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1.
Nature ; 629(8011): 384-392, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38600385

RESUMO

Debate remains around the anatomical origins of specific brain cell subtypes and lineage relationships within the human forebrain1-7. Thus, direct observation in the mature human brain is critical for a complete understanding of its structural organization and cellular origins. Here we utilize brain mosaic variation within specific cell types as distinct indicators for clonal dynamics, denoted as cell-type-specific mosaic variant barcode analysis. From four hemispheres and two different human neurotypical donors, we identified 287 and 780 mosaic variants, respectively, that were used to deconvolve clonal dynamics. Clonal spread and allele fractions within the brain reveal that local hippocampal excitatory neurons are more lineage-restricted than resident neocortical excitatory neurons or resident basal ganglia GABAergic inhibitory neurons. Furthermore, simultaneous genome transcriptome analysis at both a cell-type-specific and a single-cell level suggests a dorsal neocortical origin for a subgroup of DLX1+ inhibitory neurons that disperse radially from an origin shared with excitatory neurons. Finally, the distribution of mosaic variants across 17 locations within one parietal lobe reveals that restriction of clonal spread in the anterior-posterior axis precedes restriction in the dorsal-ventral axis for both excitatory and inhibitory neurons. Thus, cell-type-resolved somatic mosaicism can uncover lineage relationships governing the development of the human forebrain.


Assuntos
Linhagem da Célula , Células Clonais , Mosaicismo , Neurônios , Prosencéfalo , Idoso , Feminino , Humanos , Alelos , Linhagem da Célula/genética , Células Clonais/citologia , Células Clonais/metabolismo , Neurônios GABAérgicos/citologia , Neurônios GABAérgicos/metabolismo , Hipocampo/citologia , Proteínas de Homeodomínio/metabolismo , Neocórtex/citologia , Inibição Neural , Neurônios/citologia , Neurônios/metabolismo , Lobo Parietal/citologia , Prosencéfalo/anatomia & histologia , Prosencéfalo/citologia , Prosencéfalo/metabolismo , Análise de Célula Única , Transcriptoma/genética
2.
bioRxiv ; 2023 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-37961480

RESUMO

Debate remains around anatomic origins of specific brain cell subtypes and lineage relationships within the human forebrain. Thus, direct observation in the mature human brain is critical for a complete understanding of the structural organization and cellular origins. Here, we utilize brain mosaic variation within specific cell types as distinct indicators for clonal dynamics, denoted as cell-type-specific Mosaic Variant Barcode Analysis. From four hemispheres from two different human neurotypical donors, we identified 287 and 780 mosaic variants (MVs), respectively that were used to deconvolve clonal dynamics. Clonal spread and allelic fractions within the brain reveal that local hippocampal excitatory neurons are more lineage-restricted compared with resident neocortical excitatory neurons or resident basal ganglia GABAergic inhibitory neurons. Furthermore, simultaneous genome-transcriptome analysis at both a cell-type-specific and single-cell level suggests a dorsal neocortical origin for a subgroup of DLX1+ inhibitory neurons that disperse radially from an origin shared with excitatory neurons. Finally, the distribution of MVs across 17 locations within one parietal lobe reveals restrictions of clonal spread in the anterior-posterior axis precedes that of the dorsal-ventral axis for both excitatory and inhibitory neurons. Thus cell-type resolved somatic mosaicism can uncover lineage relationships governing the development of the human forebrain.

3.
Int J Mol Sci ; 24(11)2023 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-37298250

RESUMO

D3 receptors, a key component of the dopamine system, have emerged as a potential target of therapies to improve motor symptoms across neurodegenerative and neuropsychiatric conditions. In the present work, we evaluated the effect of D3 receptor activation on the involuntary head twitches induced by 2,5-dimethoxy-4-iodoamphetamine (DOI) at behavioral and electrophysiological levels. Mice received an intraperitoneal injection of either a full D3 agonist, WC 44 [4-(2-fluoroethyl)-N-[4-[4-(2-methoxyphenyl)piperazin 1-yl]butyl]benzamide] or a partial D3 agonist, WW-III-55 [N-(4-(4-(4-methoxyphenyl)piperazin-1-yl)butyl)-4-(thiophen-3-yl)benzamide] five minutes before the intraperitoneal administration of DOI. Compared to the control group, both D3 agonists delayed the onset of the DOI-induced head-twitch response and reduced the total number and frequency of the head twitches. Moreover, the simultaneous recording of neuronal activity in the motor cortex (M1) and dorsal striatum (DS) indicated that D3 activation led to slight changes in a single unit activity, mainly in DS, and increased its correlated firing in DS or between presumed cortical pyramidal neurons (CPNs) and striatal medium spiny neurons (MSNs). Our results confirm the role of D3 receptor activation in controlling DOI-induced involuntary movements and suggest that this effect involves, at least in part, an increase in correlated corticostriatal activity. A further understanding of the underlying mechanisms may provide a suitable target for treating neuropathologies in which involuntary movements occur.


Assuntos
Discinesias , Receptores de Dopamina D3 , Camundongos , Animais , Receptores de Dopamina D2/agonistas , Benzamidas/farmacologia , Receptores de Dopamina D1
4.
Nanomaterials (Basel) ; 12(22)2022 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-36432216

RESUMO

Heavy metals are one of the most important classes of environmental pollutants which are toxic to living beings. Many efforts are made by scientists to fabricate better sensors for the identification and quantification of heavy metal ions (HMI) in water and food samples to ensure good health. Electrocatalysts have been demonstrated to play an important role in enhancing the sensitivity and selectivity of HMI detection in electrochemical sensors. In this review, we presented morphologically well-tuned nanomaterials used as efficient sensor materials. Based on the molecular dimensions, shapes, and orientation, nanomaterials can be classified into 0-D, 1-D, 2-D, and 3-D nanomaterials. Active surface areas with significant exposure of active sites and adsorption-desorption abilities are extensively varied with dimensionality, which in turn ultimately influence the sensing performance for HMI.

5.
Nature ; 604(7907): 689-696, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35444276

RESUMO

The structure of the human neocortex underlies species-specific traits and reflects intricate developmental programs. Here we sought to reconstruct processes that occur during early development by sampling adult human tissues. We analysed neocortical clones in a post-mortem human brain through a comprehensive assessment of brain somatic mosaicism, acting as neutral lineage recorders1,2. We combined the sampling of 25 distinct anatomic locations with deep whole-genome sequencing in a neurotypical deceased individual and confirmed results with 5 samples collected from each of three additional donors. We identified 259 bona fide mosaic variants from the index case, then deconvolved distinct geographical, cell-type and clade organizations across the brain and other organs. We found that clones derived after the accumulation of 90-200 progenitors in the cerebral cortex tended to respect the midline axis, well before the anterior-posterior or ventral-dorsal axes, representing a secondary hierarchy following the overall patterning of forebrain and hindbrain domains. Clones across neocortically derived cells were consistent with a dual origin from both dorsal and ventral cellular populations, similar to rodents, whereas the microglia lineage appeared distinct from other resident brain cells. Our data provide a comprehensive analysis of brain somatic mosaicism across the neocortex and demonstrate cellular origins and progenitor distribution patterns within the human brain.


Assuntos
Células Clonais , Mosaicismo , Neocórtex , Linhagem da Célula , Células Cultivadas , Humanos , Microglia , Neocórtex/citologia , Neocórtex/crescimento & desenvolvimento
6.
ACS Nanosci Au ; 2(5): 414-421, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-37102132

RESUMO

The high efficiency of cascade reactions in supramolecular enzyme nanoassemblies, known as metabolons, has attracted substantial attention in various fields ranging from fundamental biochemistry and molecular biology to recent applications in biofuel cells, biosensors, and chemical synthesis. One reason for the high efficiency of metabolons is the structures formed by sequential enzymes that allow the direct transport of intermediates between consecutive active sites. The supercomplex of malate dehydrogenase (MDH) and citrate synthase (CS) is an ideal example of the controlled transport of intermediates via electrostatic channeling. Here, using a combination of molecular dynamics (MD) simulations and a Markov state model (MSM), we examined the transport process of the intermediate oxaloacetate (OAA) from MDH to CS. The MSM enables the identification of the dominant transport pathways of OAA from MDH to CS. Analysis of all pathways using a hub score approach reveals a small set of residues that control OAA transport. This set includes an arginine residue previously identified experimentally. MSM analysis of a mutated complex, where the identified arginine is replaced by alanine, led to a 2-fold decrease in transfer efficiency, also consistent with experimental results. This work provides a molecular-level understanding of the electrostatic channeling mechanism and will enable the further design of catalytic nanostructures utilizing electrostatic channeling.

7.
JACS Au ; 1(11): 1915-1924, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34849509

RESUMO

The electrochemical reduction of CO2 is widely studied as a sustainable alternative for the production of fuels and chemicals. The electrolyte's bulk pH and composition play an important role in the reaction activity and selectivity and can affect the extent of the buildup of pH gradients between the electrode surface and the bulk of the electrolyte. Quantifying the local pH and how it is affected by the solution species is desirable to gain a better understanding of the CO2 reduction reaction. Local pH measurements can be realized using Scanning Electrochemical Microscopy (SECM); however, finding a pH probe that is stable and selective under CO2 reduction reaction conditions is challenging. Here, we have used our recently developed voltammetric pH sensor to perform pH measurements in the diffusion layer during CO2 reduction using SECM, with high time resolution. Using a 4-hydroxylaminothiophenol (4-HATP)/4-nitrosothiophenol (4-NSTP) functionalized gold ultramicroelectrode, we compare the local pH developed above a gold substrate in an argon atmosphere, when only hydrogen evolution is taking place, to the pH developed in a CO2 atmosphere. The pH is monitored at a fixed distance from the surface, and the sample potential is varied in time. In argon, we observe a gradual increase of pH, while a plateau region is present in CO2 atmosphere due to the formation of HCO3 - buffering the reaction interface. By analyzing the diffusion layer dynamics once the sample reaction is turned "off", we gain insightful information on the time scale of the homogeneous reactions happening in solution and on the time required for the diffusion layer to fully recover to the initial bulk concentration of species. In order to account for the effect of the presence of the SECM tip on the measured pH, we performed finite element method simulations of the fluid and reaction dynamics. The results show the significant localized diffusion hindrance caused by the tip, so that in its absence, the pH values are more acidic than when the tip is present. Nonetheless, through the simulation, we can account for this effect and estimate the real local pH values across the diffusion layer.

8.
Anal Chem ; 93(37): 12495-12503, 2021 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-34478278

RESUMO

Mass-transport-limited catalysis and membrane transport can be characterized by concentration profiles surrounding active surfaces. Scanning electrochemical microscopy (SECM) is a tool that has been used to measure concentration profiles; however, the presence and geometry of the tip can distort these profiles due to hindered diffusion, which in turn alters chemical behavior at the catalytic surface. To fully characterize the behavior of surface features such as catalytic sites, it is essential to account for and analytically remove the effect of tip presence. In this work, atomic force microscopy-based SECM (AFM-SECM) measurements over poly(tetrafluoroethylene) (PTFE) and gold electrode surfaces are used to measure negative and positive-feedback approach curves, respectively. By inversely fitting these approach curves with a finite element method (FEM) model, we derive kinetic and geometric tip parameters that characterize the effect of tip presence. Tip effects may be removed in the model to estimate concentration profiles and reaction properties for the case where no tip is present. A maximum 120% increase in the concentration at one tip radii above the surface is observed due to the presence of the tip, where the concentration field is compressed vertically, in proportion to surface feature size and tip separation. Conical AFM-SECM tips, with a higher ratio of tip height to the base size, introduce less concentration distortion than disk-shaped AFM-SECM tips.

9.
Phys Chem Chem Phys ; 23(23): 13381-13388, 2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-34105559

RESUMO

The efficiency of cascade reactions, which consist of multiple chemical transformations that occur in a single pot without purification steps, is limited by the transport efficiency of intermediates between adjacent steps. Electrostatic channeling is a proven strategy for intermediate transfer in natural chemical cascades, but implementation into artificial cascades remains a challenge. Here, we combine infrequent metadynamics (InMetaD), umbrella sampling (US), and kinetic Monte Carlo (KMC) models to computationally study the transfer mechanism of glucose-6-phosphate (G6P) on a poly-arginine peptide bridging hexokinase (HK) and glucose-6-dehydrogenase (G6PDH). Transport of G6P by hopping in the presence of poly-arginine peptides is shown to be a rare event, and InMetaD is used to compute the hopping activation energy. US simulations capture the configurational change in the desorption process and enable the determination of the desorption energy. Parameterized by these results, a KMC model is used to estimate transport efficiency for the bridged enzyme complex. Results are compared to a similar complex using a poly-lysine bridge, using kinetic lag time as a metric. Even at a high ionic strength of 120 mM, poly-arginine peptides may be capable of more efficient transport as compared to poly-lysine, with a predicted lag time of 6 seconds for poly-arginine, compared to a previously reported lag time of 59 seconds for poly-lysine. This work indicates that poly-arginine peptides may be an improved bridge structure for electrostatic channeling of anionic intermediates.

10.
Biosensors (Basel) ; 10(10)2020 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-33080847

RESUMO

Electrochemical immunosensors (EIs) integrate biorecognition molecules (e.g., antibodies) with redox enzymes (e.g., horseradish peroxidase) to combine the advantages of immunoassays (high sensitivity and selectivity) with those of electrochemical biosensors (quantitative electrical signal). However, the complex network of mass-transfer, catalysis, and electrochemical reaction steps that produce the electrical signal makes the design and optimization of EI systems challenging. This paper presents an integrated experimental and modeling framework to address this challenge. The framework includes (1) a mechanistic mathematical model that describes the rate of key mass-transfer and reaction steps; (2) a statistical-design-of-experiments study to optimize operating conditions and validate the mechanistic model; and (3) a novel dimensional analysis to assess the degree to which individual mass-transfer and reaction steps limit the EI's signal amplitude and sensitivity. The validated mechanistic model was able to predict the effect of four independent variables (working electrode overpotential, pH, and concentrations of catechol and hydrogen peroxide) on the EI's signal magnitude. The model was then used to calculate dimensionless groups, including Damkohler numbers, novel current-control coefficients, and sensitivity-control coefficients that indicated the extent to which the individual mass-transfer or reaction steps limited the EI's signal amplitude and sensitivity.


Assuntos
Técnicas Biossensoriais , Imunoensaio , Técnicas Eletroquímicas , Eletroquímica , Peroxidase do Rábano Silvestre , Modelos Teóricos
11.
PLoS Comput Biol ; 16(4): e1007648, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32302302

RESUMO

Medium spiny neurons (MSNs) comprise over 90% of cells in the striatum. In vivo MSNs display coherent burst firing cell assembly activity patterns, even though isolated MSNs do not burst fire intrinsically. This activity is important for the learning and execution of action sequences and is characteristically dysregulated in Huntington's Disease (HD). However, how dysregulation is caused by the various neural pathologies affecting MSNs in HD is unknown. Previous modeling work using simple cell models has shown that cell assembly activity patterns can emerge as a result of MSN inhibitory network interactions. Here, by directly estimating MSN network model parameters from single unit spiking data, we show that a network composed of much more physiologically detailed MSNs provides an excellent quantitative fit to wild type (WT) mouse spiking data, but only when network parameters are appropriate for the striatum. We find the WT MSN network is situated in a regime close to a transition from stable to strongly fluctuating network dynamics. This regime facilitates the generation of low-dimensional slowly varying coherent activity patterns and confers high sensitivity to variations in cortical driving. By re-estimating the model on HD spiking data we discover network parameter modifications are consistent across three very different types of HD mutant mouse models (YAC128, Q175, R6/2). In striking agreement with the known pathophysiology we find feedforward excitatory drive is reduced in HD compared to WT mice, while recurrent inhibition also shows phenotype dependency. We show that these modifications shift the HD MSN network to a sub-optimal regime where higher dimensional incoherent rapidly fluctuating activity predominates. Our results provide insight into a diverse range of experimental findings in HD, including cognitive and motor symptoms, and may suggest new avenues for treatment.


Assuntos
Corpo Estriado/fisiologia , Doença de Huntington/fisiopatologia , Animais , Mapeamento Encefálico , Modelos Animais de Doenças , Progressão da Doença , Neurônios GABAérgicos/metabolismo , Homozigoto , Humanos , Proteína Huntingtina/metabolismo , Camundongos , Camundongos Transgênicos , Mutação , Neurônios/fisiologia , Fenótipo , Radiocirurgia
12.
J Neurophysiol ; 122(6): 2621-2629, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31693428

RESUMO

Abnormal communication between cerebral cortex and striatum plays a major role in the motor symptoms of Huntington's disease (HD), a neurodegenerative disorder caused by a mutation of the huntingtin gene (mHTT). Because cortex is the main driver of striatal processing, we recorded local field potential (LFP) activity simultaneously in primary motor cortex (M1) and dorsal striatum (DS) in BACHD mice, a full-length HD gene model, and in a conditional BACHD/Emx-1 Cre (BE) model in which mHTT is suppressed in cortical efferents, while mice freely explored a plus-shaped maze beginning at 20 wk of age. Relative to wild-type (WT) controls, BACHD mice were just as active across >40 wk of testing but became progressively less likely to turn into a perpendicular arm as they approached the choice point of the maze, a sign of HD motor inflexibility. BE mice, in contrast, turned as freely as WT throughout testing. Although BE mice did not exactly match WT in LFP activity, the reduction in alpha (8-13 Hz), beta (13-30 Hz), and low-gamma (30-50 Hz) power that occurred in M1 of turning-impaired BACHD mice was reversed. No reversal occurred in DS. In fact, BE mice showed further reductions in DS theta (4-8 Hz), beta, and low-gamma power relative to the BACHD model. Coherence analysis indicated a dysregulation of corticostriatal information flow in both BACHD and BE mice. Collectively, our results suggest that mHTT in cortical outputs drives the dysregulation of select cortical frequencies that accompany the loss of behavioral flexibility in HD.NEW & NOTEWORTHY BACHD mice, a full-length genetic model of Huntington's disease (HD), express aberrant local field potential (LFP) activity in primary motor cortex (M1) along with decreased probability of turning into a perpendicular arm of a plus-shaped maze, a motor inflexibility phenotype. Suppression of the mutant huntingtin gene in cortical output neurons prevents decline in turning and improves alpha, beta, and low-gamma activity in M1. Our results implicate cortical networks in the search for therapeutic strategies to alleviate HD motor signs.


Assuntos
Comportamento Animal/fisiologia , Ondas Encefálicas/fisiologia , Proteína Huntingtina/deficiência , Doença de Huntington/fisiopatologia , Aprendizagem em Labirinto/fisiologia , Córtex Motor/fisiopatologia , Neostriado/fisiopatologia , Rede Nervosa/fisiopatologia , Animais , Modelos Animais de Doenças , Feminino , Masculino , Camundongos , Camundongos Transgênicos
13.
J Phys Chem C Nanomater Interfaces ; 123(24): 15284-15292, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31275507

RESUMO

Electrostatic channeling is a naturally occurring approach to control the flux of charged intermediates in catalytic cascades. Computational techniques have enabled quantitative understanding of such mechanisms, augmenting experimental approaches by modeling molecular interactions in atomic detail. In this work, we report the first utilization of a Markov-state model (MSM) to describe the surface diffusion of a reaction intermediate, glucose 6-phosphate, on an artificially modified cascade where hexokinase and glucose-6-phosphate dehydrogenase are covalently conjugated by a cationic oligopeptide bridge. Conformation space networks are used to represent intermediate transport on enzyme surfaces, along with committor probabilities that assess the desorption probability of the intermediate on each segment of the channeling pathway. For the region between the peptide bridge and downstream active site, the ionic strength dependence of desorption probability by MSM agreed well with that by transition state theory. A kinetic Monte Carlo model integrates parameters from different computational methods to evaluate the contribution of desorption during each step. The approach is validated by calculation of kinetic lag time, which agrees well with experimental results. These results further demonstrate the applicability of molecular simulations and advanced sampling techniques to the design of chemical networks.

15.
J Vis Exp ; (136)2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29912193

RESUMO

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980's to investigate thin film conductive polymers.


Assuntos
Biofilmes/crescimento & desenvolvimento , Eletroquímica/métodos , Transporte de Elétrons/fisiologia
16.
eNeuro ; 5(6)2018.
Artigo em Inglês | MEDLINE | ID: mdl-30627632

RESUMO

Abnormal gamma band power across cortex and striatum is an important phenotype of Huntington's disease (HD) in both patients and animal models, but neither the origin nor the functional relevance of this phenotype is well understood. Here, we analyzed local field potential (LFP) activity in freely behaving, symptomatic R6/2 and Q175 mouse models and corresponding wild-type (WT) controls. We focused on periods of quiet rest, which show strong γ activity in HD mice. Simultaneous recording from motor cortex and its target area in dorsal striatum in the R6/2 model revealed exaggerated functional coupling over that observed in WT between the phase of delta frequencies (1-4 Hz) in cortex and striatum and striatal amplitude modulation of low γ frequencies (25-55 Hz; i.e., phase-amplitude coupling, PAC), but no evidence that abnormal cortical activity alone can account for the increase in striatal γ power. Both HD mouse models had stronger coupling of γ amplitude to δ phase and more unimodal phase distributions than their WT counterparts. To assess the possible role of striatal fast-spiking interneurons (FSIs) in these phenomena, we developed a computational model based on additional striatal recordings from Q175 mice. Changes in peak γ frequency and power ratio were readily reproduced by our computational model, accounting for several experimental findings reported in the literature. Our results suggest that HD is characterized by both a reorganization of cortico-striatal drive and specific population changes related to intrastriatal synaptic coupling.


Assuntos
Córtex Cerebral/fisiopatologia , Simulação por Computador , Corpo Estriado/fisiopatologia , Ritmo Gama/fisiologia , Doença de Huntington/patologia , Modelos Neurológicos , Animais , Modelos Animais de Doenças , Ritmo Gama/genética , Proteína Huntingtina/genética , Doença de Huntington/genética , Doença de Huntington/fisiopatologia , Camundongos , Camundongos Transgênicos , Vias Neurais/fisiopatologia , Análise Espectral , Repetições de Trinucleotídeos/genética
17.
Phys Chem Chem Phys ; 19(23): 15463-15470, 2017 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-28580995

RESUMO

Efficient catalytic cascades that involve several sequential reactions are found frequently in nature. The efficiency of multi-step biochemical pathways is enhanced by substrate channelling, wherein the product of one reaction is directed toward and acts as substrate to the next sequential reaction. Such mechanisms can partially overcome diffusion, which is often fast compared to reaction rates, and promotes loss of intermediates. Biochemical substrate channelling is achieved by the architecture and scaffolding of enzymes, and mimicking these natural structures could lead to innovative catalyst designs. We investigate the efficiency of two channelling approaches - electrostatic interactions and surface adsorption - through continuum modelling, to identify the limits of these modes and the extent to which they can interact. The model considers transport between two active sites where an intermediate is produced at the first active site and consumed at the second. The system includes mass transport through diffusion and migration, and reaction kinetics at the active sites. The effectiveness of this model is quantified by yield of the second reaction relative to the first. Channelling via proximity between active sites and via surface adsorption are found to be inefficient, requiring high values of the rate constant at the second active site to obtain significant yields. The introduction of electrostatic interactions, however, leads to yields of over 90% at much lower values of the rate constant.

18.
J Dev Behav Pediatr ; 38 Suppl 1: S38-S40, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28141717

RESUMO

CASE: Marcus is a 10-year-old boy who was followed by his pediatrician for several years. She knows him as a socially engaged, active athlete, playing soccer and baseball, out-going, and a good student. He has been in good health without a significant medical history.At the beginning of this academic year, a new student was placed in Marcus's fourth grade class. This student is disruptive, impulsive, and abusive. He has frequent violent outbursts, yelling, kicking, and throwing objects, including recently throwing a desk across the room. The school has made efforts to manage this student. The teacher sets up behavior contracts, and the school has temporarily suspended the child; however, the school is unable to remove the child from the classroom. Many students, including Marcus, have been significantly affected by this disruption.Marcus describes the classroom environment as "tense." He reports he is never sure what is going to make the student "so mad." Over the last 3-4 months, Marcus developed nightmares, enuresis, and trichotillomania. The hair pulling is the most distressing feature for both Marcus and his parents. Marcus acknowledges that he is usually unaware of the behavior at first but then finds the sensation is relaxing. Afterward, he is typically embarrassed by the behavior. There is a family history of anxiety in both parents.He has been seeing a psychologist with some mild improvement in his enuresis. However, the hair pulling has not improved and has worsened. They were seeking additional advice regarding the next steps.


Assuntos
Comportamento Infantil/psicologia , Enurese Noturna/psicologia , Comportamento Problema/psicologia , Transtornos do Sono-Vigília/psicologia , Estudantes/psicologia , Tricotilomania/psicologia , Criança , Humanos , Masculino , Instituições Acadêmicas
19.
ChemSusChem ; 10(7): 1534-1542, 2017 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-28152261

RESUMO

Catalytic activity toward the oxygen reduction reaction (ORR) of platinum group metal-free (PGM-free) electrocatalysts integrated with an enzyme (bilirubin oxidase, BOx) in neutral media was studied. The effects of chemical and morphological characteristics of PGM-free materials on the enzyme enhancement of the overall ORR kinetics was investigated. The surface chemistry of the PGM-free catalyst was studied using X-ray Photoelectron Spectroscopy. Catalyst surface morphology was characterized using two independent methods: length-scale specific image analysis and nitrogen adsorption. Good agreement of macroscopic and microscopic morphological properties was found. Enhancement of ORR activity by the enzyme is influenced by chemistry and surface morphology of the catalyst itself. Catalysts with a higher nitrogen content, specifically pyridinic moieties, showed the greatest enhancement. Furthermore, catalysts with a higher fraction of surface roughness in the range of 3-5 nm exhibited greater performance enhancement than catalysts lacking features of this size.


Assuntos
Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxigênio/química , Platina/química , Catálise , Eletroquímica , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Propriedades de Superfície
20.
Neuropharmacology ; 113(Pt A): 502-510, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27816502

RESUMO

The substituted amphetamine, 2,5-dimethoxy-4-iodoamphetamine (DOI), is a hallucinogen that has been used to model a variety of psychiatric conditions. Here, we studied the effect of DOI on neural activity recorded simultaneously in the primary motor cortex (M1) and dorsal striatum of freely behaving FvB/N mice. DOI significantly decreased the firing rate of individually isolated neurons in M1 and dorsal striatum relative to pre-drug baseline. It also induced a bursting pattern of activity by increasing both the number of spikes within a burst and burst duration. In addition, DOI increased coincident firing between simultaneously recorded neuron pairs within the striatum and between M1 and dorsal striatum. Local field potential (LFP) activity also increased in coherence between M1 and dorsal striatum after DOI in the low frequency gamma band (30-50 Hz), while corticostriatal coherence in delta, theta, alpha, and beta activity decreased. We also assessed corticostriatal LFP activity in relation to the DOI-induced head-twitch response (HTR), a readily identifiable behavior used to assess potential treatments for the conditions it models. The HTR was associated with increased delta and decreased theta power in both M1 and dorsal striatum. Together, our results suggest that DOI dysregulates corticostriatal communication and that the HTR is associated with this dysregulation.


Assuntos
Anfetaminas/toxicidade , Comportamento Exploratório/fisiologia , Alucinógenos/toxicidade , Movimentos da Cabeça/fisiologia , Córtex Motor/fisiologia , Neostriado/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Ondas Encefálicas/efeitos dos fármacos , Ondas Encefálicas/fisiologia , Comportamento Exploratório/efeitos dos fármacos , Movimentos da Cabeça/efeitos dos fármacos , Masculino , Camundongos , Córtex Motor/efeitos dos fármacos , Neostriado/efeitos dos fármacos
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