Myelination, the insulating ensheathment of axons by oligodendrocytes, is thought to both optimize signal propagation and provide metabolic support. Despite the well-established physiological ...importance of myelination to neuronal function, relatively little is known about the myelination of GABAergic interneurons in the cerebral cortex. Here, we report that a large fraction of myelin in mouse cerebral cortex ensheaths GABAergic interneurons, reaching up to 80% in hippocampal subregions. Moreover, we find that a very high proportion of neocortical and hippocampal parvalbumin (PV) interneurons exhibit axonal myelination. Using a combination of intracellular recordings and biocytin labeling of ex vivo human neocortex, we also confirm that axons of fast-spiking PV interneurons are extensively myelinated in the human brain. PV interneuron myelination in both mice and humans exhibits a stereotyped topography with a bias towards proximal axonal segments and relatively short internodes (~27 μm) interspersed with branch points. Interestingly, myelin-deficient Shiverer mice exhibit an increased density and more proximal location of en passant boutons, suggesting that myelination might function in part to regulate synapse formation along PV interneuron axons. Taken together, fast-spiking interneuron myelination is likely to have broad implications for cerebral cortex function in health and disease.
Memories are encoded within sparsely distributed neuronal ensembles. However, the defining cellular properties of neurons within a memory trace remain incompletely understood. Using a ...fluorescence-based Arc reporter, we were able to visually identify the distinct subset of lateral amygdala (LA) neurons activated during auditory fear conditioning. We found that Arc-expressing neurons have enhanced intrinsic excitability and are preferentially recruited into newly encoded memory traces. Furthermore, synaptic potentiation of thalamic inputs to the LA during fear conditioning is learning-specific, postsynaptically mediated and highly localized to Arc-expressing neurons. Taken together, our findings validate the immediate-early gene Arc as a molecular marker for the LA neuronal ensemble recruited during fear learning. Moreover, these results establish a model of fear memory formation in which intrinsic excitability determines neuronal selection, whereas learning-related encoding is governed by synaptic plasticity.
Abstract
Flight tests are performed to gather data for flight vehicle parameter estimation. If an a priori model is available, the inputs during the runtime of the flight test experiment can be ...designed, such that the information content in the gathered data is maximized. These optimal inputs, however, are based on an inaccurate system model, and the improvement of the system model is the ultimate goal of the system identification and therewith, the flight tests. There is an implicit relationship between the optimal inputs and the system model. In this paper, we investigate a scheme to update the optimal inputs during the flight using an online optimization technique, while performing online parameter estimation. An extended Kalman filter is used to compute new parameter values during the maneuver runtime. Concurrent to that, an interior point NLP solver computes the optimal maneuver updates, as new parameters become available in each iteration. The method is validated via a numerical example.
In order to study the effect of phenylalanine-functionalized carbon nanotubes (f-MWCNT) on the parameters of callus induction and variations in antioxidant enzymes activity as well as secondary ...metabolites biosynthesis of basil (
Ocimum basilicum
L.), optimum concentrations of functionalized and pristine carbon nanotubes were applied in optimized hormonal culture. Basil hypocotyl fragments were cultured in completely sterile conditions in culture medium with 0, 50, 100 and 200 mg/L concentrations of functionalized and pristine carbon nanotubes. The callus induction frequency C
if
and dry matter content (DMC), catalase, polyphenol oxidase (PPO), peroxidase (POD), and L-phenylalanine ammonia-lyase activity were also measured in the present study. Additionally, the content of total phenolics and flavonoids, as well as individual phenolic acids, was quantified. Functionalized MWCNTs exhibited the highest callus induction as well as fresh and dry weight in the concentration, 100 mg/L of f-MWCNT. No significant differences in dry matter content between the levels was observed in this study. Catalase activity was also increased with increasing functionalized and non-functionalized carbon nanotube concentration. The highest activity of PPO, POD, and individual phenolic compounds were observed at 200 mg/L of f-MWCNT, 50 mg/L of pristine MWCNT and 100 mg/L of MWCNT, respectively.
Atropa belladonna
L. from the Solanaceae family is one of the major commercial sources of tropane alkaloids such as atropine and scopolamine. These types of alkaloids are more often used as ...anti-spasmodic, anti-cholinergic, sedative, analgesic, and dilatation of the pupil. The effect of different iron oxide nano-particles concentrations (0, 250, 500, 750, and 1000 mg/L) with two exposure time (24 and 48 hours) on total phenol and flavonoid content, antioxidant enzymes activity, tropane alkaloids content (atropine and scopolamine), and hyoscyamine 6β-hydroxylase (
h6h
) gene expression level were evaluated. The results of ANOVA analysis revealed that the antioxidant enzymes, including catalase, guaiacol peroxidase and ascorbate peroxidase activity was significantly enhanced in induced samples compared to control treatments. The highest amounts of phenol (4.05 mg gallic acid per gram fresh weight) and flavonoid (2.66 mg quercetin per gram fresh weight) were obtained in hairy roots elicited with 250 mg/L elicitor. The maximum content of atropine (345.74 μg/g dry weight, about 34.6-fold compared to the control) and scopolamine (979.45 μg/g dry weight, about 51.5-fold compared to the control) were recorded in hairy roots treated with 250 and 1000 mg/L iron oxide nano-particles during 48-hourexposure time, respectively. The semi-quantitative RT-PCR analysis declared that the highest
h6h
expression in hairy roots stimulated with 750 mg/L iron oxide for 48 hours. Based on these results, it can be concluded that iron oxide nano-particles may be used as an effective stimulant for the production of tropane alkaloids due to the stimulation effects on the expression of
h6h
gene.
In the past two decades, the U.S. Geological Survey and the National Park Service have studied hydrothermal activity across the Yellowstone Plateau Volcanic Field (YPVF) to improve the understanding ...of the magmatic‐hydrothermal system and to provide a baseline for detecting future anomalous activity. In 2017 and 2018 we sampled water and gas over a large area in the southwest YPVF and used Landsat 8 thermal infrared data to estimate radiative heat flow. Most of the thermal activity in this region is in close proximity to the Yellowstone Caldera boundary. Springs and fumaroles discharge from a variety of lithologies, including some of the youngest rhyolites in the YPVF. Gas compositions and helium isotope ratios of most samples resemble those in other parts of the YPVF. The waters have meteoric origins, and tritium was detected in several samples. Thermal waters from some areas have compositions that plot along a line connecting thermal and nonthermal water endmember compositions. The thermal water endmember equilibrated at 160°C–170°C, lower than waters in Yellowstone's geyser basins. Heat discharged by springs and fumaroles originates from within the Yellowstone Caldera and is transported laterally by advection, mainly along the base of rhyolite flows that cover the inferred caldera boundaries.
Plain Language Summary
The Yellowstone Plateau Volcanic Field has had three cataclysmic volcanic eruptions over the past ~2.1 million years. The youngest of these eruptions at 0.631 Ma resulted in the formation of the Yellowstone Caldera and was followed by several smaller eruptive episodes of large volume rhyolite flows up to ~70,000 years ago. The diversity of Yellowstone's hydrothermal system is unparalleled with more than 10,000 thermal features that have diverse chemical compositions. To improve the understanding of Yellowstone's magmatic‐hydrothermal system and to provide a baseline for detecting future anomalous activity, we sampled water and gas in southwest Yellowstone and analyzed satellite‐derived thermal infrared images. Most of the hot springs and fumaroles in the study area are near the Yellowstone Caldera boundary. The area is characterized by different rock types including some of the youngest rhyolites in Yellowstone. Whereas gas compositions mostly resemble those in other parts of Yellowstone, the chemical compositions of waters differ from those within the Yellowstone Caldera. The heat and gas discharged by springs and fumaroles originate from within the Yellowstone Caldera and are transported laterally, mainly along the base of rhyolite flows that cover the inferred Yellowstone Caldera boundary.
Key Points
Hot springs and fumaroles discharge from a variety of lithologies in proximity to the Yellowstone Caldera boundary
The thermal water endmember equilibrates with rhyolite at temperatures lower than in Yellowstone's geyser basins
Heat and gases discharged by springs and fumaroles originate in the Yellowstone Caldera and are transported laterally by advection
The use of routine magnetic resonance imaging (MRI) to potentially assess skeletal fragility has been widely studied in osteoporosis. The aim of this study was to evaluate bone texture attributes ...(TA) from routine lumbar spine (LS) MRI and their correlation with vertebral fragility fractures (VFF) and bone mineral density (BMD). Sixty-four post-menopausal women were submitted to LS densitometry, total spine radiographs, and routine T2-weighted LS MRI. Twenty-two TA were extracted with the platform IBEX from L3 vertebra. The statistical difference was evaluated using ANOVA and Duncan's post-test. Correlation analyses were performed using Spearman's coefficient. Statistical significance was considered when P<0.05. The results did not show a significant difference in BMD between the women with and without fractures. Two bone TA (cluster tendency and variance) were significantly lower in the fracture group. Cluster tendency with VFF in osteopenia was 1.54±1.37 and in osteoporosis was 1.11±58. Cluster tendency without VFF in osteopenia was 2.23±1.38 and in osteoporosis was 1.88±1.14). Variance with VFF in osteopenia was 1.44±1.37 and in osteoporosis was 1.13±59. Variance without VFF in osteopenia was 2.34±1.38 and in osteoporosis was 1.89±1.14. There was a significant correlation between BMD and cluster prominence (r=0.409), cluster tendency (r=0.345), correlation (r=0.570), entropy (r=0.364), information measure corr1 (r=0.378), inverse variance (r=0.449), sum entropy (r=0.320), variance (r=0.338), sum average (r=-0.274), and sum variance (r=-0.266). Our results demonstrated the potential use of TA extracted from routine MRI as a biomarker to assess osteoporosis and identify the tendency of skeletal fragility vertebral fractures.
In the present research, first, the equivalent material concept (EMC), proposed originally by the first author to equate a ductile material with a virtual brittle material, was utilized in ...conjunction with two stressbased brittle fracture criteria, namely the point-stress (PS) and the mean-stress (MS) criteria, to develop two combined failure criteria capable of predicting tensile crack initiation from U-notches in ductile materials. Then, to verify the two failure criteria, several rectangular thin plates weakened by a central bean-shaped slit with two U-shaped ends and made of aluminum alloys Al 7075-T6 and Al 6061-T6 were tested under tension. Experimental observations indicated that Al 7075-T6 plates failed by moderate-scale yielding while Al 6061-T6 by largescale yielding. It was found that the EMC-MS criterion could predict the experimental results of both materials successfully. Meanwhile, the EMC-PS criterion was found to be accurate for moderate and large notch radii, particularly for Al 6061-T6 material.
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