Multiple dynamic representations in the motor cortex during sensorimotor learning.

The mechanisms linking sensation and action during learning are poorly understood. Layer 2/3 neurons in the motor cortex might participate in sensorimotor integration and learning; they receive input from sensory cortex and excite deep layer neurons, which control movement. Here we imaged activity in the same set of layer 2/3 neurons in the motor cortex over weeks, while mice learned to detect objects with their whiskers and report detection with licking. Spatially intermingled neurons represented sensory (touch) and motor behaviours (whisker movements and licking). With learning, the population-level representation of task-related licking strengthened. In trained mice, population-level representations were redundant and stable, despite dynamism of single-neuron representations. The activity of a subpopulation of neurons was consistent with touch driving licking behaviour. Our results suggest that ensembles of motor cortex neurons couple sensory input to multiple, related motor programs during learning.

Mitigation of gaseous mercury emissions from waste-to-energy facilities: Homogeneous and heterogeneous Hg-oxidation pathways in presence of fly ashes.

This study describes the main mechanisms that take part in the mercury homogeneous oxidation pathway in presence of some of the main reactive compounds formed during waste incineration processes (O2, HCl, SO2 and NO). Series of model, synthetic dry flue gases were used to elucidate the effects of HCl, SO2, NO and their proportions in the gas on mercury behaviour. Three samples of fly ash collected from a MSWI facility were characterized and evaluated both for Hg heterogeneous oxidation and Hg removal in a laboratory scale device. The results obtained in this study showed that homogeneous mercury oxidation in the models MSWI and coal combustion flue gas atmospheres was 52 ± 5% and 25%, respectively. SO2, NO and HCl have a synergetic effect in Hg oxidation in presence of oxygen, but the main differences found are mainly caused by the strong influence of HCl and the likely inhibitory oxidation effects of SO2. Surface area together with carbon and chloride content of the fly ashes were correlated with their capacity for Hg-heterogeneous oxidation and adsorption. The sample of fly ash with relatively high content of unburnt carbon and chlorine, and with BET surface (2.42 m2/g) was able to remove up to 100% of Hg0 (g) during 300 min. The results obtained in this study provide a complete overview of the behaviour of mercury during MSWI processes and may help to clarify the fate/behaviour of mercury in a filter (e.g. electrostatic precipitator) providing a deeper knowledge about the impacts of fly ash properties on mercury fate in waste incineration.

Gli1+ Periodontal Mesenchymal Stem Cells in Periodontitis.

Periodontal mesenchymal stem cells (MSCs) play a crucial role in maintaining periodontium homeostasis and in tissue repair. However, little is known about how periodontal MSCs in vivo respond under periodontal disease conditions, posing a challenge for periodontium tissue regeneration. In this study, Gli1 was used as a periodontal MSC marker and combined with a Gli1-cre ERT2 mouse model for lineage tracing to investigate periodontal MSC fate in an induced periodontitis model. Our findings show significant changes in the number and contribution of Gli1+ MSCs within the inflamed periodontium. The number of Gli1+ MSCs that contributed to periodontal ligament homeostasis decreased in the periodontitis-induced teeth. While the proliferation of Gli1+ MSCs had no significant difference between the periodontitis and the control groups, more Gli1+ MSCs underwent apoptosis in diseased teeth. In addition, the number of Gli1+ MSCs for osteogenic differentiation decreased during the progression of periodontitis. Following tooth extraction, the contribution of Gli1+ MSCs to the tooth socket repair was significantly reduced in the periodontitis-induced teeth. Collectively, these findings indicate that the function of Gli1+ MSCs in periodontitis was compromised, including reduced contribution to periodontium homeostasis and impaired injury response.

[Penetrating laryngotracheal injury during a suicide attempt]. / Penetrierende laryngotracheale Verletzung beim Suizid.

The authors present a case of a 40-year-old man who intentionally stabbed himself several times in the trachea and larynx during a suicide attempt, and also inflicted other penetrating injuries of the stomach and liver upon himself. The preoperative examination using fiber-optic tracheoscopy and CT revealed only transection of the ligamentum cricothyroideum; the remaining two defects were discovered later, during the surgical revision. All three injuries were successfully treated with sutures, in one case using the transtracheal approach.

Dental Pulp Stem Cell Polarization: Effects of Biophysical Factors.

Dental pulp stem cells (DPSCs) have the potential to polarize, differentiate, and form tubular dentin under certain conditions. However, the factors that initiate and regulate DPSC polarization and its underlying mechanism remain unclear. Identification of the factors that control DPSC polarization is a prerequisite for tubular dentin regeneration. We recently developed a unique bioinspired 3-dimensional platform that is capable of deciphering the factors that initiate and modulate cell polarization. The bioinspired platform has a simple background and confines a single cell on each microisland of the platform; therefore, it is an effective tool to study DPSC polarization at the single-cell level. In this work, we explored the effects of biophysical factors (surface topography, microisland area, geometry, tubular size, and gravity) on single DPSC polarization. Our results demonstrated that nanofibrous architecture, microisland area, tubular size, and gravity participated in regulating DPSC polarization by influencing the formation of the DPSC process and relocation of the Golgi apparatus. Among these factors, nanofibrous architecture, tubular size, and appropriate microisland area were indispensable for initiating DPSC polarization, whereas gravity served as an auxiliary factor to the process of DPSC polarization. Meanwhile, microisland geometry had a limited effect on DPSC polarization. Collectively, this work provides information on DPSC polarization and paves the way for the development of new biomaterials for tubular dentin regeneration.

Resistance of cloned cytotoxic T lymphocytes to cell-mediated cytotoxicity.

Cloned CTLs show an unusually high resistance to lysis by effector CTLs. Several cloned CTL lines in our laboratories are absolutely refractory to lysis by other cloned CTLs, either (a) directly, (b) in the presence of lectin, or (c) by PMA-induced CTLs. They can be lysed to some extent by primary CTL, although they are less than 5% as sensitive as target cells normally used to assay primary CTL lytic activity. Lysis of cloned CTLs by primary CTL effector cells is not enhanced by the presence of lectin, and cloned T cells are also highly resistant to lysis by primary lymphokine-activated killer cells. Cloned CTLs are highly resistant to lysis by isolated CTL granules that contain the membranolytic pore-forming protein (PFP or perforin), while non-CTL targets are highly susceptible to granule-mediated killing, indicating that cloned CTLs resist lysis not only at the intact effector cell level but also when soluble effector proteins are used. This resistance mechanism may explain how CTLs kill but spare themselves from being killed during the cytolytic event.

Cortical rewiring and information storage.

Current thinking about long-term memory in the cortex is focused on changes in the strengths of connections between neurons. But ongoing structural plasticity in the adult brain, including synapse formation/elimination and remodelling of axons and dendrites, suggests that memory could also depend on learning-induced changes in the cortical 'wiring diagram'. Given that the cortex is sparsely connected, wiring plasticity could provide a substantial boost in storage capacity, although at a cost of more elaborate biological machinery and slower learning.

Direct measurement of coupling between dendritic spines and shafts.

Characterization of the diffusional and electrotonic coupling of spines to the dendritic shaft is crucial to understanding neuronal integration and synaptic plasticity. Two-photon photobleaching and photorelease of fluorescein dextran were used to generate concentration gradients between spines and shafts in rat CA1 pyramidal neurons. Diffusional reequilibration was monitored with two-photon fluorescence imaging. The time course of reequilibration was exponential, with time constants in the range of 20 to 100 milliseconds, demonstrating chemical compartmentalization on such time scales. These values imply that electrical spine neck resistances are unlikely to exceed 150 megohms and more likely range from 4 to 50 megohms.

Rapid dendritic morphogenesis in CA1 hippocampal dendrites induced by synaptic activity.

Activity shapes the structure of neurons and their circuits. Two-photon imaging of CA1 neurons expressing enhanced green fluorescent protein in developing hippocampal slices from rat brains was used to characterize dendritic morphogenesis in response to synaptic activity. High-frequency focal synaptic stimulation induced a period (longer than 30 minutes) of enhanced growth of small filopodia-like protrusions (typically less than 5 micrometers long). Synaptically evoked growth was long-lasting and localized to dendritic regions close (less than 50 micrometers) to the stimulating electrode and was prevented by blockade of N-methyl-D-aspartate receptors. Thus, synaptic activation can produce rapid input-specific changes in dendritic structure. Such persistent structural changes could contribute to the development of neural circuitry.

Transcription against an applied force.

The force produced by a single molecule of Escherichia coli RNA polymerase during transcription was measured optically. Polymerase immobilized on a surface was used to transcribe a DNA template attached to a polystyrene bead 0.5 micrometer in diameter. The bead position was measured by interferometry while a force opposing translocation of the polymerase along the DNA was applied with an optical trap. At saturating nucleoside triphosphate concentrations, polymerase molecules stalled reversibly at a mean applied force estimated to be 14 piconewtons. This force is substantially larger than those measured for the cytoskeletal motors kinesin and myosin and exceeds mechanical loads that are estimated to oppose transcriptional elongation in vivo. The data are consistent with efficient conversion of the free energy liberated by RNA synthesis into mechanical work.

Rapid spine delivery and redistribution of AMPA receptors after synaptic NMDA receptor activation.

To monitor changes in alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor distribution in living neurons, the AMPA receptor subunit GluR1 was tagged with green fluorescent protein (GFP). This protein (GluR1-GFP) was functional and was transiently expressed in hippocampal CA1 neurons. In dendrites visualized with two-photon laser scanning microscopy or electron microscopy, most of the GluR1-GFP was intracellular, mimicking endogenous GluR1 distribution. Tetanic synaptic stimulation induced a rapid delivery of tagged receptors into dendritic spines as well as clusters in dendrites. These postsynaptic trafficking events required synaptic N-methyl-D-aspartate (NMDA) receptor activation and may contribute to the enhanced AMPA receptor-mediatedtransmission observed during long-term potentiation and activity-dependent synaptic maturation.

Existence of a flat phase in red cell membrane skeletons.

Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h alpha L zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 +/- 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.

MRI of the knee: how do field strength and radiologist's experience influence diagnostic accuracy and interobserver correlation in assessing chondral and meniscal lesions and the integrity of the anterior cruciate ligament?

Accuracy of MRI reports is taken for granted. In this paper the inter-observer reliability in the interpretation of meniscal lesions, degree of chondropathy, and integrity of the ACL was analyzed while taking the radiologist's experience and field strength into account. Fifty-two MRI studies of knees were interpreted by 11 radiologists independently. Twenty-two were acquired on 1.0-T, 20 on 1.5-T, and 10 on 3.0-T systems. Four of the radiologists had more than 5 years and seven had 3 to 5 years of experience in interpreting MRI studies. The findings were compared with the intra-operative findings. Inter-observer variance, specificity, and sensitivity were evaluated for each field strength. Inter-observer correlation ranged between 0.370 for cartilage lesions and 0.597 for meniscal tears. Correlation values did not increase with experience or field strength. The number of false reports was dependent on the observer, but not on field strength. The rate of false interpretations was significantly higher for most criteria in the less experienced group. In conclusion, inter-observer correlation was low, although the diagnostic criteria were defined. The use of the classification scheme should be standardized by uniform training. Radiologist experience seems to be more important than field strength.

Rapid development and plasticity of layer 2/3 maps in rat barrel cortex in vivo.

Cortical synaptic circuitry develops rapidly in the second postnatal week, simultaneous with experience-dependent turnover of dendritic spines. To relate the emergence of sensory maps to synaptogenesis, we recorded synaptic potentials evoked by whisker deflection in layer 2/3 neurons from postnatal day (P) 12 to 20. At P12, synaptic responses were undetectable. Only 2 days later in life (P14), receptive fields had mature organization. Sensory deprivation, if initiated before P14, disrupted receptive field structure. In layer 4, responses and maps were already mature by P12 and insensitive to deprivation, implying that barrel cortex develops from layer 4 to layer 2/3. Thus, P12-14 is a critical period shared by layer 2/3 synapses and their spines, suggesting that spine plasticity is involved in the refinement of maps.

Genetic manipulation of the odor-evoked distributed neural activity in the Drosophila mushroom body.

Odor-induced neural activity was recorded by Ca2+ imaging in the cell body region of the Drosophila mushroom body (MB), which is the second relay of the olfactory central nervous system. The signals recorded are mainly from the cell layers on the brain surface because of the limited penetration of Ca2+-sensitive dyes. The densely packed cell bodies and their accessibility allow visualization of odor-induced population neural activity. It is revealed that odors evoke diffused neural activities in the MB. Although the signals cannot be attributed to individual neurons, patterns of the population neural activity can be analyzed. The activity pattern, but not the amplitude, of an odor-induced population response is specific for the chemical identity of an odor and its concentration. The distribution pattern of neural activity can be altered specifically by genetic manipulation of an odor binding protein and this alteration is closely associated with a behavioral defect of odor preference. These results suggest that the spatial pattern of the distributed neural activity may contribute to coding of odor information at the second relay of the olfactory system.

Central neurocytoma: the neuroradiological perspective.

BACKGROUND: Central neurocytoma (CN) represents a rare, relatively recently described primary central nervous system tumor. It ranks among intraventricular tumors due to its predominant location within the lateral brain ventricles. CN occurs mostly in young adults around the 3rd decade of life; almost a fifth of the cases are children under 18 years of age. OBJECTIVES: The authors present three cases of patients with histopathologically confirmed CN, emphasizing diagnostic imaging issues. A review of the literature concerning differential diagnosis and clinical and therapeutic aspects is also presented. CONCLUSION: Literature reports of CN comprise most likely case reports, small cohorts of patients, and meta-analytic studies due to the generally low incidence of this tumor. In the current paper, the authors summarize up-to-date knowledge of this rare disease on the background of their own observations. CN should be included in the list for differential diagnostics of intraventricular brain tumors, especially those located in lateral ventricles.

In vivo dendritic calcium dynamics in deep-layer cortical pyramidal neurons.

Dendritic Ca2+ action potentials in neocortical pyramidal neurons have been characterized in brain slices, but their presence and role in the intact neocortex remain unclear. Here we used two-photon microscopy to demonstrate Ca2+ electrogenesis in apical dendrites of deep-layer pyramidal neurons of rat barrel cortex in vivo. During whisker stimulation, complex spikes recorded intracellularly from distal dendrites and sharp waves in the electrocorticogram were accompanied by large dendritic [Ca2+ ] transients; these also occurred during bursts of action potentials recorded from somata of identified layer 5 neurons. The amplitude of the [Ca 2+] transients was largest proximal to the main bifurcation, where sodium action potentials produced little Ca2+ influx. In some cases, synaptic stimulation evoked [Ca2+] transients without a concomitant action potential burst, suggesting variable coupling between dendrite and soma.

Spread of dendritic excitation in layer 2/3 pyramidal neurons in rat barrel cortex in vivo.

In layer 2/3 pyramidal neurons of barrel cortex in vivo, calcium ion concentration ([Ca2+]) transients in apical dendrites evoked by sodium action potentials are limited to regions close to the soma. To study the mechanisms underlying this restricted pattern of calcium influx, we combined two-photon imaging of dendritic [Ca2+] dynamics with dendritic membrane potential measurements. We found that sodium action potentials attenuated and broadened rapidly with distance from the soma. However, dendrites of layer 2/3 cells were electrically excitable, and direct current injections could evoke large [Ca2+] transients. The restricted pattern of dendritic [Ca2+] transients is therefore due to a failure of sodium action-potential propagation into dendrites. Also, stimulating subcortical activating systems by tail pinch can enhance dendritic [Ca2+] influx induced by a sensory stimulus by increasing cellular excitability, consistent with the importance of these systems in plasticity and learning.

Mercury removal from MSW incineration flue gas by mineral-based sorbents.

Three samples of commercially available mineral-based sorbents (zeolite, bentonite and diatomaceous earth) were selected and evaluated for Hg capture under conditions of simulated dry flue gas atmosphere typical in Municipal Solid Waste Incineration (MSWI). The experiments were carried out in a lab-scale fixed-bed device at temperatures between 120 and 200 °C. Two samples of activated carbons (AC) (raw-AC and sulphur impregnated AC) were tested under the same conditions. The mineral-based sorbents were chemically promoted by sulphur, FeCl3 and CaBr2, achieving an improvement in the overall reduction percentage of Hg0out (g) up to 85%, which was comparable to that obtained using a commercial activated carbon for Hg capture (sulphur impregnated AC). The study demonstrates that sorbents with a matrix relatively richer in TiO2, Fe2O3 and Al2O3, as bentonite, favour Hg heterogeneous oxidation. The best Hg capture capacity was achieved with a zeolite sorbent sample characterized by high specific surface (132 m2/g) and impregnated with elemental sulphur. The final form of mercury retained in this sorbent was HgS with proved long-term stability in disposal and landfilling. The higher the temperature, the lower the efficiency of Hg capture being the optimum temperature for Hg-capture in the range of 120-150 °C. This study provides a basis for the development of new efficient non-carbon sorbents for mercury removal in the air pollution control lines of MSWI facilities considering the non-hazardous final form of mercury and its long-term landfilling/sequestration.

Oral Sciences PhD Program Enrollment, Graduates, and Placement: 1994 to 2016.

For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no national database to track those trainees and no evidence to indicate that they entered academia upon graduation. The objective of this study was to assess outcomes of dental school-affiliated oral sciences PhD program enrollment, graduates, and placement between 1994 and 2016. Using the American Dental Association annual survey of advanced dental education programs not accredited by the Commission on Dental Accreditation and data obtained from 22 oral sciences PhD programs, we assessed student demographics, enrollment, graduation, and placement. Based on the data provided by program directors, the average new enrollment was 33, and graduation was 26 per year. A total of 605 graduated; 39 did not complete; and 168 were still in training. Among those 605 graduates, 211 were faculty in U.S. academic institutions, and 77 were faculty in foreign institutions. Given that vacant budgeted full-time faculty positions averaged 257 per year during this period, graduates from those oral sciences PhD programs who entered academia in the United States would have filled 9 (3.6%) vacant faculty positions per year. Therefore, PhD programs have consistently generated only a small pipeline of dental school faculty. Better mentoring to retain talent in academia is necessary. Stronger support and creative funding plans are essential to sustain the PhD program. Furthermore, the oral sciences PhD program database should be established and maintained by dental professional organizations to allow assessments of training models, trends of enrollment, graduation, and placement outcomes.