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Dendrite Morphology (dendrite + morphology)
Selected AbstractsDifferential roles of Rap1 and Rap2 small GTPases in neurite retraction and synapse elimination in hippocampal spiny neuronsJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Zhanyan Fu Abstract The Rap family of small GTPases is implicated in the mechanisms of synaptic plasticity, particularly synaptic depression. Here we studied the role of Rap in neuronal morphogenesis and synaptic transmission in cultured neurons. Constitutively active Rap2 expressed in hippocampal pyramidal neurons caused decreased length and complexity of both axonal and dendritic branches. In addition, Rap2 caused loss of dendritic spines and spiny synapses, and an increase in filopodia-like protrusions and shaft synapses. These Rap2 morphological effects were absent in aspiny interneurons. In contrast, constitutively active Rap1 had no significant effect on axon or dendrite morphology. Dominant-negative Rap mutants increased dendrite length, indicating that endogenous Rap restrains dendritic outgrowth. The amplitude and frequency of ,-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-mediated miniature excitatory postsynaptic currents (mEPSCs) decreased in hippocampal neurons transfected with active Rap1 or Rap2, associated with reduced surface and total levels of AMPA receptor subunit GluR2. Finally, increasing synaptic activity with GABAA receptor antagonists counteracted Rap2's inhibitory effect on dendrite growth, and masked the effects of Rap1 and Rap2 on AMPA-mediated mEPSCs. Rap1 and Rap2 thus have overlapping but distinct actions that potentially link the inhibition of synaptic transmission with the retraction of axons and dendrites. [source] Neurogenin 3 cellular and subcellular localization in the developing and adult hippocampusTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 10 2010Julia Simon-Areces Abstract Neurogenin 3 (Ngn3), a proneural gene controlled by the Notch receptor, is implicated in the control of dendrite morphology and synaptic plasticity of cultured hippocampal neurons. Here we report the localization and subcellular distribution of Ngn3 in the hippocampus in vivo and in neuronal cultures. In situ hybridization showed Ngn3 mRNA expression in the pyramidal layer and dentate gyrus of adult mouse hippocampus. Immunohistochemistry studies revealed that Ngn3 localization is mostly cytoplasmic in the hippocampal eminence at embryonic day (E)17 and postnatal day (P)0. At P10 it is cytoplasmic in CA1,CA3 pyramidal neurons and nuclear in granule cells of the dentate gyrus. In the adult hippocampus Ngn3 is localized in the nucleus and cytoplasm of both pyramidal neurons and granule cells. During development of cultured hippocampal neurons, Ngn3 mRNA expression is higher at stages of neuronal polarization, as judged by reverse-transcription polymerase chain reaction (RT-PCR), and it is mostly cytoplasmic. The tracking of the subcellular localization of Ngn3 in neurons infected with a virus expressing myc-Ngn3 suggests that the protein is quickly translocated to the cell nucleus after synthesis and then reexported to the cytoplasm. Treatment with leptomycinB, a potent and specific inhibitor of the exportin CRM1, induced its accumulation into the nucleus, suggesting that CRM1 mediates the nuclear export of Ngn3. These results suggest that Ngn3 may play a role in neuronal development by actions in the cytoplasm. J. Comp. Neurol. 518:1814,1824, 2010. © 2009 Wiley-Liss, Inc. [source] Age-Related Three-Dimensional Morphological Changes in Rat Motoneurons Innervating Diaphragm and Longissimus MusclesANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2008H. Miyata Summary We investigated age-related morphological changes of rat motoneurons innervating diaphragm muscle (DI-MN) and lumber longissimus muscle (LL-MN) in which quite different activation patterns exist. In young (2,4 months) and old (24,26 months) rats, the motoneurons innervating both muscles were labelled retrogradely by intramuscular injection of cholera toxin B subunit. After a 4-day survival, horizontal slices of the spinal cord were processed with immunohistochemical staining (first antibody to cholera toxin B subunit and second antibody with Cy3) and observed with a confocal microscope. Three-dimensional reconstruction of labelled motoneurons was performed to examine soma and dendrite morphology. As compared to the soma volume in young rats, significantly smaller values were found in old rats in both motoneurons and the degrees of decline were 16.1% in DI-MN and 20.3% in LL-MN. Significant decreases in the thickness of primary dendrites were also found in both motoneurons, and the degrees of decline were 17.5% in DI-MN and 22.3% in LL-MN. Smaller changes were found in DI-MN than in LL-MN, indicating the possibility that increased activation by central drives can attenuate age-related morphological changes of the motor system in the spinal cord. [source] A New Photothermal Therapeutic Agent: Core-Free Nanostructured AuxAg1,x DendritesCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2008Kuo-Wei Hu Abstract A new class of AuxAg1,x nanostructures with dendrite morphology and a hollow interior were synthesized by using a replacement reaction between Ag dendrites and an aqueous solution of HAuCl4. The Ag nanostructured dendrites were generated by the reaction of AgNO3 with ascorbic acid in a methanol/water system. The dendrites resemble a coral shape and are built up of many stems with an asymmetric arrangement. Each stem is approximately 400,nm in length and 65,nm in diameter. The bimetallic composition of AuxAg1,x can be tuned by the addition of different amounts of HAuCl4 to the Ag dendritic solution. The hollowing process resulted in tubular structures with a wall thickness of 10.5,nm in Au0.3Ag0.7 dendrites. The UV/Vis spectra indicate that the strongest NIR absorption among the resulting hollow AuxAg1,x dendrites was in Au0.3Ag0.7. The MTT assay was conducted to evaluate the cytotoxicity of Ag dendrites, hollow Au0.06Ag0.94 and Au0.3Ag0.7 dendrites, and Au nanorods. It was found that hollow Au0.06Ag0.94 and Au0.3Ag0.7 dendrites exhibited good biocompatibility, while both Ag dendrites and Au nanorods showed dose-dependent toxicity. Because of absorption in the NIR region, hollow Au0.3Ag0.7 dendrites were used as photothermal absorbers for destroying A549 lung cancer cells. Their photothermal performance was compared to that of Au nanorod photothermal therapeutic agents. As a result, the particle concentration and laser power required for efficient cancer cell damage were significantly reduced for hollow Au0.3Ag0.7 dendrites relative to those used for Au nanorods. The hollow Au0.3Ag0.7 nanostructured dendrites show potential in photothermolysis for killing cancer cells. [source] | ||||||||||