bluuebunny/crossref_metadata_2025 huggingface dataset:
Glial Cell Line-Derived Neurotrophic Factor and Developing Mammalian Motoneurons: Regulation of Programmed Cell Death Among Motoneuron Subtypes
Authors: Oppenheim Ronald W. , Houenou Lucien J. , Parsadanian Alexender S. , Prevette David , Snider William D. , Shen Liya
Published: April 2018

Because of discrepancies in previous reports regarding the role of glial cell line-derived neurotrophic factor (GDNF) in motoneuron (MN) development and survival, we have reexamined MNs in GDNF-deficient mice and in mice exposed to increased GDNF afterin uterotreatment or in transgenic animals overexpressing GDNF under the control of the muscle-specific promoter myogenin (myo-GDNF). With the exception of oculomotor and abducens MNs, the survival of all other populations of spinal and cranial MNs were reduced in GDNF-deficient embryos and increased in myo-GDNF andin uterotreated animals. By contrast, the survival of spinal sensory neurons in the dorsal root ganglion and spinal interneurons were not affected by any of the perturbations of GDNF availability.

In wild-type control embryos, all brachial and lumbar MNs appear to express the GDNF receptors c-ret and GFRα1 and the MN markers ChAT, islet-1, and islet-2, whereas only a small subset express GFRα2. GDNF-dependent MNs that are lost in GDNF-deficient animals express ret/GFRα1/islet-1, whereas many surviving GDNF-independent MNs express ret/GFRα1/GFRα2 and islet-1/islet-2. This indicates that many GDNF-independent MNs are characterized by the presence of GFRα2/islet-2. It seems likely that the GDNF-independent population represent MNs that require other GDNF family members (neurturin, persephin, artemin) for their survival. GDNF-dependent and -independent MNs may reflect subtypes with distinct synaptic targets and afferent inputs.
Functional Nicotinic Acetylcholine Receptors That Mediate Ganglionic Transmission in Cardiac Parasympathetic Neurons
Authors: Bibevski Steve , Zhou Yuefang , McIntosh J. Michael , Zigmond Richard E. , Dunlap Mark E.
Published: April 2018

Nicotinic acetylcholine receptors (nAChRs) mediate ganglionic transmission in the peripheral autonomic nervous system in mammals. Functional neuronal nAChRs have been shown to assemble from a combination of α and β subunits, including α3, α5, α7, β2, and β4 in RNA-injected oocytes, but the subunit composition of functional neuronal nAChRsin vivoin mammals remains unknown. We examined the subunit composition of functional nAChRs in the intracardiac parasympathetic ganglion in a physiologically intact systemin vivo. We report here that localized perfusion of the canine intracardiac ganglionin situwith an antagonist specific for nAChRs containing an α3/β2 subunit interface (α-conotoxin MII 100–200 nm) resulted in reversible attenuation of the sinus cycle length (SCL) response by ∼70% to electrical stimulation of the preganglionic vagus nerve. Perfusion with antagonist specific for receptors containing an α3/β4 subunit interface (α-conotoxin AuIB 1 μm) resulted in attenuation in SCL responses (∼20%) compared with baseline when applied by itself, but not in animals pretreated with α-conotoxin MII. Perfusion of the ganglion with α-bungarotoxin (1 μm, which blocks α7 receptors) caused a reduction in SCL response by ∼30% compared with baseline when perfused on its own and when added after blockade with MII and AuIB. Perfusion with hexamethonium bromide resulted in complete blockade of ganglionic transmission, confirming total perfusion of the ganglion and the nicotinic nature of ganglionic transmission at this synapse. Immunohistochemistry using monoclonal antibodies against specific nicotinic subunits confirmed the presence of α3, α7, β2, and β4 subunits. We conclude that functional ganglionic transmission in the canine intracardiac ganglion is mediated primarily by receptors containing an α3/β2 subunit interface, with a smaller contribution by receptors containing α7 nAChRs. Despite the presence of β4 subunits in functional channels, a contribution of a distinct α3/β4 receptor population that does not include an α3/β2 subunit interface was less clear.
Activation of Locomotion in Adult Chronic Spinal Rats Is Achieved by Transplantation of Embryonic Raphe Cells Reinnervating a Precise Lumbar Level
Authors: y Ribotta Minerva Giménez , Provencher Jeanine , Feraboli-Lohnherr Delphine , Rossignol Serge , Privat Alain , Orsal Didier
Published: April 2018

Traumatic lesions of the spinal cord yield a loss of supraspinal control of voluntary locomotor activity, although the spinal cord contains the necessary circuitry to generate the basic locomotor pattern. In spinal rats, this network, known as central pattern generator (CPG), was shown to be sensitive to serotonergic pharmacological stimulation. In previous works we have shown that embryonic raphe cells transplanted into the sublesional cord of adult rats can reinnervate specific targets, restore the lesion-induced increase in receptor densities of neurotransmitters, promote hindlimb weight support, and trigger a locomotor activity on a treadmill without any other pharmacological treatment or training.

With the aim of discriminating whether the action of serotonin on CPG is associated to a specific level of the cord, we have transplanted embryonic raphe cells at two different levels of the sublesional cord (T9 and T11) and then performed analysis of the kinematic and EMG activity synchronously recorded during locomotion. Locomotor performances were correlated to the reinnervated level of the cord and compared to that of intact and transected nontransplanted animals. The movements expressed by T11 transplanted animals correspond to a well defined locomotor pattern comparable to that of the intact animals. On the contrary, T9 transplanted animals developed limited and disorganized movements as those of nontransplanted animals. The correlation of the locomotor performances with the level of reinnervation of the spinal cord suggests that serotonergic reinnervation of the L1-L2 level constitutes a key element in the genesis of this locomotor rhythmic activity. This is the firstin vivodemonstration that transplanted embryonic raphe cells reinnervating a specific level of the cord activate a locomotor behavior.
Changes in Functional Connectivity in Orbitofrontal Cortex and Basolateral Amygdala during Learning and Reversal Training
Authors: Schoenbaum Geoffrey , Chiba Andrea A. , Gallagher Michela
Published: April 2018

Interconnections between orbitofrontal cortex (OFC) and basolateral amygdala (ABL) are critical for encoding and using associative information about the motivational significance of stimuli. Previously, we reported that neurons in OFC and ABL fired selectively to cues during odor discrimination learning and reversal training. Here we conducted an analysis of correlated firing in the cell pairs recorded in the previous study. Correlated firing during the intertrial intervals was compared across task phases during different phases of acquisition and reversal learning. Changes in correlated activity during initial learning and subsequent accurate performance on the discrimination problems closely resembled the changes in odor selectivity in OFC and ABL reported earlier. Increased correlated firing was most pronounced in OFC during accurate go, no-go performance in the postcriterion phase of performance, whereas correlated firing in ABL increased primarily during an earlier phase of learning. In contrast, findings during subsequent reversal training diverged from our earlier report in which odor selectivity diminished in OFC and reversed in ABL. When the reinforcement contingencies of the odors were reversed after the rat had learned the original associations, correlated firing further increased significantly in OFC but remained stable in ABL. This evidence that associative encoding increments with reversal learning in OFC suggests that the original associations, although not expressed as stimulus driven activity, may be maintained within the network as new associations are acquired.
A Dominant Negative Egr Inhibitor Blocks Nerve Growth Factor-Induced Neurite Outgrowth by Suppressing c-Jun Activation: Role of an Egr/c-Jun Complex
Authors: Levkovitz Yechiel , Baraban Jay M.
Published: April 2018

Members of the Egr family of transcription factors are rapidly and robustly induced by neurotransmitters and neurotrophins and have been implicated in mediating enduring changes in neuronal function elicited by these stimuli. Because we have found in previous studies that a dominant negative inhibitor of Egr action, the Egr zinc finger domain (ZnEgr), blocks NGF-induced neurite outgrowth in PC12 cells, we have used this preparation to help identify the downstream targets of Egr proteins involved in plasticity. Our investigation into the mechanism of action of ZnEgr indicates that it blocks NGF-induced neurite outgrowth by suppressing activation of c-Jun, a critical step in the signaling pathway mediating this response. Although we had assumed that ZnEgr exerts its effects by binding to the Egr response element (ERE) and thereby blocking target gene regulation by Egr proteins, this classical mode of action appears to be too slow to mediate the effects of Egr proteins on c-Jun activation. In evaluating alternative ERE-independent mechanisms of Egr (and ZnEgr) action, we found that Egr1 and c-Jun coprecipitate and that ZnEgr disrupts formation of the Egr1/c-Jun complex. Furthermore, mutations of ZnEgr that greatly impair or abolish its ability to bind to the ERE do not block its ability to suppress c-Jun activation or neurite outgrowth induced by NGF. Accordingly, our studies indicate that Egr and ZnEgr proteins regulate c-Jun activation via a novel mechanism, protein–protein interaction with c-Jun, rather than via their classical mode of action, binding to the ERE.
Transforming Growth Factor-β1 Increases Bad Phosphorylation and Protects Neurons Against Damage
Authors: Zhu Yuan , Yang Guo-Yuan , Ahlemeyer Barbara , Pang Li , Che Xiao-Ming , Culmsee Carsten , Klumpp Susanne , Krieglstein Josef
Published: April 2018

Despite the characterization of neuroprotection by transforming growth factor-β1 (TGF-β1), the signaling pathway mediating its protective effect is unclear. Bad is a proapoptotic member of the Bcl-2 family and is inactivated on phosphorylation via mitogen-activated protein kinase (MAPK). This study attempted to address whether MAPK signaling and Bad phosphorylation were influenced by TGF-β1 and, furthermore, whether these two events were involved in the antiapoptotic effect of TGF-β1. We found a gradual activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and MAPK-activated protein kinase-1 (also called Rsk1) and a concomitant increase in Bad phosphorylation at Ser112in mouse brains after adenovirus-mediated TGF-β1 transduction under nonischemic and ischemic conditions induced by transient middle cerebral artery occlusion. Consistent with these effects, the ischemia-induced increase in Bad protein level and caspase-3 activation were suppressed in TGF-β1-transduced brain. Consequently, DNA fragmentation, ischemic lesions, and neurological deficiency were significantly reduced. In cultured rat hippocampal cells, TGF-β1 inhibited the increase in Bad expression caused by staurosporine. TGF-β1 concentration- and time-dependently activated Erk1/2 and Rsk1 accompanied by an increase in Bad phosphorylation. These effects were blocked by U0126, a mitogen-activated protein kinase/Erk kinase 1/2 inhibitor, suggesting an association between Bad phosphorylation and MAPK activation. Notably, U0126 and a Rsk1 inhibitor (Ro318220) abolished the neuroprotective activity of TGF-β1 in staurosporine-induced apoptosis, indicating that activation of MAPK is necessary for the antiapoptotic effect of TGF-β1 in cultured hippocampal cells. Together, we demonstrate that TGF-β1 suppresses Bad expression under lesion conditions, increases Bad phosphorylation, and activates the MAPK/Erk pathway, which may contribute to its neuroprotective activity.
Glial Cell Line-Derived Neurotrophic Factor Promotes the Survival of Early Postnatal Spinal Motor Neurons in the Lateral and Medial Motor Columns in Slice Culture
Authors: Rakowicz Wojtek P. , Staples Christopher S. , Milbrandt Jeffrey , Brunstrom Janice E. , Johnson Eugene M.
Published: April 2018

The mechanisms by which trophic factors bring about spinal motor neuron (MN) survival and regulate their number during development are not well understood. We have developed an organotypic slice culture model for thein vitrostudy of the trophic requirements and cell death pathways in MNs of postnatal day 1–2 mice. Both lateral motor column (LMC) and medial motor column (MMC) neurons died within 72 hr when grown in serum-free medium without trophic factors. Brain-derived neurotrophic factor, ciliary neurotrophic factor, and 8-(4-chlorophenylthio)-cAMP promoted the survival of a proportion of the neurons, but glial cell line-derived neurotrophic factor (GDNF) was the most effective trophic factor, supporting ∼60% of MNs for 1 week in culture. Homozygous deficiency forbax, a proapoptotic member of theBcl-2family, saved the same proportion of neurons as GDNF, suggesting that GDNF alone was sufficient to maintain all “rescuable” MNs for at least 1 week. Analysis of MN survival inGFRα-1−/−mice demonstrated that the trophic effect of GDNF was completely mediated by its preferred coreceptor, GDNF family receptor α-1 (GFRα-1). None of the other GDNF family ligands supported significant MN survival, suggesting that there is little ligand–coreceptor cross talk within the slice preparation. Although MN subtypes can be clearly defined by both anatomical distribution and ontogenetic specification, the pattern of trophic factor responsiveness of neurons from the MMC was indistinguishable from that seen in the LMC. Thus, in contrast to all other factors and drugs studied to date, GDNF is likely to be a critical trophic agent for all early postnatal MN populations.
Ionic Basis of Cold Receptors Acting as Thermostats
Authors: Okazawa Makoto , Takao Keizo , Hori Aiko , Shiraki Takuma , Matsumura Kiyoshi , Kobayashi Shigeo
Published: April 2018

When temperature (T) of skin decreases stepwise, cold fibers evoke transient afferent discharges, inducing cold sensation and heat-gain responses. Hence we have proposed that cold receptors at distal ends of cold fibers are thermostats to regulate skin T against cold. Here, with patch-clamp techniques, we studied the ionic basis of cold receptors in cultured dorsal root ganglion (DRG) neurons of rats, as a model of nerve endings. Cells that increased cytosolic Ca2+level in response to moderate cooling were identified as neurons with cold receptors. In whole-cell current-clamp recordings of these cells, in response to cooling, cold receptors evoked a dynamic receptor potential (RP), eliciting impulses briefly. In voltage-clamp recordings (-60 mV), step cooling induced an inward cold current (Icold) with inactivation, underlying the dynamic RP. Ca2+ions that entered into cells from extracellular side induced the inactivation. Analysis of the reversal potential implied thatIcoldwas nonselective cation current with high Ca2+permeability. Threshold temperatures of cooling-induced Ca2+response andIcoldwere different primarily among cells. In outside-out patches, when T decreased, single nonselective cation channels became active at a critical T. This implies that a cold receptor is an ion channel and acts as the smallest thermostat. Because these thermal properties were consistent with that in cold fibers, we conclude that the same cold receptors exist at nerve endings and generate afferent impulses for cold sensation and heat-gain behaviors in response to cold.
Evidence of Common Progenitors and Patterns of Dispersion in Rat Striatum and Cerebral Cortex
Authors: Reid Christopher B. , Walsh Christopher A.
Published: April 2018

To correlate clonal patterns in the rat striatum with adult neuronal phenotypes, we labeled striatal progenitors between embryonic day 14 (E14) and E19 with a retroviral library encoding alkaline phosphatase. In the adult striatum, the majority of E14-labeled neurons (87%) were members of discrete horizontal or radial cell clusters. Radial clusters accounted for only 23% of cell clusters but >34% of labeled cells. Striatal clones also demonstrated an unexpected widespread pattern of clonal dispersion. The majority of striatal clones were widely dispersed within the striatum, and 80% of clones were part of even larger clones that included cortical interneurons. Finally, we observed that PCR-positive cortical interneurons were members of clones containing both interneurons and pyramids (44%), exclusively interneuron clones (24%), or combined striatal–cortical clones (16%), consistent with the view that cortical interneurons have multiple origins in differentially behaving progenitor cells. Our data are also consistent with the notion that similar mechanisms underpin striatal and cortical development.
The Spatial Dimensions of Electrically Coupled Networks of Interneurons in the Neocortex
Authors: Amitai Yael , Gibson Jay R. , Beierlein Michael , Patrick Saundra L. , Ho Alice M. , Connors Barry W. , Golomb David
Published: April 2018

Inhibitory interneurons of the neocortex are electrically coupled to cells of the same type through gap junctions. We studied the spatial organization of two types of interneurons in the rat somatosensory cortex: fast-spiking (FS) parvalbumin-immunoreactive (PV+) cells, and low threshold-spiking (LTS) somatostatin-immunoreactive (SS+) cells. Paired recordings in layer 4 demonstrated that both the probability of coupling and the coupling coefficient drop steeply with intersomatic distance, reaching zero beyond 200 μm. The dendritic arbors of FS and LTS cells were reconstructed from electrophysiologically characterized, biocytin-filled cells; the two cell types had only minor differences in the number and span of their dendrites. However, there was a markedly higher density of PV+ cells than SS+ cells. PV+ cells were densest in layer 4, while SS+ cell density peaked in the subgranular layers. From these data we estimate that there is measurable electrical coupling (directly or indirectly via intermediary cells) between each interneuron and 20–50 others. The large number of electrical synapses implies that each interneuron participates in a large, continuous syncytium. To evaluate the functional significance of these findings, we examined several simple architectures of coupled networks analytically. We present a mathematical method to estimate the average summated coupling conductance that each cell receives from all of its neighbors, and the average leak conductance of individual cells, and we suggest that these have the same order of magnitude. These quantitative results have important implications for the effects of electrical coupling on the dynamic behavior of interneuron networks.
Extracellular Peptidase Activity Tunes Motor Pattern Modulation
Authors: Wood Debra E. , Nusbaum Michael P.
Published: April 2018

We are examining how extracellular peptidase activity sculpts the peptidergic actions of modulatory projection neurons on rhythmically active neuronal circuits, using the pyloric circuit in the stomatogastric ganglion (STG) of the crabCancer borealis. Neurally released peptides can diffuse long distances to bind to their receptors. Hence, different neurons releasing the same neuropeptide into the same neuropil may reach the same receptor complement. However, extracellular peptidases can limit neuropeptide diffusion and terminate its actions.

Distinct versions of the pyloric rhythm are elicited by selective activation of different projection neurons, including those with overlapping sets of cotransmitters. Two of these projection neurons, modulatory commissural neuron 1 (MCN1) and the modulatory proctolin neuron (MPN), contain the neuropeptide proctolin plus GABA. MCN1 also containsCancer borealistachykinin-related peptide Ia (CabTRP Ia). CabTRP Ia is not fully responsible for the distinct actions of MCN1 and MPN. Because there is aminopeptidase activity in the STG that terminates proctolin actions, we tested the hypothesis that the differences in the actions of MCN1 and MPN that are not mediated by CabTRP Ia result from the differential actions of aminopeptidase activity on proctolin released from these two projection neurons. We found that the pyloric circuit response to these two projection neurons becomes more similar when this aminopeptidase activity is blocked. This result supports the hypothesis that extracellular peptidase activity enables different projection neurons to use the same neuropeptide transmitter for eliciting distinct outputs from the same neuronal circuit.
Plasma Membrane GABA Transporters Reside on Distinct Vesicles and Undergo Rapid Regulated Recycling
Authors: Deken Scott L. , Wang Dan , Quick Michael W.
Published: April 2018

Plasma membrane neurotransmitter transporters affect synaptic signaling through transmitter sequestration. Transporters redistribute to and from the plasma membrane, suggesting a role for trafficking in regulating synaptic transmitter levels. One method for controlling transmitter levels would be to regulate transporter redistribution in parallel with transmitter release. Thus, how similar are these processes? We show that the trafficking of the GABA transporter GAT1 resembles the trafficking of neurotransmitter-filled synaptic vesicles: (1) transporters located on the plasma membrane are internalized and reinserted into the plasma membrane on the order of minutes; (2) the rate of recycling is depolarization and calcium dependent; (3) GAT1 internalization is associated with clathrin and dynamin; and (4) intracellular GAT1 is associated with multiple compartments and, more importantly, is found on a distinct class of vesicles. These vesicles are clear, ∼50 nm in diameter, and contain many proteins found on neurotransmitter-containing small synaptic vesicles; however, they appear to lack several traditional small synaptic vesicle proteins, such as synaptophysin and the vesicular GABA transporter. These data provide additional support for the hypothesis that GABA transporters traffic in parallel with neurotransmitter-containing small synaptic vesicles and also raise the possibility that some fraction of vesicles found in GABAergic neurons may not be participating in transmitter release but rather in the rapid regulated redistribution of membrane proteins involved in transmitter uptake.
Opposing Roles of D1and D2Receptors in Appetitive Conditioning
Authors: Eyny Yaniv S. , Horvitz Jon C.
Published: April 2018

Previous studies have shown that D1receptor blockade disrupts and D2receptor blockade enhances long-term potentiation. These data lead to the prediction that D1antagonists will attenuate and D2antagonists will potentiate at least some types of learning. The prediction is difficult to test, however, because disruptions in either D1or D2transmission lead to reduced locomotion, exploration, and response execution and are therefore likely to impair learning that requires behavioral responding (including exploration of an environment) during the learning episode. Under a paradigm that minimizes motor requirements, rats were trained to enter a food compartment during pellet presentation. Animals then received tone–food pairings under the influence of D1antagonist SCH23390 (0, 0.4, 0.8, and 0.16 mg/kg) or D2antagonist raclopride (0, 0.2, 0.4, and 0.8 mg/kg). An additional group received unpaired presentations of tone and food. On a drug-free test day 24 hr later, animals that had been under the influence of SCH23390 (like animals that had received unpaired presentations of tone and food) showed reduced head entries in response to the tone, whereas animals that had been under the influence of raclopride showed increased head entries in response to the tone compared with vehicle controls. These data demonstrate that, under a conditioned approach paradigm, D1and D2family receptor antagonists disrupt and promote learning, respectively, as predicted by the effects of D1and D2receptor blockade on neuronal plasticity.
Metabotropic Glutamate Receptor Activation Enhances the Activities of Two Types of Ca2+-Activated K+Channels in Rat Hippocampal Astrocytes
Authors: Gebremedhin Debebe , Yamaura Ken , Zhang Chenyang , Bylund Johan , Koehler Raymond C. , Harder David R.
Published: April 2018

The influence of activation of glutamate receptor (GluR) on outward K+current in cultured neonate rat hippocampal astrocytes was investigated. Patch-clamp analysis of K+channel currents in cultured astrocytes identified the existence of 71 ± 6 and 161 ± 11 pS single-channel K+currents that were sensitive to changes in voltage and [Ca2+]iand blocked by external TEA but not by charybdotoxin, iberiotoxin, apamin, or 4-aminopyridine. Reverse transcriptase (RT)-PCR and Northern blot analysis revealed transcripts of the Ca2+-activated K+channel (KCa) β4-subunit (β4) (KCNMB4) in cultured astrocytes. Expression of the metabotropic glutamate receptor (mGluR) subtypes mGluR1 and mGluR5 and the ionotropic glutamate receptor (iGluR) subtypes iGluR1 and iGluR4 were detected by RT-PCR and immunofluorescence analysis in cultured astrocytes. The mGluR agonistsl-glutamate and quisqualate increased the open state probability (NPo) of the 71 and 161 pS K+channel currents that were prevented by the mGluR receptor antagonists 1-aminoindan-1,5-dicarboxylic acid orl-(+)-2-amino-3-phosphonopropionic acid and not by the iGluR antagonists (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate or CNQX. Activation of the two types of K+channel currents by mGluR agonists was attenuated by pertussis toxin and by inhibition of phospholipase C (PLC) or cytochrome P450 arachidonate epoxygenase. These results indicate that brain astrocytes contain the KCNMB4 transcript and express two novel types of KCachannels that are gated by activation of a G-protein coupled metabotropic glutamate receptor functionally linked to PLC and cytochrome P450 arachidonate epoxygenase activity.
Overexpression of Copper/Zinc Superoxide Dismutase in Transgenic Mice Protects against Neuronal Cell Death after Transient Focal Ischemia by Blocking Activation of the Bad Cell Death Signaling Pathway
Authors: Saito Atsushi , Hayashi Takeshi , Okuno Shuzo , Ferrand-Drake Michel , Chan Pak H.
Published: April 2018

The Bad signaling pathway contributes to the regulation of apoptosis after a variety of cell death stimuli, and Bad plays a key role in determining cell death or survival. We have reported that overexpression of copper/zinc superoxide dismutase (SOD1) reduces apoptotic cell death after transient focal cerebral ischemia (tFCI). However, both the role of the Bad pathway after tFCI and the role of oxygen free radicals in the regulation of apoptosis remain unknown. To clarify these issues, we used anin vivotFCI model of SOD1 transgenic mice and wild-type mice. Moreover, to examine the role of protein kinase A (PKA) in the Bad pathway after tFCI, we administered the PKA inhibitor, H89, into the mouse brain after tFCI. Immunohistochemistry and Western blot analysis showed that dephosphorylation and translocation of Bad were detected early after tFCI and that they were promoted by H89 treatment but prevented by SOD1. Coimmunoprecipitation revealed that the dimerization of Bad progressed with 14-3-3 (Bad/14-3-3) and with Bcl-xL(Bad/Bcl-xL) after tFCI. Moreover, Bad/14-3-3 was prevented by H89 treatment but promoted by SOD1. Bad/Bcl-xLwas prevented by SOD1 but promoted by H89 treatment. A cell death assay revealed that apoptotic-related DNA fragmentation was aggravated by H89 treatment but reduced by SOD1. These results suggest that the Bad pathway mediated by PKA is involved in apoptotic cell death after tFCI and that overexpression of SOD1 may attenuate this apoptotic cell death.
Segregated Expression of AMPA-Type Glutamate Receptors and Glutamate Transporters Defines Distinct Astrocyte Populations in the Mouse Hippocampus
Authors: Matthias Katja , Kirchhoff Frank , Seifert Gerald , Hüttmann Kerstin , Matyash Marina , Kettenmann Helmut , Steinhäuser Christian
Published: April 2018

Recent data have suggested the existence of direct signaling pathways between glial cells and neurons. Here we report the coexistence of distinct types of cells expressing astrocyte-specific markers within the hippocampus that display diverse morphological, molecular, and functional profiles. Usage of transgenic mice with GFAP promoter-controlled enhanced green fluorescent protein (EGFP) expression allowed the identification of astroglial cells after fresh isolation or in brain slices. Combining patch-clamp recordings and single-cell reverse transcription-PCR, we distinguished two morphologically distinct types of EGFP-positive cells, one expressing glutamate transporters and the other expressing ionotropic glutamate receptors. None of the EGFP-positive cells coexpressed glutamate receptors and transporters. Subpopulations of glutamate receptor-bearing EGFP-positive cells expressed AN2, the mouse homolog of the rat NG2 proteoglycan or transcripts for excitatory amino acid carrier 1, a neuronal glutamate transporter. Our data demonstrate the presence of distinct, independent populations of cells with astroglial properties in the developing hippocampus that can differently modulate neuronal signaling pathways. The observed heterogeneity of cells with GFAP promoter-regulated EGFP expression and S100β/GFAP immunoreactivity challenges the hitherto accepted definition of astrocytes.
Widespread Defects in the Primary Olfactory Pathway Caused by Loss ofMash1Function
Authors: Murray Richard C. , Navi Daniel , Fesenko John , Lander Arthur D. , Calof Anne L.
Published: April 2018

MASH1, a basic helix-loop-helix transcription factor, is widely expressed by neuronal progenitors in the CNS and PNS, suggesting that it plays a role in the development of many neural regions. However, in mice lacking a functionalMash1gene, major alterations have been reported in only a few neuronal populations; among these is a generalized loss of olfactory receptor neurons of the olfactory epithelium. Here, we use a transgenic reporter mouse line, in which the cell bodies and growing axons of subsets of central and peripheral neurons are marked by expression of atau-lacZreporter gene (theTattler-4allele), to look both more broadly and deeply at defects in the nervous system ofMash1−/−mice. In addition to the expected lack of olfactory receptor neurons in the main olfactory epithelium, developingMash1−/−;Tattler-4+/−mice exhibited reductions in neuronal cell number in the vomeronasal organ and in the olfactory bulb; the morphology of the rostral migratory stream, which gives rise to olfactory bulb interneurons, was also abnormal. Further examination of cell proliferation, cell death, and cell type-specific markers inMash1−/−animals uncovered parallels between the main olfactory epithelium and the vomeronasal organ in the regulation of sensory neuron development. Interestingly, this analysis also revealed that, in the olfactory epithelium ofMash1−/−animals, there is an overproduction of proliferating cells that co-express markers of both neuronal progenitors and supporting cells. This finding suggests that olfactory receptor neurons and olfactory epithelium supporting cells may share a common progenitor, and that expression ofMash1may be an important factor in determining whether these progenitors ultimately generate neurons or glia.
Sensory Neuron Subtypes Have Unique Substratum Preference and Receptor Expression before Target Innervation
Authors: Guan Wei , Puthenveedu Manojkumar A. , Condic Maureen L.
Published: April 2018

The factors controlling the specification and subsequent differentiation of sensory neurons are poorly understood. Data from embryological manipulations suggest that either sensory neuron fates are specified by the targets they encounter or sensory neurons are considerably more “plastic” with respect to specification than are neurons of the CNS. The prevailing view that sensory neurons are specified late in development is not consistent, however, with the directed outgrowth of sensory neurons to their targets and the characteristic spatial distribution of sensory neuron fates within the peripheral ganglia. To address when in development different classes of sensory neurons can first be distinguished, we investigated the interactions of early dorsal root ganglia neurons with the extracellular matrix before neurite outgrowth to targets. We found that subclasses of sensory neurons in early dorsal root ganglia show different patterns of neurite outgrowth and integrin expression that are predictive of their fates. In the absence of neurotrophins, presumptive proprioceptive neurons extend neurites robustly on both laminin and fibronectin, whereas presumptive cutaneous neurons show a strong preference for laminin. Cutaneous afferents that have innervated targets show a similar strong preference for laminin and show higher levels of integrin α7β1 than do proprioceptive neurons. Finally, presumptive proprioceptive neurons express fibronectin receptors, integrin α3β1, α4β1, and α5β1, at higher levels than do presumptive cutaneous neurons. Our results indicate that subtypes of sensory neurons have unique patterns of neurite outgrowth and receptor expression before target innervation.
Leukemia Inhibitory Factor Is a Key Signal for Injury-Induced Neurogenesis in the Adult Mouse Olfactory Epithelium
Authors: Bauer S. , Rasika S. , Han Jing , Mauduit C. , Raccurt M. , Morel G. , Jourdan F. , Benahmed M. , Moyse E. , Patterson P. H.
Published: April 2018

The mammalian olfactory epithelium (OE) is composed of primary olfactory sensory neurons (OSNs) that are renewed throughout adulthood by local, restricted neuronal progenitor cells. The molecular signals that control this neurogenesisin vivoare unknown. Using olfactory bulb ablation (OBX) in adult mice to trigger synchronous mitotic stimulation of neuronal progenitors in the OE, we show thein vivoinvolvement of a cytokine in the cellular events leading to the regeneration of the OE. We find that, of many potential mitogenic signals, only leukemia inhibitory factor (LIF) is induced before the onset of neuronal progenitor proliferation. The rise in LIF mRNA expression peaks at 8 hr after OBX, andin situRT-PCR and immunocytochemistry indicate that LIF is upregulated, in part, in the injured neurons themselves. This rise in LIF is necessary for injury-induced neurogenesis, as OBX in the LIF knock-out mouse fails to stimulate cell proliferation in the OE. Moreover, delivery of exogenous LIF to the intact adult OE using an adenoviral vector stimulates BrdU labeling in the apical OE. Taken together, these results suggest that injured OSNs release LIF as a stimulus to initiate their own replacement.
Discharge of Raphe Magnus on and offCells Is Predictive of the Motor Facilitation Evoked by Repeated Laser Stimulation
Authors: Foo H. , Mason Peggy
Published: April 2018

Medullary raphe magnus (RM)onandoffcells are thought to modulate spinal nociception by gating withdrawals evoked by noxious stimulation. To test whether withdrawal initiation is the target of RM modulation, we examined the relationship betweenonandoffcell discharge and motor withdrawal evoked by noxious laser heat in halothane-anesthetized rats. The cellular responses of both cell types began during the 50 msec after onset of the tail flick, peaked within 200 msec, and outlasted the duration of the motor reaction. Thus, it is unlikely that the target ofonandoffcell modulation is withdrawal initiation; instead,onandoffcells may modulate reactions to repeated noxious stimulation. We therefore tested whether laser heat-evoked changes in RM cell discharge were predictive of the modulatory effects of one noxious stimulus on the reaction to a subsequent noxious stimulus. Two pulses of laser heat were presented at interpulse intervals of 0.8, 2.0, or 10.0 sec. The motor withdrawal evoked by the second pulse was significantly enhanced relative to that evoked by the first pulse. The observed motor enhancement depended on supraspinal input because it was not present in spinalized rats. Comparison of the relative changes in motor and cellular activity preceding double laser heat stimulation revealed parallel changes between motor facilitation, decreases inoffcell discharge, and increases inoncell discharge. This finding suggests a preparatory role for RMonandoffcells in enhancing reactions to a noxious stimulus that closely follows another noxious stimulus.
On the Role of Nitric Oxide in Hippocampal Long-Term Potentiation
Authors: Bon Christelle L. M. , Garthwaite John
Published: April 2018

Nitric oxide (NO) functions in several types of synaptic plasticity, including hippocampal long-term potentiation (LTP), in which it may serve as a retrograde messenger after postsynaptic NMDA receptor activation. In accordance with a prediction of this hypothesis, and with previous findings using guinea pig tissue, exogenous NO, when paired with a short tetanus (ST) to afferent fibers, generated a stable NMDA receptor-independent potentiation of rat CA1 hippocampal synaptic transmission that occluded LTP. Contrary to predictions, however, the pairing-induced potentiation was abolished in the presence of NO synthase inhibitors, indicating that endogenous NO is required for exogenous NO to facilitate LTP. Periodic application of NO while endogenous NO synthesis was blocked indicated that a tonic low level is necessary on both sides of the NO–ST pairing for the plasticity to occur. A similar dependence on tonic NO seems to extend to LTP, because application of an NO synthase inhibitor 5 min after tetanic stimulation blocked LTP as effectively as adding it beforehand. The posttetanus time window during which NO operated was restricted to <15 min. Inhibition of the guanylyl cyclase-coupled NO receptor indicated that the potentiation resulting from NO–ST pairing and the NO signal transduction pathway during early LTP are both through cGMP. We conclude that NO does not function simply as an acute signaling molecule in LTP induction but has an equally important role outside this phase. The results resonate with observations concerning the role of the hippocampal NO–cGMP pathway in certain types of learning behavior.
Feedback Inhibition Defines Transverse Processing Modules in the Lateral Amygdala
Authors: Samson Rachel D. , Dumont Éric C. , Paré Denis
Published: April 2018

The lateral amygdaloid (LA) nucleus is the main input station of the amygdala for sensory afferents. However, it is unclear how the lateral nucleus transforms these inputs, because its intrinsic connectivity is poorly understood. Here, we took advantage of the fact that glutamatergic neurons of the lateral nucleus send a primarily unidirectional projection to the basomedial nucleus. Consequently, it was possible to infer the targets of their intranuclear axons (projection cells vs inhibitory interneurons) by backfiring some projection neurons from the basomedial nucleus and analyzing evoked responses in other LA projection cells. Basomedial stimuli evoked markedly different synaptic responses depending on the orientation of the slices. In coronal slices (intact and decorticated), the prevalent response of LA neurons was an inhibition, regardless of the stimulation intensity. This inhibition was sensitive to GABAAand non-NMDA receptor antagonists, suggesting that it was mediated by the activation of GABAergic cells of the LA. In contrast, basomedial stimuli primarily evoked EPSPs in horizontal slices, regardless of the position of recorded neurons. In light of these findings, we conclude that the prevalent target of the intrinsic axon collaterals of projection cells depend on the rostrocaudal position of target neurons with respect to the parent cell body: inhibitory interneurons at rostrocaudal proximity versus other projection cells at a distance. Thus, feedback interneurons effectively divide the lateral nucleus in transverse processing modules that prevent runaway excitation within each module but allow intermixing of sensory information in the rostrocaudal plane.
Wingless Signaling: A Genetic Journey from Morphogenesis to Metastasis
Authors: Bejsovec Amy
Published: April 2018

This FlyBook chapter summarizes the history and the current state of our understanding of the Wingless signaling pathway. Wingless, the fly homolog of the mammalian Wnt oncoproteins, plays a central role in pattern generation during development. Much of what we know about the pathway was learned from genetic and molecular experiments in Drosophila melanogaster, and the core pathway works the same way in vertebrates. Like most growth factor pathways, extracellular Wingless/Wnt binds to a cell surface complex to transduce signal across the plasma membrane, triggering a series of intracellular events that lead to transcriptional changes in the nucleus. Unlike most growth factor pathways, the intracellular events regulate the protein stability of a key effector molecule, in this case Armadillo/β-catenin. A number of mysteries remain about how the “destruction complex” destabilizes β-catenin and how this process is inactivated by the ligand-bound receptor complex, so this review of the field can only serve as a snapshot of the work in progress.
Biology in Bloom: A Primer on the Arabidopsis thaliana Model System
Authors: Woodward Andrew W , Bartel Bonnie
Published: April 2018

Arabidopsis thaliana could have easily escaped human scrutiny. Instead, Arabidopsis has become the most widely studied plant in modern biology despite its absence from the dinner table. Pairing diminutive stature and genome with prodigious resources and tools, Arabidopsis offers a window into the molecular, cellular, and developmental mechanisms underlying life as a multicellular photoautotroph. Many basic discoveries made using this plant have spawned new research areas, even beyond the verdant fields of plant biology. With a suite of resources and tools unmatched among plants and rivaling other model systems, Arabidopsis research continues to offer novel insights and deepen our understanding of fundamental biological processes.
The enemy votes: Weapons improvisation and bargaining failure
Authors: Wood Garrett
Published: April 2018

Belligerents could in principle avoid the ex post costs of conflict by revealing all private information about their violent capabilities and then calculating odds of success ex ante. Incentives to misrepresent private information for strategic gain, however, can cause miscalculations that lead to war. I argue some private information can lead to miscalculation not because it is purposefully misrepresented for strategic gain but because it is too decentralized to be easily revealed. The decentralized private information that produces improvised weapons requires a process of discovering suitable local resources and battlefield testing driven by local military entrepreneurs which frustrates information revelation. Decentralized private information used to improvise new weapons and capabilities like those which emerged in Afghanistan and Iraq show that it can take many years, decades, or even an indeterminate amount of time for fighting to reveal relevant information about violent capabilities.
Reducing Electrolyte Testing in Hospitalized Children by Using Quality Improvement Methods
Authors: Tchou Michael J. , Tang Girdwood Sonya , Wormser Benjamin , Poole Meifawn , Davis-Rodriguez Stephanie , Caldwell J. Timothy , Shannon Lauren , Hagedorn Philip A. , Biondi Eric , Simmons Jeffrey , Anderson Jeffrey , Brady Patrick W.
Published: April 2018

BACKGROUND AND OBJECTIVES:

Despite studies indicating a high rate of overuse, electrolyte testing remains common in pediatric inpatient care. Frequently repeated electrolyte tests often return normal results and can lead to patient harm and increased cost. We aimed to reduce electrolyte testing within a hospital medicine service by >25% within 6 months.

METHODS:

We conducted an improvement project in which we targeted 6 hospital medicine teams at a large academic children’s hospital system by using the Model for Improvement. Interventions included standardizing communication about the electrolyte testing plan and education about the costs and risks associated with overuse of electrolyte testing. Our primary outcome measure was the number of electrolyte tests per patient day. Secondary measures included testing charges and usage rates of specific high-charge panels. We tracked medical emergency team calls and readmission rates as balancing measures.

RESULTS:

The mean baseline rate of electrolyte testing was 2.0 laboratory draws per 10 patient days, and this rate decreased by 35% after 1 month of initial educational interventions to 1.3 electrolyte laboratory draws per 10 patient days. This change has been sustained for 9 months and could save an estimated $292 000 in patient-level charges over the course of a year. Use of our highest-charge electrolyte panel decreased from 67% to 22% of testing. No change in rates of medical emergency team calls or readmission were found.

CONCLUSIONS:

Our improvement intervention was associated with significant and rapid reduction in electrolyte testing and has not been associated with unintended adverse events.
New occurrences of Salicaceae from the Atlantic Forest and Caatinga (Brazil)
Authors: Nepomuceno Álvaro , Alves Marccus
Published: April 2018

Based on new records, we expand the geographical distributions of 6 species of Salicaceae: Banara nitida Spruce ex Benth., Casearia marquetei Nepom. & M. Alves, C. souzae R. Marquete & Mansano, Macrothumia kuhlmannii (Sleumer) Alford, Xylosma glaberrima Sleumer, and X. pseudosalzmanii Sleumer, from the Atlantic Forest and Caatinga. Illustrations of the diagnostic characters of the species, maps of geographic distribution, and a key for identification of the genera of Salicaceae occurring in the Atlantic Forest and Caatinga are provided.
Private environmental consultancy reveals five genera and ten species of angiosperms new to Rio Grande do Norte state, northeastern Brazil
Authors: Moura Edweslley Otaviano de , de Sousa Valdeci Fontes , Soares Arthur de Souza , Versieux Leonardo M.
Published: April 2018

New occurrences of 10 species of angiosperms from Rio Grande do Norte state are reported. These data were collected by an environmental consultancy prior to the establishment of a wind farm. These records demonstrate the presence of knowledge gaps in the Caatinga flora of the state and show how an environmental consultancy can positively contribute towards the documentation of biodiversity in areas prior to their modification by human activities. In particular, at a time when the Brazilian Congress is discussing the elimination of environmental studies for licensing new developments, these new occurrence data highlight the importance of environmental studies.