Neuron Morphology Influences Axon Initial Segment Plasticity

In most vertebrate neurons, action potentials are initiated in the axon initial segment (AIS), a specialized region of the axon containing a high density of voltage-gated sodium and potassium channels. It has recently been proposed that neurons use plasticity of AIS length and/or location to regulate their intrinsic excitability. Here we quantify the impact of neuron morphology on AIS plasticity using computational models of simplified and realistic somatodendritic morphologies. In small neurons (e.g., dentate granule neurons), excitability was highest when the AIS was of intermediate length and located adjacent to the soma. Conversely, neurons having larger dendritic trees (e.g., pyramidal neurons) were most excitable when the AIS was longer and/or located away from the soma. For any given somatodendritic morphology, increasing dendritic membrane capacitance and/or conductance favored a longer and more distally located AIS. Overall, changes to AIS length, with corresponding changes in total sodium conductance, were far more effective in regulating neuron excitability than were changes in AIS location, while dendritic capacitance had a larger impact on AIS performance than did dendritic conductance. The somatodendritic influence on AIS performance reflects modest soma-to-AIS voltage attenuation combined with neuron size-dependent changes in AIS input resistance, effective membrane time constant, and isolation from somatodendritic capacitance. We conclude that the impact of AIS plasticity on neuron excitability will depend largely on somatodendritic morphology, and that, in some neurons, a shorter or more distally located AIS may promote, rather than limit, action potential generation

Physical injury stimulates aerobic methane emissions from terrestrial plants

Physical injury is common in terrestrial plants as a result of grazing, harvesting, trampling, and extreme weather events. Previous studies demonstrated enhanced emission of non-microbial CH<sub>4</sub> under aerobic conditions from plant tissues when they were exposed to increasing UV radiation and temperature. Since physical injury is also a form of environmental stress, we sought to determine whether it would also affect CH<sub>4</sub> emissions from plants. Physical injury (cutting) stimulated CH<sub>4</sub> emission from fresh twigs of <i>Artemisia</i> species under aerobic conditions. More cutting resulted in more CH<sub>4</sub> emissions. Hypoxia also enhanced CH<sub>4</sub> emission from both uncut and cut <i>Artemisia frigida</i> twigs. Physical injury typically results in cell wall degradation, which may either stimulate formation of reactive oxygen species (ROS) or decrease scavenging of them. Increased ROS activity might explain increased CH<sub>4</sub> emission in response to physical injury and other forms of stress. There were significant differences in CH<sub>4</sub> emissions among 10 species of <i>Artemisia</i>, with some species emitting no detectable CH<sub>4</sub> under any circumstances. Consequently, CH<sub>4</sub> emissions may be species-dependent and therefore difficult to estimate in nature based on total plant biomass. Our results and those of previous studies suggest that a variety of environmental stresses stimulate CH<sub>4</sub> emission from a wide variety of plant species. Global change processes, including climate change, depletion of stratospheric ozone, increasing ground-level ozone, spread of plant pests, and land-use changes, could cause more stress in plants on a global scale, potentially stimulating more CH<sub>4</sub> emission globally

Preoperative PROMIS Scores Predict Postoperative Improvements Following Rotator Cuff Repair

Background: The Patient-Reported Outcomes Measurement Information System (PROMIS) has emerged as a valid and efficient means of collecting patient outcomes in patients with rotator cuff tear. The purpose of this study was to examine the role of pre-operative PROMIS computer adaptive test (CAT) scores in predicting post-operative PROMIS CAT scores as well as likelihood of achieving minimal clinically important difference (MCID) following rotator cuff repair. We hypothesize that pre-operative PROMIS CAT scores will directly impact both post-operative PROMIS CAT scores and likelihood of achieving MCID.Methods: Patients undergoing arthroscopic rotator cuff repair by one of three fellowship-trained surgeons were identified over a 12-month period. Only patients that completed pre-operative and 6-month post-operative PROMIS CAT assessments were included in this cohort. PROMIS CAT forms for upper extremity physical function (PROMIS-U), pain interference (PROMIS-PI), and depression (PROMIS-D) were utilized. MCID was calculated according to the distribution methodology, and receiver operating characteristics (ROC) were utilized to determine if pre-operative scores were predictive of post-operative outcomes. Preoperative cutoffs were used to predict which patients would likely meet MCID using 95% specificity. Results: A total of 80 patients met our inclusion criteria. PROMIS-UE, PROMIS-PI and PROMIS-D improved 6 months after surgery (p\u3c0.001). 76% of patients met MCID for PROMIS-UE, while 89% met MCID for PROMIS-PI, and 54% met MCID for PROMIS-D. Preoperative PROMIS scores were predictive of post-operative outcomes based on ROC analysis which demonstrated significant area under the curve (AUC) of .725 (p=0.003), .757 (p=0.013), and .789 (p\u3c0.001) for PROMIS-UE, PROMIS-PI, and PROMIS-D, respectively. Individuals with PROMIS-UE scores below 24.95 and PROMIS-PI scores above 65.65 yielded a 100% probability of achieving MCID, while a cutoff of 56.45 for PROMIS-D yielded a 91% probability of achieving MCID with 95% specificity. Conclusion: Patients undergoing arthroscopic rotator cuff repair experience significant improvements in upper extremity physical function, pain interference and depression as measured by PROMIS CAT domains. In particular, patients presenting with PROMIS upper extremity scores of \u3c24.95 are especially likely to achieve MCID.https://scholarlycommons.henryford.com/merf2019clinres/1053/thumbnail.jp

Transgenic Loblolly Pine Trees from Diverse Elite Families

Loblolly pine (Pinus taeda L.) has been the focus of genetic improvement for nearly 100 years because of the value of this species to the forestry industry. The application of gene transfer technology to loblolly pine improvement has been limited by the regeneration of transgenic tissue into plants. We have developed gene transfer systems that allow the regeneration of trees after the transformation of embryogenic cultures from a large number of genetically diverse families. Genetic transformation was achieved by biolistic and Agrobacterium-mediated techniques. Biolistic transformation efficiency was increased by identifying the optimal target using secondary somatic embryogenesis and by determining the long-term effects of tissue culture manipulations. Improvements to selection and the tissue culture system facilitated the production of stable transformants from 72% of the cell lines attempted from 15 elite families, with an escape rate of less than 1%. Molecular analysis of transgenic trees produced from biolistic transformation found that 36% of the trees had three inserts or less. Transgenic trees produced by biolistics have exhibited normal morphology for up to five growing seasons, to date. An Agrobacterium-mediated transformation system was developed for loblolly pine using tissue culture and selection procedures of the biolistic system. Agrobacterium tumefaciens has been used to produce transgenic trees of clones from elite loblolly families, as well as clones of P. radiata and P. taeda x rigida. Genomic blot analysis of Agrobacterium-transformed somatic embryos is ongoing. Field tests with Agrobacterium-transformed loblolly and the hybrid loblolly have been established each year since 2001. The efficiency of the Agrobacterium transformation system has made it possible for ArborGen to scale-up for high-throughput gene testing in a conifer. Transgenic trees have been produced with genes for lignin modification, accelerated growth, and flowering control.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Optimization principles of dendritic structure

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Social use of facial expressions in hylobatids

Non-human primates use various communicative means in interactions with others. While primate gestures are commonly considered to be intentionally and flexibly used signals, facial expressions are often referred to as inflexible, automatic expressions of affective internal states. To explore whether and how non-human primates use facial expressions in specific communicative interactions, we studied five species of small apes (gibbons) by employing a newly established Facial Action Coding System for hylobatid species (GibbonFACS). We found that, despite individuals often being in close proximity to each other, in social (as opposed to non-social contexts) the duration of facial expressions was significantly longer when gibbons were facing another individual compared to non-facing situations. Social contexts included grooming, agonistic interactions and play, whereas non-social contexts included resting and self-grooming. Additionally, gibbons used facial expressions while facing another individual more often in social contexts than non-social contexts where facial expressions were produced regardless of the attentional state of the partner. Also, facial expressions were more likely ‘responded to’ by the partner’s facial expressions when facing another individual than non-facing. Taken together, our results indicate that gibbons use their facial expressions differentially depending on the social context and are able to use them in a directed way in communicative interactions with other conspecifics

The methanol dehydrogenase gene, mxaF, as a functional and phylogenetic marker for proteobacterial methanotrophs in natural environments

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e56993, doi:10.1371/journal.pone.0056993.The mxaF gene, coding for the large (α) subunit of methanol dehydrogenase, is highly conserved among distantly related methylotrophic species in the Alpha-, Beta- and Gammaproteobacteria. It is ubiquitous in methanotrophs, in contrast to other methanotroph-specific genes such as the pmoA and mmoX genes, which are absent in some methanotrophic proteobacterial genera. This study examined the potential for using the mxaF gene as a functional and phylogenetic marker for methanotrophs. mxaF and 16S rRNA gene phylogenies were constructed based on over 100 database sequences of known proteobacterial methanotrophs and other methylotrophs to assess their evolutionary histories. Topology tests revealed that mxaF and 16S rDNA genes of methanotrophs do not show congruent evolutionary histories, with incongruencies in methanotrophic taxa in the Methylococcaceae, Methylocystaceae, and Beijerinckiacea. However, known methanotrophs generally formed coherent clades based on mxaF gene sequences, allowing for phylogenetic discrimination of major taxa. This feature highlights the mxaF gene’s usefulness as a biomarker in studying the molecular diversity of proteobacterial methanotrophs in nature. To verify this, PCR-directed assays targeting this gene were used to detect novel methanotrophs from diverse environments including soil, peatland, hydrothermal vent mussel tissues, and methanotroph isolates. The placement of the majority of environmental mxaF gene sequences in distinct methanotroph-specific clades (Methylocystaceae and Methylococcaceae) detected in this study supports the use of mxaF as a biomarker for methanotrophic proteobacteria.This work was supported in part by grants from the U.S. National Science Foundation Ecosystems Studies program (awards # DEB9708092 and DEB0089738)

Dendritic Morphology Predicts Pattern Recognition Performance in Multi-compartmental Model Neurons with and without Active Conductances

This is an Open Access article published under the Creative Commons Attribution license CC BY 4.0 which allows users to read, copy, distribute and make derivative works, as long as the author of the original work is citedIn this paper we examine how a neuron’s dendritic morphology can affect its pattern recognition performance. We use two different algorithms to systematically explore the space of dendritic morphologies: an algorithm that generates all possible dendritic trees with 22 terminal points, and one that creates representative samples of trees with 128 terminal points. Based on these trees, we construct multi-compartmental models. To assess the performance of the resulting neuronal models, we quantify their ability to discriminate learnt and novel input patterns. We find that the dendritic morphology does have a considerable effect on pattern recognition performance and that the neuronal performance is inversely correlated with the mean depth of the dendritic tree. The results also reveal that the asymmetry index of the dendritic tree does not correlate with the performance for the full range of tree morphologies. The performance of neurons with dendritic tapering is best predicted by the mean and variance of the electrotonic distance of their synapses to the soma. All relationships found for passive neuron models also hold, even in more accentuated form, for neurons with active membranesPeer reviewedFinal Published versio

Cholinergic Activation of M2 Receptors Leads to Context-Dependent Modulation of Feedforward Inhibition in the Visual Thalamus

The temporal dynamics of inhibition within a neural network is a crucial determinant of information processing. Here, the authors describe in the visual thalamus how neuromodulation governs the magnitude and time course of inhibition in an input-dependent way