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  • 1
    Electronic Resource
    Electronic Resource
    Feedback inhibition controls spike transfer in hybrid thalamic circuits (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 417 (2002), S. 854-858 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sensory information reaches the cerebral cortex through the thalamus, which differentially relays this input depending on the state of arousal. Such ‘gating’ involves inhibition of the thalamocortical relay neurons by the reticular nucleus of the thalamus, but the underlying ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature00825
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  • 2
    Electronic Resource
    Electronic Resource
    Comparing Investments in New Transport Infrastructure: Roads versus Railways? (2003)
    London, UK : The Institute for Fiscal Studies
    Fiscal studies 24 (2003), S. 0 
    Details
    ISSN: 1475-5890
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: This paper contributes to the debate on investment in transport infrastructure and the allocation of public funds between road and railway projects. We model the two options and provide a consistent framework to appraise investment in typical new inter–urban road and rail projects. Our results suggest that road improvements have substantially higher returns than railway schemes. These findings cast doubt on the rationale of the new transport policy for the UK, which proposes to allocate more public funds to the (private) railways than total new investment in strategic roads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-5890.2003.tb00085.x
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  • 3
    Electronic Resource
    Electronic Resource
    Widespread fluid expulsion along the seafloor of the Costa Rica convergent margin (2002)
    Oxford UK : Blackwell Science Ltd
    Terra nova 14 (2002), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Active fluid and gas transport were measured and observed along more than 200 km of the convergent margin of Costa Rica during cruise SO144-2 aboard RV Sonne. Ten profiles were run with the TV-sled OFOS, eight of which detected the dense occurrence of cold vent sites. This discovery shows that seafloor fluid expulsion is widely spread along the Pacific margin of Costa Rica. Surficial evidence of fluid expulsion is indicated by the appearance of chemosynthetic vent organisms such as bacterial mats, vesicomyid, solemyid and mytilid bivalves and tubeworms. Numerous active vents were indicated by elevated methane concentrations (≤ 200 nmol L–) in the bottom water. Although fluid-venting activity was known previously from a small area south of Nicoya Peninsula, the present study documents active seepage at landslides, headwall scarps related to seamount subduction, morphological intersections of faults and mid-slope mud volcanoes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3121.2002.00400.x
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  • 4
    Electronic Resource
    Electronic Resource
    ROOT GRAVITROPISM: An Experimental Tool to Investigate Basic Cellular and Molecular Processes Underlying Mechanosensing and Signal Transmission in Plants (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 53 (2002), S. 421-447 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract The ability of plant organs to use gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for gravity sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for gravity sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for gravity perception. Such studies have also allowed the identification of several molecules that appear to function as second messengers in gravity signal transduction and of potential signal transducers. Auxin has been implicated as a probable component of the signal that carries the gravitropic information between the gravity-sensing cap and the gravity-responding EZs. This has allowed the identification and characterization of important molecular processes underlying auxin transport and response in plants. New molecular models can be elaborated to explain how the gravity signal transduction pathway might regulate the polarity of auxin transport in roots. Further studies are required to test these models, as well as to study the molecular mechanisms underlying a poorly characterized phase of gravitropism that is independent of an auxin gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.53.100301.135158
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  • 5
    Electronic Resource
    Electronic Resource
    Pattern formation in a thin random copolymer film: Evolution of an intermediate morphology (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 349-355 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Previous studies of structural instabilities in thin, nonwetting, liquid homopolymer films on substrates have focused on systems that dewet, forming patterns that reflect fluctuations in the local film thickness. These patterns range from discrete cylindrical holes throughout the surface of the film to bicontinuous "spinodallike" patterns. In this paper we show that a thin liquid film, a random copolymer, styrene-ran-acrylonitrile (SAN) comprised of 75% styrene and 25% acrylonitrile, of thickness h=12 nm becomes unstable and dewets silicon substrates, forming what we describe here as an intermediate morphology. During the early stage of dewetting, discrete noncylindrical, irregular, shaped holes appear spontaneously in the film. The number of holes, N, initially increase with time and the morphology of the late stage of growth, after 18 days, is characterized by a bicontinuous pattern, distinct from conventional spinodal dewetting patterns. The dynamics of pattern evolution of this intermediate morphology are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480585
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  • 6
    Electronic Resource
    Electronic Resource
    Pattern formation and evolution in diblock copolymer thin films above the order–disorder transition (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10963-10967 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Research on diblock copolymer thin films has been devoted primarily toward understanding and controlling microstructural and topographical features at temperatures below the order–disorder transition (ODT), where ordered phase separated structures exist. Recently, we showed that the topography of thin liquid diblock films above the ODT form a hierarchy of patterns, depending on the film thickness. One of these topographies is a "spinodal-like" pattern. Through the use of a pair correlation analysis we show that the structural evolution of this pattern is characterized by four stages. The first involves the amplification of surface perturbations, followed by the formation of an interconnected, "spinodal-like," pattern. The onset of the third stage is associated with the breakup of the interconnected pattern and the eventual formation of droplets of irregular shapes. The final stage involves evolution toward the formation of circular droplets. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370565
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  • 7
    Electronic Resource
    Electronic Resource
    Photic Regulation of mt1 Melatonin Receptors in the Siberian Hamster Pars Tuberalis and Suprachiasmatic Nuclei: Involvement of the Circadian Clock and Intergeniculate Leaflet (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 12 (2000), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In the Siberian hamster suprachiasmatic nuclei and pars tuberalis of the pituitary, high affinity mt1 melatonin receptors are present. We have previously shown that night applied light pulse induced an increase in mt1 mRNA expression in the suprachiasmatic nuclei of this species, independently of the endogenous melatonin. Here, we report the photic regulation of melatonin receptor density and mRNA expression in the suprachiasmatic nuclei and pars tuberalis of pinealectomized Siberian hamsters and the implication in this control of either the circadian clock or the intergeniculate leaflet. The results show that: (1) A 1-h light pulse, delivered during the night, induces a transitory increase in mt1 mRNA expression in the suprachiasmatic nuclei and pars tuberalis. After 3 h this increase has totally disappeared (suprachiasmatic nuclei) or is greatly reduced (pars tuberalis). (2) The melatonin receptor density, in the suprachiasmatic nuclei, is not affected by 1 or 3 h of light, while it is strongly increased in the pars tuberalis. (3) In hamsters kept in constant darkness, the mt1 mRNA rise is gated to the subjective night in the suprachiasmatic nuclei and pars tuberalis. In contrast, the light-induced increase in melatonin binding is also observed in the subjective day in the pars tuberalis. (4) intergeniculate leaflet lesion totally inhibits the mt1 mRNA expression rise in the suprachiasmatic nuclei, while it has no effect on the light-induced increase in mt1 mRNA in the pars tuberalis. However, the light-induced increase in melatonin receptor density is totally prevented by the intergeniculate leaflet lesion in the pars tuberalis. These results show that: (1) the photic regulations of mt1 mRNA expression and receptor density are independent of each other in both the suprachiasmatic nuclei and pars tuberalis; and (2) the circadian clock and the intergeniculate leaflet are implicated in the photic regulation of melatonin receptors but their level of action differs totally between the suprachiasmatic nuclei and pars tuberalis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2000.00039.x
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  • 8
    Electronic Resource
    Electronic Resource
    MT1 Melatonin Receptor mRNA Expressing Cells in the Pars Tuberalis of the European Hamster: Effect of Photoperiod (2003)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 15 (2003), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Melatonin, secreted only during the night by the pineal gland, transduces the photoperiodic message to the organism. One important target for the hormone is the pars tuberalis (PT) of the adenohypophysis which displays a very high number of melatonin binding sites in mammals and is implicated in the seasonal regulation of prolactin secretion. To gain insight into the mechanism by which the melatonin signal is decoded in the PT, we studied the effect of photoperiod on the PT cells expressing the MT1 melatonin receptor in a highly photoperiodic species, the European hamster. Recently, we showed that, in the rat, the MT1 receptor mRNA is expressed in PT-specific cells characterized by their expression of β-thyroid stimulating hormone (β-TSH) along with the α-glycoprotein subunit (α-GSU). As the cellular composition of the PT shows variability among species, we first identified the cell type expressing the MT1 receptor in the European hamster by combining immunocytochemistry and nonradioactive in situ hybridization for the MT1 receptor mRNA. Our results show that, in the European hamster, as in the rat, the MT1 receptor is only expressed by the PT-specific-cells, β-TSH and α-GSU positive. In a second step, we analysed the effects of photoperiod on the MT1 mRNA, and on β-TSH and α-GSU both at the mRNA and protein levels. Our data show that, compared to long photoperiod, short photoperiod induces a dramatic decrease of MT1, β-TSH and α-GSU expression. Protein levels of β-TSH and α-GSU were also dramatically reduced in short photoperiod. Together, our data suggest that melatonin exerts its seasonal effects in the PT by signalling to PT specific-cells through the MT1 receptor subtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2003.01060.x
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  • 9
    Electronic Resource
    Electronic Resource
    Sedimentary environment of the Faroe-Shetland and Faroe Bank Channels, north-east Atlantic, and the use of bedforms as indicators of bottom current velocity in the deep ocean (2004)
    Oxford, UK : Blackwell Science Ltd
    Sedimentology 51 (2004), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In the northeast Atlantic, much of the deep cold water flow between the Norwegian Sea and the main North Atlantic basin passes through the Faroe-Shetland and Faroe Bank Channels, generating strong persistent bottom currents capable of eroding and transporting sediment up to and including gravel. A large variety of sedimentary bedforms, including scours, furrows, comet marks, barchan dunes, sand sheets and sediment drifts, is documented using sidescan sonar images, seismic profiles, seabed photographs and sediment cores from the floor of the channel. Published information on current velocities associated with the various bedforms has been used to reconstruct the pattern of bottom currents acting on the channel floor. The results broadly reflect the current pattern predicted on the basis of regional oceanographic observations, but add considerable detail. The internal consistency of the results suggests that the methods used are robust, giving confidence in the fine detail of the observed bottom current structure. Bottom current velocities in the range 〈 0·3 to 〉 1·0 m s−1 are indicated by the range of observed bedforms, with the strongest currents associated with south-west transport of Norwegian Sea Deep Water (NSDW) at water depths of 800–1200 m. The main NSDW flow forms a relatively narrow core that follows the base of the Faroes slope. This core follows the 90° change in trend of the Faroes slope at the junction between the Faroe-Shetland and Faroe Bank Channels. The strongest currents within the NSDW core are found over the shallowest sill in the Faroe-Shetland Channel and in the narrowest part of the channel immediately downstream of the sill, and are generated by topographic constriction of the flow. Eastward flow of deep water along the northern flank of the Wyville-Thomson ridge suggests a complex current pattern with some recirculation of deep water within the deep Faroe Bank Channel basin. The observations suggest that Coriolis force is the main agent controlling the westward deflection of the NSDW into the Faroe Bank Channel, contradicting a previous suggestion that this was controlled by the topography of the Wyville Thomson Ridge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.2004.00668.x
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  • 10
    Electronic Resource
    Electronic Resource
    Whole-cell recording from honeybee olfactory receptor neurons: ionic currents, membrane excitability and odourant response in developing workerbee and drone (2002)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 15 (2002), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Whole-cell recording techniques were used to characterize ionic membrane currents and odourant responses in honeybee olfactory receptor neurons (ORNs) in primary cell culture. ORNs of workerbee (female) and drone (male) were isolated at an early stage of development before sensory axons connect to their target in the antennal lobe. The results collectively indicate that honeybee ORNs have electrical properties similar, but not necessarily identical to, those currently envisaged for ORNs of other species. Under voltage clamp at least four ionic currents could be distinguished. Inward currents were made of a fast transient, tetrodotoxin-sensitive sodium current. In some ORNs a cadmium-sensitive calcium current was detected. ORNs showed heterogeneity in their outward currents: either outward currents were made of a delayed rectifier type potassium current, which was partially blocked by tetraethyl ammonium or quinidine, or were composed of a delayed rectifier type and a transient calcium-dependent potassium current, which was cadmium-sensitive and abolished by removal of external calcium. The proportion of each of the two outward currents, however, was different within the ORNs of the two sexes suggesting a gender-specific functional heterogeneity. ORNs showed heterogeneity in action potential firing properties: depolarizing current steps elicited either one action potential or, as in most of the cells, it led to repetitive spiking. Action potentials were tetrodotoxin-sensitive suggesting they are carried by sodium. Odourant stimulation with different mixtures and pure substances evoked depolarizing receptor potentials with superimposed action potentials when spike threshold was reached. In summary, honeybee ORNs are remarkably mature at early stages in their development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2002.01954.x
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