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@INPROCEEDINGS{Yakoubi:834210,
      author       = {Yakoubi, Rachida and Rollenhagen, Astrid and Marec, von
                      Lehe and Kurt, Sätzler and Lübke, Joachim},
      title        = {{S}ynaptic organization in layer 5 of the human temporal
                      lobe: {A} quantitative electron microscopic analysis},
      reportid     = {FZJ-2017-04193},
      year         = {2016},
      abstract     = {Synapses are the key elements for signal transduction and
                      plasticity in the brain, thus controlling the induction,
                      maintenance and termination of signal transduction in any
                      given neuronal microcircuit.Despite a relatively large
                      number of publications on structural and functional aspects
                      of various synapses in the central nervous system of
                      different animal species, very little is known about these
                      structures in humans, in particular about their quantitative
                      geometry. Hence, synapses in cortical layer 5 - the main
                      output station of the neocortex and a recipient layer of
                      thalamocortical afferents of the human temporal lobe - were
                      investigated using serial ultrathin sectioning and digital
                      electron microscopic images. This was followed by three
                      dimensional (3D) volume reconstructions leading in the
                      generation of quantitative 3D-models of synapses. We focused
                      on structural parameters that are the most critical factors
                      underlying synaptic transmission and plasticity, such as the
                      shape, size, number, and distribution of active zones (AZs,
                      functional transmitter release sites) as well as the
                      organization and size of the three pools of synaptic
                      vesicles, namely the readily releasable, the recycling and
                      reserve pool. In addition, immunohistochemistry against
                      glutamine synthetase was carried out to investigate the
                      structural relationship of synapses and astrocytes and thus
                      their contribution to synaptic transmission and plasticity.A
                      total of 152 synaptic boutons and their target structures
                      were completely analyzed. The majority were established
                      either on dendritic spines $(~76\%)$ the remainder on
                      shafts. Synaptic boutons were highly variable in both shape
                      and size (6.20±0.77 μm2; 0.42±0.07 μm3, ranging from
                      0.46 to 27.33 μm2; 0.10 to 1.93 μm3) with a skew to
                      middle-sized boutons. Several mitochondria (0-26) were found
                      in the presynaptic bouton constituting $~6\%$ of the total
                      volume. The majority of boutons $(~88\%)$ had a single pre-
                      (0.452±0.358 µm2; 0.003±0,001 μm3) and postsynaptic
                      densities (0.405±0.100 μm2; 0.01±0.01 μm3), sometimes
                      perforated. The mean total pool size of synaptic vesicles
                      was 1580.19±255.19 (ranging from 142 to 8413) with a mean
                      diameter of 31.99±0.87 nm. Strikingly, no correlation was
                      found between the size of the boutons with that of
                      mitochondria, AZs and the pool of vesicles. Synaptic
                      complexes were surrounded by a dense network of fine
                      astrocytic processes reaching the synaptic cleft, thus
                      regulating the temporal and spatial glutamate
                      concentration.The quantitative 3D-models of synapses will
                      lead to an improved understanding of the function of
                      synapses in cortical networks in humans.},
      month         = {Nov},
      date          = {2016-11-12},
      organization  = {SfN's 46th annual meeting, San Diego
                       (USA), 12 Nov 2016 - 16 Nov 2016},
      subtyp        = {Other},
      cin          = {INM-2 / JARA-BRAIN},
      cid          = {I:(DE-Juel1)INM-2-20090406 / $I:(DE-82)080010_20140620$},
      pnm          = {571 - Connectivity and Activity (POF3-571)},
      pid          = {G:(DE-HGF)POF3-571},
      typ          = {PUB:(DE-HGF)24},
      url          = {https://juser.fz-juelich.de/record/834210},
}