this pattern allowed 2 different methods of epidermal cell specialization in monocots to be precisely described. Additionally, a recently published paper describing root hair development in barley shed new light on the evolutionary context of the mechanism of root epidermis cell specialization, which is discussed in the presented work.

  14. The evolutionary context of root epidermis cell patterning in grasses (Poaceae)

    Science.gov (United States)

    Marzec, Marek; Melzer, Michael; Szarejko, Iwona

    2014-01-01

    In the last century, the mechanism for establishing the root epidermal pattern in grasses was proposed as a differentiating trait that can be used in taxonomic studies and as a useful tool to indicate the relationships between genera. However, knowledge about root hair differentiation in monocots is still scarce. During the last few years, this process has been studied intensively, mainly based on genetics and histological studies. A histological analysis of the root epidermis pattern composed from root hairs (trichoblasts) and non-root hair cells (atrichoblasts), as well as observations of the mechanism of the establishment of this pattern allowed 2 different methods of epidermal cell specialization in monocots to be precisely described. Additionally, a recently published paper describing root hair development in barley shed new light on the evolutionary context of the mechanism of root epidermis cell specialization, which is discussed in the presented work. PMID:24521825

  15. Patterning of fibronectin using laser writer for force measurement in cells

    Science.gov (United States)

    Codan, B.; Gaiotto, T.; Di Niro, R.; Marzari, R.; Sergo, V.

    2009-02-01

    Mechanical forces and living cells are closely related, in particular in connections, named Focal Adhesions (FAs), between cells and extracellular matrix. FAs are mechanosensors and regulate physiological processes. The aim of this contribution is to explore the possibility of performing micrometric and submicrometric protein pattern in order to study FAs on different materials. Typical substrates for microelectromechanical systems (MEMS) are tested and the results are reported. A laser is used to produce a pattern of extracellular matrix proteins, like fibronectin. A new use of a Raman microprobe is described. Cells arrange in a regular shape, following the geometry of the pattern. Protein spots last for more than 24 hours. It is very important to have a complete control on FAs and the technique proposed is a suitable solution.

  16. 46 CFR 28.820 - Fire pumps, fire mains, fire hydrants, and fire hoses.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Fire pumps, fire mains, fire hydrants, and fire hoses... REQUIREMENTS FOR COMMERCIAL FISHING INDUSTRY VESSELS Aleutian Trade Act Vessels § 28.820 Fire pumps, fire mains... pump connected to a fixed piping system. This pump must be capable of delivering an effective stream...

  17. 46 CFR 28.315 - Fire pumps, fire mains, fire hydrants, and fire hoses.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Fire pumps, fire mains, fire hydrants, and fire hoses... After September 15, 1991, and That Operate With More Than 16 Individuals on Board § 28.315 Fire pumps... be equipped with a self-priming, power driven fire pump connected to a fixed piping system. (1)...

  18. Patterning pallet arrays for cell selection based on high-resolution measurements of fluorescent biosensors.

    Science.gov (United States)

    Shadpour, Hamed; Zawistowski, Jon S; Herman, Annadele; Hahn, Klaus; Allbritton, Nancy L

    2011-06-24

    Pallet arrays enable cells to be separated while they remain adherent to a surface and provide a much greater range of cell selection criteria relative to that of current technologies. However there remains a need to further broaden cell selection criteria to include dynamic intracellular signaling events. To demonstrate the feasibility of measuring cellular protein behavior on the arrays using high resolution microscopy, the surfaces of individual pallets were modified to minimize the impact of scattered light at the pallet edges. The surfaces of the three-dimensional pallets on an array were patterned with a coating such as fibronectin using a customized stamping tool. Micropatterns of varying shape and size were printed in designated regions on the pallets in single or multiple steps to demonstrate the reliability and precision of patterning molecules on the pallet surface. Use of a fibronectin matrix stamped at the center of each pallet permitted the localization of H1299 and mouse embryonic fibroblast (MEF) cells to the pallet centers and away from the edges. Compared to pallet arrays with fibronectin coating the entire top surface, arrays with a central fibronectin pattern increased the percentage of cells localized to the pallet center by 3-4-fold. Localization of cells to the pallet center also enabled the physical separation of cells from optical artifacts created by the rough pallet side walls. To demonstrate the measurement of dynamic intracellular signaling on the arrays, fluorescence measurements of high spatial resolution were performed using a RhoA GTPase biosensor. This biosensor utilized fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) to measure localized RhoA activity in cellular ruffles at the cell periphery. These results demonstrated the ability to perform spatially resolved measurements of fluorescence-based sensors on the pallet arrays. Thus, the patterned pallet arrays

  19. Kv2 channel regulation of action potential repolarization and firing patterns in superior cervical ganglion neurons and hippocampal CA1 pyramidal neurons.

    Science.gov (United States)

    Liu, Pin W; Bean, Bruce P

    2014-04-02

    Kv2 family "delayed-rectifier" potassium channels are widely expressed in mammalian neurons. Kv2 channels activate relatively slowly and their contribution to action potential repolarization under physiological conditions has been unclear. We explored the function of Kv2 channels using a Kv2-selective blocker, Guangxitoxin-1E (GxTX-1E). Using acutely isolated neurons, mixed voltage-clamp and current-clamp experiments were done at 37°C to study the physiological kinetics of channel gating and action potentials. In both rat superior cervical ganglion (SCG) neurons and mouse hippocampal CA1 pyramidal neurons, 100 nm GxTX-1E produced near-saturating block of a component of current typically constituting ∼60-80% of the total delayed-rectifier current. GxTX-1E also reduced A-type potassium current (IA), but much more weakly. In SCG neurons, 100 nm GxTX-1E broadened spikes and voltage clamp experiments using action potential waveforms showed that Kv2 channels carry ∼55% of the total outward current during action potential repolarization despite activating relatively late in the spike. In CA1 neurons, 100 nm GxTX-1E broadened spikes evoked from -70 mV, but not -80 mV, likely reflecting a greater role of Kv2 when other potassium channels were partially inactivated at -70 mV. In both CA1 and SCG neurons, inhibition of Kv2 channels produced dramatic depolarization of interspike voltages during repetitive firing. In CA1 neurons and some SCG neurons, this was associated with increased initial firing frequency. In all neurons, inhibition of Kv2 channels depressed maintained firing because neurons entered depolarization block more readily. Therefore, Kv2 channels can either decrease or increase neuronal excitability depending on the time scale of excitation.

  20. Patterned carbon nanotubes as a new three-dimensional scaffold for mesenchymal stem cells.

    Science.gov (United States)

    Bitirim, Verda Ceylan; Kucukayan-Dogu, Gokce; Bengu, Erman; Akcali, Kamil Can

    2013-07-01

    We investigated the cellular adhesive features of mesenchymal stem cells (MSC) on non-coated and collagen coated patterned and vertically aligned carbon nanotube (CNT) structures mimicking the natural extra cellular matrix (ECM). Patterning was achieved using the elasto-capillary induced by water treatment on the CNT arrays. After confirmation with specific markers both at transcript and protein levels, MSCs from different passages were seeded on either collagen coated or non-coated patterned CNTs. Adhesion and growth of MSCs on the patterned CNT arrays were examined using scanning electron microscopy image analysis and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-tetrazolium bromide (MTT) assays. The highest MSC count was observed on the non-coated patterned CNTs at passage zero, while decreasing numbers of MSCs were found at the later passages. Similarly, MTT assay results also revealed a decrease in the viability of the MSCs for the later passages. Overall, the cell count and viability experiments indicated that MSCs were able to better attach to non-coated patterned CNTs compared to those coated with collagen. Therefore, the patterned CNT surfaces can be potentially used as a scaffold mimicking the ECM environment for MSC growth which presents an alternative approach to MSC-based transplantation therapy applications.

  1. Fire Brigade

    CERN Multimedia

    2004-01-01

    With effect from 15 April 2004, the Fire Brigade will no longer issue master keys on loan. Contractors' personnel requiring access to locked premises in order to carry out work must apply to the CERN staff member responsible for the contract concerned.

  2. Variability in the recognition of distinctive immunofluorescence patterns in different brands of HEp-2 cell slides

    Directory of Open Access Journals (Sweden)

    Alessandra Dellavance

    2013-06-01

    Full Text Available INTRODUCTION: Indirect immunofluorescence on HEp-2 cells is considered the gold standard for the detection of autoantibodies against cellular antigens. However, the culture conditions, cell fixation and permeabilization processes interfere directly in the preservation and spatial distribution of antigens. Therefore, one can assume that certain peculiarities in the processing of cellular substrate may affect the recognition of indirect immunofluorescence patterns associated with several autoantibodies. OBJECTIVE: To evaluate a panel of serum samples representing nuclear, nucleolar, cytoplasmic, mitotic apparatus, and chromosome plate patterns on HEp-2 cell substrates from different suppliers. MATERIALS AND METHODS: Seven blinded observers, independent from the three selected reference centers, evaluated 17 samples yielding different nuclear, nucleolar, cytoplasmic and mitotic apparatus patterns on HEp-2 cell slides from eight different brands. The slides were coded to maintain confidentiality of both brands and participating centers. RESULTS: The 17 HEp-2 cell patterns were identified on most substrates. Nonetheless, some slides showed deficit in the expression of several patterns: nuclear coarse speckled/U1-ribonucleoprotein associated with antibodies against RNP (U1RNP, centromeric protein F (CENP-F, proliferating cell nuclear antigen (PCNA, cytoplasmic fine speckled associated with anti-Jo-1 antibodies (histidyl synthetase, nuclear mitotic apparatus protein 1 (NuMA-1 and nuclear mitotic apparatus protein 2 (NuMA-2. CONCLUSION: Despite the overall good quality of the assessed HEp-2 substrates, there was considerable inconsistency in results among different commercial substrates. The variations may be due to the evaluated batches, hence generalizations cannot be made as to the respective brands. It is recommended that each new batch or new brand be tested with a panel of reference sera representing the various patterns.

  3. 3D patterned stem cell differentiation using thermo-responsive methylcellulose hydrogel molds

    Science.gov (United States)

    Lee, Wonjae; Park, Jon

    2016-07-01

    Tissue-specific patterned stem cell differentiation serves as the basis for the development, remodeling, and regeneration of the multicellular structure of the native tissues. We herein proposed a cytocompatible 3D casting process to recapitulate this patterned stem cell differentiation for reconstructing multicellular tissues in vitro. We first reconstituted the 2D culture conditions for stem cell fate control within 3D hydrogel by incorporating the sets of the diffusible signal molecules delivered through drug-releasing microparticles. Then, utilizing thermo-responsivity of methylcellulose (MC), we developed a cytocompatible casting process to mold these hydrogels into specific 3D configurations, generating the targeted spatial gradients of diffusible signal molecules. The liquid phase of the MC solution was viscous enough to adopt the shapes of 3D impression patterns, while the gelated MC served as a reliable mold for patterning the hydrogel prepolymers. When these patterned hydrogels were integrated together, the stem cells in each hydrogel distinctly differentiated toward individually defined fates, resulting in the formation of the multicellular tissue structure bearing the very structural integrity and characteristics as seen in vascularized bones and osteochondral tissues.

  4. Immunoprofiling reveals unique cell-specific patterns of wall epitopes in the expanding Arabidopsis stem.

    Science.gov (United States)

    Hall, Hardy C; Cheung, Jingling; Ellis, Brian E

    2013-04-01

    The Arabidopsis inflorescence stem undergoes rapid directional growth, requiring massive axial cell-wall extension in all its tissues, but, at maturity, these tissues are composed of cell types that exhibit markedly different cell-wall structures. It is not clear whether the cell-wall compositions of these cell types diverge rapidly following axial growth cessation, or whether compositional divergence occurs at earlier stages in differentiation, despite the common requirement for cell-wall extensibility. To examine this question, seven cell types were assayed for the abundance and distribution of 18 major cell-wall glycan classes at three developmental stages along the developing inflorescence stem, using a high-throughput immunolabelling strategy. These stages represent a phase of juvenile growth, a phase displaying the maximum rate of stem extension, and a phase in which extension growth is ceasing. The immunolabelling patterns detected demonstrate that the cell-wall composition of most stem tissues undergoes pronounced changes both during and after rapid extension growth. Hierarchical clustering of the immunolabelling signals identified cell-specific binding patterns for some antibodies, including a sub-group of arabinogalactan side chain-directed antibodies whose epitope targets are specifically associated with the inter-fascicular fibre region during the rapid cell expansion phase. The data reveal dynamic, cell type-specific changes in cell-wall chemistry across diverse cell types during cell-wall expansion and maturation in the Arabidopsis inflorescence stem, and highlight the paradox between this structural diversity and the uniform anisotropic cell expansion taking place across all tissues during stem growth.

  5. Spontaneously immortalised bovine mammary epithelial cells exhibit a distinct gene expression pattern from the breast cancer cells

    Directory of Open Access Journals (Sweden)

    Li Qianqian

    2010-10-01

    Full Text Available Abstract Background Spontaneous immortalisation of cultured mammary epithelial cells (MECs is an extremely rare event, and the molecular mechanism behind spontaneous immortalisation of MECs is unclear. Here, we report the establishment of a spontaneously immortalised bovine mammary epithelial cell line (BME65Cs and the changes in gene expression associated with BME65Cs cells. Results BME65Cs cells maintain the general characteristics of normal mammary epithelial cells in morphology, karyotype and immunohistochemistry, and are accompanied by the activation of endogenous bTERT (bovine Telomerase Reverse Transcriptase and stabilisation of the telomere. Currently, BME65Cs cells have been passed for more than 220 generations, and these cells exhibit non-malignant transformation. The expression of multiple genes was investigated in BME65Cs cells, senescent BMECs (bovine MECs cells, early passage BMECs cells and MCF-7 cells (a human breast cancer cell line. In comparison with early passage BMECs cells, the expression of senescence-relevant apoptosis-related gene were significantly changed in BME65Cs cells. P16INK4a was downregulated, p53 was low expressed and Bax/Bcl-2 ratio was reversed. Moreover, a slight upregulation of the oncogene c-Myc, along with an undetectable level of breast tumor-related gene Bag-1 and TRPS-1, was observed in BME65Cs cells while these genes are all highly expressed in MCF-7. In addition, DNMT1 is upregulated in BME65Cs. These results suggest that the inhibition of both senescence and mitochondrial apoptosis signalling pathways contribute to the immortality of BME65Cs cells. The expression of p53 and p16INK4a in BME65Cs was altered in the pattern of down-regulation but not "loss", suggesting that this spontaneous immortalization is possibly initiated by other mechanism rather than gene mutation of p53 or p16INK4a. Conclusions Spontaneously immortalised BME65Cs cells maintain many characteristics of normal BMEC cells and

  6. Managing the human component of fire regimes: lessons from Africa.

    Science.gov (United States)

    Archibald, Sally

    2016-06-05

    Human impacts on fire regimes accumulated slowly with the evolution of modern humans able to ignite fires and manipulate landscapes. Today, myriad voices aim to influence fire in grassy ecosystems to different ends, and this is complicated by a colonial past focused on suppressing fire and preventing human ignitions. Here, I review available evidence on the impacts of people on various fire characteristics such as the number and size of fires, fire intensity, fire frequency and seasonality of fire in African grassy ecosystems, with the intention of focusing the debate and identifying areas of uncertainty. Humans alter seasonal patterns of fire in grassy systems but tend to decrease total fire emissions: livestock have replaced fire as the dominant consumer in many parts of Africa, and fragmented landscapes reduce area burned. Humans alter the season and time of day when fires occur, with important implications for fire intensity, tree-grass dynamics and greenhouse gas (GHG) emissions. Late season fires are more common when fire is banned or illegal: these later fires are far more intense but emit fewer GHGs. The types of fires which preserve human livelihoods and biodiversity are not always aligned with the goal of reducing GHG concentrations. Current fire management challenges therefore involve balancing the needs of a large rural population against national and global perspectives on the desirability of different types of fire, but this cannot happen unless the interests of all parties are equally represented. In the future, Africa is expected to urbanize and land use to intensify, which will imply different trajectories for the continent's fire regimes.This article is part of the themed issue 'The interaction of fire and mankind.

  7. SK channels modulate the excitability and firing precision of projection neurons in the robust nucleus of the arcopallium in adult male zebra finches

    Institute of Scientific and Technical Information of China (English)

    Guo-Qiang Hou; Xuan Pan; Cong-Shu Liao; Song-Hua Wang; Dong-Feng Li

    2012-01-01

    [Objective] Motor control is encoded by neuronal activity.Small conductance Ca2+-activated Kˉ channels (SK channels) maintain the regularity and precision of firing by contributing to the afterhyperpolarization (AHP) of the action potential in mammals.However,it is not clear how SK channels regulate the output of the vocal motor system in songbirds.The premotor robust nucleus of the arcopallium (RA) in the zebra finch is responsible for the output of song information.The temporal pattern of spike bursts in RA projection neurons is associated with the timing of the acoustic features of birdsong.[Methods] The firing properties of RA projection neurons were analyzed using patch clamp wholecell and cell-attached recording techniques.[Results] SK channel blockade by apamin decreased the AHP amplitude and increased the evoked firing rate in RA projection neurons.It also caused reductions in the regularity and precision of firing.RA projection neurons displayed regular spontaneous action potentials,while apamin caused irregular spontaneous firing but had no effect on the firing rate.In the absence of synaptic inputs,RA projection neurons still had spontaneous firing,and apamin had an evident effect on the firing rate,but caused no significant change in the firing regularity,compared with apamin application in the presence of synaptic inputs.[Conclusion]SK channels contribute to the maintenance of firing regularity in RA projection neurons whichrequires synaptic activity,and consequently ensures the precision of song encoding.

  8. The rapid recovery of 5-HT cell firing induced by the antidepressant vortioxetine involves 5-HT(3) receptor antagonism.

    Science.gov (United States)

    Bétry, Cécile; Pehrson, Alan L; Etiévant, Adeline; Ebert, Bjarke; Sánchez, Connie; Haddjeri, Nasser

    2013-06-01

    The therapeutic effect of current antidepressant drugs appears after several weeks of treatment and a significant number of patients do not respond to treatment. Here, we report the effects of the multi-modal antidepressant vortioxetine (Lu AA21004), a 5-HT(3) and 5-HT(7) receptor antagonist, 5-HT(1B) receptor partial agonist, 5-HT(1A) receptor agonist and 5-HT transporter (SERT) inhibitor, on rat 5-HT neurotransmission. Using in vivo electrophysiological recordings in the dorsal raphe nucleus of anaesthetized rats, we assessed the acute and subchronic effects of vortioxetine and/or the selective 5-HT(3) receptor agonist, SR57227 or the selective 5-HT(1A) receptor agonist flesinoxan, on 5-HT neuronal firing activity. Using ex-vivo autoradiography, we correlated SERT occupancy and presumed 5-HT firing activity. The selective serotonin reuptake inhibitor, fluoxetine, was used as comparator. Importantly, the recovery of 5-HT neuronal firing was achieved after 1 d with vortioxetine and 14 d with fluoxetine. SR57227 delayed this recovery. In contrast, vortioxetine failed to alter the reducing action of 3 d treatment of flesinoxan. Acute dosing of vortioxetine inhibited neuronal firing activity more potently than fluoxetine. SR57227 prevented the suppressant effect of vortioxetine, but not of fluoxetine. In contrast, flesinoxan failed to modify the suppressant effect of vortioxetine acutely administered. Differently to fluoxetine, vortioxetine suppressed neuronal firing without saturating occupancy at the SERT. Vortioxetine produced a markedly faster recovery of 5-HT neuronal firing than fluoxetine. This is at least partly due to 5-HT(3) receptor antagonism of vortioxetine in association with its reduced SERT occupancy.

  9. Desmosomal plaque-associated vimentin filaments in human ovarian granulosa cell tumors of various histologic patterns.

    OpenAIRE

    Czernobilsky, B; Moll, R.; Leppien, G.; Schweikhart, G.; Franke, W W

    1987-01-01

    Proteins of intermediate-sized filaments and desmosomal plaques (desmoplakins) of four human ovarian granulosa cell tumors were studied by immunofluorescence and immunoelectron microscopy and by two-dimensional gel electrophoresis of microdissected tissue samples. All tumor cells, irrespective of their specific histologic patterns, contained both vimentin and desmoplakins. Cytokeratin-positive structures were absent or very scant in most tumor regions, but more common in trabecular, insular, ...

  10. Nuclear DNA Content and Chromatin Pattern of Rat Rhabdomyosarcoma Cell Sublines with Different Metastatic Potentials

    Directory of Open Access Journals (Sweden)

    Jean Dufer

    2000-01-01

    Full Text Available There is a constant need of features able to characterize potentially metastatic cells among the heterogeneous cell subpopulations which constitute a tumor. Image cytometry of metastatic tumor cells give rise to variable results, partly because of a heterogeneous origin of cells, or potential drug effects. The aim of this work was to characterize nuclear changes observed in metastatic cell clones issued in vitro from the same parental cell population The nuclear phenotypes of 6 cell sublines isolated from a rat rhabdomyosarcoma cell line and differing in their metastatic ability were evaluated by image cytometry on Feulgen‐stained preparations. Densitometric [5], geometric [3] and textural [9] features were computed from each nuclear image. For each cell subline, a metastatic score, ranging from 0 to 10, was calculated on the basis of in vitro invasivity data, by measuring the number of pulmonary metastases observed after s.c. graft of tumor cells in rats. Data obtained were compared to karyotype, growth characteristics, and oncogene expressions of cell lines. The nuclear DNA content, the chromosome numbers, the cell sublines doubling times, and the distribution of cells within the cell cycle appear unrelated with this score. On the contrary, increase in metastatic ability is accompanied by changes in chromatin pattern as assessed by textural features. Progressive increase in chromatin condensation can be observed in cell sublines with increasing metastatic score. These results were confirmed by an unsupervised multivariate partitioning of rhabdomyosarcoma cells which identified two separate subsets whose distributions within the analyzed cell lines correlate with their metastatic ability. These data suggest that, in rat rhabdomyosarcoma cell sublines, metastatic ability could be associated with nuclear morphological changes at the level of chromatin texture.

  11. Fire Symfonier

    DEFF Research Database (Denmark)

    Nielsen, Svend Hvidtfelt

    2009-01-01

    sidste fire symfonier. Den er måske snarere at opfatte som et præludium til disse. At påstå, at symfonierne fra Holmboes side er planlagt til at være beslægtede, ville være at gå for vidt. Alene de 26 år, der skiller den 10. fra den 13., gør påstanden - i bedste fald - dubiøs. Når deres udformning...... udkrystallisering som i de sidste små 30 år af hans virke har afkastet disse fire variationer over en grundlæggende central holmboesk fornemmelse for form, melodi, klang og rytme. Denne oplevelse har fået mig til at udforske symfonierne, for at finde til bunds i dette holmboeske fællestræk, som jeg mener her står...

  12. Effects of pattern shape on adaptation of dLGN cell

    Institute of Scientific and Technical Information of China (English)

    JIN Jianzhong; XU Pengjing; LI Xiangrui; ZHOU Yifeng

    2003-01-01

    Pattern adaptation is one of the fundamental sensory processes in the visual system. In this study, we compared pattern adaptation induced by two types of sinusoidal drifting grating in dLGN cells of cat. The two types ofgrating have the same parameters (e.g. spatial frequency, temporal frequency and contrast) except their pattern shapes, one of which is normal grating and the other annular grating. The results suggested that the annular grating elicited stronger response and stronger pattern adaptation than the normal grating. This is consistent with the adaptation and aftereffect to the two types of drifting gratings seen in psychology and may reflect the subcortical neural mechanism underlying these psychological phenomena.

  13. HER/ErbB receptor interactions and signaling patterns in human mammary epithelial cells

    Directory of Open Access Journals (Sweden)

    Chrisler William B

    2009-10-01

    Full Text Available Abstract Background Knowledge about signaling pathways is typically compiled based on data gathered using different cell lines. This approach implicitly assumes that the cell line dependence is not important. However, different cell lines do not always respond to a particular stimulus in the same way, and lack of coherent data collected from closely related cellular systems can be detrimental to the efforts to understand the regulation of biological processes. To address this issue, we created a clone library of human mammary epithelial (HME cells that expresses different levels of HER2 and HER3 receptors in combination with endogenous EGFR/HER1. Using our clone library, we have quantified the receptor activation patterns and systematically tested the validity of the existing hypotheses about the interaction patterns between HER1-3 receptors. Results Our study identified HER2 as the dominant dimerization partner for both EGFR and HER3. Contrary to earlier suggestions, we find that lateral interactions with HER2 do not lead to strong transactivation between EGFR and HER3, i.e., EGFR activation and HER3 activation are only weakly linked in HME cells. We also find that observed weak transactivation is uni-directional where stimulation of EGFR leads to HER3 activation whereas HER3 stimulation does not activate the EGFR. Repeating our experiments at lower cell confluency established that cell confluency is not a major factor in the observed interaction patterns. We have also quantified the dependence of the kinetics of Erk and Akt activation on different HER receptors. We found that HER3 signaling makes the strongest contribution to Akt activation and that, stimulation of either EGFR or HER3 leads to significant Erk activation. Conclusion Our study shows that clone cell libraries can be a powerful resource in systems biology research by making it possible to differentiate between various hypotheses in a consistent cellular background. Using our

  14. Key bifurcations of bursting polyrhythms in 3-cell central pattern generators.

    Directory of Open Access Journals (Sweden)

    Jeremy Wojcik

    Full Text Available We identify and describe the key qualitative rhythmic states in various 3-cell network motifs of a multifunctional central pattern generator (CPG. Such CPGs are neural microcircuits of cells whose synergetic interactions produce multiple states with distinct phase-locked patterns of bursting activity. To study biologically plausible CPG models, we develop a suite of computational tools that reduce the problem of stability and existence of rhythmic patterns in networks to the bifurcation analysis of fixed points and invariant curves of a Poincaré return maps for phase lags between cells. We explore different functional possibilities for motifs involving symmetry breaking and heterogeneity. This is achieved by varying coupling properties of the synapses between the cells and studying the qualitative changes in the structure of the corresponding return maps. Our findings provide a systematic basis for understanding plausible biophysical mechanisms for the regulation of rhythmic patterns generated by various CPGs in the context of motor control such as gait-switching in locomotion. Our analysis does not require knowledge of the equations modeling the system and provides a powerful qualitative approach to studying detailed models of rhythmic behavior. Thus, our approach is applicable to a wide range of biological phenomena beyond motor control.

  15. Central Cell-Derived Peptides Regulate Early Embryo Patterning in Flowering Plants

    NARCIS (Netherlands)

    Costa, L.M.; Marshall, E.; Tesfaye, M.; Silverstein, K.A.T.; Mori, M.; Umetsu, Y.; Otterbach, S.L.; Papareddy, R.; Dickinson, H.G.; Boutilier, K.A.; VandenBosch, K.A.; Ohki, S.; Gutierrez-Marcos, J.F.

    2014-01-01

    Plant embryogenesis initiates with the establishment of an apical-basal axis; however, the molecular mechanisms accompanying this early event remain unclear. Here, we show that a small cysteine-rich peptide family is required for formation of the zygotic basal cell lineage and proembryo patterning i

  16. (18)F-FDG PET patterns and BAL cell profiles in pulmonary sarcoidosis.

    NARCIS (Netherlands)

    Keijsers, R.G.; Grutters, J.C.; Velzen-Blad, H. van; Bosch, J.M. van den; Oyen, W.J.G.; Verzijlbergen, F.J.

    2010-01-01

    PURPOSE: Bronchoalveolar lavage (BAL) and (18)F-fluorodeoxyglucose ((18)F-FDG) PET can both demonstrate sarcoid activity. To assess whether metabolic activity imaged by (18)F-FDG PET represents signs of disease activity as reflected by BAL, (18)F-FDG PET patterns were compared with BAL cell profiles

  17. Temporal protein expression pattern in intracellular signalling cascade during T-cell activation: A computational study

    Indian Academy of Sciences (India)

    Piyali Ganguli; Saikat Chowdhury; Rupa Bhowmick; Ram Rup Sarkar

    2015-10-01

    Various T-cell co-receptor molecules and calcium channel CRAC play a pivotal role in the maintenance of cell’s functional responses by regulating the production of effector molecules (mostly cytokines) that aids in immune clearance and also maintaining the cell in a functionally active state. Any defect in these co-receptor signalling pathways may lead to an altered expression pattern of the effector molecules. To study the propagation of such defects with time and their effect on the intracellular protein expression patterns, a comprehensive and largest pathway map of T-cell activation network is reconstructed manually. The entire pathway reactions are then translated using logical equations and simulated using the published time series microarray expression data as inputs. After validating the model, the effect of in silico knock down of co-receptor molecules on the expression patterns of their downstream proteins is studied and simultaneously the changes in the phenotypic behaviours of the T-cell population are predicted, which shows significant variations among the proteins expression and the signalling routes through which the response is propagated in the cytoplasm. This integrative computational approach serves as a valuable technique to study the changes in protein expression patterns and helps to predict variations in the cellular behaviour.

  18. Texture analysis of cervical cell nuclei by segmentation of chromatin patterns

    NARCIS (Netherlands)

    Smeulders, A.W.M.; Leyte-Veldstra, L.; Ploem, J.S.; Cornelisse, C.JJ.

    1979-01-01

    Texture parameters of the nuclear chromatin pattern can contribute to the automated classification of specimens on the basis of single cell analysis in cervical cytology. Current texture parameters are abstract and therefore hamper understanding. In this paper texture parameters are described that c

  19. Associations between somatic cell count patterns and the incidence of clinical mastitis

    NARCIS (Netherlands)

    Haas, de Y.; Barkema, H.W.; Schukken, Y.H.; Veerkamp, R.F.

    2005-01-01

    Associations between clinical mastitis (CM) and the proportional distribution of patterns in somatic cell count (SCC) on a herd level were determined in this study. Data on CM and SCC over a 12-month period from 274 Dutch herds were used. The dataset contained parts of 29,719 lactations from 22,955

  20. Expression pattern of embryonic stem cell markers in DFAT cells and ADSCs.

    Science.gov (United States)

    Gao, Qian; Zhao, Lili; Song, Ziyi; Yang, Gongshe

    2012-05-01

    Mature adipocytes can revert to a more primitive phenotype and gain cell proliferative ability under the condition of ceiling method, named dedifferentiated fat cells (DFAT cells). These cells exhibit multilineage potential as adipose tissue-derived stromal cells (ADSCs). However, the stem molecular signature of DFAT cells and the difference distinct from ADSCs are still not sure. To study the molecular signature of DFAT cells better, highly purified mature adipocytes were obtained from rats and the purity was more than 98%, and about 98.6% were monocytes. These mature adipocytes dedifferentiated into fibroblast-like cells spontaneously by the ceiling culture method, these cells proliferated rapidly in vitro, grew in the same direction and formed vertex, and expressed extensively embryonic stem cell markers such as Oct4, Sox2, c-Myc, and Nanog, surface antigen SSEA-1, CD105, and CD31, moreover, these cells possessed ALP and telomerase activity. The expression level was Oct4 1.3%, Sox2 1.3%, c-Myc 1.2%, Nanog 1.2%, CD105 0.6%, CD31 0.6% and SSEA-1 0.4%, respectively, which was lower than that in ADSCs, but the purity of DFAT cells was much higher than that of ADSCs. In conclusion, DFAT cells is a highly purified stem cell population, and expressed some embryonic stem cell markers like ADSCs, which seems to be a good candidate source of adult stem cells for the future cell replacement therapy.

  1. Hole Pattern Design of Fired Shale Hollow Brick%烧结页岩空心砖孔型结构设计研究

    Institute of Scientific and Technical Information of China (English)

    黄孝云; 朱惠英; 陶尚儒; 卢凌寰; 张小静

    2013-01-01

    Fired shale hollow brick is a new type of energy-saving walling material. The factors affected the architectural designing of the shale hollow bricks were studied and discussed on its mechanical and thermal properties, proposing the best selection of different hole shapes, number of holes, holes arranged in size and platoon, hole wall thickness and hole chamfer.%  烧结页岩空心砖是一种新型的节能墙体材料。从力学和热工性能的角度,研究讨论了烧结页岩空心砖孔型结构设计的影响因素。提出不同孔洞形状、孔洞大小、孔洞排列及排数、孔壁厚度、孔洞倒角的最佳选取方案。

  2. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    KAUST Repository

    Liu, Jia

    2014-12-01

    Power production in microbial reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis stack. Typical MRC stacks use non-conductive spacers that block ion transport by the so-called spacer shadow effect. These spacers can be relatively thick compared to the membrane, and thus they increase internal stack resistance due to high solution (ohmic) resistance associated with a thick spacer. New types of patterned anion and cation exchange membranes were developed by casting membranes to create hemispherical protrusions on the membranes, enabling fluid flow between the membranes without the need for a non-conductive spacer. The use of the patterned membrane decreased the MRC stack resistance by ∼22 Ω, resulting in a 38% increase in power density from 2.50 ± 0.04 W m-2 (non-patterned membrane with a non-conductive spacer) to 3.44 ± 0.02 W m-2 (patterned membrane). The COD removal rate, coulombic efficiency, and energy efficiency of the MRC also increased using the patterned membranes compared to the non-patterned membranes. These results demonstrate that these patterned ion exchange membranes can be used to improve performance of an MRC. © 2014 Elsevier B.V. All rights reserved.

  3. Direct laser patterning of transparent ITO-Ag-ITO multilayer anodes for organic solar cells

    Science.gov (United States)

    Kim, Hyo-Joong; Seo, Ki-Won; Kim, Yong Hyeon; Choi, Jiyeon; Kim, Han-Ki

    2015-02-01

    Direct laser patterning of transparent ITO-Ag-ITO (IAI) multilayer anodes is investigated using a femtosecond fiber laser for application in organic solar cells (OSC) fabrication. By adjusting laser fluence and scan speed, we successfully patterned the IAI multilayer anode without changing the electrical or optical properties. At an optimized laser fluence of 0.6 J/cm2 and a scan speed of 200 mm/s, the patterned IAI multilayer was electrically isolated with a clean edge. The metallic Ag interlayer of the IAI multilayer plays an important role in direct laser patterning because it absorbed the laser and increases the maximum temperature in the IAI multilayer. In addition, the Ag layer could effectively decrease the temperature of the IAI multilayer after irradiation of laser. The OSC fabricated on the laser patterned IAI multilayer showed power conversion efficiencies of 3.12% (Ag 8 nm) and 2.85% (Ag 12 nm). Successful operation of the OSC indicates that direct laser patterning of IAI multilayer anodes is a promising, simple patterning technology for fabrication of IAI-based OSCs.

  4. Microfluidic devices for label-free separation of cells through transient interaction with asymmetric receptor patterns

    Science.gov (United States)

    Bose, S.; Singh, R.; Hollatz, M. H.; Lee, C.-H.; Karp, J.; Karnik, R.

    2012-02-01

    Cell sorting serves an important role in clinical diagnosis and biological research. Most of the existing microscale sorting techniques are either non-specific to antigen type or rely on capturing cells making sample recovery difficult. We demonstrate a simple; yet effective technique for isolating cells in an antigen specific manner by using transient interactions of the cell surface antigens with asymmetric receptor patterned surface. Using microfluidic devices incorporating P-selectin patterns we demonstrate separation of HL60 cells from K562 cells. We achieved a sorting purity above 90% and efficiency greater than 85% with this system. We also present a mathematical model incorporating flow mediated and adhesion mediated transport of cells in the microchannel that can be used to predict the performance of these devices. Lastly, we demonstrate the clinical significance of the method by demonstrating single step separation of neutrophils from whole blood. When whole blood is introduced in the device, the granulocyte population gets separated exclusively yielding neutrophils of high purity (<10% RBC contamination). To our knowledge, this is the first ever demonstration of continuous label free sorting of neutrophils from whole blood. We believe this technology will be useful in developing point-of-care diagnostic devices and also for a host of cell sorting applications.

  5. Cell state switching factors and dynamical patterning modules: complementary mediators of plasticity in development and evolution

    Indian Academy of Sciences (India)

    Stuart A Newman; Ramray Bhat; Nadejda V Mezentseva

    2009-10-01

    Ancient metazoan organisms arose from unicellular eukaryotes that had billions of years of genetic evolution behind them. The transcription factor networks present in single-celled ancestors at the origin of the Metazoa (multicellular animals) were already capable of mediating the switching of the unicellular phenotype among alternative states of gene activity in response to environmental conditions. Cell differentiation, therefore, had its roots in phenotypic plasticity, with the ancient regulatory proteins acquiring new targets over time and evolving into the ``developmental transcription factors” (DTFs) of the ``developmental-genetic toolkit.” In contrast, the emergence of pattern formation and morphogenesis in the Metazoa had a different trajectory. Aggregation of unicellular metazoan ancestors changed the organisms’ spatial scale, leading to the first ``dynamical patterning module” (DPM): cell-cell adhesion. Following this, other DPMs (defined as physical forces and processes pertinent to the scale of the aggregates mobilized by a set of toolkit gene products distinct from the DTFs), transformed simple cell aggregates into hollow, multilayered, segmented, differentiated and additional complex structures, with minimal evolution of constituent genes. Like cell differentiation, therefore, metazoan morphologies also originated from plastic responses of cells and tissues. Here we describe examples of DTFs and most of the important DPMs, discussing their complementary roles in the evolution of developmental mechanisms. We also provide recently characterized examples of DTFs in cell type switching and DPMs in morphogenesis of avian limb bud mesenchyme, an embryo-derived tissue that retains a high degree of developmental plasticity.

  6. Single-cell and coupled GRN models of cell patterning in the Arabidopsis thaliana root stem cell niche

    Directory of Open Access Journals (Sweden)

    Alvarez-Buylla Elena R

    2010-10-01

    Full Text Available Abstract Background Recent experimental work has uncovered some of the genetic components required to maintain the Arabidopsis thaliana root stem cell niche (SCN and its structure. Two main pathways are involved. One pathway depends on the genes SHORTROOT and SCARECROW and the other depends on the PLETHORA genes, which have been proposed to constitute the auxin readouts. Recent evidence suggests that a regulatory circuit, composed of WOX5 and CLE40, also contributes to the SCN maintenance. Yet, we still do not understand how the niche is dynamically maintained and patterned or if the uncovered molecular components are sufficient to recover the observed gene expression configurations that characterize the cell types within the root SCN. Mathematical and computational tools have proven useful in understanding the dynamics of cell differentiation. Hence, to further explore root SCN patterning, we integrated available experimental data into dynamic Gene Regulatory Network (GRN models and addressed if these are sufficient to attain observed gene expression configurations in the root SCN in a robust and autonomous manner. Results We found that an SCN GRN model based only on experimental data did not reproduce the configurations observed within the root SCN. We developed several alternative GRN models that recover these expected stable gene configurations. Such models incorporate a few additional components and interactions in addition to those that have been uncovered. The recovered configurations are stable to perturbations, and the models are able to recover the observed gene expression profiles of almost all the mutants described so far. However, the robustness of the postulated GRNs is not as high as that of other previously studied networks. Conclusions These models are the first published approximations for a dynamic mechanism of the A. thaliana root SCN cellular pattering. Our model is useful to formally show that the data now available are not

  7. Immunostaining for substance P receptor labels GABAergic cells with distinct termination patterns in the hippocampus.

    Science.gov (United States)

    Acsády, L; Katona, I; Gulyás, A I; Shigemoto, R; Freund, T F

    1997-02-17

    A specific antiserum against substance P receptor (SPR) labels nonprincipal neurons in the cerebral cortex of the rat (T. Kaneko et al. [1994], Neuroscience 60:199-211; Y. Nakaya et al. [1994], J. Comp. Neurol. 347:249-274). In the present study, we aimed to identify the types of SPR-immunoreactive neurons in the hippocampus according to their content of neurochemical markers, which label interneuron populations with distinct termination patterns. Markers for perisomatic inhibitory cells, parvalbumin and cholecystokinin (CCK), colocalized with SPR in pyramidallike basket cells in the dentate gyrus and in large multipolar or bitufted cells within all hippocampal subfields respectively. A dense meshwork of SPR-immunoreactive spiny dendrites in the hilus and stratum lucidum of the CA3 region belonged largely to inhibitory cells terminating in the distal dendritic region of granule cells, as indicated by the somatostatin and neuropeptide Y (NPY) content. In addition, SPR and NPY were colocalized in numerous multipolar interneurons with dendrites branching close to the soma. Twenty-five percent of the SPR-immunoreactive cells overlapped with calretinin-positive neurons in all hippocampal subfields, showing that interneurons specialized to contact other gamma-aminobutyric acid-ergic cells may also contain SPR. On the basis of the known termination pattern of the colocalized markers, we conclude that SPR-positive interneurons are functionally heterogeneous and participate in different inhibitory processes: (1) perisomatic inhibition of principal cells (CCK-containing cells, and parvalbumin-positive cells in the dentate gyrus), (2) feedback dendritic inhibition in the entorhinal termination zone (somatostatin and NPY-containing cells), and (3) innervation of other interneurons (calretinin-containing cells).

  8. Temporal trends in mammal responses to fire reveals the complex effects of fire regime attributes.

    Science.gov (United States)

    Lindenmayer, David B; Blanchard, Wade; MacGregor, Christopher; Barton, Philip; Banks, Sam C; Crane, Mason; Michael, Damian; Okada, Sachiko; Berry, Laurence; Florance, Daniel; Gill, Malcolm

    2016-03-01

    Fire is a major ecological process in many ecosystems worldwide. We sought to identify which attributes of fire regimes affect temporal change in the presence and abundance of Australian native mammals. Our detailed study was underpinned by time series data on 11 mammal species at 97 long-term sites in southeastern Australia between 2003 and 2013. We explored how temporal aspects of fire regimes influenced the presence and conditional abundance of species. The key fire regime components examined were: (1) severity of a major fire in 2003, (2) interval between the last major fire (2003) and the fire prior to that, and (3) number of past fires. Our long-term data set enabled quantification of the interactions between survey year and each fire regime variable: an ecological relationship missing from temporally restricted studies. We found no evidence of any appreciable departures from the assumption of independence of the sites. Multiple aspects of fire regimes influenced temporal variation in the presence and abundance of mammals. The best models indicated that six of the 11 species responded to two or more fire regime variables, with two species influenced by all three fire regime attributes. Almost all species responded to time since fire, either as an interaction with survey year or as a main effect. Fire severity or its interaction with survey year was important for most terrestrial rodents. The number of fires at a site was significant for terrestrial rodents and several other species. Our findings contain evidence of the effects on native mammals of heterogeneity in fire regimes. Temporal response patterns of mammal species were influenced by multiple fire regime attributes, often in conjunction with survey year. This underscores the critical importance of long-term studies of biota that are coupled with data sets characterized by carefully documented fire history, severity, and frequency. Long-term studies are essential to predict animal responses to fires and

  9. Fast-reset of pacemaking and theta-frequency resonance patterns in cerebellar golgi cells: Simulations of their impact in vivo

    Directory of Open Access Journals (Sweden)

    Sergio Solinas

    2007-12-01

    Full Text Available The Golgi cells are inhibitory interneurons of the cerebellar granular layer, which respond to afferent stimulation in vivo with a burst-pause sequence interrupting their irregular background low-frequency firing (Vos et al., 1999a. Eur. J. Neurosci. 11, 2621–2634. However, Golgi cells in vitro are regular pacemakers (Forti et al., 2006. J. Physiol. 574, 711–729, raising the question how their ionic mechanisms could impact on responses during physiological activity. Using patch-clamp recordings in cerebellar slices we show that the pacemaker cycle can be suddenly reset by spikes, making the cell highly sensitive to input variations. Moreover, the neuron resonates around the pacemaker frequency, making it specifically sensitive to patterned stimulation in the theta-frequency band. Computational analysis based on a model developed to reproduce Golgi cell pacemaking (Solinas et al., 2008 Front. Neurosci., 1:2 predicted that phase-reset required spike-triggered activation of SK channels and that resonance was sustained by a slow voltage-dependent potassium current and amplified by a persistent sodium current. Adding balanced synaptic noise to mimic the irregular discharge observed in vivo, we found that pacemaking converts into spontaneous irregular discharge, that phase-reset plays an important role in generating the burst-pause pattern evoked by sensory stimulation, and that repetitive stimulation at theta-frequency enhances the time-precision of spike coding in the burst. These results suggest that Golgi cell intrinsic properties exert a profound impact on time-dependent signal processing in the cerebellar granular layer.

  10. Fast-reset of pacemaking and theta-frequency resonance patterns in cerebellar golgi cells: simulations of their impact in vivo.

    Science.gov (United States)

    Solinas, Sergio; Forti, Lia; Cesana, Elisabetta; Mapelli, Jonathan; De Schutter, Erik; D'Angelo, Egidio

    2007-01-01

    The Golgi cells are inhibitory interneurons of the cerebellar granular layer, which respond to afferent stimulation in vivo with a burst-pause sequence interrupting their irregular background low-frequency firing (Vos et al., 1999a. Eur. J. Neurosci. 11, 2621-2634). However, Golgi cells in vitro are regular pacemakers (Forti et al., 2006. J. Physiol. 574, 711-729), raising the question how their ionic mechanisms could impact on responses during physiological activity. Using patch-clamp recordings in cerebellar slices we show that the pacemaker cycle can be suddenly reset by spikes, making the cell highly sensitive to input variations. Moreover, the neuron resonates around the pacemaker frequency, making it specifically sensitive to patterned stimulation in the theta-frequency band. Computational analysis based on a model developed to reproduce Golgi cell pacemaking (Solinas et al., 2008Front. Neurosci., 2:2) predicted that phase-reset required spike-triggered activation of SK channels and that resonance was sustained by a slow voltage-dependent potassium current and amplified by a persistent sodium current. Adding balanced synaptic noise to mimic the irregular discharge observed in vivo, we found that pacemaking converts into spontaneous irregular discharge, that phase-reset plays an important role in generating the burst-pause pattern evoked by sensory stimulation, and that repetitive stimulation at theta-frequency enhances the time-precision of spike coding in the burst. These results suggest that Golgi cell intrinsic properties exert a profound impact on time-dependent signal processing in the cerebellar granular layer.

  11. Vitamin D3 modulated gene expression patterns in human primary normal and cancer prostate cells.

    Science.gov (United States)

    Guzey, Meral; Luo, Jianhua; Getzenberg, Robert H

    2004-10-01

    The vitamin D receptor (VDR) is a member of the steroid/retinoid receptor superfamily of nuclear receptors and has potential tumor-suppressive functions in prostate and other cancer types. Vitamin D3 (VD3) exerts its biological actions by binding within cells to VDR. The VDR then interacts with specific regions of the DNA in cells, and triggers changes in the activity of genes involved in cell division, cell survival, and cellular function. Using human primary cultures and the prostate cancer (PCa) cell line, ALVA-31, we examined the effects of VD3 under different culture conditions. Complete G0/G1 arrest of ALVA-31 cells and approximately 50% inhibition of tumor stromal cell growth was observed. To determine changes in gene expression patterns related to VD3 activity, microarray analysis was performed. More than approximately 20,000 genes were evaluated for twofold relative increases and decreases in expression levels. A number of the gene targets that were up- and down-regulated are related to potential mechanisms of prostatic growth regulation. These include estrogen receptor (ER), heat shock proteins: 70 and 90, Apaf1, Her-2/neu, and paxillin. Utilizing antibodies generated against these targets, we were able to confirm the changes at the protein level. These newly reported gene expression patterns provide novel information not only potential markers, but also on the genes involved in VD3 induced apoptosis in PCa.

  12. Patterns of cell proliferation and rod photoreceptor differentiation in shark retinas.

    Science.gov (United States)

    Ferreiro-Galve, Susana; Rodríguez-Moldes, Isabel; Anadón, Ramón; Candal, Eva

    2010-01-01

    We studied the pattern of cell proliferation and its relation with photoreceptor differentiation in the embryonic and postembryonic retina of two elasmobranchs, the lesser spotted dogfish (Scyliorhinus canicula) and the brown shyshark (Haploblepharus fuscus). Cell proliferation was studied with antibodies raised against proliferating cell nuclear antigen (PCNA) and phospho-histone-H3, and early photoreceptor differentiation with an antibody raised against rod opsin. As regards the spatiotemporal distribution of PCNA-immunoreactive cells, our results reveal a gradual loss of PCNA that coincides in a spatiotemporal sequence with the gradient of layer maturation. The presence of a peripheral growth zone containing pure-proliferating retinal progenitors (the ciliary marginal zone) in the adult retina matches with the general pattern observed in other groups of gnathostomous fishes. However, in the shark retina the generation of new cells is not restricted to the ciliary marginal zone but also occurs in retinal areas that contain differentiated cells: (1) in a transition zone that lies between the pure-proliferating ciliary marginal zone and the central (layered) retina; (2) in the differentiating central area up to prehatching embryos where large amounts of PCNA-positive cells were observed even in the inner and outer nuclear layers; (3) and in the retinal pigment epithelium of prehatching embryos. Rod opsin immunoreactivity was observed in both species when the outer plexiform layer begins to be recognized in the central retina and, as we previously observed in trout, coincided temporally with the weakening in PCNA labelling.

  13. Fire Protection for Buildings

    Science.gov (United States)

    Edmunds, Jane

    1972-01-01

    Reviews attack on fire safety in high rise buildings made by a group of experts representing the iron and steel industry at a recent conference. According to one expert, fire problems are people oriented, which calls for emphasis on fire prevention rather than reliance on fire suppression and for fire pretection to be built into a structure.…

  14. Cell-alignment patterns in the collective migration of cells with polarized adhesion

    Science.gov (United States)

    Matsushita, Katsuyoshi

    2017-03-01

    Dictyostelium discoideum (Dd) utilizes inhomogeneities in the distribution of cell-cell adhesion molecules on cell membranes for collective cell migration. A simple example of an inhomogeneity is a front-side (leading-edge) polarization in the distribution at the early streaming stage. Experiments have shown that the polarized cell-cell adhesion induces side-by-side contact between cells [Beug et al., Nature (London) 274, 445 (1978), 10.1038/274445a0]. This result is counterintuitive, as one would expect cells to align front to front in contact with each other on the basis of front-side polarization. In this work, we theoretically examine whether front-side polarization induces side-by-side contact in collective cell migration. We construct a model for expressing cells with this polarization based on the two-dimensional cellular Potts model. By a numerical simulation with this model, we find cell-cell alignment wherein cells form lateral arrays with side-by-side contacts as observed in the experiments.

  15. A robust in vivo-like persistent firing supported by a hybrid of intracellular and synaptic mechanisms.

    Directory of Open Access Journals (Sweden)

    Arthur Jochems

    Full Text Available Persistent firing is believed to support short-term information retention in the brain. Established hypotheses make use of the recurrent synaptic connectivity to support persistent firing. However, this mechanism is known to suffer from a lack of robustness. On the other hand, persistent firing can be supported by an intrinsic cellular mechanism in multiple brain areas. However, the consequences of having both the intrinsic and the synaptic mechanisms (a hybrid model on persistent firing remain largely unknown. The goal of this study is to investigate whether a hybrid neural network model with these two mechanisms has advantages over a conventional recurrent network based model. Our computer simulations were based on in vitro recordings obtained from hippocampal CA3 pyramidal cells under cholinergic receptor activation. Calcium activated non-specific cationic (CAN current supported persistent firing in the Hodgkin-Huxley style cellular models. Our results suggest that the hybrid model supports persistent firing within a physiological frequency range over a wide range of different parameters, eliminating parameter sensitivity issues generally recognized in network based persistent firing. In addition, persistent firing in the hybrid model is substantially more robust against distracting inputs, can coexist with theta frequency oscillations, and supports pattern completion.

  16. Aligned, isotropic and patterned carbon nanotube substrates that control the growth and alignment of Chinese hamster ovary cells

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Che Azurahanim Che; Asanithi, Piyapong; Brunner, Eric W; Jurewicz, Izabela; Bo, Chiara; Sear, Richard P; Dalton, Alan B [Department of Physics and Surrey Materials Institute, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Azad, Chihye Lewis; Ovalle-Robles, Raquel; Fang Shaoli; Lima, Marcio D; Lepro, Xavier; Collins, Steve; Baughman, Ray H, E-mail: r.sear@surrey.ac.uk [Alan G MacDiarmid NanoTech Institute, The University of Texas at Dallas, Richardson, TX 75080-3021 (United States)

    2011-05-20

    Here we culture Chinese hamster ovary cells on isotropic, aligned and patterned substrates based on multiwall carbon nanotubes. The nanotubes provide the substrate with nanoscale topography. The cells adhere to and grow on all substrates, and on the aligned substrate, the cells align strongly with the axis of the bundles of the multiwall nanotubes. This control over cell alignment is required for tissue engineering; almost all tissues consist of oriented cells. The aligned substrates are made using straightforward physical chemistry techniques from forests of multiwall nanotubes; no lithography is required to make inexpensive large-scale substrates with highly aligned nanoscale grooves. Interestingly, although the cells strongly align with the nanoscale grooves, only a few also elongate along this axis: alignment of the cells does not require a pronounced change in morphology of the cell. We also pattern the nanotube bundles over length scales comparable to the cell size and show that the cells follow this pattern.

  17. Aligned, isotropic and patterned carbon nanotube substrates that control the growth and alignment of Chinese hamster ovary cells

    Science.gov (United States)

    Azurahanim Che Abdullah, Che; Asanithi, Piyapong; Brunner, Eric W.; Jurewicz, Izabela; Bo, Chiara; Azad, Chihye Lewis; Ovalle-Robles, Raquel; Fang, Shaoli; Lima, Marcio D.; Lepro, Xavier; Collins, Steve; Baughman, Ray H.; Sear, Richard P.; Dalton, Alan B.

    2011-05-01

    Here we culture Chinese hamster ovary cells on isotropic, aligned and patterned substrates based on multiwall carbon nanotubes. The nanotubes provide the substrate with nanoscale topography. The cells adhere to and grow on all substrates, and on the aligned substrate, the cells align strongly with the axis of the bundles of the multiwall nanotubes. This control over cell alignment is required for tissue engineering; almost all tissues consist of oriented cells. The aligned substrates are made using straightforward physical chemistry techniques from forests of multiwall nanotubes; no lithography is required to make inexpensive large-scale substrates with highly aligned nanoscale grooves. Interestingly, although the cells strongly align with the nanoscale grooves, only a few also elongate along this axis: alignment of the cells does not require a pronounced change in morphology of the cell. We also pattern the nanotube bundles over length scales comparable to the cell size and show that the cells follow this pattern.

  18. Micro patterning of cell and protein non-adhesive plasma polymerized coatings for biochip applications

    DEFF Research Database (Denmark)

    Bouaidat, Salim; Berendsen, C.; Thomsen, P.;

    2004-01-01

    Micro scale patterning of bioactive surfaces is desirable for numerous biochip applications. Polyethyleneoxide-like (PEO-like) coating with non-fouling functionality has been deposited using low frequency AC plasma polymerization. The non-fouling properties of the coating were tested with human...... cells ( HeLa) and fluorescence labeled proteins (isothiocyanate-labeled bovine serum albumin, i.e. FITC-BSA). The PEO-like coatings were fabricated by plasma polymerization of 12-crown-4 (ppCrown) with plasma polymerized hexene (ppHexene) as adhesion layer. The coatings were micro patterned using...

  19. Distinguishing Structure Change of Cells Based on Analysis of Light Scattering Patterns

    Institute of Scientific and Technical Information of China (English)

    JIN Yong-Long; YANG Fang; WANG Meng; ZHANG Yu; GU Ning

    2008-01-01

    We develop a new method to distinguish structural change of cells based on light scattering and Fourier spectra analysis. The light scattering detection system is composed of a laser source, an optical microscope, a CCD with high resolution and low distortion. After the scattering patterns of cells are recorded by the CCD, the Fourier spectra are obtained by the intensity distribution of scattered light. In the experiment, the change of cell structure is designed by sonication treatment. It is found that different typical peaks can be shown in the Fourier spectra of MCF7 cells with and without sonication treatment, which indicates that this method can be used to distinguish the structural change of cells.

  20. Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

    KAUST Repository

    Kachalo, Sëma

    2015-05-14

    Geometric and mechanical properties of individual cells and interactions among neighboring cells are the basis of formation of tissue patterns. Understanding the complex interplay of cells is essential for gaining insight into embryogenesis, tissue development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating properties of individual cells as well as detailed description of the dynamic growth process, with all topological changes accounted for. Cell size, shape, and division plane orientation are modeled realistically. In addition, cell birth, cell growth, cell shrinkage, cell death, cell division, cell collision, and cell rearrangements are now fully accounted for. Different models of cell-cell interactions, such as lateral inhibition during the process of growth, can be studied in detail. Cellular pattern formation for monolayered tissues from arbitrary initial conditions, including that of a single cell, can also be studied in detail. Computational efficiency is achieved through the employment of a special data structure that ensures access to neighboring cells in constant time, without additional space requirement. We have successfully generated tissues consisting of more than 20,000 cells starting from 2 cells within 1 hour. We show that our model can be used to study embryogenesis, tissue fusion, and cell apoptosis. We give detailed study of the classical developmental process of bristle formation on the epidermis of D. melanogaster and the fundamental problem of homeostatic size control in epithelial tissues. Simulation results reveal significant roles of solubility of secreted factors in both the bristle formation and the homeostatic control of tissue size. Our method can be used to study broad problems in monolayered tissue formation. Our software is publicly

  1. Time markers for Drosophila morphogenesis based on cell-pattern topology.

    Science.gov (United States)

    Zallen, Richard; Zallen, Jennifer A.

    2007-03-01

    Recent work on convergent extension in Drosophila has shown that the accumulation of actin-myosin networks at specific cell interfaces initiates planar polarity and the formation of multicellular rosette structures that contribute to elongation of the body axis [1]. This cell-rearrangement process takes place within a one-cell-thick layer, and the changing two-dimensional cell pattern can be characterized using topological measures such as cell-shape statistics [2]. We find that the timeline for the process contains a well-defined marker corresponding to a sharp increase in the slope of the time dependence of the variance of the cell-shape (number-of-sides) distribution. A rosette in this context is a cluster of cells enclosing high-order vertices at which 4 or 5 or more cells meet. While the cell-shape variance climbs steadily during axis elongation, the frequency of high-order vertices and large rosettes plateaus after 10 and 13 minutes, respectively. These time markers calibrate the conventional timeline descriptors referred to as stages 7 and 8 of embryonic development [3]. [1] J.T. Blankenship et al., Developmental Cell 11, 459 (2006); [2] J.A. Zallen and R. Zallen, J. Phys.: Condensed Matter 16, S5073 (2004); [3] J.A. Campos-Ortega and V. Hartenstein, The embryonic development of Drosophila melanogaster (1985).

  2. A hydrophobic perfluoropolyether elastomer as a patternable biomaterial for cell culture and tissue engineering.

    Science.gov (United States)

    Schulte, Vera A; Hu, Yibing; Diez, Mar; Bünger, Daniel; Möller, Martin; Lensen, Marga C

    2010-11-01

    We present a systematic study of a perfluoropolyether (PFPE)-based elastomer as a new biomaterial. Besides its excellent long-term stability and inertness, PFPE can be decorated with topographical surface structures by replica molding. Micrometer-sized pillar structures led to considerably different cell morphology of fibroblasts. Although PFPE is a very hydrophobic material we could show that PFPE substrates allow cell adhesion and spreading of primary human fibroblasts (HDF) very similar to that observed on standard cell culture substrates. Less advanced cell spreading was observed for L929 (murine fibroblast cell line) cells during the first 5 h in culture which was accompanied by retarded recruitment of α(v)β(3)-integrin into focal adhesions (FAs). After 24 h distinct FAs were evident also in L929 cells on PFPE. Furthermore, organization of soluble FN into a fibrillar ECM network was shown for hdF and L929 cells. Based on these results PFPE is believed to be a suitable substrate for several biological applications. On the one hand it is an ideal cell culture substrate for fundamental research of substrate-independent adhesion signaling due to its different characteristics (e.g. wettability, elasticity) compared to glass or TCPS. On the other hand it could be a promising implant material, especially due to its straightforward patternability, which is a tool to direct cell growth and differentiation.

  3. Metabolic patterns and biotransformation activities of resveratrol in human glioblastoma cells: relevance with therapeutic efficacies.

    Directory of Open Access Journals (Sweden)

    Xiao-Hong Shu

    Full Text Available BACKGROUND: Trans-resveratrol rather than its biotransformed monosulfate metabolite exerts anti-medulloblastoma effects by suppressing STAT3 activation. Nevertheless, its effects on human glioblastoma cells are variable due to certain unknown reason(s. METHODOLOGY/PRINCIPAL FINDINGS: Citing resveratrol-sensitive UW228-3 medulloblastoma cell line and primarily cultured rat brain cells/PBCs as controls, the effect of resveratrol on LN-18 human glioblastoma cells and its relevance with metabolic pattern(s, brain-associated sulfotransferase/SULT expression and the statuses of STAT3 signaling and protein inhibitor of activated STAT3 (PIAS3 were elucidated by multiple experimental approaches. Meanwhile, the expression patterns of three SULTs (SULT1A1, 1C2 and 4A1 in human glioblastoma tumors were profiled immunohistochemically. The results revealed that 100 µM resveratrol-treated LN-18 generated the same metabolites as UW228-3 cells, while additional metabolite in molecular weight of 403.0992 in negative ion mode was found in PBCs. Neither growth arrest nor apoptosis was found in resveratrol-treated LN-18 and PBC cells. Upon resveratrol treatment, the levels of SULT1A1, 1C2 and 4A1 expression in LN-18 cells were more up-regulated than that expressed in UW228-3 cells and close to the levels in PBCs. Immunohistochemical staining showed that 42.0%, 27.1% and 19.6% of 149 glioblastoma cases produced similar SULT1A1, 1C2 and 4A1 levels as that of tumor-surrounding tissues. Unlike the situation in UW228-3 cells, STAT3 signaling remained activated and its protein inhibitor PIAS3 was restricted in the cytosol of resveratrol-treated LN-18 cells. No nuclear translocation of STAT3 and PIAS3 was observed in resveratrol-treated PBCs. Treatment with STAT3 chemical inhibitor, AG490, committed majority of LN-18 and UW228-3 cells but not PBCs to apoptosis within 48 hours. CONCLUSIONS/SIGNIFICANCE: LN-18 glioblastoma cells are insensitive to resveratrol due to the

  4. Programmable Laser-Assisted Surface Microfabrication on a Poly(Vinyl Alcohol)-Coated Glass Chip with Self-Changing Cell Adhesivity for Heterotypic Cell Patterning.

    Science.gov (United States)

    Li, Yi-Chen; Lin, Meng-Wei; Yen, Meng-Hua; Fan, Sabrina Mai-Yi; Wu, June-Tai; Young, Tai-Horng; Cheng, Ji-Yen; Lin, Sung-Jan

    2015-10-14

    Organs are composed of heterotypic cells with patterned architecture that enables intercellular interaction to perform specific functions. In tissue engineering, the ability to pattern heterotypic cells into desired arrangement will allow us to model complex tissues in vitro and to create tissue equivalents for regeneration. This study was aimed at developing a method for fast heterotypic cell patterning with controllable topological manipulation on a glass chip. We found that poly(vinyl alcohol)-coated glass showed a biphasic change in adhesivity to cells in vitro: low adhesivity in the first 24 h and higher adhesivity at later hours due to increased serum protein adsorption. Combining programmable CO2 laser ablation to remove poly(vinyl alcohol) and glass, we were able to create arrays of adhesive microwells of adjustable patterns. We tested whether controllable patterns of epithelial-mesenchymal interaction could be created. When skin dermal papilla cells and fibroblasts were seeded respectively 24 h apart, we were able to pattern these two cells into aggregates of dermal papilla cells in arrays of microwells in a background of fibroblasts sheet. Seeded later, keratinocytes attached to these mesenchymal cells. Keratinocytes contacting dermal papilla cells started to differentiate toward a hair follicle fate, demonstrating patternable epithelial-mesenchymal interaction. This method allows fast adjustable heterotypic cell patterning and surface topology control and can be applied to the investigation of heterotypic cellular interaction and creation of tissue equivalent in vitro.

  5. Low cost, patterning of human hNT brain cells on parylene-C with UV & IR laser machining.

    Science.gov (United States)

    Raos, Brad J; Unsworth, C P; Costa, J L; Rohde, C A; Doyle, C S; Delivopoulos, E; Murray, A F; Dickinson, M E; Simpson, M C; Graham, E S; Bunting, A S

    2013-01-01

    This paper describes the use of 800nm femtosecond infrared (IR) and 248nm nanosecond ultraviolet (UV) laser radiation in performing ablative micromachining of parylene-C on SiO2 substrates for the patterning of human hNT astrocytes. Results are presented that support the validity of using IR laser ablative micromachining for patterning human hNT astrocytes cells while UV laser radiation produces photo-oxidation of the parylene-C and destroys cell patterning. The findings demonstrate how IR laser ablative micromachining of parylene-C on SiO2 substrates can offer a low cost, accessible alternative for rapid prototyping, high yield cell patterning.

  6. Quantitative application of Monte Carlo simulation in Fire-PSA

    Energy Technology Data Exchange (ETDEWEB)

    Mangs, J.; Hostikka, S.; Korhonen, T. [Valtion Teknillinen Tutkimuskeskus, Espoo (Finland); Keski-Rahkonen, O.

    2007-05-15

    In a power plant a fire cell forms the basic subunit. Since the fire is initially located there, the full-scale time dependent fire simulation and estimation of target response must be performed within the fire cell. Conditional, time dependent damage probabilities in a fire cell can now be calculated for arbitrary targets (component or a subsystem) combining probabilistic (Monte Carlo) and deterministic simulation. For the latter a spectrum from simple correlations up to latest computational fluid dynamics models is available. Selection of the code is made according to the requirements form the target cell. Although calculations are numerically heavy, it is now economically possible and feasible to carry out quantitative fire-PSA for a complete plant iteratively with the main PSA. From real applications examples are shown on assessment of fire spread possibility in a relay room, and potential of fire spread on cables in a tunnel. (orig.)

  7. A fast and accessible methodology for micro-patterning cells on standard culture substrates using Parafilm™ inserts.

    Science.gov (United States)

    Javaherian, Sahar; O'Donnell, Kylie A; McGuigan, Alison P

    2011-01-01

    Micropatterning techniques provide direct control over the spatial organization of cells at the sub-mm scale. Regulation of these spatial parameters is important for controlling cell fate and cell function. While micropatterning has proved a powerful technique for understanding the impact of cell organization on cell behaviour, current methods for micropatterning cells require complex, specialized equipment that is not readily accessible in most biological and bioengineering laboratories. In addition, currently available methods require significant protocol optimization to ensure reliable and reproducible patterning. The inaccessibility of current methods has severely limited the widespread use of micropatterning as a tool in both biology and tissue engineering laboratories. Here we present a simple, cheap, and fast method to micropattern mammalian cells into stripes and circular patterns using Parafilm™, a common material found in most biology and bioengineering laboratories. Our method does not require any specialized equipment and does not require significant method optimization to ensure reproducible patterning. Although our method is limited to simple patterns, these geometries are sufficient for addressing a wide range of biological problems. Specifically, we demonstrate i) that using our Parafilm™ insert method we can pattern and co-pattern ARPE-19 and MDCK epithelial cells into circular and stripe micropatterns in tissue culture polystyrene (TCPS) wells and on glass slides, ii) that we can contain cells in the desired patterns for more than one month and iii) that upon removal of the Parafilm™ insert we can release the cells from the containment pattern and allow cell migration outward from the original pattern. We also demonstrate that we can exploit this confinement release feature to conduct an epithelial cell wound healing assay. This novel micropatterning method provides a reliable and accessible tool with the flexibility to address a wide range

  8. A fast and accessible methodology for micro-patterning cells on standard culture substrates using Parafilm™ inserts.

    Directory of Open Access Journals (Sweden)

    Sahar Javaherian

    Full Text Available Micropatterning techniques provide direct control over the spatial organization of cells at the sub-mm scale. Regulation of these spatial parameters is important for controlling cell fate and cell function. While micropatterning has proved a powerful technique for understanding the impact of cell organization on cell behaviour, current methods for micropatterning cells require complex, specialized equipment that is not readily accessible in most biological and bioengineering laboratories. In addition, currently available methods require significant protocol optimization to ensure reliable and reproducible patterning. The inaccessibility of current methods has severely limited the widespread use of micropatterning as a tool in both biology and tissue engineering laboratories. Here we present a simple, cheap, and fast method to micropattern mammalian cells into stripes and circular patterns using Parafilm™, a common material found in most biology and bioengineering laboratories. Our method does not require any specialized equipment and does not require significant method optimization to ensure reproducible patterning. Although our method is limited to simple patterns, these geometries are sufficient for addressing a wide range of biological problems. Specifically, we demonstrate i that using our Parafilm™ insert method we can pattern and co-pattern ARPE-19 and MDCK epithelial cells into circular and stripe micropatterns in tissue culture polystyrene (TCPS wells and on glass slides, ii that we can contain cells in the desired patterns for more than one month and iii that upon removal of the Parafilm™ insert we can release the cells from the containment pattern and allow cell migration outward from the original pattern. We also demonstrate that we can exploit this confinement release feature to conduct an epithelial cell wound healing assay. This novel micropatterning method provides a reliable and accessible tool with the flexibility to

  9. Optimization of multi-layer front-contact grid patterns for solar cells

    Science.gov (United States)

    Flat, A.; Milnes, A. G.

    1979-01-01

    In a front-contact grid pattern for a solar cell there is a trade-off necessary between shadowing loss and excessive power loss due to voltage drop in the metalization itself. If the metalization is too little there may be excessive contact resistance to the underlying semiconductor and insufficient coverage to control losses in the thin front-surface layer of the solar cell. Optimization of grid pattern area and geometry is considered analytically to minimize total losses. Worthwhile performance advantages are shown to be possible, particularly in concentrator systems, if multi-layer grid patterns are used. The current carrying fingers should be approximately square in metal cross section and the main current feedout bars should not only be wider but also thicker than the primary collecting fingers. This is termed multi-level metalization. Effective use of multi-level grid metalization allows much greater concentration-to-loss ratio for a cell of large area and permits good performance from cells of high front-layer sheet resistance.

  10. Fire Ant Bites

    Science.gov (United States)

    ... Name: Category: Share: Yes No, Keep Private Fire Ant Bites Share | Fire ants are aggressive, venomous insects that have pinching mandibles ... the United States, even into Puerto Rico. Fire ant stings usually occur on the feet or legs ...

  11. Crown Fire Potential

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Crown fire potential was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The...

  12. Fire safety at home

    Science.gov (United States)

    ... over the smoke alarm as needed. Using a fire extinguisher can put out a small fire to keep it from getting out of control. Tips for use include: Keep fire extinguishers in handy locations, at least one on ...

  13. Social observation enhances cross-environment activation of hippocampal place cell patterns

    Science.gov (United States)

    Mou, Xiang; Ji, Daoyun

    2016-01-01

    Humans and animals frequently learn through observing or interacting with others. The local enhancement theory proposes that presence of social subjects in an environment facilitates other subjects' understanding of the environment. To explore the neural basis of this theory, we examined hippocampal place cells, which represent spatial information, in rats as they stayed in a small box while a demonstrator rat running on a separate, nearby linear track, and as they ran on the same track themselves. We found that place cell firing sequences during self-running on the track also appeared in the box. This cross-environment activation occurred even prior to any self-running experience on the track and was absent without a demonstrator. Our data thus suggest that social observation can facilitate the observer’s spatial representation of an environment without actual self-exploration. This finding may contribute to neural mechanisms of local enhancement. DOI: http://dx.doi.org/10.7554/eLife.18022.001

  14. MicroRNA expression pattern of undifferentiated and differentiated human embryonic stem cells.

    Science.gov (United States)

    Lakshmipathy, Uma; Love, Brad; Goff, Loyal A; Jörnsten, Rebecka; Graichen, Ralph; Hart, Ronald P; Chesnut, Jonathan D

    2007-12-01

    Many of the currently established human embryonic stem (hES) cell lines have been characterized extensively in terms of their gene expression profiles and genetic stability in culture. Recent studies have indicated that microRNAs (miRNAs), a class of noncoding small RNAs that participate in the regulation of gene expression, may play a key role in stem cell self-renewal and differentiation. Using both microarrays and quantitative PCR, we report here the differences in miRNA expression between undifferentiated hES cells and their corresponding differentiated cells that underwent differentiation in vitro over a period of 2 weeks. Our results confirm the identity of a signature miRNA profile in pluripotent cells, comprising a small subset of differentially expressed miRNAs in hES cells. Examining both mRNA and miRNA profiles under multiple conditions using cross-correlation, we find clusters of miRNAs grouped with specific, biologically interpretable mRNAs. We identify patterns of expression in the progression from hES cells to differentiated cells that suggest a role for selected miRNAs in maintenance of the undifferentiated, pluripotent state. Profiling of the hES cell "miRNA-ome" provides an insight into molecules that control cellular differentiation and maintenance of the pluripotent state, findings that have broad implications in development, homeostasis, and human disease states.

  15. Infiltration patterns in monoclonal plasma cell disorders: correlation of magnetic resonance imaging with matched bone marrow histology

    Energy Technology Data Exchange (ETDEWEB)

    Andrulis, Mindaugas [Institute of Pathology, University of Heidelberg, Heidelberg (Germany); Bäuerle, Tobias [Department of Diagnostic and Interventional Radiology, University of Hamburg, Hamburg (Germany); Goldschmidt, Hartmut [Department of Hematology and Oncology, University of Heidelberg, Heidelberg (Germany); Delorme, Stefan [Department of Radiology, German Cancer Research Center (DKFZ), Heidelberg (Germany); Landgren, Ola [Multiple Myeloma Section, Metabolism Branch, National Cancer Institute, Bethesda (United States); Schirmacher, Peter [Institute of Pathology, University of Heidelberg, Heidelberg (Germany); Hillengass, Jens, E-mail: jens.hillengass@med.uni-heidelberg.de [Department of Hematology and Oncology, University of Heidelberg, Heidelberg (Germany); Department of Radiology, German Cancer Research Center (DKFZ), Heidelberg (Germany)

    2014-06-15

    Objectives: To investigate how plasma cell infiltration patterns detected by MRI match the plasma cell distribution in bone marrow biopsy. Methods: We assessed 50 patients with monoclonal plasma cell disorders of all clinical stages. MRI infiltration pattern was compared with matched BM histology from the same anatomic region. Results: MRI revealed a minimal (n = 11, 22%), focal (n = 5, 10%), diffuse (n = 14, 28%) and mixed (n = 20, 40%) infiltration pattern. Diffuse MRI pattern was predominant in smoldering myeloma patients whereas the MRI patterns with “focal component” (i.e. focal and mixed) were most common in symptomatic myeloma (p < 0.01). In histology an interstitial (n = 13, 26%), nodular (n = 23, 46%) and packed marrow (n = 14, 28%) was found respectively. All three histological types of infiltration were observed in patients with diffuse and mixed MRI patterns. Minimal MRI pattern was found in all MGUS patients and was associated with an interstitial BM infiltration. In two patients with minimal MRI pattern an extensive micro-nodular BM infiltration was found in histology. Conclusions: Infiltration patterns in MRI represent different histological growth patterns of plasma cells, but the MRI resolution is not sufficient to visualize micro-nodular aggregates of plasma cells.

  16. Controls on variations in MODIS fire radiative power in Alaskan boreal forests: implications for fire severity conditions

    Science.gov (United States)

    Barrett, Kirsten; Kasischke, Eric S.

    2013-01-01

    Fire activity in the Alaskan boreal forest, though episodic at annual and intra-annual time scales, has experienced an increase over the last several decades. Increases in burned area and fire severity are not only releasing more carbon to the atmosphere, but likely shifting vegetation composition in the region towards greater deciduous dominance and a reduction in coniferous stands. While some recent studies have addressed qualitative differences between large and small fire years in the Alaskan boreal forest, the ecological effects of a greater proportion of burning occurring during large fire years and during late season fires have not yet been examined. Some characteristics of wildfires that can be detected remotely are related to fire severity and can provide new information on spatial and temporal patterns of burning. This analysis focused on boreal wildfire intensity (fire radiative power, or FRP) contained in the Moderate Resolution Imaging Spectroradiometer (MODIS) daily active fire product from 2003 to 2010. We found that differences in FRP resulted from seasonality and intra-annual variability in fire activity levels, vegetation composition, latitudinal variation, and fire spread behavior. Our studies determined two general categories of active fire detections: new detections associated with the spread of the fire front and residual pixels in areas that had already experienced front burning. Residual pixels had a lower average FRP than front pixels, but represented a high percentage of all pixels during periods of high fire activity (large fire years, late season burning, and seasonal periods of high fire activity). As a result, the FRP from periods of high fire activity was less intense than those from periods of low fire activity. Differences related to latitude were greater than expected, with higher latitudes burning later in the season and at a higher intensity than lower latitudes. Differences in vegetation type indicate that coniferous vegetation

  17. Growth pattern of single fission yeast cells is bilinear and depends on temperature and DNA synthesis.

    Science.gov (United States)

    Baumgärtner, Stephan; Tolić-Nørrelykke, Iva M

    2009-05-20

    Cell growth and division have to be tightly coordinated to keep the cell size constant over generations. Changes in cell size can be easily studied in the fission yeast Schizosaccharomyces pombe because these cells have a cylindrical shape and grow only at the cell ends. However, the growth pattern of single cells is currently unclear. Linear, exponential, and bilinear growth models have been proposed. Here we measured the length of single fission yeast cells with high spatial precision and temporal resolution over the whole cell cycle by using time-lapse confocal microscopy of cells with green fluorescent protein-labeled plasma membrane. We show that the growth profile between cell separation and the subsequent mitosis is bilinear, consisting of two linear segments separated by a rate-change point (RCP). The change in growth rate occurred at the same relative time during the cell cycle and at the same relative extension for different temperatures. The growth rate before the RCP was independent of temperature, whereas the growth rate after the RCP increased with an increase in temperature, leading to clear bilinear growth profiles at higher temperatures. The RCP was not directly related to the initiation of growth at the new end (new end take-off). When DNA synthesis was inhibited by hydroxyurea, the RCP was not detected. This result suggests that completion of DNA synthesis is required for the increase in growth rate. We conclude that the growth of fission yeast cells is not a simple exponential growth, but a complex process with precise rates regulated by the events during the cell cycle.

  18. Expression and alternative splicing pattern of human telomerase reverse transcriptase in human lung cancer cells.

    Science.gov (United States)

    Fujiwara, Masachika; Kamma, Hiroshi; Wu, Wenwen; Hamasaki, Makoto; Kaneko, Setsuko; Horiguchi, Hisashi; Matsui-Horiguchi, Miwa; Satoh, Hiroaki

    2004-04-01

    Telomerase activity is generally considered to be necessary for cancer cells to avoid senescence. The expression of human telomerase reverse transcriptase (hTERT) is believed to be a rate-limiting step in telomerase activation. Recently, it has been proposed that the alternative splicing of hTERT is also involved in regulation of telomerase activity. However, the regulatory mechanism of telomerase in cancer cells has not been thoroughly investigated. To clarify it in lung cancer cells, we measured the expression of the hTERT transcript, analyzed its alternative splicing by RT-PCR, and compared it with telomerase activity and telomere length. The expression of the hTERT transcript was positively correlated with telomerase activity in lung cancer cells. Cancer cells with high telomerase activity contained 4 splicing variants of hTERT, and the full-length variant was 31.3-54.2% of the total transcripts. Cells of the TKB-20 cell line, which has extremely low telomerase activity, showed a different splicing pattern of hTERT in addition to low expression. The functional full-length variant was scarcely detected in TKB-20 cells, suggesting that the telomerase activity was repressed by alternative splicing of hTERT. Telomere length was not necessarily correlated with telomerase activity or hTERT expression in lung cancer cells. Cells of the TKB-4 cell line that also showed relatively low telomerase activity (as TKB-20 cells) had long telomeres. In conclusion, hTERT expression is regulated at both the transcriptional and post-transcriptional levels in lung cancer cells, and the alternative splicing of hTERT is involved in the control of telomerase activity.

  19. Widely divergent transcriptional patterns between SLE patients of different ancestral backgrounds in sorted immune cell populations.

    Science.gov (United States)

    Sharma, Shruti; Jin, Zhongbo; Rosenzweig, Elizabeth; Rao, Swapna; Ko, Kichul; Niewold, Timothy B

    2015-06-01

    Systemic lupus erythematosus (SLE) is a complex autoimmune disease of uncertain etiology. Patients from different ancestral backgrounds demonstrate differences in clinical manifestations and autoantibody profiles. We examined genome-wide transcriptional patterns in major immune cell subsets across different ancestral backgrounds. Peripheral blood was collected from African-American (AA) and European-American (EA) SLE patients and controls. CD4 T-cells, CD8 T-cells, monocytes, and B cells were purified by flow sorting, and each cell subset from each subject was run on a genome-wide expression array. Cases were compared to controls of the same ancestral background. The overlap in differentially expressed gene (DEG) lists between different cell types from the same ancestral background was modest (type between different ancestral backgrounds. IFN-stimulated gene (ISG) expression was not up-regulated synchronously in all cell types from a given patient, for example a given subject could have high ISG expression in T and B cells, but not in monocytes. AA subjects demonstrated more concordance in ISG expression between cell types from the same individual, and AA patients demonstrated significant down-regulation of metabolic gene expression which was not observed in EA patients. ISG expression was significantly decreased in B cells in patients taking immunosuppressants, while ISGs in other cell types did not differ with medication use. In conclusion, gene expression was strikingly different between immune cell subsets and between ancestral backgrounds in SLE patients. These findings emphasize the critical importance of studying multiple ancestral backgrounds and multiple cell types in gene expression studies. Ancestral backgrounds which are not studied will not benefit from personalized medicine strategies in SLE.

  20. The intensity of T cell receptor engagement determines the cytokine pattern of human allergen-specific T helper cells.

    Science.gov (United States)

    Carballido, J M; Faith, A; Carballido-Perrig, N; Blaser, K

    1997-02-01

    Enhanced production of T helper (Th)2 cytokines by allergen-specific Th cells plays a major role in the induction and maintenance of IgE-mediated allergic disorders. The mechanism that triggers this type of response in atopic individuals is not fully understood. Allergen-specific human Th cell clones produce interleukin (IL)-4 and low or undetectable levels of interferon (IFN)-gamma after stimulation with low concentrations of antigen. However, these Th cell clones are capable of generating significant amounts of IFN-gamma after optimal activation through their T cell receptor (TcR). Allergen-specific Th cell clones isolated from allergic individuals required higher doses of antigen to reach the plateau of proliferation and to generate Th0 cytokine responses than their counterparts isolated from nonallergic subjects. On the other hand, if allergen was replaced by anti-CD3 monoclonal antibody (mAb), both allergic and nonallergic Th cell clones attained the highest level of proliferation and significant IFN-gamma production in response to equivalent concentrations of anti-CD3 mAb. These results indicate that the strength of T cell ligation, which can be modulated by the availability of the TcR ligand, controls the balance of Thl/Th2 cytokines produced by memory Th cells in vitro. In the particular case of bee venom phospholipase A2, it is shown that the expression of allergen-specific surface Ig on antigen-presenting B cells has little influence on antigen uptake and therefore in determining the levels of T cell activation and cytokine production. Alternatively, the affinity of particular major histocompatibility complex class II molecules on antigen-presenting cells for allergen-derived peptides might determine the amount of specific ligand presented to the Th cells and play a decisive role skewing the Th cell cytokine production towards Th1 or Th2 phenotypes. These findings, which are consistent with the changes in cytokine patterns observed following clinical

  1. Avian response to fire in pine–oak forests of Great Smoky Mountains National Park following decades of fire suppression

    Science.gov (United States)

    Rose, Eli T.; Simons, Theodore R.

    2016-01-01

    Fire suppression in southern Appalachian pine–oak forests during the past century dramatically altered the bird community. Fire return intervals decreased, resulting in local extirpation or population declines of many bird species adapted to post-fire plant communities. Within Great Smoky Mountains National Park, declines have been strongest for birds inhabiting xeric pine–oak forests that depend on frequent fire. The buildup of fuels after decades of fire suppression led to changes in the 1996 Great Smoky Mountains Fire Management Plan. Although fire return intervals remain well below historic levels, management changes have helped increase the amount of fire within the park over the past 20 years, providing an opportunity to study patterns of fire severity, time since burn, and bird occurrence. We combined avian point counts in burned and unburned areas with remote sensing indices of fire severity to infer temporal changes in bird occurrence for up to 28 years following fire. Using hierarchical linear models that account for the possibility of a species presence at a site when no individuals are detected, we developed occurrence models for 24 species: 13 occurred more frequently in burned areas, 2 occurred less frequently, and 9 showed no significant difference between burned and unburned areas. Within burned areas, the top models for each species included fire severity, time since burn, or both, suggesting that fire influenced patterns of species occurrence for all 24 species. Our findings suggest that no single fire management strategy will suit all species. To capture peak occupancy for the entire bird community within xeric pine–oak forests, at least 3 fire regimes may be necessary; one applying frequent low severity fire, another using infrequent low severity fire, and a third using infrequently applied high severity fire.

  2. Creating "living" polymer surfaces to pattern biomolecules and cells on common plastics.

    Science.gov (United States)

    Li, Chunyan; Glidle, Andrew; Yuan, Xiaofei; Hu, Zhixiong; Pulleine, Ellie; Cooper, Jon; Yang, Wantai; Yin, Huabing

    2013-05-13

    Creating patterns of biomolecules and cells has been applied widely in many fields associated with the life sciences, including diagnostics. In these applications it has become increasingly apparent that the spatiotemporal arrangement of biological molecules in vitro is important for the investigation of the cellular functions found in vivo. However, the cell patterning techniques often used are limited to creating 2D functional surfaces on glass and silicon. In addition, in general, these procedures are not easy to implement in conventional biological laboratories. Here, we show the formation of a living poly(ethylene glycol) (PEG) layer that can be patterned with visible light on plastic surfaces. This new and simple method can be expanded to pattern multiple types of biomolecule on either a previously formed PEG layer or a plastic substrate. Using common plastic wares (i.e., polyethylene films and polystyrene cell culture Petri-dishes), we demonstrate that these PEG-modified surfaces have a high resistance to protein adsorption and cell adhesion, while at the same time, being capable of undergoing further molecular grafting with bioactive motifs. With a photomask and a fluid delivery system, we illustrate a flexible way to immobilize biological functions with a high degree of 2D and 3D spatial control. We anticipate that our method can be easily implemented in a typical life science laboratory (without the need for specialized lithography equipment) offering the prospect of imparting desirable properties to plastic products, for example, the creation of functional microenvironments in biological studies or reducing biological adhesion to surfaces.

  3. Laser assisted patterning of hydrogenated amorphous silicon for interdigitated back contact silicon heterojunction solar cell

    Science.gov (United States)

    De Vecchi, S.; Desrues, T.; Souche, F.; Muñoz, D.; Lemiti, M.

    2012-10-01

    This work reports on the elaboration of a new industrial process based on laser selective ablation of dielectric layers for Interdigitated Back Contact Silicon Heterojunction (IBC Si-HJ) solar cells fabrication. Choice of the process is discussed and cells are processed to validate its performance. A pulsed green laser (515nm) with 10-20ns pulse duration is used for hydrogenated amorphous silicon (a-Si:H) layers patterning steps, whereas metallization is made by screen printed. High Open-Circuit Voltage (Voc=699mV) and Fill Factor (FF=78.5%) values are obtained simultaneously on IBC Si-HJ cells, indicating a high surface passivation level and reduced resistive losses. An efficiency of 19% on non textured 26 cm² solar cells has been reached with this new industrial process.

  4. Diverse spatio-temporal dynamical patterns of p53 and cell fate decisions

    Science.gov (United States)

    Clairambault, Jean; Eliaš, Ján

    2016-06-01

    The protein p53 as a tumour suppressor protein accumulates in cells in response to DNA damage and transactivates a large variety of genes involved in apoptosis, cell cycle regulation and numerous other processes. Recent biological observations suggest that specific spatio-temporal dynamical patterns of p53 may be associated with specific cellular response, and thus the spatio-temporal heterogeneity of the p53 dynamics contributes to the overall complexity of p53 signalling. Reaction-diffusion equations taking into account spatial representation of the cell and motion of the species inside the cell can be used to model p53 protein network and could be thus of some help to biologists and pharmacologists in anticancer treatment.

  5. Electrochemical communication with the inside of cells using micro-patterned vertical carbon nanofibre electrodes

    Science.gov (United States)

    Rawson, F. J.; Cole, M. T.; Hicks, J. M.; Aylott, J. W.; Milne, W. I.; Collins, C. M.; Jackson, S. K.; Silman, N. J.; Mendes, P. M.

    2016-12-01

    With the rapidly increasing demands for ultrasensitive biodetection, the design and applications of new nano-scale materials for development of sensors based on optical and electrochemical transducers have attracted substantial interest. In particular, given the comparable sizes of nanomaterials and biomolecules, there exist plenty of opportunities to develop functional nanoprobes with biomolecules for highly sensitive and selective biosensing, shedding new light on cellular behaviour. Towards this aim, herein we interface cells with patterned nano-arrays of carbon nanofibers forming a nanosensor-cell construct. We show that such a construct is capable of electrochemically communicating with the intracellular environment.

  6. Degradation Patterns in Water and Oxygen of an Inverted Polymer Solar Cell

    DEFF Research Database (Denmark)

    Norrman, Kion; Vesterager Madsen, Morten; Gevorgyan, Suren

    2010-01-01

    The spatial distribution of reaction products in multilayer polymer solar cells induced by water and oxygen atmospheres was mapped and used to elucidate the degradation patterns and failure mechanisms in an inverted polymer solar cell. The active material comprised a bulk heterojunction formed....... A comparison was made between the use of a humid (oxygen-free) atmosphere and a dry oxygen atmosphere during testing of devices that were kept in the dark and devices that were subjected to illumination under simulated sunlight. It was found that the reactions taking place at the interface between the active...

  7. Smouldering Subsurface Fires in the Earth System

    Science.gov (United States)

    Rein, Guillermo

    2010-05-01

    influence carbon-climate feedbacks. This presentation will revise the current knowledge on smouldering fires in the Earth system regarding ignition, spread patterns and emissions. It will explain the key differences between shallow and deep fires, and flaming fires.

  8. Analysis of changes in the expression pattern of claudins using salivary acinar cells in primary culture.

    Science.gov (United States)

    Fujita-Yoshigaki, Junko

    2011-01-01

    Primary saliva is produced from blood plasma in the acini of salivary glands and is modified by ion adsorption and secretion as the saliva passes through the ducts. In rodents, acinar cells of salivary glands express claudin-3 but not claudin-4, whereas duct cells express both claudins-3 and -4. The distinct claudin expression patterns may reflect differences in the permeability of tight junctions between acinar and duct cells. To analyze the role of claudins in salivary glands, we established a system for the primary culture of parotid acinar cells, where the expression patterns of claudins are remarkably changed. Real-time RT-PCR and immunoblot analyses reveal that the expression levels of claudins-4 and -6 increased, whereas claudins-3 and -10 decreased. We found that the signal to induce those changes is triggered during cell isolation and is mediated by Src and p38 MAP kinase. Here, we introduce the methods used to determine the signal pathway that induces the change in claudin expression.

  9. The application of pattern recognition to the classification of regular gasoline in fire investigation%模式识别在火灾调查中的汽油分类问题的应用研究

    Institute of Scientific and Technical Information of China (English)

    支有冉; 宗若雯; 王荣辉; 李松阳

    2009-01-01

    在火灾调查中,检测汽油成分并对其进行正确分类尤为重要.运用GC-MS对90#和93#两种普通汽油的共50个样本进行检测,所得的GC-MS原始数据通过PCA方法进行处理,以提取有用信息,避免冗余变量进入后续计算.在此基础上应用KNN方法对这两种汽油助燃剂进行分类.结果表明, KNN方法对这两种汽油的分类准确率达到100%,且当初始数据未经标准化预处理时也能达到同样准确的分类效果.研究表明:将模式识别方法正确地运用到助燃剂鉴定和分类工作中有助于火灾调查.%Detection and accurate classification of gasoline is very important in fire investigation. In this paper, a total of 50 samples of regular gasoline, covering two different grades (90# and 93 #), were examined by gas chromatography-mass spectrometry (GC-MS). The GC-MS data were treated by Principal Component Analysis (PCA) to distill the information from the original dataset in order to avoid the redundant variables to be calculated. And k-nearest neighbors algorithm (KNN) was further applied to classify the two types of accelerant. The results showed that KNN could classify the two types of gasoline effectively, with the 100% probability (no prediction error), whether the data were normalized or not. The results indicated that the proper application of pattern recognition to the identification and classification of accelerant provided positive help in fire investigation.

  10. Rectified cell migration on saw-like micro-elastically patterned hydrogels with asymmetric gradient ratchet teeth.

    Directory of Open Access Journals (Sweden)

    Satoru Kidoaki

    Full Text Available To control cell motility is one of the essential technologies for biomedical engineering. To establish a methodology of the surface design of elastic substrate to control the long-range cell movements, here we report a sophisticated cell culture hydrogel with a micro-elastically patterned surface that allows long-range durotaxis. This hydrogel has a saw-like pattern with asymmetric gradient ratchet teeth, and rectifies random cell movements. Durotaxis only occurs at boundaries in which the gradient strength of elasticity is above a threshold level. Consequently, in gels with unit teeth patterns, durotaxis should only occur at the sides of the teeth in which the gradient strength of elasticity is above this threshold level. Therefore, such gels are expected to support the long-range biased movement of cells via a mechanism similar to the Feynman-Smoluchowski ratchet, i.e., rectified cell migration. The present study verifies this working hypothesis by using photolithographic microelasticity patterning of photocurable gelatin gels. Gels in which each teeth unit was 100-120 µm wide with a ratio of ascending:descending elasticity gradient of 1:2 and a peak elasticity of ca. 100 kPa supported the efficient rectified migration of 3T3 fibroblast cells. In addition, long-range cell migration was most efficient when soft lanes were introduced perpendicular to the saw-like patterns. This study demonstrates that asymmetric elasticity gradient patterning of cell culture gels is a versatile means of manipulating cell motility.

  11. A Simple Hydrophilic Treatment of SU-8 Surfaces for Cell Culturing and Cell Patterning

    DEFF Research Database (Denmark)

    Wang, Zhenyu; Stangegaard, Michael; Dufva, Hans Martin;

    2005-01-01

    SU-8, an epoxy-based photoresist, widely used in constitution different mTAS systems, is incompatible with mammalian cell adhesion and culture in its native form. Here, we demonstrate a simple, cheap and robust two-step method to render a SU-8 surface hydrophilic and compatible with cell culture...

  12. A computational study of enzyme patterning on microfluidic biofuel cell electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kjeang, E.; Sinton, D.; Harrington, D.; Djilali, N. [Victoria Univ., BC (Canada). Inst. for Integrated Energy Systems

    2005-07-01

    In an enzymatic fuel cell, chemical reactions are catalyzed by biological redox enzymes that can be separated and purified from suitable organisms. Enzyme catalysts are specific to particular substances and the presence of other substances does not usually impact the rate of catalysis. Enzyme catalysis enables the combination of fuel and oxidant streams in a single manifold, with many benefits regarding fuel cell design and operation. This study examined ways to produce biofuel cell systems through experiments that modeled species transfer associated with heterogenous chemical reactions and enzyme kinetics based on a microchannel geometry. An electrically conducting material was deposited on the interior surfaces to form the anode and cathode, and the enzymes were tethered directly to the layers. The intent was to determine whether the process was diffusion limited or reaction rate limited. Various enzyme-electrode patterns coupled with coherent bulk velocities were investigated in order to realize efficient fuel cell operation. A microstructured multi-step enzymatic biofuel cell structure was proposed. Species transport coupled with laminar flow and Michaelis-Menten kinetics was examined using a 2-dimensional numerical solution. Biofuel cell performance was shown to be limited by the reactions rates associated with enzyme kinetics. Turnover rates for individual enzymes were key parameters throughout the analysis and directly determined the realizable current densities. The pumping power required for the microchannel flow was determined to be negligible compared to the output power of the unit cell. It was concluded that methanol is the better fuel in terms of energy density. Four separated and mixed electrode enzyme strategies were presented and tested with bulk velocities to optimize overall current density and fuel consumption. It was suggested that the mixed transport regime is particularly attractive for biofuel cell operation, with superior characteristics

  13. Enhanced invasion in vitro and the distribution patterns in vivo of CD133+ glioma stem cells

    Institute of Scientific and Technical Information of China (English)

    YU Sheng-ping; YANG Xue-jun; ZHANG Bin; MING Hao-lang; CHEN Cong; REN Bing-cheng; LIU Zhi-feng; LIU Bin

    2011-01-01

    Background Recent studies have suggested that cancer stem cells cause tumor recurrence based on their resistance to radiotherapy and chemotherapy.Although the highly invasive nature of glioblastoma cells is also implicated in the failure of current therapies,it is not clear whether cancer stem cells are involved in invasiveness.This study aimed to assess invasive ability of glioma stem cells (GSCs) derived from C6 glioma cell line and the distribution patterns of GSCs in Sprague-Dawley (SD) rat brain tumor.Methods Serum-free medium culture and magnetic isolation were used to gain purely CD133+ GSCs.The invasive stem cell markers and luxol fast blue staining for white matter tracts were performed to show the distribution patterns of GSCs in brain tumor of rats and the relationship among GSCs,vessels,and white matter tracts.The results of matrigel invasion assay were estimated using the Student's t test and the analysis of Western blotting was performed using the one-way analysis of variance (ANOVA) test.Results CD133+GSCs(number:85.3±4.1)were significantly more invasive in vitro than matched CD133- cells(number:25.9±3.1) (t=14.5,P <0.005).GSCs invaded into the brain diffusely and located in perivascular niche of tumor-brain interface or resided within perivascular niche next to white fiber tracts.The polarity of glioma cells containing GSCs was parallel to the white matter tracts.Conclusions Our data suggest that CD133+ GSCs exhibit more aggressive invasion in vitro and GSCs in vivo probably disseminate along the long axis of blood vessels and transit through the white matter tracts.The therapies targeting GSCs invasion combined with traditional glioblastoma multiforme therapeutic paradigms might be a new approach for avoiding malignant glioma recurrence.

  14. Coupling mechanical deformations and planar cell polarity to create regular patterns in the zebrafish retina.

    Directory of Open Access Journals (Sweden)

    Guillaume Salbreux

    Full Text Available The orderly packing and precise arrangement of epithelial cells is essential to the functioning of many tissues, and refinement of this packing during development is a central theme in animal morphogenesis. The mechanisms that determine epithelial cell shape and position, however, remain incompletely understood. Here, we investigate these mechanisms in a striking example of planar order in a vertebrate epithelium: The periodic, almost crystalline distribution of cone photoreceptors in the adult teleost fish retina. Based on observations of the emergence of photoreceptor packing near the retinal margin, we propose a mathematical model in which ordered columns of cells form as a result of coupling between planar cell polarity (PCP and anisotropic tissue-scale mechanical stresses. This model recapitulates many observed features of cone photoreceptor organization during retinal growth and regeneration. Consistent with the model's predictions, we report a planar-polarized distribution of Crumbs2a protein in cone photoreceptors in both unperturbed and regenerated tissue. We further show that the pattern perturbations predicted by the model to occur if the imposed stresses become isotropic closely resemble defects in the cone pattern in zebrafish lrp2 mutants, in which intraocular pressure is increased, resulting in altered mechanical stress and ocular enlargement. Evidence of interactions linking PCP, cell shape, and mechanical stresses has recently emerged in a number of systems, several of which show signs of columnar cell packing akin to that described here. Our results may hence have broader relevance for the organization of cells in epithelia. Whereas earlier models have allowed only for unidirectional influences between PCP and cell mechanics, the simple, phenomenological framework that we introduce here can encompass a broad range of bidirectional feedback interactions among planar polarity, shape, and stresses; our model thus represents a

  15. Gene expression pattern of functional neuronal cells derived from human bone marrow mesenchymal stromal cells

    Directory of Open Access Journals (Sweden)

    Bron Dominique

    2008-04-01

    Full Text Available Abstract Background Neuronal tissue has limited potential to self-renew or repair after neurological diseases. Cellular therapies using stem cells are promising approaches for the treatment of neurological diseases. However, the clinical use of embryonic stem cells or foetal tissues is limited by ethical considerations and other scientific problems. Thus, bone marrow mesenchymal stomal cells (BM-MSC could represent an alternative source of stem cells for cell replacement therapies. Indeed, many studies have demonstrated that MSC can give rise to neuronal cells as well as many tissue-specific cell phenotypes. Methods BM-MSC were differentiated in neuron-like cells under specific induction (NPBM + cAMP + IBMX + NGF + Insulin. By day ten, differentiated cells presented an expression profile of real neurons. Functionality of these differentiated cells was evaluated by calcium influx through glutamate receptor AMPA3. Results Using microarray analysis, we compared gene expression profile of these different samples, before and after neurogenic differentiation. Among the 1943 genes differentially expressed, genes down-regulated are involved in osteogenesis, chondrogenesis, adipogenesis, myogenesis and extracellular matrix component (tuftelin, AGC1, FADS3, tropomyosin, fibronectin, ECM2, HAPLN1, vimentin. Interestingly, genes implicated in neurogenesis are increased. Most of them are involved in the synaptic transmission and long term potentialisation as cortactin, CASK, SYNCRIP, SYNTL4 and STX1. Other genes are involved in neurite outgrowth, early neuronal cell development, neuropeptide signaling/synthesis and neuronal receptor (FK506, ARHGAP6, CDKRAP2, PMCH, GFPT2, GRIA3, MCT6, BDNF, PENK, amphiregulin, neurofilament 3, Epha4, synaptotagmin. Using real time RT-PCR, we confirmed the expression of selected neuronal genes: NEGR1, GRIA3 (AMPA3, NEF3, PENK and Epha4. Functionality of these neuron-like cells was demonstrated by Ca2+ influx through glutamate

  16. A trend analysis of global fire activity. Is it land use or climate the main driver?

    Science.gov (United States)

    Bistinas, Ioannis; Oom, Duarte; Silva, Joao M. N.; Lopez-Saldaña, Gerardo; Pereira, Jose M. C.

    2016-04-01

    We perform a global trend analysis of active fire counts at 0.5o spatial resolution, using 156 months (January 2001 - December 2013) of MODIS Climate Modelling Grid data (TERRA). We use the Contextual Mann-Kendall (CMK) test to assess the statistical significance at cell level and found that 13% of the global land area displays statistically significant active fire count trends, with a slight predominance of negative trends (50.63% of the total significant cells). We perform the same trend analysis with the unexplained variability (residuals) between active fires and the Fire Weather Index (FWI) that is used as a proxy for climate. There is agreement between the main patterns from the trend analysis coming from the residuals and the active fire trends, implying that the main contemporary fire trends are not climate driven. Spatially coherent patches with significant trends were found in all continents (with the obvious exception of Antarctica). The majority of significant trends occur in areas of high fire incidence, and both increasing and decreasing trends appear to be associated with land use change processes. The analysis reveals large negative trends at the Sahel and between Russia and Kazakhstan, whereas a massive and coherent positive trend appears in southeastern Asia. Smaller patches of positive trends appear in southeastern United States and in Mexico, as well as in Brazil and between Argentina and Paraguay, and in Asia in India. There are also negative trends in Brazil, Argentina and in Australia. The study highlights the land use activities as the main driver of these trends, but also the need for data driven analyses and longer time series for future studies in order to gain better knowledge on fire occurrence.

  17. Influence of geography and climate on patterns of cell size and body size in the lizard Anolis carolinensis.

    Science.gov (United States)

    Goodman, Rachel M; Echternacht, Arthur C; Hall, Jim C; Deng, Lihan D; Welch, Jessica N

    2013-06-01

    Geographic patterns in body size are often associated with latitude, elevation, or environmental and climatic variables. This study investigated patterns of body size and cell size of the green anole lizard, Anolis carolinensis, and potential associations with geography or climatic variables. Lizards were sampled from 19 populations across the native range, and body size, red blood cell size and size and number of muscle cells were measured. Climatic data from local weather stations and latitude and longitude were entered into model selection with Akaike's information criterion to explain patterns in cell and body sizes. Climatic variables did not drive any major patterns in cell size or body size; rather, latitude and longitude were the best predictors of cell and body size. In general, smaller body and cell sizes in Florida anoles drove geographic patterns in A. carolinensis. Small size in Florida may be attributable to the geological history of the peninsular state or the unique ecological factors in this area, including a recently introduced congener. In contrast to previous studies, we found that A. carolinensis does not follow Bergmann's rule when the influence of Florida is excluded. Rather, the opposite pattern of larger lizards in southern populations is evident in the absence of Florida populations, and mirrors the general pattern in squamates. Muscle cell size was negatively related to latitude and red blood cell size showed no latitudinal trend outside of Florida. Different patterns in the sizes of the 2 cell types confirm the importance of examining multiple cell types when studying geographic variation in cell size.

  18. Engineering the growth pattern and cell morphology for enhanced PHB production by Escherichia coli.

    Science.gov (United States)

    Wu, Hong; Chen, Jinchun; Chen, Guo-Qiang

    2016-12-01

    E. coli JM109∆envC∆nlpD deleted with genes envC and nlpD responsible for degrading peptidoglycan (PG) led to long filamentous cell shapes. When cell fission ring location genes minC and minD of Escherichia coli were deleted, E. coli JM109∆minCD changed the cell growth pattern from binary division to multiple fissions. Bacterial morphology can be further engineered by overexpressing sulA gene resulting in inhibition on FtsZ, thus generating very long cellular filaments. By overexpressing sulA in E. coli JM109∆envC∆nlpD and E. coli JM109∆minCD harboring poly(3-hydroxybutyrate) (PHB) synthesis operon phbCAB encoded in plasmid pBHR68, respectively, both engineered cells became long filaments and accumulated more PHB compared with the wild-type. Under same shake flask growth conditions, E. coli JM109∆minCD (pBHR68) overexpressing sulA grown in multiple fission pattern accumulated approximately 70 % PHB in 9 g/L cell dry mass (CDM), which was significantly higher than E. coli JM109∆envC∆nlpD and the wild type, that produced 7.6 g/L and 8 g/L CDM containing 64 % and 51 % PHB, respectively. Results demonstrated that a combination of the new division pattern with elongated shape of E. coli improved PHB production. This provided a new vision on the enhanced production of inclusion bodies.

  19. Deep immune profiling by mass cytometry links human T and NK cell differentiation and cytotoxic molecule expression patterns.

    Science.gov (United States)

    Bengsch, Bertram; Ohtani, Takuya; Herati, Ramin Sedaghat; Bovenschen, Niels; Chang, Kyong-Mi; Wherry, E John

    2017-03-19

    The elimination of infected or tumor cells by direct lysis is a key T and NK cell effector function. T and NK cells can kill target cells by coordinated secretion of cytotoxic granules containing one or both pore-forming proteins, perforin and granulysin and combinations of granzyme (Gzm) family effector proteases (in humans: Gzm A, B, K, M and H). Understanding the pattern of expression of cytotoxic molecules and the relationship to different states of T and NK cells may have direct relevance for immune responses in autoimmunity, infectious disease and cancer. Approaches capable of simultaneously evaluating expression of multiple cytotoxic molecules with detailed information on T and NK differentiation state, however, remain limited. Here, we established a high dimensional mass cytometry approach to comprehensively interrogate single cell proteomic expression of cytotoxic programs and lymphocyte differentiation. This assay identified a coordinated expression pattern of cytotoxic molecules linked to CD8 T cell differentiation stages. Coordinated high expression of perforin, granulysin, Gzm A, Gzm B and Gzm M was associated with markers of late effector memory differentiation and expression of chemokine receptor CX3CR1. However, classical gating and dimensionality reduction approaches also identified other discordant patterns of cytotoxic molecule expression in CD8 T cells, including reduced perforin, but high Gzm A, Gzm K and Gzm M expression. When applied to non-CD8 T cells, this assay identified different patterns of cytotoxic molecule co-expression by CD56(hi) versus CD56(dim) defined NK cell developmental stages; in CD4 T cells, low expression of cytotoxic molecules was found mainly in TH1 phenotype cells, but not in Tregs or T follicular helper cells (TFH). Thus, this comprehensive, single cell, proteomic assessment of cytotoxic protein co-expression patterns demonstrates specialized cytotoxic programs in T cells and NK cells linked to their differentiation

  20. The topologic and chronologic patterns of hematopoietic cell seeding in host femoral bone marrow after transplantation.

    Science.gov (United States)

    Askenasy, Nadir; Stein, Jeremiah; Yaniv, Isaac; Farkas, Daniel L

    2003-08-01

    The early stages of homing, seeding, and engraftment of hematopoietic stem and progenitor cells are poorly characterized. We have developed an optical technique that allows in vivo tracking of transplanted, fluorescent-tagged cells in the host femurs. In this study we used fluorescence microscopy to monitor the topologic and chronologic patterns of hematopoietic cell seeding in the femoral bone marrow (BM) of mice. PKH-labeled cells homed to the femur within minutes after injection into a peripheral vein. Most cells drifted within the marrow space and gradually seeded in clusters close to the endosteal surface of the epiphyseal cortex. Three days after transplantation 85% to 94% (14%) of PKH-labeled cells in the femoral marrow were located within 100 microm of the epiphyseal bone surface (P <.001 versus the more central cells), whereas labeled cells were absent in the femoral diaphysis. Primary seeding of juxtaendosteal, epiphyseal marrow occurred independently of recipient conditioning (myeloablated and nonconditioned hosts), donor-recipient antigen disparity, or the phenotype of the injected cells (whole BM and lineage-negative cells) and was consistently observed in secondary recipients of BM-homed cells. Seeding in regions close to the epiphyseal bone was also observed in freshly excised femurs perfused ex vivo and in femurs assessed without prior placement of optical windows, indicating that the site of primary seeding was not affected by surgical placement of optical windows. Four to 5 days after transplantation, cellular clusters appeared in the more central regions of the epiphyses and in the diaphyses. Centrally located cells showed decreased PKH fluorescence, suggesting that they were progeny of the seeding cells, and brightly fluorescent cells (quiescent first-generation seeding cells) were observed close to the bone surface for as long as 24 days after transplantation. These data indicate that the periphery of the femoral marrow hosts primary seeding

  1. Expression pattern of matrix metalloproteinases in human gynecological cancer cell lines

    Directory of Open Access Journals (Sweden)

    Feix Sonja

    2010-10-01

    Full Text Available Abstract Background Matrix metalloproteinases (MMPs are involved in the degradation of protein components of the extracellular matrix and thus play an important role in tumor invasion and metastasis. Their expression is related to the progression of gynecological cancers (e.g. endometrial, cervical or ovarian carcinoma. In this study we investigated the expression pattern of the 23 MMPs, currently known in humans, in different gynecological cancer cell lines. Methods In total, cell lines from three endometrium carcinomas (Ishikawa, HEC-1-A, AN3 CA, three cervical carcinomas (HeLa, Caski, SiHa, three chorioncarcinomas (JEG, JAR, BeWo, two ovarian cancers (BG-1, OAW-42 and one teratocarcinoma (PA-1 were examined. The expression of MMPs was analyzed by RT-PCR, Western blot and gelatin zymography. Results We demonstrated that the cell lines examined can constitutively express a wide variety of MMPs on mRNA and protein level. While MMP-2, -11, -14 and -24 were widely expressed, no expression was seen for MMP-12, -16, -20, -25, -26, -27 in any of the cell lines. A broad range of 16 MMPs could be found in the PA1 cells and thus this cell line could be used as a positive control for general MMP experiments. While the three cervical cancer cell lines expressed 10-14 different MMPs, the median expression in endometrial and choriocarcinoma cells was 7 different enzymes. The two investigated ovarian cancer cell lines showed a distinctive difference in the number of expressed MMPs (2 vs. 10. Conclusions Ishikawa, Caski, OAW-42 and BeWo cell lines could be the best choice for all future experiments on MMP regulation and their role in endometrial, cervical, ovarian or choriocarcinoma development, whereas the teratocarcinoma cell line PA1 could be used as a positive control for general MMP experiments.

  2. Fabrication of 3D cell-laden hydrogel microstructures through photo-mold patterning.

    Science.gov (United States)

    Occhetta, P; Sadr, N; Piraino, F; Redaelli, A; Moretti, M; Rasponi, M

    2013-09-01

    Native tissues are characterized by spatially organized three-dimensional (3D) microscaled units which functionally define cells-cells and cells-extracellular matrix interactions. The ability to engineer biomimetic constructs mimicking these 3D microarchitectures is subject to the control over cell distribution and organization. In the present study we introduce a novel protocol to generate 3D cell laden hydrogel micropatterns with defined size and shape. The method, named photo-mold patterning (PMP), combines hydrogel micromolding within polydimethylsiloxane (PDMS) stamps and photopolymerization through a recently introduced biocompatible ultraviolet (UVA) activated photoinitiator (VA-086). Exploiting PDMS micromolds as geometrical constraints for two methacrylated prepolymers (polyethylene glycol diacrylate and gelatin methacrylate), micrometrically resolved structures were obtained within a 3 min exposure to a low cost and commercially available UVA LED. The PMP was validated both on a continuous cell line (human umbilical vein endothelial cells expressing green fluorescent protein, HUVEC GFP) and on primary human bone marrow stromal cells (BMSCs). HUVEC GFP and BMSCs were exposed to 1.5% w/v VA-086 and UVA light (1 W, 385 nm, distance from sample = 5 cm). Photocrosslinking conditions applied during the PMP did not negatively affect cells viability or specific metabolic activity. Quantitative analyses demonstrated the potentiality of PMP to uniformly embed viable cells within 3D microgels, creating biocompatible and favorable environments for cell proliferation and spreading during a seven days' culture. PMP can thus be considered as a promising and cost effective tool for designing spatially accurate in vitro models and, in perspective, functional constructs.

  3. Differentiation of human embryonic stem cells into pancreatic endoderm in patterned size-controlled clusters.

    Science.gov (United States)

    Van Hoof, Dennis; Mendelsohn, Adam D; Seerke, Rina; Desai, Tejal A; German, Michael S

    2011-05-01

    Pancreatic β-cells function optimally when clustered in islet-like structures. However, nutrient and oxygen deprivation limits the viability of cells at the core of excessively large clusters. Hence, production of functional β-cells from human embryonic stem cells (hESCs) for patients with diabetes would benefit from the growth and differentiation of these cells in size-controlled aggregates. In this study, we controlled cluster size by seeding hESCs onto glass cover slips patterned by the covalent microcontact-printing of laminin in circular patches of 120 μm in diameter. These were used as substrates to grow and differentiate hESCs first into SOX17-positive/SOX7-negative definitive endoderm, after which many clusters released and formed uniformly sized three-dimensional clusters. Both released clusters and those that remained attached differentiated into HNF1β-positive primitive gut tube-like cells with high efficiency. Further differentiation yielded pancreatic endoderm-like cells that co-expressed PDX1 and NKX6.1. Controlling aggregate size allows efficient production of uniformly-clustered pancreatic endocrine precursors for in vivo engraftment or further in vitro maturation.

  4. Differential consolidation and pattern reverberations within episodic cell assemblies in the mouse hippocampus.

    Directory of Open Access Journals (Sweden)

    Remus Oşan

    Full Text Available One hallmark feature of consolidation of episodic memory is that only a fraction of original information, which is usually in a more abstract form, is selected for long-term memory storage. How does the brain perform these differential memory consolidations? To investigate the neural network mechanism that governs this selective consolidation process, we use a set of distinct fearful events to study if and how hippocampal CA1 cells engage in selective memory encoding and consolidation. We show that these distinct episodes activate a unique assembly of CA1 episodic cells, or neural cliques, whose response-selectivity ranges from general-to-specific features. A series of parametric analyses further reveal that post-learning CA1 episodic pattern replays or reverberations are mostly mediated by cells exhibiting event intensity-invariant responses, not by the intensity-sensitive cells. More importantly, reactivation cross-correlations displayed by intensity-invariant cells encoding general episodic features during immediate post-learning period tend to be stronger than those displayed by invariant cells encoding specific features. These differential reactivations within the CA1 episodic cell populations can thus provide the hippocampus with a selection mechanism to consolidate preferentially more generalized knowledge for long-term memory storage.

  5. Piezoelectric Drop-on-Demand Inkjet Printing of Rat Fibroblast Cells: Survivability Study and Pattern Printing

    CERN Document Server

    Li, Er Qiang; Thoroddsen, Sigurdur Tryggvi

    2013-01-01

    A novel piezoelectric, drop-on-demand (DOD) inkjet system has been developed and used to print L929 rat fibroblast cells. We investigate the survivability of the cells subjected to the large stresses during the printing process. These stresses are varied by changing the diameter of the orifice (36 to 119 microns) through which the cells are dispensed, as well as changing the electrical pulse used to drive the piezoelectric element. It is shown that for the smallest 36 microns diameter orifice, cell survival rates fall from 95% to approximately 76% when the ejection velocity is increased from 2 to 16 m/s. This decrease in survival rates is less significant when the larger orifice diameters of 81 microns and 119 microns are used. Analysis shows that there is a clear inverse relationship between cell survival rates and the mean shear rates during drop formation. By using the same printing set-up, fibroblast cells are printed onto alginate and collagen into patterns. Printed cells are cultured over a period of da...

  6. Fire severity and ecosytem responses following crown fires in California shrublands.

    Science.gov (United States)

    Keeley, Jon E; Brennan, Teresa; Pfaff, Anne H

    2008-09-01

    Chaparral shrublands burn in large high-intensity crown fires. Managers interested in how these wildfires affect ecosystem processes generally rely on surrogate measures of fire intensity known as fire severity metrics. In shrublands burned in the autumn of 2003, a study of 250 sites investigated factors determining fire severity and ecosystem responses. Using structural equation modeling we show that stand age, prefire shrub density, and the shortest interval of the prior fire history had significant direct effects on fire severity, explaining > 50% of the variation in severity. Fire severity per se is of interest to resource managers primarily because it is presumed to be an indicator of important ecosystem processes such as vegetative regeneration, community recovery, and erosion. Fire severity contributed relatively little to explaining patterns of regeneration after fire. Two generalizations can be drawn: fire severity effects are mostly shortlived, i.e., by the second year they are greatly diminished, and fire severity may have opposite effects on different functional types. Species richness exhibited a negative relationship to fire severity in the first year, but fire severity impacts were substantially less in the second postfire year and varied by functional type. Much of this relationship was due to alien plants that are sensitive to high fire severity; at all scales from 1 to 1000 m2, the percentage of alien species in the postfire flora declined with increased fire severity. Other aspects of disturbance history are also important determinants of alien cover and richness as both increased with the number of times the site had burned and decreased with time since last fire. A substantial number of studies have shown that remote-sensing indices are correlated with field measurements of fire severity. Across our sites, absolute differenced normalized burn ratio (dNBR) was strongly correlated with field measures of fire severity and with fire history at a

  7. Length-scale mediated adhesion and directed growth of neural cells by surface-patterned poly(ethylene glycol) hydrogels.

    Science.gov (United States)

    Krsko, Peter; McCann, Thomas E; Thach, Thu-Trang; Laabs, Tracy L; Geller, Herbert M; Libera, Matthew R

    2009-02-01

    We engineered surfaces that permit the adhesion and directed growth of neuronal cell processes but that prevent the adhesion of astrocytes. This effect was achieved based on the spatial distribution of sub-micron-sized cell-repulsive poly(ethylene glycol) [PEG] hydrogels patterned on an otherwise cell-adhesive substrate. Patterns were identified that promoted cellular responses ranging from complete non-attachment, selective attachment, and directed growth at both cellular and subcellular length scales. At the highest patterning density where the individual hydrogels almost overlapped, there was no cellular adhesion. As the spacing between individual hydrogels was increased, patterns were identified where neurites could grow on the adhesive surface between hydrogels while astrocytes were unable to adhere. Patterns such as lines or arrays were identified that could direct the growth of these subcellular neuronal processes. At higher hydrogel spacings, both neurons and astrocytes adhered and grew in a manner approaching that of unpatterned control surfaces. Patterned lines could once again direct growth at cellular length scales. Significantly, we have demonstrated that the patterning of sub-micron/nano scale cell-repulsive features at microscale lengths on an otherwise cell-adhesive surface can differently control the adhesion and growth of cells and cell processes based on the difference in their characteristic sizes. This concept could potentially be applied to an implantable nerve-guidance device that would selectively enable regrowing axons to bridge a spinal-cord injury without interference from the glial scar.

  8. Swarming and complex pattern formation in Paenibacillus vortex studied by imaging and tracking cells

    Directory of Open Access Journals (Sweden)

    Jacob Eshel

    2008-02-01

    Full Text Available Abstract Background Swarming motility allows microorganisms to move rapidly over surfaces. The Gram-positive bacterium Paenibacillus vortex exhibits advanced cooperative motility on agar plates resulting in intricate colonial patterns with geometries that are highly sensitive to the environment. The cellular mechanisms that underpin the complex multicellular organization of such a simple organism are not well understood. Results Swarming by P. vortex was studied by real-time light microscopy, by in situ scanning electron microscopy and by tracking the spread of antibiotic-resistant cells within antibiotic-sensitive colonies. When swarming, P. vortex was found to be peritrichously flagellated. Swarming by the curved cells of P. vortex occurred on an extremely wide range of media and agar concentrations (0.3 to 2.2% w/v. At high agar concentrations (> 1% w/v rotating colonies formed that could be detached from the main mass of cells by withdrawal of cells into the latter. On lower percentage agars, cells moved in an extended network composed of interconnected "snakes" with short-term collision avoidance and sensitivity to extracts from swarming cells. P. vortex formed single Petri dish-wide "supercolonies" with a colony-wide exchange of motile cells. Swarming cells were coupled by rapidly forming, reversible and non-rigid connections to form a loose raft, apparently connected via flagella. Inhibitors of swarming (p-Nitrophenylglycerol and Congo Red were identified. Mitomycin C was used to trigger filamentation without inhibiting growth or swarming; this facilitated dissection of the detail of swarming. Mitomycin C treatment resulted in malcoordinated swarming and abortive side branch formation and a strong tendency by a subpopulation of the cells to form minimal rotating aggregates of only a few cells. Conclusion P. vortex creates complex macroscopic colonies within which there is considerable reflux and movement and interaction of cells. Cell

  9. Simultaneous engagement of mechanical stretching and surface pattern promotes cardiomyogenic differentiation of human mesenchymal stem cells.

    Science.gov (United States)

    Gu, Seo Rin; Kang, Yun Gyeong; Shin, Ji Won; Shin, Jung-Woog

    2017-02-01

    It has been widely recognized and proved that biophysical factors for mimicking in vivo conditions should be also considered to have stem cells differentiated into desired cell type in vitro along with biochemical factors. Biophysical factors include substrate and biomechanical conditions. This study focused on the effect of biomimetic mechanical stretching along with changes in substrate topography to influence on cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs). Elastic micropatterned substrates were made to mimic the geometric conditions surrounding cells in vivo. To mimic biomechanical conditions due to beating of the heart, mechanical stretching was applied parallel to the direction of the pattern (10% elongation, 0.5 Hz, 4 h/day). Suberoylanilide hydroxamic acid (SAHA) was used as a biochemical factor. The micropatterned substrate was found more effective in the alignment of cytoskeleton and cardiomyogenic differentiation compared with flat substrate. Significantly higher expression levels of related markers [GATA binding protein 4 (GATA4), troponin I, troponin T, natriuretic peptide A (NPPA)] were observed when mechanical stretching was engaged on micropatterned substrate. In addition, 4 days of mechanical stretching was associated with higher levels of expression than 2 days of stretching. These results indicate that simultaneous engagement of biomimetic environment such as substrate pattern and mechanical stimuli effectively promotes the cardiomyogenic differentiation of hMSCs in vitro. The suggested method which tried to mimic in vivo microenvironment would provide systematic investigation to control cardiomyogenic differentiation of hMSCs.

  10. Cell Death-Associated Molecular-Pattern Molecules: Inflammatory Signaling and Control

    Directory of Open Access Journals (Sweden)

    Beatriz Sangiuliano

    2014-01-01

    Full Text Available Apoptosis, necroptosis, and pyroptosis are different cellular death programs characterized in organs and tissues as consequence of microbes infection, cell stress, injury, and chemotherapeutics exposure. Dying and death cells release a variety of self-proteins and bioactive chemicals originated from cytosol, nucleus, endoplasmic reticulum, and mitochondria. These endogenous factors are named cell death-associated molecular-pattern (CDAMP, damage-associated molecular-pattern (DAMP molecules, and alarmins. Some of them cooperate or act as important initial or delayed inflammatory mediators upon binding to diverse membrane and cytosolic receptors coupled to signaling pathways for the activation of the inflammasome platforms and NF-κB multiprotein complexes. Current studies show that the nonprotein thiols and thiol-regulating enzymes as well as highly diffusible prooxidant reactive oxygen and nitrogen species released together in extracellular inflammatory milieu play essential role in controlling pro- and anti-inflammatory activities of CDAMP/DAMP and alarmins. Here, we provide an overview of these emerging concepts and mechanisms of triggering and maintenance of tissue inflammation under massive death of cells.

  11. From pluripotency to forebrain patterning: an in vitro journey astride embryonic stem cells.

    Science.gov (United States)

    Lupo, Giuseppe; Bertacchi, Michele; Carucci, Nicoletta; Augusti-Tocco, Gabriella; Biagioni, Stefano; Cremisi, Federico

    2014-08-01

    Embryonic stem cells (ESCs) have been used extensively as in vitro models of neural development and disease, with special efforts towards their conversion into forebrain progenitors and neurons. The forebrain is the most complex brain region, giving rise to several fundamental structures, such as the cerebral cortex, the hypothalamus, and the retina. Due to the multiplicity of signaling pathways playing different roles at distinct times of embryonic development, the specification and patterning of forebrain has been difficult to study in vivo. Research performed on ESCs in vitro has provided a large body of evidence to complement work in model organisms, but these studies have often been focused more on cell type production than on cell fate regulation. In this review, we systematically reassess the current literature in the field of forebrain development in mouse and human ESCs with a focus on the molecular mechanisms of early cell fate decisions, taking into consideration the specific culture conditions, exogenous and endogenous molecular cues as described in the original studies. The resulting model of early forebrain induction and patterning provides a useful framework for further studies aimed at reconstructing forebrain development in vitro for basic research or therapy.

  12. Comparison of the lectin-binding pattern in different human melanoma cell lines.

    Science.gov (United States)

    Lityńska, A; Przybyło, M; Pocheć, E; Hoja-Łukowicz, D; Ciołczyk, D; Laidler, P; Gil, D

    2001-06-01

    Glycosylation is generally altered in tumour cells in comparison with their normal counterparts. These alterations are thought to be important because they contribute to the abnormal behaviour of cancer cells. Therefore, we have comparatively analysed the glycoproteins in cell extracts from human melanoma (primary site--WM35; metastatic sites-- WM239, WM9 and A375) cell lines using sodium dodecyl sulphate-polyacrylamide gel electrophoresis and lectin staining. The glycoprotein pattern of the WM35 line differed from that of the other cell lines in having less proteins that reacted with Sambucus nigra, Maackia amurensis and Phaseolus vulgaris agglutinins. A glycoprotein of about 70 kDa had a significantly increased reaction with Sambucus nigra agglutinin in all the cell lines from metastatic sites. In the WM9, WM239 and A375 cell lines, additional bands (160-100 kDa) were stained with Phaseolus vulgaris agglutinin, suggesting that cells from metastatic sites contain more glycoproteins with beta1-6 branches. On the other hand, only minor changes in the reaction with Galanthus nivalis agglutinin, a mannose-specific lectin, were detected. Among the proteins showing different lectin staining, one, with an apparent molecular weight of 133 kDa, was recognized by antibodies as N-cadherin. The present results suggest that in human melanoma the expression of branched and sialylated complex type N-oligosaccharides consistently increased in cells from metastatic sites, and support the view that carbohydrates are associated with the acquisition of the metastatic potential of tumour cells.

  13. Identification of tissue-specific cell death using methylation patterns of circulating DNA.

    Science.gov (United States)

    Lehmann-Werman, Roni; Neiman, Daniel; Zemmour, Hai; Moss, Joshua; Magenheim, Judith; Vaknin-Dembinsky, Adi; Rubertsson, Sten; Nellgård, Bengt; Blennow, Kaj; Zetterberg, Henrik; Spalding, Kirsty; Haller, Michael J; Wasserfall, Clive H; Schatz, Desmond A; Greenbaum, Carla J; Dorrell, Craig; Grompe, Markus; Zick, Aviad; Hubert, Ayala; Maoz, Myriam; Fendrich, Volker; Bartsch, Detlef K; Golan, Talia; Ben Sasson, Shmuel A; Zamir, Gideon; Razin, Aharon; Cedar, Howard; Shapiro, A M James; Glaser, Benjamin; Shemer, Ruth; Dor, Yuval

    2016-03-29

    Minimally invasive detection of cell death could prove an invaluable resource in many physiologic and pathologic situations. Cell-free circulating DNA (cfDNA) released from dying cells is emerging as a diagnostic tool for monitoring cancer dynamics and graft failure. However, existing methods rely on differences in DNA sequences in source tissues, so that cell death cannot be identified in tissues with a normal genome. We developed a method of detecting tissue-specific cell death in humans based on tissue-specific methylation patterns in cfDNA. We interrogated tissue-specific methylome databases to identify cell type-specific DNA methylation signatures and developed a method to detect these signatures in mixed DNA samples. We isolated cfDNA from plasma or serum of donors, treated the cfDNA with bisulfite, PCR-amplified the cfDNA, and sequenced it to quantify cfDNA carrying the methylation markers of the cell type of interest. Pancreatic β-cell DNA was identified in the circulation of patients with recently diagnosed type-1 diabetes and islet-graft recipients; oligodendrocyte DNA was identified in patients with relapsing multiple sclerosis; neuronal/glial DNA was identified in patients after traumatic brain injury or cardiac arrest; and exocrine pancreas DNA was identified in patients with pancreatic cancer or pancreatitis. This proof-of-concept study demonstrates that the tissue origins of cfDNA and thus the rate of death of specific cell types can be determined in humans. The approach can be adapted to identify cfDNA derived from any cell type in the body, offering a minimally invasive window for diagnosing and monitoring a broad spectrum of human pathologies as well as providing a better understanding of normal tissue dynamics.

  14. Fire-driven alien invasion in a fire-adapted ecosystem

    Science.gov (United States)

    Keeley, Jon E.; Brennan, Teresa J.

    2012-01-01

    Disturbance plays a key role in many alien plant invasions. However, often the main driver of invasion is not disturbance per se but alterations in the disturbance regime. In some fire-adapted shrublands, the community is highly resilient to infrequent, high-intensity fires, but changes in the fire regime that result in shorter fire intervals may make these communities more susceptible to alien plant invasions. This study examines several wildfire events that resulted in short fire intervals in California chaparral shrublands. In one study, we compared postfire recovery patterns in sites with different prefire stand ages (3 and 24 years), and in another study we compared sites that had burned once in four years with sites that had burned twice in this period. The population size of the dominant native shrub Adenostoma fasciculatum was drastically reduced following fire in the 3-year sites relative to the 24-year sites. The 3-year sites had much greater alien plant cover and significantly lower plant diversity than the 24-year sites. In a separate study, repeat fires four years apart on the same sites showed that annual species increased significantly after the second fire, and alien annuals far outnumbered native annuals. Aliens included both annual grasses and annual forbs and were negatively correlated with woody plant cover. Native woody species regenerated well after the first fire but declined after the second fire, and one obligate seeding shrub was extirpated from two sites by the repeat fires. It is concluded that some fire-adapted shrublands are vulnerable to changes in fire regime, and this can lead to a loss of native diversity and put the community on a trajectory towards type conversion from a woody to an herbaceous system. Such changes result in alterations in the proportion of natives to non-natives, changes in functional types from deeply rooted shrubs to shallow rooted grasses and forbs, increased fire frequency due to the increase in fine fuels

  15. Impact of Substrate Bias on Fixed-Pattern-Noise in Active Pixel Sensor Cells

    Science.gov (United States)

    Terauchi, Mamoru

    2007-11-01

    The effect of substrate (body) bias on fixed-pattern-noise (FPN) in active pixel sensor (APS) cells is studied. Through measuring test devices consisting of two metal-oxide-semiconductor field-effect transistors (MOSFETs) connected in series with each of the transistors located in the same well region, it has been revealed that substrate bias, which is inevitably applied in a normal circuit configuration in conventional APS cells, worsens the characteristics fluctuation in source-follower amplifiers in APS cells, leading to FPN that cannot be mitigated by conventional correction methods such as correlated double sampling. In addition it has been confirmed that the current-voltage characteristics of logarithmic converters, each of which is realized using a MOSFET with gate and drain terminals connected together, are also affected by substrate bias, resulting in increased characteristics fluctuation as compared with the case with no substrate bias.

  16. Specific recognition of AVR4 and AVR9 results in distinct patterns of hypersensitive cell death in tomato, but similar patterns of defence-related gene expression

    NARCIS (Netherlands)

    Cai, X.; Takken, F.L.W.; Joosten, M.H.A.J.; Wit, De P.J.G.M.

    2001-01-01

    Hypersensitive cell death occurs in tomato seedlings that are derived from a cross between plants that express a resistance (Cf) gene against the pathogenic fungus Cladosporium fulvum and plants that contain the matching avirulence (Avr) gene originating from this fungus. The pattern of Cf-9/Avr9- a

  17. Wave Patterns in Cell Membrane and Actin Cortex Uncoupled from Chemotactic Signals.

    Science.gov (United States)

    Gerisch, Günther; Ecke, Mary

    2016-01-01

    When cells of Dictyostelium discoideum orientate in a gradient of chemoattractant, they are polarized into a protruding front pointing toward the source of attractant, and into a retracting tail. Under the control of chemotactic signal inputs, Ras is activated and PIP3 is synthesized at the front, while the PIP3-degrading phosphatase PTEN decorates the tail region. As a result of signal transduction, actin filaments assemble at the front into dendritic structures associated with the Arp2/3 complex, in contrast to the tail region where a loose actin meshwork is associated with myosin-II and cortexillin, an antiparallel actin-bundling protein. In axenically growing strains of D. discoideum, wave patterns built by the same components evolve in the absence of any external signal input. Since these autonomously generated patterns are constrained to the plane of the substrate-attached cell surface, they are optimally suited to the optical analysis of state transitions between front-like and tail-like states of the membrane and the actin cortex. Here, we describe imaging techniques using fluorescent proteins to probe for the state of the membrane, the reorganization of the actin network, and the dynamics of wave patterns.

  18. Analysis of spatial relationships in three dimensions: tools for the study of nerve cell patterning

    Directory of Open Access Journals (Sweden)

    Raven Mary A

    2008-07-01

    Full Text Available Abstract Background Multiple technologies have been brought to bear on understanding the three-dimensional morphology of individual neurons and glia within the brain, but little progress has been made on understanding the rules controlling cellular patterning. We describe new matlab-based software tools, now available to the scientific community, permitting the calculation of spatial statistics associated with 3D point patterns. The analyses are largely derived from the Delaunay tessellation of the field, including the nearest neighbor and Voronoi domain analyses, and from the spatial autocorrelogram. Results Our tools enable the analysis of the spatial relationship between neurons within the central nervous system in 3D, and permit the modeling of these fields based on lattice-like simulations, and on simulations of minimal-distance spacing rules. Here we demonstrate the utility of our analysis methods to discriminate between two different simulated neuronal populations. Conclusion Together, these tools can be used to reveal the presence of nerve cell patterning and to model its foundation, in turn informing on the potential developmental mechanisms that govern its establishment. Furthermore, in conjunction with analyses of dendritic morphology, they can be used to determine the degree of dendritic coverage within a volume of tissue exhibited by mature nerve cells.

  19. Sub-sets of cancer stem cells differ intrinsically in their patterns of oxygen metabolism.

    Directory of Open Access Journals (Sweden)

    Luke Gammon

    Full Text Available The glycolytic response of hypoxic cells is primarily mediated by the hypoxia inducible factor alpha (HIF-1α but even in the presence of abundant oxygen tumours typically show high rates of glycolysis. Higher levels of HIF-1α in tumours are associated with a poorer prognosis and up-regulation of markers of epithelial mesenchymal transition (EMT due to HIF-1α actions. We have recently shown that EMT occurs within the CD44(high cancer stem cell (CSC fraction and that epithelial and EMT CSCs are distinguished by high and low ESA expression, respectively. We here show that hypoxia induces a marked shift of the CSC fraction towards EMT leading to altered cell morphology, an increased proportion of CD44(high/ESA(low cells, patterns of gene expression typical of EMT, and enhanced sphere-forming ability. The size of EMT fractions returned to control levels in normoxia indicating a reversible process. Surprisingly, however, even under normoxic conditions a fraction of EMT CSCs was present and maintained high levels of HIF-1α, apparently due to actions of cytokines such as TNFα. Functionally, this EMT CSC fraction showed decreased mitochondrial mass and membrane potential, consumed far less oxygen per cell, and produced markedly reduced levels of reactive oxygen species (ROS. These differences in the patterns of oxygen metabolism of sub-fractions of tumour cells provide an explanation for the general therapeutic resistance of CSCs and for the even greater resistance of EMT CSCs. They also identify potential mechanisms for manipulation of CSCs.

  20. Dendritic Arborization Patterns of Small Juxtaglomerular Cell Subtypes within the Rodent Olfactory Bulb

    Science.gov (United States)

    Bywalez, Wolfgang G.; Ona-Jodar, Tiffany; Lukas, Michael; Ninkovic, Jovica; Egger, Veronica

    2017-01-01

    Within the glomerular layer of the rodent olfactory bulb, numerous subtypes of local interneurons contribute to early processing of incoming sensory information. Here we have investigated dopaminergic and other small local juxtaglomerular cells in rats and mice and characterized their dendritic arborization pattern with respect to individual glomeruli by fluorescent labeling via patching and reconstruction of dendrites and glomerular contours from two-photon imaging data. Dopaminergic neurons were identified in a transgenic mouse line where the expression of dopamine transporter (DAT) was labeled with GFP. Among the DAT+ cells we found a small short-axon cell (SAC) subtype featuring hitherto undescribed dendritic specializations. These densely ramifying structures clasped mostly around somata of other juxtaglomerular neurons, which were also small, non-dopaminergic and to a large extent non-GABAergic. Clasping SACs were observed also in wild-type mice and juvenile rats. In DAT+ SAC dendrites, single backpropagating action potentials evoked robust calcium entry throughout both clasping and non-clasping compartments. Besides clasping SACs, most other small neurons either corresponded to the classical periglomerular cell type (PGCs), which was never DAT+, or were undersized cells with a small dendritic tree and low excitability. Aside from the presence of clasps in SAC dendrites, many descriptors of dendritic morphology such as the number of dendrites and the extent of branching were not significantly different between clasping SACs and PGCs. However, a detailed morphometric analysis in relation to glomerular contours revealed that the dendrites of clasping SACs arborized mostly in the juxtaglomerular space and never entered more than one glomerulus (if at all), whereas most PGC dendrites were restricted to their parent glomerulus, similar to the apical tufts of mitral cells. These complementary arborization patterns might underlie a highly complementary functional

  1. Diversity and species composition of West African ungulate assemblages: effects of fire, climate and soil

    NARCIS (Netherlands)

    Klop, L.F.; Prins, H.H.T.

    2008-01-01

    Aim Anthropogenic fires are a major component of the ecology of rangelands throughout the world. To assess the effects of these fires on the diversity patterns of herbivores, we related gradients in fire occurrence, climate and soil fertility to patterns in alpha and beta diversity of African ungula

  2. Cell polarity and patterning by PIN trafficking through early endosomal compartments in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Hirokazu Tanaka

    2013-05-01

    Full Text Available PIN-FORMED (PIN proteins localize asymmetrically at the plasma membrane and mediate intercellular polar transport of the plant hormone auxin that is crucial for a multitude of developmental processes in plants. PIN localization is under extensive control by environmental or developmental cues, but mechanisms regulating PIN localization are not fully understood. Here we show that early endosomal components ARF GEF BEN1 and newly identified Sec1/Munc18 family protein BEN2 are involved in distinct steps of early endosomal trafficking. BEN1 and BEN2 are collectively required for polar PIN localization, for their dynamic repolarization, and consequently for auxin activity gradient formation and auxin-related developmental processes including embryonic patterning, organogenesis, and vasculature venation patterning. These results show that early endosomal trafficking is crucial for cell polarity and auxin-dependent regulation of plant architecture.

  3. Fire-Walking

    Science.gov (United States)

    Willey, David

    2010-01-01

    This article gives a brief history of fire-walking and then deals with the physics behind fire-walking. The author has performed approximately 50 fire-walks, took the data for the world's hottest fire-walk and was, at one time, a world record holder for the longest fire-walk (www.dwilley.com/HDATLTW/Record_Making_Firewalks.html). He currently…

  4. GLUCOSE METABOLITE PATTERNS AS MARKERS OF FUNCTIONAL DIFFERENTIATION IN FRESHLY ISOLATED AND CULTURED MOUSE MAMMARY EPITHELIAL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Emerman, J.T.; Bartley, J.C.; Bissell, M.J.

    1980-06-01

    In the mammary gland of nonruminant animals, glucose is utilized in a characteristic and unique way during lactation. We have measured the incorporation of glucose carbon from [U-{sup 14}C] glucose into intermediary metabolites and metabolic products in mammary epithelial cells from virgin, pregnant, and lactating mice and demonstrate that glucose metabolite patterns can be used to recognize stages of differentiated function. For these cells, the rates of synthesis of glycogen and lactose, the ratio of lactate to alanine, and the ratio of citrate to malate were important parameters in identifying the degree of expression of differentiation. We further show that these patterns can be used as markers to determine the differentiated state of cultured mammary epithelial cells. Cells maintained on plastic substrates lose their distinctive glucose metabolite patterns while those on floating collagen gels do not. Cells from pregnant mice have a pattern similar to freshly isolated cells from pregnant mice. The pattern of cells from lactating mice is different from that of the cells of origin, and resembles that of the cells from pregnant mice. Our findings suggest that the floating collagen gels under the culture conditions used in these experiments provide an environment for the functional expression of the pregnant state, while additional factors are needed for the expression of the lactating state.

  5. Microfluidic-based patterning of embryonic stem cells for in vitro development studies.

    Science.gov (United States)

    Suri, Shalu; Singh, Ankur; Nguyen, Anh H; Bratt-Leal, Andres M; McDevitt, Todd C; Lu, Hang

    2013-12-07

    In vitro recapitulation of mammalian embryogenesis and examination of the emerging behaviours of embryonic structures require both the means to engineer complexity and accurately assess phenotypes of multicellular aggregates. Current approaches to study multicellular populations in 3D configurations are limited by the inability to create complex (i.e. spatially heterogeneous) environments in a reproducible manner with high fidelity thus impeding the ability to engineer microenvironments and combinations of cells with similar complexity to that found during morphogenic processes such as development, remodelling and wound healing. Here, we develop a multicellular embryoid body (EB) fusion technique as a higher-throughput in vitro tool, compared to a manual assembly, to generate developmentally relevant embryonic patterns. We describe the physical principles of the EB fusion microfluidic device design; we demonstrate that >60 conjoined EBs can be generated overnight and emulate a development process analogous to mouse gastrulation during early embryogenesis. Using temporal delivery of bone morphogenic protein 4 (BMP4) to embryoid bodies, we recapitulate embryonic day 6.5 (E6.5) during mouse embryo development with induced mesoderm differentiation in murine embryonic stem cells leading to expression of Brachyury-T-green fluorescent protein (T-GFP), an indicator of primitive streak development and mesoderm differentiation during gastrulation. The proposed microfluidic approach could be used to manipulate hundreds or more of individual embryonic cell aggregates in a rapid fashion, thereby allowing controlled differentiation patterns in fused multicellular assemblies to generate complex yet spatially controlled microenvironments.

  6. Protein coverage on polymer nanolayers leading to mesenchymal stem cell patterning.

    Science.gov (United States)

    You, Jungmok; Yoshida, Akihito; Heo, June Seok; Kim, Han-Soo; Kim, Hyun Ok; Tamada, Kaoru; Kim, Eunkyoung

    2011-10-21

    Interactions of gelatin and albumin with a photo-reactive diphenylamino-s-triazine bridged p-phenylene vinylene polymer (DTOPV) were examined by using surface plasmon resonance (SPR) spectroscopy to explore the effect of the polymer structure on protein coverage of DTOPV nanofilms. The SPR data revealed a significant increase of gelatin adsorption on UV-DTOPV nanofilms, while the adsorption of albumin was decreased by UV exposure in the time frame of the experiment. We also found that the selective adsorption of these proteins was highly dependent on the protein concentration; the highest selectivity of protein adsorption was obtained at the lowest concentration (3.5 μg ml(-1)), while no selective adsorption was confirmed at high concentrations (350 and 1000 μg ml(-1)). The selective attachment of mesenchymal stem cells (MSCs) was directly correlated with the selective adsorption of these proteins onto DTOPV nanofilms. The MSCs attachment onto UV-DTOPV films was promoted with only small mass coverage of gelatin, which led to MSC patterning onto the patterned DTOPV nanofilms successfully. The role of cell adhesion proteins that we found in this study will be a clue to elucidate the complex response of biomolecules on functional polymer nanolayers, and contribute to build up biocompatible surfaces on various advanced materials for the sake of cell engineering and medical implants.

  7. A Single Cell Extraction Chip Using Vibration-Induced Whirling Flow and a Thermo-Responsive Gel Pattern

    Directory of Open Access Journals (Sweden)

    Takeshi Hayakawa

    2014-09-01

    Full Text Available We propose a single cell extraction chip with an open structure, which utilizes vibration-induced whirling flow and a single cell catcher. By applying a circular vibration to a micropillar array spiral pattern, a whirling flow is induced around the micropillars, and target cells are transported towards the single cell catcher placed at the center of the spiral. The single cell catcher is composed of a single-cell-sized hole pattern of thermo-responsive gel. The gel swells at low temperatures (≲32 ◦C and shrinks at high temperatures (≳32 ◦C, therefore, its volume expansion can be controlled by an integrated microheater. When the microheater is turned on, a single cell is trapped by the hole pattern of the single cell catcher. Then, when the microheater is turned off, the single cell catcher is cooled by the ambient temperature. The gel swells at this temperature, and the hole closes to catch the single cell. The caught cell can then be released into culture wells on a microtiter plate by heating the gel again. We conducted single cell extraction with the proposed chip and achieved a 60% success rate, of which 61% cells yielded live cells.

  8. Frequency patterns of T-cell exposed motifs in immunoglobulin heavy chain peptides presented by MHCs

    Directory of Open Access Journals (Sweden)

    Robert D. Bremel

    2014-10-01

    Full Text Available Immunoglobulins are highly diverse protein sequences that are processed and presented to T-cells by B-cells and other antigen presenting cells. We examined a large dataset of immunoglobulin heavy chain variable regions (IGHV to assess the diversity of T-cell exposed motifs (TCEM. TCEM comprise those amino acids in a MHC-bound peptide which face outwards, surrounded by the MHC histotope, and which engage the T-cell receptor. Within IGHV there is a distinct pattern of predicted MHC class II binding and a very high frequency of re-use of the TCEMs. The re-use frequency indicates that only a limited number of different cognate T-cells are required to engage many different clonal B-cells. The amino acids in each outward-facing TCEM are intercalated with the amino acids of inward-facing MHC groove-exposed motifs (GEM. Different GEM may have differing, allele-specific, MHC binding affinities. The intercalation of TCEM and GEM in a peptide allows for a vast combinatorial repertoire of epitopes, each eliciting a different response. Outcome of T-cell receptor binding is determined by overall signal strength, which is a function of the number of responding T-cells and the duration of engagement. Hence, the frequency of T-cell exposed motif re-use appears to be an important determinant of whether a T-cell response is stimulatory or suppressive. The frequency distribution of TCEMs implies that somatic hypermutation is followed by clonal expansion that develop along repeated pathways. The observations of TCEM and GEM derived from immunoglobulins suggest a relatively simple, yet powerful, mechanism to correlate T-cell polyspecificity, through re-use of TCEMs, with a very high degree of specificity achieved by combination with a diversity of GEMs. The frequency profile of TCEMs also points to an economical mechanism for maintaining T-cell memory, recall, and self-discrimination based on an endogenously generated profile of motifs.

  9. Fire and deforestation dynamics in Amazonia (1973–2014)

    Science.gov (United States)

    Field, Robert D.; van der Werf, Guido R.; Estrada de Wagt, Ivan A.; Houghton, Richard A.; Rizzo, Luciana V.; Artaxo, Paulo; Tsigaridis, Kostas

    2017-01-01

    Abstract Consistent long‐term estimates of fire emissions are important to understand the changing role of fire in the global carbon cycle and to assess the relative importance of humans and climate in shaping fire regimes. However, there is limited information on fire emissions from before the satellite era. We show that in the Amazon region, including the Arc of Deforestation and Bolivia, visibility observations derived from weather stations could explain 61% of the variability in satellite‐based estimates of bottom‐up fire emissions since 1997 and 42% of the variability in satellite‐based estimates of total column carbon monoxide concentrations since 2001. This enabled us to reconstruct the fire history of this region since 1973 when visibility information became available. Our estimates indicate that until 1987 relatively few fires occurred in this region and that fire emissions increased rapidly over the 1990s. We found that this pattern agreed reasonably well with forest loss data sets, indicating that although natural fires may occur here, deforestation and degradation were the main cause of fires. Compared to fire emissions estimates based on Food and Agricultural Organization's Global Forest and Resources Assessment data, our estimates were substantially lower up to the 1990s, after which they were more in line. These visibility‐based fire emissions data set can help constrain dynamic global vegetation models and atmospheric models with a better representation of the complex fire regime in this region. PMID:28286373

  10. Fire and deforestation dynamics in Amazonia (1973-2014).

    Science.gov (United States)

    van Marle, Margreet J E; Field, Robert D; van der Werf, Guido R; Estrada de Wagt, Ivan A; Houghton, Richard A; Rizzo, Luciana V; Artaxo, Paulo; Tsigaridis, Kostas

    2017-01-01

    Consistent long-term estimates of fire emissions are important to understand the changing role of fire in the global carbon cycle and to assess the relative importance of humans and climate in shaping fire regimes. However, there is limited information on fire emissions from before the satellite era. We show that in the Amazon region, including the Arc of Deforestation and Bolivia, visibility observations derived from weather stations could explain 61% of the variability in satellite-based estimates of bottom-up fire emissions since 1997 and 42% of the variability in satellite-based estimates of total column carbon monoxide concentrations since 2001. This enabled us to reconstruct the fire history of this region since 1973 when visibility information became available. Our estimates indicate that until 1987 relatively few fires occurred in this region and that fire emissions increased rapidly over the 1990s. We found that this pattern agreed reasonably well with forest loss data sets, indicating that although natural fires may occur here, deforestation and degradation were the main cause of fires. Compared to fire emissions estimates based on Food and Agricultural Organization's Global Forest and Resources Assessment data, our estimates were substantially lower up to the 1990s, after which they were more in line. These visibility-based fire emissions data set can help constrain dynamic global vegetation models and atmospheric models with a better representation of the complex fire regime in this region.

  11. Fire fatality study: demographics of fire victims.

    Science.gov (United States)

    Barillo, D J; Goode, R

    1996-03-01

    Injury or death caused by fire is frequent and largely preventable. This study was undertaken to define the populations, locations, times and behaviours associated with fatal fires. Seven hundred and twenty-seven fatalities occurring within the State of New Jersey, between the years 1985 and 1991, were examined retrospectively. Most deaths were attributed to a combination of smoke inhalation and burn injury. Five hundred and seventy-four fatalities occurred in residential fires. Smoking materials were the most common source of ignition for residential fires. More than half of the fatal residential fires started between the hours of 11 p.m. and 7 a.m. Children and the elderly represented a disproportionate percentage of fire victims. Victims under the age of 11 years or over the age of 70 years constituted 22.1 per cent of the state population but 39.5 per cent of all fire fatalities. Fire-prevention efforts should target home fire safety, and should concentrate on children and the elderly. The development of fire-safe smoking materials should be encouraged.

  12. Mutation Pattern of Paired Immunoglobulin Heavy and Light Variable Domains in Chronic Lymphocytic Leukemia B Cells

    KAUST Repository

    Ghiotto, Fabio

    2011-01-01

    B-cell chronic lymphocytic leukemia (CLL) patients display leukemic clones bearing either germline or somatically mutated immunoglobulin heavy variable (IGHV ) genes. Most information on CLL immunoglobulins (Igs), such as the definition of stereotyped B-cell receptors (BCRs), was derived from germline unmutated Igs. In particular, detailed studies on the distribution and nature of mutations in paired heavy- and light-chain domains of CLL clones bearing mutated Igs are lacking. To address the somatic hyper-mutation dynamics of CLL Igs, we analyzed the mutation pattern of paired IGHV-diversity-joining (IGHV-D-J ) and immunoglobulin kappa/lambda variable-joining (IGK/LV-J ) rearrangements of 193 leukemic clones that displayed ≥ 2% mutations in at least one of the two immunoglobulin variable (IGV ) genes (IGHV and/or IGK/LV ). The relationship between the mutation frequency in IGHV and IGK/LV complementarity determining regions (CDRs) and framework regions (FRs) was evaluated by correlation analysis. Replacement (R) mutation frequency within IGK/LV chain CDRs correlated significantly with mutation frequency of paired IGHV CDRs in λ but not κ isotype CLL clones. CDRs of IGKV-J rearrangements displayed a lower percentage of R mutations than IGHVs. The frequency/pattern of mutations in kappa CLL Igs differed also from that in κ-expressing normal B cells described in the literature. Instead, the mutation frequency within the FRs of IGHV and either IGKV or IGLV was correlated. Notably, the amount of diversity introduced by replaced amino acids was comparable between IGHVs and IGKVs. The data indicate a different mutation pattern between κ and λ isotype CLL clones and suggest an antigenic selection that, in κ samples, operates against CDR variation.

  13. Expression pattern of epithelial cell adhesion molecule on normal and malignant colon tissues

    Institute of Scientific and Technical Information of China (English)

    Xin Xie; Chun-Yan Wang; Yun-Xin Cao; Wei Wang; Ran Zhuang; Li-Hua Chen; Na-Na Dang; Liang Fang; Bo-Quan Jin

    2005-01-01

    AIM: To investigate the expression pattern of epithelial cell adhesion molecule (Ep-CAM) on normal and malignant colon tissues to evaluate its diagnostic and therapeutic significance.METHODS: cDNA encoding Ep-CAv extracellular domain was cloned by reverse transcription-polymerase chain reaction (RT-PCR) from excised malignant colon tissues and inserted into a glutathione S-transferase (GST)-tagged vector. EpCAM-GST fusion protein was induced by isopropyl-β-D-thiogalactopyranoside (IPTG) and purified with glutathionesepharose. The Ep-CAM-GST fusion protein was mixed with Freund's adjuvant and Balb/c mice were immunized with it. Sp2/0 myeloma cells were fused with the spleen cells of the immunized mice. After having selected by indirect ELISA, the anti-Ep-CAM monoclonal antibodies (NAbs) were generated and the corresponding ascites were obtained.Finally, the human colon carcinoma tissue array prepared from seventy individual patients was stained with the antiEp-CAM NAbs.RESULTS: The isolated Ep-CAM cDNA sequence was identical to the data in GenBank. The expressed fusion protein was almost soluble and had a molecular weight (NW) of 53 ku.Four NAbs against Ep-CAM were obtained and designated as FMU-Ep1, FMU-Ep2, FMU-Ep3 and FMU-Ep4 respectively.Among them, FMU-Ep4 could recognize the natural EpCAM on Colo205 and SW480 cells, and all of them could be used for immunohistochemical staining of tissue sections.It was found that Ep-CAM was distributed differently in normal and various malignant colon tissues, including squamous cell carcinoma, signet-ring cell carcinoma and adenocarcinoma.In normal colon gland epithelia, Ep-CAM antigen was mainly distributed on the basolateral membrane and in the region between the basolateral membrane and the cytoplastic part near the nuclei, whereas the expression pattern of colon malignancies was mainly on the whole surface of epithelia and the expression was much higher than the normal colon tissues. The staining pattern of tissue array

  14. Cell expression patterns of CD147 in N-diethylnitrosamine/phenobarbital-induced mouse hepatocellular carcinoma.

    Science.gov (United States)

    Lu, Meng; Wu, Jiao; He, Feng; Wang, Xi-Long; Li, Can; Chen, Zhi-Nan; Bian, Huijie

    2015-02-01

    Overexpression of CD147/basigin in hepatic cells promotes the progression of hepatocellular carcinoma (HCC). Whether CD147 also expressed in liver non-parenchymal cells and associated with HCC development was unknown. The aim of the study was to explore time-dependent cell expression patterns of CD147 in a widely accepted N-diethylnitrosamine/phenobarbital (DEN/PB)-induced HCC mouse model. Liver samples collected at month 1-12 of post-DEN/PB administration were assessed the localization of CD147 in hepatocytes, endothelial cells, hepatic stellate cells, and macrophages. Immunohistochemistry analysis showed that CD147 was upregulated in liver tumors during month 1-8 of DEN/PB induction. Expression of CD147 was positively correlated with cytokeratin 18, a hepatocyte marker (r = 0.7857, P = 0.0279), CD31 (r = 0.9048, P = 0.0046), an endothelial cell marker, and CD68, a macrophage marker (r = 0.7619, P = 0.0368). A significant correlation was also observed between CD147 and alpha-smooth muscle actin (r = 0.8857, P = 0.0333) at DEN/PB initiation and early stage of tumor formation. Immunofluorescence and fluorescence in situ hybridization showed that CD147 co-expressed with cytokeratin 18, CD31, alpha-smooth muscle actin, and CD68. Moreover, there existed positive correlations between CD147 and microvessel density (r = 0.7857, P = 0.0279), CD147 and Ki-67 (r = 0.9341, P = 0.0022) in the development of DEN/PB-induced HCC. In conclusion, our results demonstrated that CD147 was upregulated in the liver parenchymal and mesenchymal cells and involved in angiogenesis and tumor cell proliferation in the development of DEN/PB-induced HCC.

  15. Electrochemical analysis of transparent oxide-less photovoltaic cell with perforation patterned metal substrate

    Science.gov (United States)

    Kim, Myoung; You, In-Kyu; Lee, Kyoung-Won; Lee, In-Hwan; Yun, Ho-Gyeong

    2013-05-01

    In terms of electrochemical behaviour, a transparent conductive oxide (TCO)-less dye-sensitized solar cell (DSSC) with two metal foils was compared with those of a metal foil-based DSSC with a TCO-coated substrate. By virtue of electrochemical impedance spectroscopy, intensity modulated photocurrent spectroscopy, intensity modulated photovoltage spectroscopy, open-circuit voltage decay, and photocurrent transient measurements, it was clearly confirmed that the limited performance of the TCO-less DSSC was caused by the restricted transport of ion species in the electrolyte due to the perforation patterned metal foil.

  16. Multilineage differentiation of porcine bone marrow stromal cells associated with specific gene expression pattern

    DEFF Research Database (Denmark)

    Zou, Lijin; Zou, Xuenong; Chen, Li;

    2007-01-01

    genes along those three mesenchymal lineages during a particular lineage differentiation of porcine BMSC by means of real-time PCR measurement. In an osteogenic medium, the mRNA levels of cbfa1, osterix, alkaline phosphatase, type 1 collagen, osteonectin, bone sialoprotein, and osteocalcin were induced...... differentiation was induced in cell pellet culture by expression of sox9, type 2 collagen, and aggrecan. Cbfa1 and PPARgamma2 were inhibited in chondrogenic medium. These results indicate that the differentiation potential of BMSC to a particular mesenchymal lineage relies upon specific gene expression pattern...

  17. Multilineage differentiation of porcine bone marrow stromal cells associated with specific gene expression pattern

    DEFF Research Database (Denmark)

    Zou, Lijin; Zou, Xuenong; Chen, Li;

    2008-01-01

    genes along those three mesenchymal lineages during a particular lineage differentiation of porcine BMSC by means of real-time PCR measurement. In an osteogenic medium, the mRNA levels of cbfa1, osterix, alkaline phosphatase, type 1 collagen, osteonectin, bone sialoprotein, and osteocalcin were induced...... differentiation was induced in cell pellet culture by expression of sox9, type 2 collagen, and aggrecan. Cbfa1 and PPARγ2 were inhibited in chondrogenic medium. These results indicate that the differentiation potential of BMSC to a particular mesenchymal lineage relies upon specific gene expression pattern...

  18. Spray nozzle for fire control

    Science.gov (United States)

    Papavergos, Panayiotis G.

    1990-09-01

    The design of a spray nozzle for fire control is described. It produces a spray of gas and liquid having an oval transverse cross section and it comprises a mixing chamber with an oval transverse cross section adapted to induce a toroidal mixing pattern in pressurized gas and liquid introduced to the mixing chamber through a plurality of inlets. In a preferred embodiment the mixing chamber is toroidal. The spray nozzle produces an oval spray pattern for more efficient wetting of narrow passages and is suitable for fire control systems in vehicles or other confined spaces. Vehicles to which this invention may be applied include trains, armoured vehicles, ships, hovercraft, submarines, oil rigs, and most preferably, aircraft.

  19. Neural Conversion and Patterning of Human Pluripotent Stem Cells: A Developmental Perspective

    Directory of Open Access Journals (Sweden)

    Alexandra Zirra

    2016-01-01

    Full Text Available Since the reprogramming of adult human terminally differentiated somatic cells into induced pluripotent stem cells (hiPSCs became a reality in 2007, only eight years have passed. Yet over this relatively short period, myriad experiments have revolutionized previous stem cell dogmata. The tremendous promise of hiPSC technology for regenerative medicine has fuelled rising expectations from both the public and scientific communities alike. In order to effectively harness hiPSCs to uncover fundamental mechanisms of disease, it is imperative to first understand the developmental neurobiology underpinning their lineage restriction choices in order to predictably manipulate cell fate to desired derivatives. Significant progress in developmental biology provides an invaluable resource for rationalising directed differentiation of hiPSCs to cellular derivatives of the nervous system. In this paper we begin by reviewing core developmental concepts underlying neural induction in order to provide context for how such insights have guided reductionist in vitro models of neural conversion from hiPSCs. We then discuss early factors relevant in neural patterning, again drawing upon crucial knowledge gained from developmental neurobiological studies. We conclude by discussing open questions relating to these concepts and how their resolution might serve to strengthen the promise of pluripotent stem cells in regenerative medicine.

  20. Phenomenon of "contact guidance" on the surface with nano-micro-groove-like pattern and cell physiological effects

    Institute of Scientific and Technical Information of China (English)

    ZHOU Feng; YUAN Lin; HUANG He; CHEN Hong

    2009-01-01

    The topography of material surface has important influence on cell behavior and physiological functions. Groove-like pattern has drawn much attention among various patterns,due to the phenomenon of "contact guidance" induced by this kind of topography. This review mainly focuses on "contact guidance" formation as well as its influence on cell behavior and physiological effects. The possible mechanisms of "contact guidance" formation were discussed. The research trend and the potential applications were also suggested.

  1. Tailor-made cell patterning using a near-infrared-responsive composite gel composed of agarose and carbon nanotubes.

    Science.gov (United States)

    Koga, Haruka; Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi; Nakazawa, Kohji

    2013-03-01

    Micropatterning is useful for regulating culture environments. We developed a highly efficient near-infrared-(NIR)-responsive gel and established a new technique that enables cell patterning by NIR irradiation. As a new culture substratum, we designed a tissue culture plate that was coated with a composite gel composed of agarose and carbon nanotubes (CNTs). A culture plate coated with agarose only showed no response to NIR irradiation. In contrast, NIR laser irradiation induced heat generation by CNTs; this permitted local solation of the CNT/agarose gel, and consequently, selective cell-adhesive regions were exposed on the tissue culture plate. The solation area was controlled by the NIR intensity, magnification of the object lens and CNT concentration in the gel. Furthermore, we formed circular patterns of HeLa cells and linear patterns of 3T3 cells on the same culture plate through selective and stepwise NIR irradiation of the CNT/agarose gel, and we also demonstrated that individual 3T3 cells migrated along a linear path formed on the CNT/agarose gel by NIR irradiation. These results indicate that our technique is useful for tailor-made cell patterning of stepwise and/or complex cell patterns, which has various biological applications such as stepwise co-culture and the study of cell migration.

  2. Methylation patterns of immunoglobulin genes in lymphoid cells: correlation of expression and differentiation with undermethylation.

    Science.gov (United States)

    Storb, U; Arp, B

    1983-11-01

    Different states of eukaryotic gene expression are often correlated with different levels of methylation of DNA sequences containing structural genes and their flanking regions. To assess the potential role of DNA methylation in the expression of immunoglobulin genes, which require complex rearrangements prior to expression, methylation patterns were examined in cell lines representing different stages of lymphocyte maturation. Methylation of the second cytosine in the sequence 5' C-C-G-G 3' was determined by using Hpa II/Msp I endonuclease digestion. Four CH genes (C mu, C delta, C gamma 2b, and C alpha), C kappa, V kappa, C lambda, and V lambda genes were analyzed. The results lead to the following conclusions: (i) transcribed immunoglobulin genes are undermethylated; (ii) the C gene allelic to an expressed C gene is always also undermethylated; and (iii) all immunoglobulin loci tend to become increasingly undermethylated as B cells mature.

  3. Light Coupling and Trapping in Ultrathin Cu(In,Ga)Se2 Solar Cells Using Dielectric Scattering Patterns.

    Science.gov (United States)

    van Lare, Claire; Yin, Guanchao; Polman, Albert; Schmid, Martina

    2015-10-27

    We experimentally demonstrate photocurrent enhancement in ultrathin Cu(In,Ga)Se2 (CIGSe) solar cells with absorber layers of 460 nm by nanoscale dielectric light scattering patterns printed by substrate conformal imprint lithography. We show that patterning the front side of the device with TiO2 nanoparticle arrays results in a small photocurrent enhancement in almost the entire 400-1200 nm spectral range due to enhanced light coupling into the cell. Three-dimensional finite-difference time-domain simulations are in good agreement with external quantum efficiency measurements. Patterning the Mo/CIGSe back interface using SiO2 nanoparticles leads to strongly enhanced light trapping, increasing the efficiency from 11.1% for a flat to 12.3% for a patterned cell. Simulations show that optimizing the array geometry could further improve light trapping. Including nanoparticles at the Mo/CIGSe interface leads to substantially reduced parasitic absorption in the Mo back contact. Parasitic absorption in the back contact can be further reduced by fabricating CIGSe cells on top of a SiO2-patterned In2O3:Sn (ITO) back contact. Simulations show that these semitransparent cells have similar spectrally averaged reflection and absorption in the CIGSe active layer as a Mo-based patterned cell, demonstrating that the absorption losses in the Mo can be partially turned into transmission through the semitransparent geometry.

  4. Developing a Cell-Based Spatial Optimization Model for Land-Use Patterns Planning

    Directory of Open Access Journals (Sweden)

    Chun-Wei Huang

    2014-12-01

    Full Text Available This study developed a cell-based spatial optimization model compatible with the ArcGIS platform, termed Dynamically Dimensioned Search Landscape Optimization Planning model (DDSLOP, for landscape planning. The development of the proposed model was based on the Dynamically Dimensioned Search Algorithm, which can efficiently find an optimal global solution within the massive solution space inherent to multi-dimensional analysis. Therefore, the DDSLOP model can reveal landscape pattern scenarios suited to specific managerial purposes at a cellular level. To evaluate the DDSLOP model, we applied it to a landscape planning initiative that focused on the conservation of three bird species in the National Taiwan University Highland Experimental Farm (NTU-HEF. We compared the proposed model with the Land-Use Pattern Optimization-library (LUPOlib, which was used in the optimization of landscapes at a patch level. The results of the comparison revealed that our fine scale optimization method has better flexibility, and can therefore form landscape structures, which, overall, provides not only better individual habitats for the target species, but also landscape patterns that foster high habitat connectivity, both important aspects of conservation efforts.

  5. Challenges Found When Patterning Semiconducting Polymers with Electric Fields for Organic Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Fernando A. de Castro

    2012-01-01

    Full Text Available A material-independent, contactless structuring method of semiconducting organic materials for the fabrication of interface-enhanced bilayer solar cells is not available so far. Patterning of thin films using electrohydrodynamic instabilities possesses many desired characteristics and has convincingly been used as a simple method to structure and replicate patterns of nonconducting polymers on submicrometer length scales. However, the applicability of this technique to a wider range of materials has not been demonstrated yet. Here, we report attempts to structure poly(p-phenylene vinylene in a similar way. We found that thin films of poly(2-methoxy-5-(2′-ethylhexyl-oxy-1,4-phenylene-vinylene (MEH-PPV and poly(2-methoxy-5-(3′,7′-dimethyloctyloxy-1,4-phenylene-vinylene (MDMO-PPV could not be destabilized at all in the limited accessible range of the experimental parameters set by the delicate chemical nature of these materials. We discuss failure origins and present possible loopholes for the patterning of semiconducting polymers using electric fields.

  6. WEREWOLF, a MYB-related protein in Arabidopsis, is a position-dependent regulator of epidermal cell patterning.

    Science.gov (United States)

    Lee, M M; Schiefelbein, J

    1999-11-24

    The formation of the root epidermis of Arabidopsis provides a simple and elegant model for the analysis of cell patterning. A novel gene, WEREWOLF (WER), is described here that is required for position-dependent patterning of the epidermal cell types. The WER gene encodes a MYB-type protein and is preferentially expressed within cells destined to adopt the non-hair fate. Furthermore, WER is shown to regulate the position-dependent expression of the GLABRA2 homeobox gene, to interact with a bHLH protein, and to act in opposition to the CAPRICE MYB. These results suggest a simple model to explain the specification of the two root epidermal cell types, and they provide insight into the molecular mechanisms used to control cell patterning.

  7. Arid3b is essential for second heart field cell deployment and heart patterning.

    Science.gov (United States)

    Uribe, Verónica; Badía-Careaga, Claudio; Casanova, Jesús C; Domínguez, Jorge N; de la Pompa, José Luis; Sanz-Ezquerro, Juan José

    2014-11-01

    Arid3b, a member of the conserved ARID family of transcription factors, is essential for mouse embryonic development but its precise roles are poorly understood. Here, we show that Arid3b is expressed in the myocardium of the tubular heart and in second heart field progenitors. Arid3b-deficient embryos show cardiac abnormalities, including a notable shortening of the poles, absence of myocardial differentiation and altered patterning of the atrioventricular canal, which also lacks epithelial-to-mesenchymal transition. Proliferation and death of progenitors as well as early patterning of the heart appear normal. However, DiI labelling of second heart field progenitors revealed a defect in the addition of cells to the heart. RNA microarray analysis uncovered a set of differentially expressed genes in Arid3b-deficient tissues, including Bhlhb2, a regulator of cardiomyocyte differentiation, and Lims2, a gene involved in cell migration. Arid3b is thus required for heart development by regulating the motility and differentiation of heart progenitors. These findings identify Arid3b as a candidate gene involved in the aetiology of human congenital malformations.

  8. Haploinsufficiency of EHMT1 improves pattern separation and increases hippocampal cell proliferation

    Science.gov (United States)

    Benevento, Marco; Oomen, Charlotte A.; Horner, Alexa E.; Amiri, Houshang; Jacobs, Tessa; Pauwels, Charlotte; Frega, Monica; Kleefstra, Tjitske; Kopanitsa, Maksym V.; Grant, Seth G. N.; Bussey, Timothy J.; Saksida, Lisa M.; Van der Zee, Catharina E.E.M.; van Bokhoven, Hans; Glennon, Jeffrey C.; Kasri, Nael Nadif

    2017-01-01

    Heterozygous mutations or deletions of the human Euchromatin Histone Methyltransferase 1 (EHMT1) gene are the main causes of Kleefstra syndrome, a neurodevelopmental disorder that is characterized by impaired memory, autistic features and mostly severe intellectual disability. Previously, Ehmt1+/− heterozygous knockout mice were found to exhibit cranial abnormalities and decreased sociability, phenotypes similar to those observed in Kleefstra syndrome patients. In addition, Ehmt1+/− knockout mice were impaired at fear extinction and novel- and spatial object recognition. In this study, Ehmt1+/− and wild-type mice were tested on several cognitive tests in a touchscreen-equipped operant chamber to further investigate the nature of learning and memory changes. Performance of Ehmt1+/− mice in the Visual Discrimination & Reversal learning, object-location Paired-Associates learning- and Extinction learning tasks was found to be unimpaired. Remarkably, Ehmt1+/− mice showed enhanced performance on the Location Discrimination test of pattern separation. In line with improved Location Discrimination ability, an increase in BrdU-labelled cells in the subgranular zone of the dentate gyrus was observed. In conclusion, reduced levels of EHMT1 protein in Ehmt1+/− mice does not result in general learning deficits in a touchscreen-based battery, but leads to increased adult cell proliferation in the hippocampus and enhanced pattern separation ability. PMID:28071689

  9. Regulation of cell behavior and tissue patterning by bioelectrical signals: challenges and opportunities for biomedical engineering.

    Science.gov (United States)

    Levin, Michael; Stevenson, Claire G

    2012-01-01

    Achieving control over cell behavior and pattern formation requires molecular-level understanding of regulatory mechanisms. Alongside transcriptional networks and biochemical gradients, there functions an important system of cellular communication and control: transmembrane voltage gradients (V(mem)). Bioelectrical signals encoded in spatiotemporal changes of V(mem) control cell proliferation, migration, and differentiation. Moreover, endogenous bioelectrical gradients serve as instructive cues mediating anatomical polarity and other organ-level aspects of morphogenesis. In the past decade, significant advances in molecular physiology have enabled the development of new genetic and biophysical tools for the investigation and functional manipulation of bioelectric cues. Recent data implicate V(mem) as a crucial epigenetic regulator of patterning events in embryogenesis, regeneration, and cancer. We review new conceptual and methodological developments in this fascinating field. Bioelectricity offers a novel way of quantitatively understanding regulation of growth and form in vivo, and it reveals tractable, powerful control points that will enable truly transformative applications in bioengineering, regenerative medicine, and synthetic biology.

  10. Paramagnetic Structures within a Microfluidic Channel for Enhanced Immunomagnetic Isolation and Surface Patterning of Cells

    Science.gov (United States)

    Sun, Chen; Hassanisaber, Hamid; Yu, Richard; Ma, Sai; Verbridge, Scott S.; Lu, Chang

    2016-07-01

    In this report, we demonstrate a unique method for embedding magnetic structures inside a microfluidic channel for cell isolation. We used a molding process to fabricate these structures out of