TY - JOUR AB - To better understand the role of neurotransmitter receptors in neuronal differentiation and maturation a detailed knowledge of their identity, location and function in the plasma membrane of specific neuronal populations during development is required. Combining pre-embedding immunocytochemistry with cell tracking in embryonic brain slice cultures we show that virtually all neurons (∼98%) migrating through the lower intermediate zone (LIZ) on their way from the medial ganglionic eminence to the cerebral cortex, express GABA BR1. Blockade of GABABRs with a specific antagonist, CGP52432, resulted in a concentration-dependent accumulation of these tangentially migrating neurons in the ventricular/subventricular zones (VZ/SVZ) of the cortex and fewer cells were observed in the cortical plate/marginal zone (CP/MZ) and LIZ. Moreover, they had significantly shorter leading processes compared with similar migrating cells in control slices. Electrophysiological recording in LIZ and CP cells revealed no direct effect of either CGP52432 or the GABABR agonist, baclofen, on resting membrane properties suggesting that the effect of CGP52432 on migration might be mediated through a metabotropic action or the regulation of release of factors controlling migration. These results suggest that GABABRs have an important modulatory role in the migration of cortical interneurons. AU - López-Bendito, Guillermina AU - Luján, Rafael AU - Ryuichi Shigemoto AU - Ganter, Paul AU - Paulsen, Ole AU - Molnár, Zoltán ID - 2634 IS - 9 JF - Cerebral Cortex TI - Blockade of GABAB receptors alters the tangential migration of cortical neurons VL - 13 ER - TY - JOUR AB - Taste-metabotropic glutamate receptor 4 (taste-mGluR4) and the heteromers of T1R1 and T1R3 are candidate receptors involved in the sense of umami (monosodium glutamate) taste. Although the expression of group III mGluRs (taste-mGluR4) has been demonstrated in taste tissues, no mention has been made of the expression of group I mGluRs (mGluR1 and mGluR5) in taste tissues. We examined the expression of mGluR1 and mGluR5 in rat gustatory tissues by using reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, immunohistochemistry and immunoelectron microscopy. RT-PCR assay showed that mGluR1α and mGluR1β mRNAs were expressed in circumvallate papillae, but mGluR5 mRNA was not expressed. The positive signals of mGluR1 mRNA were detected only in circumvallate taste buds by in situ hybridization analysis. In cryosections of fungiform, foliate and circumvallate papillae, the antibody against mGluRla gave intense labeling on the taste hairs in all taste pores examined. In the developing taste buds, the positive signals of mGluR1α in taste hairs gradually increased with the increase in number of taste bud cells. These results show that, in addition to taste-mGluR4 and the heteromer of T1R1 and T1R3, mGluR1α may function as a receptor for glutamate (umami) taste sensation. AU - Toyono, Takashi AU - Seta, Yuji AU - Kataoka, Shinji AU - Kawano, Shintaro AU - Ryuichi Shigemoto AU - Toyoshima, Kuniaki ID - 2630 IS - 1 JF - Cell and Tissue Research TI - Expression of metabotropic glutamate receptor group I in rat gustatory papillae VL - 313 ER - TY - JOUR AB - While the cholinergic depletion in Alzheimer's disease (AD) has been known for some time, a definitive involvement of other neurotransmitter systems has been somewhat more elusive. Our study demonstrates a clear involvement of both glutamatergic and, to a lesser extent, GABAergic neurons in an early onset transgenic mouse model of AD-like amyloid pathology. Immunohistochemical staining and subsequent quantification has revealed a statistically significant increased density of glutamatergic and GABAergic presynaptic boutons in both the plaque free and plaque adjacent cortical neuropile areas of transgenic mice as compared to non-transgenic controls. Furthermore, amyloid plaque size was shown to have a statistically significant effect on the relative area occupied by dystrophic glutamatergic neurites in the peri-plaque neuropile. These findings support our hypothesis that the amyloid pathology progresses in a time and neurotransmitter specific manner, first in the cholinergic system which appears to be most vulnerable, followed by the glutamatergic presynaptic boutons and finally the somewhat more resilient GABAergic terminals. AU - Bell, Karen F AU - De Kort, G J AU - Steggerda, S AU - Ryuichi Shigemoto AU - Ribeiro-da-Silva, Alfredo AU - Cuello, Augusto C ID - 2637 IS - 2 JF - Neuroscience Letters TI - Structural involvement of the glutamatergic presynaptic boutons in a transgenic mouse model expressing early onset amyloid pathology VL - 353 ER - TY - JOUR AB - We report the results of an experimental study of magnetohydrodynamic damping of sidewall convection in a rectangular enclosure filled with gallium. In particular we investigate the suppression of convection when a steady magnetic field is applied separately in each of the three principal directions of the flow. The strongest damping of the steady flow is found for a vertical magnetic field, which is in agreement with theory. However, we observe that the application of a field transverse to the flow provides greater damping than a longitudinal one, which seems to contradict available theory. We provide a possible resolution of this apparent dichotomy in terms of the length scale of the experiment. AU - Björn Hof AU - Juel, Anne AU - Mullin, Tom P ID - 2784 JF - Journal of Fluid Mechanics TI - Magnetohydrodynamic damping of convective flows in molten gallium VL - 482 ER - TY - JOUR AB - Experimental evidence for the scaling of the finite amplitude of perturbation theory required to promote transition in Poiseuille flow was found. The exponent is -1 and was uncovered using considerable care in the design and execution of the experiment. Interestingly, this exponent was also found in experiments on transition in boundary layers. AU - Björn Hof AU - Juel, Anne AU - Mullin, Tom P ID - 2785 IS - 24 JF - Physical Review Letters TI - Scaling of the turbulence transition threshold in a pipe VL - 91 ER - TY - JOUR AB - Plant growth is marked by its adaptability to continuous changes in environment. A regulated, differential distribution of auxin underlies many adaptation processes including organogenesis, meristem patterning and tropisms. In executing its multiple roles, auxin displays some characteristics of both a hormone and a morphogen. Studies on auxin transport, as well as tracing the intracellular movement of its molecular components, have suggested a possible scenario to explain how growth plasticity is conferred at the cellular and molecular level. The plant perceives stimuli and changes the subcellular position of auxin-transport components accordingly. These changes modulate auxin fluxes, and the newly established auxin distribution triggers the corresponding developmental response. AU - Friml, Jirí ID - 2990 IS - 1 JF - Current Opinion in Plant Biology TI - Auxin transport - Shaping the plant VL - 6 ER - TY - JOUR AB - Plants have many polarized cell types, but relatively little is known about the mechanisms that establish polarity. The orc mutant was identified originally by defects in root patterning, and positional cloning revealed that the affected gene encodes STEROL METHYLTRANSFERASE1, which is required for the appropriate synthesis and composition of major membrane sterols. smt1orc mutants displayed several conspicuous cell polarity defects. Columella root cap cells revealed perturbed polar positioning of different organelles, and in the smt1orc root epidermis, polar initiation of root hairs was more randomized. Polar auxin transport and expression of the auxin reporter DR5-β-glucuronidase were aberrant in smt1orc. Patterning defects in smt1orc resembled those observed in mutants of the PIN gene family of putative auxin efflux transporters. Consistently, the membrane localization of the PIN1 and PIN3 proteins was disturbed in smt1orc, whereas polar positioning of the influx carrier AUX1 appeared normal. Our results suggest that balanced sterol composition is a major requirement for cell polarity and auxin efflux in Arabidopsis. AU - Willemsen, Viola AU - Jirí Friml AU - Grebe, Markus AU - Van Den Toorn, Albert AU - Palme, Klaus AU - Scheres, Ben ID - 2992 IS - 3 JF - Plant Cell TI - Cell polarity and PIN protein positioning in Arabidopsis require STEROL METHYLTRANSFERASE1 function VL - 15 ER - TY - JOUR AB - Plants, compared to animals, exhibit an amazing adaptability and plasticity in their development. This is largely dependent on the ability of plants to form new organs, such as lateral roots, leaves, and flowers during postembryonic development. Organ primordia develop from founder cell populations into organs by coordinated cell division and differentiation. Here, we show that organ formation in Arabidopsis involves dynamic gradients of the signaling molecule auxin with maxima at the primordia tips. These gradients are mediated by cellular efflux requiring asymmetrically localized PIN proteins, which represent a functionally redundant network for auxin distribution in both aerial and underground organs. PIN1 polar localization undergoes a dynamic rearrangement, which correlates with establishment of auxin gradients and primordium development. Our results suggest that PIN-dependent, local auxin gradients represent a common module for formation of all plant organs, regardless of their mature morphology or developmental origin. AU - Eva Benková AU - Michniewicz, Marta AU - Sauer, Michael AU - Teichmann, Thomas AU - Seifertová, Daniela AU - Jürgens, Gerd AU - Jirí Friml ID - 2996 IS - 5 JF - Cell TI - Local, efflux-dependent auxin gradients as a common module for plant organ formation VL - 115 ER - TY - JOUR AB - Axis formation occurs in plants, as in animals, during early embryogenesis. However, the underlying mechanism is not known. Here we show that the first manifestation of the apical-basal axis in plants, the asymmetric division of the zygote, produces a basal cell that transports and an apical cell that responds to the signalling molecule auxin. This apical-basal auxin activity gradient triggers the specification of apical embryo structures and is actively maintained by a novel component of auxin efflux, PIN7, which is located apically in the basal cell. Later, the developmentally regulated reversal of PIN7 and onset of PIN1 polar localization reorganize the auxin gradient for specification of the basal root pole. An analysis of pin quadruple mutants identifies PIN-dependent transport as an essential part of the mechanism for embryo axis formation. Our results indicate how the establishment of cell polarity, polar auxin efflux and local auxin response result in apical-basal axis formation of the embryo, and thus determine the axiality of the adult plant. AU - Jirí Friml AU - Vieten, Anne AU - Sauer, Michael AU - Weijers, Dolf AU - Schwarz, Heinz AU - Hamann, Thorsten AU - Offringa, Remko AU - Jürgens, Gerd ID - 2995 IS - 6963 JF - Nature TI - Efflux dependent auxin gradients establish the apical basal axis of Arabidopsis VL - 426 ER - TY - JOUR AB - The regular arrangement of leaves around a plant's stem, called phyllotaxis, has for centuries attracted the attention of philosophers, mathematicians and natural scientists; however, to date, studies of phyllotaxis have been largely theoretical. Leaves and flowers are formed from the shoot apical meristem, triggered by the plant hormone auxin. Auxin is transported through plant tissues by specific cellular influx and efflux carrier proteins. Here we show that proteins involved in auxin transport regulate phyllotaxis. Our data indicate that auxin is transported upwards into the meristem through the epidermis and the outermost meristem cell layer. Existing leaf primordia act as sinks, redistributing auxin and creating its heterogeneous distribution in the meristem. Auxin accumulation occurs only at certain minimal distances from existing primordia, defining the position of future primordia. This model for phyllotaxis accounts for its reiterative nature, as well as its regularity and stability. AU - Reinhardt, Didier AU - Pesce, Eva-Rachele AU - Stieger, Pia AU - Mandel, Therese AU - Baltensperger, Kurt AU - Bennett, Malcolm AU - Traas, Jan AU - Jirí Friml AU - Kuhlemeier, Cris ID - 2994 IS - 6964 JF - Nature TI - Regulation of phyllotaxis by polar auxin transport VL - 426 ER -