The possible role of GABA B receptor mechanisms in information processing in primary somatosensory (S1) cortex was assessed by use of extracellular recording combined with microiontophoretic methods from 161 neurones in anaesthetized, paralysed cats. Baclofen‐induced suppressions of cell responses were reversible and stereoselective, the (+)‐isomer being inactive and the (−)−isomer having two to three times the apparent potency of γ‐aminobutyric acid (GABA). The responses measured were threshold to natural stimulation of receptive fields (RFs), responsiveness to thalamic electrical stimulation, change in RF size and magnitude of firing elicited by iontophoretic glutamate. The action of GABA always was mimicked by muscimol or 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol (THIP) but not always by (−)−baclofen; in certain cases (−)−baclofen enhanced neuronal responses while the opposite occurred with GABA or with the other GABA A agonists. The elevation of response thresholds by (−)−baclofen was relatively stronger in peripheral than in central subregions of cutaneous RFs, by contrast with the action of muscimol which was relatively non‐selective as to the area in which it was effective. Glutamate‐induced and thalamically‐evoked cortical responses as well as spontaneous activity were differentially sensitive to the suppressant effects of muscimol and (−)−baclofen. Bicuculline methiodide reversibly blocked THIP‐ and muscimol‐induced suppressions of tactile‐ (air puffer)‐induced S1 responses but spared those produced by (−)−baclofen. Phaclofen and δ‐amino‐n‐valeric acid were essentially inactive as blockers of (−)−baclofen‐induced effects and in fact often acted as (−)−baclofen‐like agonists, phaclofen being considerably weaker than δ‐amino‐n‐valeric acid in this respect. The range of suppressant effects produced by GABA as well as by muscimol and THIP, considered in conjunction with the actions of bicuculline methiodide, suggest that the effects observed by ejected GABA are likely to be due principally to GABA A processes, those mediated by GABA B receptors largely being masked. However, GABA B mechanisms are extant and do appear to be active, probably presynaptically and probably at sites distal to the soma.
In cells, motor proteins do not work alone but rather move in ensemble when they support several cellular functions including mitosis and beating of flagellum. Until now, collective transportation by motors was poorly understood due to the experimental difficulty in controlling the number and arrangement of motors, which are considered to affect the transportation. In this report, we propose a novel nano-patterning method to control the number of kinesin molecules and the spacing between molecules, which transport a single microtubule filament. We fabricated Au nano-pillar array on Si/SiO 2 substrates. The SiO 2 surface was coated with a silane-poly(ethylene glycol) (PEG) self-assembled monolayer (SAM) using a silane-coupling reaction to eliminate non-specific adsorption of kinesin molecules. By designing the arrangement of pillars, the number of kinesin molecules and the spacing between molecules can be defined, and their effects on kinesin motility was investigated. Two motor species with different processivity, kinesin-1 and Ncd, were patterned individually. We found the number of motors affected the microtubule velocity in the case of non-processive Ncd, but not in the case of processive kinesin-1.
MOMBE (metalorganic molecular beam epitaxy) growth characteristics of Sb containing ternary alloys, InGaSb, and GaAsSb are investigated. In the growth of InGaSb using TEGa (triethylgallium), TMIn (trimethylindium), and Sb4 (elemental antimony), the enhanced desorption of methyl-In molecules at a substrate temperature Tsub of around 500 °C as well as the enhanced desorption of ethyl-Ga molecules at around 515 °C are observed. They are due to the weak bond strength of antimonide compounds. Furthermore, the decrease of Ga solid composition with increasing Sb4 flux and the increase of GaSb partial growth rate with TMIn flow rate are also observed at as high as 500 °C. This is caused by the fact that the site blocking effect of excess Sb atoms exists up to higher Tsub. In the growth of GaAsSb using TEGa, TEAs (triethylarsine), and TESb (triethylstibine), the Sb composition versus TESb/(TEAs+TESb) curve exhibits a bowing characteristic, which is similar to that in the MOVPE (metalorganic vapor phase epitaxy) growth and is different from that in the MBE (molecular beam epitaxy) growth. Mass transport properties of Sb molecules in the MOMBE are considered to be similar to that in the MOVPE. It is found that the Tsub dependence of Sb composition is much weaker than that in the MBE, which is a superior point of MOMBE in the growth of antimonide alloys.
Nine strains of Pseudomonas maltophilia which do not require methionine are described. Methionine-requiring and -nonrequiring strains of P. maltophilia belong to different biovars, which are designated I and II, respectively; they differ from each other with respect to phenotypic characteristics, cellular fatty acid composition, deoxyribonucleic acid base composition, and deoxyribonucleic acid-deoxyribonucleic acid hybridization. The relationship of P. maltophilia to Xan-thomonas species is also discussed.
The influence of surface reconstructions on the surface morphology during in situ layer-by-layer etching of GaAs(001) has been studied based on the observation of reflection high-energy electron-diffraction measurements. For the etching, AsBr3 is used as a reactive source etchant under solid source molecular beam epitaxy conditions, focusing on a high temperature region in which the etching rate is limited by a supply rate of AsBr3 resulting in a constant value. Despite the fact that the etching starts on a layer-by-layer basis, an initially smooth surface turns considerably rougher depending on the stoichiometry associated with the surface reconstruction. The best morphology after a removal of 250 nm is obtained in the Ga-rich (3×1) reconstruction region close to the phase transition boundary to the As-rich (2×4). This is also verified by the measurement of scanning electron microscopy and atomic force microscopy.
Various kinds of semiconductor microstructures have been fabricated based on the conventional lithography where a mask pattern is projected onto an organic photoresist on the substrate using light, electron beam, or X-ray. However, these lithographic processes have a potential difficulty in order to reach a nano-scale controllability due to the resolution limits of the mask and the photoresist as well as the wavelength of the light sources used. Therefore, the elimination of both mask and resist from patterning processes by employing a direct writing method using energetic beams is considered to be one way to go in order to directly fabricate nano-scale structures. This simplification is contributed to reduce a number of process steps resulting in the improvement of surface cleanliness. Moreover, a resistless technique is essential for in-situ wafer processing involving direct regrowth of epitaxial semiconductor layers for maintaining device quality at the interfaces.
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