In addition, they gathered new insights on the organization of projection neurons in the mouse PFC, showing that these neurons could communicate with neurons in their same column and in other columns, as well as in other brain regions, allowing neural information to flow in a specific manner across PFC. Through their analyses, Yan and his colleagues were able to identify 1,515 pyramidal projection neurons and 405 atypical pyramidal projection neurons or spiny stellate neurons with unconventional axon projection patterns. "We then classified these dendrites based on their morphology and analyzed their correspondence with the classification based on axon projections for the same neurons." "We analyzed the same data in which we previously traced axons, this time selecting about 2,000 neurons with the best image quality of dendrites for complete reconstruction," Yan explained. This is essentially a software tool that can trace tera-bytes of images via a three-dimensional (3D) graphical interface. To conduct their new analyses, the researchers used data that they collected as part of a previous study, using a tool that they developed called "fast neurite tracer" (FNT). As the dendrite morphology plays an important role in defining the way neurons receive information, we thought it is natural as a next step to reconstruct the dendrites of these neurons and investigate the relationship between axons and dendrites." "The same data also contain the dendrites of these neurons. "Our previous paper reconstructed the complete axons of more than 6,000 neurons in mouse PFC," Jun Yan, one of the researchers who carried out the study, told Medical Xpress. In a recent paper published in Nature Neuroscience, they mapped thousands of dendrites and axons in the mouse PFC using an innovative tool they developed. Dendrite-like process outgrowth, on the other hand, does not appear to depend on altered intracellular Ca2+.Researchers at the Chinese Academy of Sciences have recently been conducting research aimed at better understanding how axons (i.e., regions of neurons that generate and transmit impulses) and dendrites (i.e., branches extending from neurons that receive impulses from other neurons) are organized in the PFC. Correlation with previous studies suggests that axon-like neurites result from stimulants which elevate intracellular Ca2+, a dependence not previously reported to our knowledge. Time of exposure to stimulatory agent was crucial in determining expression of the neuritic phenotype. Striking morphological differences were also noted, group 2-induced neurites being significantly shorter with more branch points than those generated by group 1 stimulants. These cytoskeletal differences were supported by immunoblot analysis with antisera to the above cytoskeletal proteins. Neurites produced by low serum had mixed properties. The next three treatments (group 2) resulted in dendrite-like processes, as evidenced in immunostaining that was positive for MAP2 and negative for NF-H and SV2. The first four of these (group 1) gave rise to neurites with axon-like characteristics, including immunostaining that was positive for phosphorylated high molecular weight neurofilament protein (NF-H) and synaptic vesicle protein-2 (SV2), but negative for microtubule-associated protein-2 (MAP2). These include neuraminidase, ionomycin, KCl+dibutyryl cAMP, cholera toxin B subunit, retinoic acid, dibutyryl cAMP (alone), GM1 ganglioside, and low serum. In an effort to identify procedures for inducing specific types of neurite outgrowth, and for distinguishing axon- from dendrite-like processes, we have subjected two neuroblastoma cell lines to a variety of stimuli previously shown to induce neurite outgrowth in these cells. This identification will be necessary in developing strategies for utilizing these models to distinguish the underlying mechanisms involved in axonogenesis vs dendritogenesis. Neuroblastoma cells are widely utilized models for the study of the neuritic outgrowth phase of neuronal differentiation, but relatively few such studies have attempted to identify the nature of the process outgrowths.
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