The combination of ciprofloxacin and dialkyldimethyl ammonium compound synergistically proliferated intracellular resistance genes in nitrifying system.

Antibiotics and quaternary ammonium compounds (QACs) usually co-exist in wastewater treatment plants. Hence, three sequencing batch reactors were established and named as R1, R2 and R3, to investigate the effects of individual and combined exposure of different concentrations of ciprofloxacin (CIP) (0.2, 1.0 and 2.0 mg/L) and dialkyldimethyl ammonium compound (DADMAC) (0.4, 2.0 and 4.0 mg/L) on the performance, microbial community structures and resistance genes (RGs) in nitrifying system during 150 days. Results showed that CIP had a slight effect on ammonia oxidation activity, while 2.0 and 4.0 mg/L DADAMAC could obviously inhibit it, and the combination of CIP and DADMAC had a synergistic inhibitory effect. Besides, both CIP and DADMAC caused partial nitrification, and the order of nitrite accumulation rate was ranked as R3 > R2 > R1. The combination of CIP and DADMAC had an antagonistic effect on the increase of sludge particle size and α-Helix/(ß-Sheet + Random coil) was lowest in R3 (0.40). The combination of CIP and DADMAC synergistically stimulated most intracellular RGs in sludge, and the relative abundances of target RGs (e.g., qacEdelta1-01, qacH-01 and qnrS) at the end of operation in R3 were increased by 4.61-18.19 folds compared with those in CK, which were 1.34-5.57 folds higher than the R1 and R2. Moreover, the combination of CIP and DADMAC also promoted the transfer of RGs from sludge to water and enriched more potential hosts of RGs, further promoting the spread of RGs in nitrifying system. Thus, the combined pollution of CIP and DADMAC in wastewaters should attract more attentions.

Mechanisms on the removal of gram-negative/positive antibiotic resistant bacteria and inhibition of horizontal gene transfer by ferrate coupled with peroxydisulfate or peroxymonosulfate.

The existence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) has been a global public environment and health issue. Due to the different cell structures, gram-positive/negative ARB exhibit various inactivation mechanisms in water disinfection. In this study, a gram-negative ARB Escherichia coli DH5α (E. coli DH5α) was used as a horizontal gene transfer (HGT) donor, while a gram-positive ARB Bacillus as a recipient. To develop an efficient and engineering applicable method in water disinfection, ARB and ARGs removal efficiency of Fe(VI) coupled peroxydisulfate (PDS) or peroxymonosulfate (PMS) was compared, wherein hydroxylamine (HA) was added as a reducing agent. The results indicated that Fe(VI)/PMS/HA showed higher disinfection efficiency than Fe(VI)/PDS/HA. When the concentration of each Fe(VI), PMS, HA was 0.48 mM, 5.15 log E. coli DH5α and 3.57 log Bacillus lost cultivability, while the proportion of recovered cells was 0.0017 % and 0.0566 %, respectively, and HGT was blocked. Intracellular tetA was reduced by 2.49 log. Fe(IV) and/or Fe(V) were proved to be the decisive reactive species. Due to the superiority of low cost as well as high efficiency and practicality, Fe(VI)/PMS/HA has significant application potential in ARB, ARGs removal and HGT inhibition, offering a new insight for wastewater treatment.

Preferential potentiation of AMPA-mediated currents in brainstem hypoglossal motoneurons by subchronic exposure of mice expressing the human superoxide dismutase 1 G93A gene mutation to neurotoxicant methylmercury in vivo.

The exact causes of Amyotrophic lateral sclerosis (ALS), a progressive and fatal neurological disorder due to loss of upper and/or lower motoneurons, remain elusive. Gene-environment interactions are believed to be an important factor in the development of ALS. We previously showed that in vivo exposure of mice overexpressing the human superoxide dismutase 1 (hSOD1) gene mutation (hSOD1G93A; G93A), a mouse model for ALS, to environmental neurotoxicant methylmercury (MeHg) accelerated the onset of ALS-like phenotype. Here we examined the time-course of effects of MeHg on AMPA receptor (AMPAR)-mediated currents in hypoglossal motoneurons in brainstem slices prepared from G93A, hSOD1wild-type (hWT) and non-carrier WT mice following in vivo exposure to MeHg. Mice were exposed daily to 3 ppm (approximately 0.7 mg/kg/day) MeHg via drinking water beginning at postnatal day 28 (P28) and continued until P47, 64 or 84, then acute brainstem slices were prepared, and spontaneous excitatory postsynaptic currents (sEPSCs) or AMPA-evoked currents were examined using whole cell patch-clamp recording technique. Brainstem slices of untreated littermates were prepared at the same time points to serve as control. MeHg exposure had no significant effect on either sEPSCs or AMPA-evoked currents in slices from hWT or WT mice during any of those exposure time periods under our experimental conditions. MeHg also did not cause any significant effect on sEPSCs or AMPA-currents in G93A hypoglossal motoneurons at P47 and P64. However, at P84, MeHg significantly increased amplitudes of both sEPSCs and AMPA-evoked currents in hypoglossal motineurons from G93A mice (p < 0.05), but not the sEPSC frequency, suggesting a postsynaptic action on AMPARs. MeHg exposure did not cause any significant effect on GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs). Therefore, MeHg exposure in vivo caused differential effects on AMPARs in hypoglossal motoneurons from mice with different genetic backgrounds. MeHg appears to preferentially stimulate the AMPAR-mediated currents in G93A hypoglossal motoneurons in an exposure time-dependent manner, which may contribute to the AMPAR-mediated motoneuron excitotoxicity, thereby facilitating development of ALS-like phenotype.

Antisense oligonucleotides restore excitability, GABA signalling and sodium current density in a Dravet syndrome model.

Dravet syndrome is an intractable developmental and epileptic encephalopathy caused by de novo variants in SCN1A resulting in haploinsufficiency of the voltage-gated sodium channel Nav1.1. We showed previously that administration of the antisense oligonucleotide STK-001, also called ASO-22, generated using targeted augmentation of nuclear gene output technology to prevent inclusion of the nonsense-mediated decay, or poison, exon 20N in human SCN1A, increased productive Scn1a transcript and Nav1.1 expression and reduced the incidence of electrographic seizures and sudden unexpected death in epilepsy in a mouse model of Dravet syndrome. Here, we investigated the mechanism of action of ASO-84, a surrogate for ASO-22 that also targets splicing of SCN1A exon 20N, in Scn1a+/- Dravet syndrome mouse brain. Scn1a +/- Dravet syndrome and wild-type mice received a single intracerebroventricular injection of antisense oligonucleotide or vehicle at postnatal Day 2. We examined the electrophysiological properties of cortical pyramidal neurons and parvalbumin-positive fast-spiking interneurons in brain slices at postnatal Days 21-25 and measured sodium currents in parvalbumin-positive interneurons acutely dissociated from postnatal Day 21-25 brain slices. We show that, in untreated Dravet syndrome mice, intrinsic cortical pyramidal neuron excitability was unchanged while cortical parvalbumin-positive interneurons showed biphasic excitability with initial hyperexcitability followed by hypoexcitability and depolarization block. Dravet syndrome parvalbumin-positive interneuron sodium current density was decreased compared to wild-type. GABAergic signalling to cortical pyramidal neurons was reduced in Dravet syndrome mice, suggesting decreased GABA release from interneurons. ASO-84 treatment restored action potential firing, sodium current density and GABAergic signalling in Dravet syndrome parvalbumin-positive interneurons. Our work suggests that interneuron excitability is selectively affected by ASO-84. This new work provides critical insights into the mechanism of action of this antisense oligonucleotide and supports the potential of antisense oligonucleotide-mediated upregulation of Nav1.1 as a successful strategy to treat Dravet syndrome.

Deriving early single-rosette brain organoids from human pluripotent stem cells.

Brain organoid methods are complicated by multiple rosette structures and morphological variability. We have developed a human brain organoid technique that generates self-organizing, single-rosette cortical organoids (SOSR-COs) with reproducible size and structure at early timepoints. Rather than patterning a 3-dimensional embryoid body, we initiate brain organoid formation from a 2-dimensional monolayer of human pluripotent stem cells patterned with small molecules into neuroepithelium and differentiated to cells of the developing dorsal cerebral cortex. This approach recapitulates the 2D to 3D developmental transition from neural plate to neural tube. Most monolayer fragments form spheres with a single central lumen. Over time, the SOSR-COs develop appropriate progenitor and cortical laminar cell types as shown by immunocytochemistry and single-cell RNA sequencing. At early time points, this method demonstrates robust structural phenotypes after chemical teratogen exposure or when modeling a genetic neurodevelopmental disorder, and should prove useful for studies of human brain development and disease modeling.

Successive exposure to traditional disinfectants and quaternary ammonium compounds enhances resistance genes expression and co-selection in biofilm-based partial nitrification-anammox systems.

Quaternary ammonium compounds (QACs) are recommended disinfectants with surfactant properties, surpassing triclosan (TCS) and chloroxylenol (PCMX). Given the transition from traditional disinfectants, it is essential to investigate their impacts on biological nitrogen removal systems and the fate of resistance genes (RGs). In this study, three biofilm-based partial nitrification-anammox (PN/A) systems were established. A reactor named PD was successively exposed to 1 mg/L PCMX and 3 mg/L dioctadecyldimethylammonium chloride (DODMAC, a common QACs). A reactor named TD was successively exposed to 1 mg/L TCS and 3 mg/L DODMAC. A reactor named CD served as a control with only 3 mg/L DODMAC exposure. Results indicated that the total nitrogen removal performance of CD deteriorated markedly with DODMAC exposure compared to that of PD and TD. This phenomenon correlated closely with variations in RGs and their co-selection patterns. Pre-exposure to PCMX or TCS increased the abundance of RGs in the extracellular DNA of the PN/A biofilm, but reduced RGs abundances in the extracellular DNA of water. The tolerance of the PN/A system to successive exposure to the two disinfectants may be strengthened through co-selection of QACs RGs (qacEdelta1-01, qacEdelta1-02, qacH-01 and qacH-02) and mobile genetic elements (intI1 and tnpA-04). Furthermore, potential hosts of RGs are crucial for maintaining PN/A performance. Accumulation of extracellular polymeric substances, reactive oxygen species, and lactate dehydrogenase plays vital roles in the accumulation and transmission of RGs within the PN/A system.

Fates of extracellular and intracellular antibiotic resistance genes in activated sludge and plastisphere under sulfadiazine pressure.

Microplastics, antibiotics, and antibiotic resistance genes (ARGs) represent prominent emerging contaminants that can potentially hinder the efficacy of biological wastewater treatment and pose health risks. Plastisphere as a distinct ecological niche for microorganisms, acts as a repository for ARGs and potential pathogenic bacteria. Nonetheless, the spread pattern of extracellular ARGs (eARGs) and intracellular ARGs (iARGs) in plastisphere under antibiotic exposure was not yet known. This study aimed to investigate disparities in extracellular polymeric substances (EPS) production, extracellular and intracellular microbial community structures, as well as the transmission of eARGs and iARGs between activated sludge and plastisphere in an anaerobic/anoxic/oxic system under sulfadiazine (SDZ) exposure. SDZ was found to enhance EPS production in activated sludge and plastisphere. Interestingly, as SDZ removal efficiency increased, EPS content decreased in activated sludge and plastisphere collected from oxic zone, and continued to increase in plastisphere samples collected from anaerobic and anoxic zones. There were significant differences in microbial community structure between activated sludge and plastisphere, and the DNA fragments of potential pathogenic bacteria were detected in extracellular samples. SDZ exhibited a promoting effect on the propagation of eARGs, which were more abundant in the plastisphere than in activated sludge, thus heightening the risk of ARGs dissemination. Extracellular mobile genetic elements played a pivotal role in driving the spread of eARGs, while the microbial community induced the changes of iARGs. Potential pathogenic bacteria emerged as potential hosts for ARGs and mobile genetic elements within activated sludge and plastisphere, leading to more serious environmental threats.

Heterogeneity of voltage gated sodium current density between neurons decorrelates spiking and suppresses network synchronization in Scn1b null mouse models.

Voltage gated sodium channels (VGSCs) are required for action potential initiation and propagation in mammalian neurons. As with other ion channel families, VGSC density varies between neurons. Importantly, sodium current (INa) density variability is reduced in pyramidal neurons of Scn1b null mice. Scn1b encodes the VGSC ß1/ ß1B subunits, which regulate channel expression, trafficking, and voltage dependent properties. Here, we investigate how variable INa density in cortical layer 6 and subicular pyramidal neurons affects spike patterning and network synchronization. Constitutive or inducible Scn1b deletion enhances spike timing correlations between pyramidal neurons in response to fluctuating stimuli and impairs spike-triggered average current pattern diversity while preserving spike reliability. Inhibiting INa with a low concentration of tetrodotoxin similarly alters patterning without impairing reliability, with modest effects on firing rate. Computational modeling shows that broad INa density ranges confer a similarly broad spectrum of spike patterning in response to fluctuating synaptic conductances. Network coupling of neurons with high INa density variability displaces the coupling requirements for synchronization and broadens the dynamic range of activity when varying synaptic strength and network topology. Our results show that INa heterogeneity between neurons potently regulates spike pattern diversity and network synchronization, expanding VGSC roles in the nervous system.

Partial S(0)-driven autotrophic denitrification process facilitated the quick natural enrichment of anammox bacteria at room temperature.

Anaerobic ammonium oxidation (anammox) is well-known to be an environmental and promising biotechnology. However, the natural enrichment of anammox bacteria is still a challenging topic. In this study, partial S(0)-driven autotrophic denitrification (PSAD) was developed to stably supply nitrite, and natural enrichment of anammox bacteria was rapidly realized in a single sequencing moving bed biofilm reactor at room temperature. With the initiation of PSAD, anammox bacteria spontaneously emerged within 12 days, and PSAD-anammox coupling system was realized successfully. And then, the influent concentration of ammonium continuously increased to the same concentration as the nitrate, and the mean total nitrogen removal efficiency reached 92.77 %, which was mainly contributed by anammox. Moreover, the coupling of PSAD and anammox reduced the risk of sulfate emissions. cDNA high throughput sequencing revealed that the relative abundance of Candidatus Brocadia and Thiobacillus reached 39.03 % and 13.48 % at the 88th day. Oligotyping analysis illustrated that GATTTAAT and GTCCCA were the dominant Ca. Brocadia and Thiobacillus oligotypes in PSAD-anammox coupling system, respectively. DNA-based stable isotope probing further deciphered that Thiobacillus was the actual performer of PSAD and supported the nitrite for anammox bacteria in PSAD-anammox coupling system. Overall, this work provided a new strategy to naturally enrich anammox bacteria.

Mice with monoallelic GNAO1 loss exhibit reduced inhibitory synaptic input to cerebellar Purkinje cells.

GNAO1 encodes Gαo, a heterotrimeric G protein α subunit in the Gi/o family. In this report, we used a Gnao1 mouse model "G203R" previously described as a "gain-of-function" Gnao1 mutant with movement abnormalities and enhanced seizure susceptibility. Here, we report an unexpected second mutation resulting in a loss-of-function Gαo protein, and describe alterations in central synaptic transmission. Whole cell patch clamp recordings from Purkinje cells (PCs) in acute cerebellar slices from Gnao1 mutant mice showed significantly lower frequencies of spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs) compared with WT mice. There was no significant change in sEPSCs or mEPSCs. Whereas mIPSC frequency was reduced, mIPSC amplitudes were not affected, suggesting a presynaptic mechanism of action. A modest decrease in the number of molecular layer interneurons was insufficient to explain the magnitude of IPSC suppression. Paradoxically, Gi/o inhibitors (pertussis toxin) enhanced the mutant-suppressed mIPSC frequency and eliminated the difference between WT and Gnao1 mice. Although GABAB receptor regulates mIPSCs, neither agonists nor antagonists of this receptor altered function in the mutant mouse PCs. This study is an electrophysiological investigation of the role of Gi/o protein in cerebellar synaptic transmission using an animal model with a loss-of-function Gi/o protein.NEW & NOTEWORTHY This report reveals the electrophysiological mechanisms of a movement disorder animal model with monoallelic Gnao1 loss. This study illustrates the role of Gαo protein in regulating GABA release in mouse cerebellum. This study could also facilitate the discovery of new drugs or drug repurposing for GNAO1-associated disorders. Moreover, since GNAO1 shares pathways with other genes related to movement disorders, developing drugs for the treatment of GNAO1-associated movement disorders could further the pharmacological intervention for other monogenic movement disorders.

Morphology library of nanosilica based on a thermally induced deformable template.

We report a versatile platform for the synthesis of shape-tunable nanosilica based on a thermally induced deformable template with diverse morphologies ranging from spheres, horns, ultrathin nanosheets, and rings to belts. This was realized by creating soft templates from a pair of anionic/cationic surfactants.

Enhanced Sensitivity of Hydrogenated Cu0.27Co2.73O4 Nanooctahedrons Having {111} Facets and the Sensing Mechanism of 3-Coordinated Co/Cu Atoms as Active Centers.

Cu0.27Co2.73O4 nanooctahedrons enclosed by polar {111} planes have been prepared through the selective adsorption of Cl-. Hydrogenation has been successfully used to enhance the responses of the Cu0.27Co2.73O4 nanooctahedron sensors to acetone, ethanol, and n-butylamine. The enhancement of the response results from the increase in the number of 3-coordinated Co/Cu atoms (Co3c/Cu3c) at the (111) plane of Cu0.27Co2.73O4 through removing O-H groups and Cl- ions at the surface by hydrogenation. The Co3c/Cu3c atoms on the (111) plane of Cu0.27Co2.73O4 are considered to function as the gas response active centers. These Co3c/Cu3c active atoms have three functions: generating electrons, adsorbing oxygen from air, and catalyzing the sensing reactions. The hydrogenation polar surface approach can be applied to improve the performances of other sensing materials. Such sensing mechanisms of the Co3c/Cu3c unsaturated atoms as the active centers can be conducive to understanding the gas-sensing essence and the development of sensing materials with high performances.

Facial Contour Rejuvenation by Reduction Malarplasty Combined With Second-Stage Fat Grafting.

BACKGROUND: With aging, the facial contour shows a double-concave deformity. Conventional facial contouring procedure, including face lifting and fat grafting, cannot yield a smooth facial contour line. This study was the first to propose a combination of reduction malarplasty and 2nd-stage autologous fat grafting so as to achieve the aesthetic goals of facial contour rejuvenation. METHODS: The study group comprised patients seeking facial contour rejuvenation from January 2017 to May 2018 (28 patients: 28 females and 0 males) at the Department of Plastic Surgery, Tian Tan Pu Hua Hospital. All of the cases underwent bilateral malarplasty with 2nd-stage autologous facial fat grafting. Radiologic and photographic documentation was completed preoperatively. The mean follow-up period was 12 months. Patients' pre-op photographs and 3 months follow-up pictures were blindly assessed. RESULTS: Most of the patients were satisfied with their results after 1-time fat grafting. Eleven patients demanded re-injection after the 1st fat grafting in temporal area, and 6 patients demanded 3rd time fat grafting in temporal area. Eleven patients demanded re-injection insubmalar area, and 8 patients demanded 3rd time fat grafting in submalar area. Meanwhile, 9 of those patients underwent fat grafting in other sites other than temporal and submalar region. The amount of fat injected was also recorded in this study. The appearance of double-concave deformity was greatly improved in all cases. Complications included infection (3.6%), hematoma (7.1%), and malar prominence relapse (7.1%), and so on. CONCLUSION: Reduction malarplasty combined with several times of fat grafting could effectively overcome the malar prominence and soft tissue deflation. Complications were minimal after these procedures. Therefore, this technique is useful to restore the youthful facial contour in Asian patients with aging double-concave deformity.

Variant-specific changes in persistent or resurgent sodium current in SCN8A-related epilepsy patient-derived neurons.

Missense variants in the SCN8A voltage-gated sodium channel gene are linked to early-infantile epileptic encephalopathy type 13, also known as SCN8A-related epilepsy. These patients exhibit a wide spectrum of intractable seizure types, severe developmental delay, movement disorders, and elevated risk of sudden unexpected death in epilepsy. The mechanisms by which SCN8A variants lead to epilepsy are poorly understood, although heterologous expression systems and mouse models have demonstrated altered sodium current properties. To investigate these mechanisms using a patient-specific model, we generated induced pluripotent stem cells from three patients with missense variants in SCN8A: p.R1872>L (Patient 1); p.V1592>L (Patient 2); and p.N1759>S (Patient 3). Using small molecule differentiation into excitatory neurons, induced pluripotent stem cell-derived neurons from all three patients displayed altered sodium currents. Patients 1 and 2 had elevated persistent current, while Patient 3 had increased resurgent current compared to controls. Neurons from all three patients displayed shorter axon initial segment lengths compared to controls. Further analyses focused on one of the patients with increased persistent sodium current (Patient 1) and the patient with increased resurgent current (Patient 3). Excitatory cortical neurons from both patients had prolonged action potential repolarization. Using doxycycline-inducible expression of the neuronal transcription factors neurogenin 1 and 2 to synchronize differentiation of induced excitatory cortical-like neurons, we investigated network activity and response to pharmacotherapies. Both small molecule differentiated and induced patient neurons displayed similar abnormalities in action potential repolarization. Patient induced neurons showed increased burstiness that was sensitive to phenytoin, currently a standard treatment for SCN8A-related epilepsy patients, or riluzole, an FDA-approved drug used in amyotrophic lateral sclerosis and known to block persistent and resurgent sodium currents, at pharmacologically relevant concentrations. Patch-clamp recordings showed that riluzole suppressed spontaneous firing and increased the action potential firing threshold of patient-derived neurons to more depolarized potentials. Two of the patients in this study were prescribed riluzole off-label. Patient 1 had a 50% reduction in seizure frequency. Patient 3 experienced an immediate and dramatic seizure reduction with months of seizure freedom. An additional patient with a SCN8A variant in domain IV of Nav1.6 (p.V1757>I) had a dramatic reduction in seizure frequency for several months after starting riluzole treatment, but then seizures recurred. Our results indicate that patient-specific neurons are useful for modelling SCN8A-related epilepsy and demonstrate SCN8A variant-specific mechanisms. Moreover, these findings suggest that patient-specific neuronal disease modelling offers a useful platform for discovering precision epilepsy therapies.

Excitatory and inhibitory neuron defects in a mouse model of Scn1b-linked EIEE52.

OBJECTIVE: Human variants in voltage-gated sodium channel (VGSC) α and ß subunit genes are linked to developmental and epileptic encephalopathies (DEEs). Inherited, biallelic, loss-of-function variants in SCN1B, encoding the ß1/ß1B subunits, are linked to early infantile DEE (EIEE52). De novo, monoallelic variants in SCN1A (Nav1.1), SCN2A (Nav1.2), SCN3A (Nav1.3), and SCN8A (Nav1.6) are also linked to DEEs. While these VGSC-linked DEEs have similar presentations, they have diverse mechanisms of altered neuronal excitability. Mouse models have suggested that Scn2a-, Scn3a-, and Scn8a-linked DEE variants are, in general, gain of function, resulting in increased persistent or resurgent sodium current (INa ) and pyramidal neuron hyperexcitability. In contrast, Scn1a-linked DEE variants, in general, are loss-of-function, resulting in decreased INa and hypoexcitability of fast-spiking interneurons. VGSC ß1 subunits associate with Nav1.1, Nav1.2, Nav1.3, and Nav1.6 and are expressed throughout the brain, raising the possibility that insults to both pyramidal and interneuron excitability may drive EIEE52 pathophysiology. METHODS: We investigated excitability defects in pyramidal and parvalbumin-positive (PV +) interneurons in the Scn1b-/- model of EIEE52. We also used Scn1bFL/FL mice to delete Scn1b in specific neuronal populations. RESULTS: Scn1b-/- cortical PV + interneurons were hypoexcitable, with reduced INa density. Scn1b-/- cortical pyramidal neurons had population-specific changes in excitability and impaired INa density. Scn1b deletion in PV + neurons resulted in 100% lethality, whereas deletion in Emx1 + or Camk2a + neurons did not affect survival. INTERPRETATION: This work suggests that SCN1B-linked DEE variants impact both excitatory and inhibitory neurons, leading to the increased severity of EIEE52 relative to other DEEs.

Acute neurotoxicant exposure induces hyperexcitability in mouse lumbar spinal motor neurons.

Spinal motor neurons (MNs) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS, has not been systematically studied. The goal of this study was to test the ability of a well-known environmental neurotoxicant to induce hyperexcitability in mouse lumbar MNs. Methylmercury (MeHg) causes neurotoxicity through mechanisms involving elevated intracellular Ca2+ concentration ([Ca2+]i), a hallmark of excitotoxicity. We tested whether acute exposure to MeHg induces hyperexcitability in MNs by altering synaptic transmission, using whole cell patch-clamp recordings of lumbar spinal MNs in vitro. Acute MeHg exposure (20 µM) led to an increase in the frequency of both spontaneous excitatory postsynaptic currents (EPSCs) and miniature EPSCs. The frequency of inhibitory postsynaptic currents (IPSCs) was also increased by MeHg. Action potential firing rates, both spontaneous and evoked, were increased by MeHg, despite increases in both EPSCs and IPSCs, indicating a shift toward hyperexcitability. Also consistent with hyperexcitability, fluo 4-AM microfluorimetry indicated that MeHg exposure induced an increase in [Ca2+]i. Spinal cord hyperexcitability is partially mediated by Ca2+-permeable AMPA receptors, as MeHg-dependent increases in EPSCs were blocked by 1-napthyl spermine. Therefore, spinal MNs appear highly susceptible to MeHg exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to eventual neurodegeneration and loss of motor function as observed in spinal cord after MeHg exposure in vivo and may contribute to MeHg-induced acceleration of ALS symptoms.NEW & NOTEWORTHY Spinal motor neurons (MN) are susceptible to glutamatergic excitotoxicity, an effect associated with lumbar MN degeneration in amyotrophic lateral sclerosis (ALS). This study investigated MN susceptibility to environmental toxicant exposure, one prospective contributor to sporadic ALS. Spinal MNs appear highly susceptible to methylmercury exposure, leading to significant increases in spontaneous network excitability and disruption of normal function. Prolonged hyperexcitability could lead to neurodegeneration and loss of motor function as observed in ALS spinal cord symptoms.

Off-spindle-axis spiral grinding of aspheric microlens array mold inserts.

A novel approach named off-spindle-axis (OSA) spiral grinding for fabricating aspheric microlens array (AMLA) mold inserts for precision glass molding (PGM) is presented. In OSA spiral grinding, three translational motions of the grinding wheel are synchronized with the rotation of the workpiece to form a local spiral wheel path for individual lens-lets. With this approach, the form accuracy of lens-lets can be compensated within sub-micrometer by means of the on-machine measurement. The determination of wheel path and form error compensation via on-machine measurement are systematically studied. A tungsten carbide mold insert with four convex aspheric lens-lets is fabricated to evaluate the grinding performance. PGM experiments are performed to produce glass AMLA using the ground insert. The experimental results indicate that both the ground and molded AMLA with homogeneous quality are achieved. The form accuracy and surface roughness of both the mold insert and the molded AMLA were less than 0.3 µm in PV and 10 nm in Sa, respectively.

Delayed maturation of GABAergic signaling in the Scn1a and Scn1b mouse models of Dravet Syndrome.

Dravet syndrome (DS) is a catastrophic developmental and epileptic encephalopathy characterized by severe, pharmacoresistant seizures and the highest risk of Sudden Unexpected Death in Epilepsy (SUDEP) of all epilepsy syndromes. Here, we investigated the time course of maturation of neuronal GABAergic signaling in the Scn1b-/- and Scn1a+/- mouse models of DS. We found that GABAergic signaling remains immature in both DS models, with a depolarized reversal potential for GABAA-evoked currents compared to wildtype in the third postnatal week. Treatment of Scn1b-/- mice with bumetanide resulted in a delay in SUDEP onset compared to controls in a subset of mice, without prevention of seizure activity or amelioration of failure to thrive. We propose that delayed maturation of GABAergic signaling may contribute to epileptogenesis in SCN1B- and SCN1A-linked DS. Thus, targeting the polarity of GABAergic signaling in brain may be an effective therapeutic strategy to reduce SUDEP risk in DS.

Enhanced Gas Sensitivity and Sensing Mechanism of Network Structures Assembled from α-Fe2O3 Nanosheets with Exposed {104} Facets.

Network structures assembled from α-Fe2O3 nanosheets with exposed {104} facets were successfully prepared by heating Fe(NO3)3 solution containing polyvinylpyrrolidone (PVP) in air. The α-Fe2O3 nanosheet-based network structures demonstrate significantly higher response to ethanol and triethylamine than α-Fe2O3 commercial powders. The excellent sensing performances can be ascribed to the exposed (104) facet terminated with Fe atoms. A concept of the unsaturated Fe atoms serving as the sensing reaction active sites is thus proposed, and the sensing reaction mechanism is described at the atomic and molecular level for the first time in detail. The concept of the surface metal atoms with dangling bonds serving as active sites can deepen understanding of the sensing and other catalytic reaction mechanisms and provides new insight into the design and fabrication of highly efficient sensing materials, catalysts, and photoelectronic devices.

Neuronal hyperexcitability in a mouse model of SCN8A epileptic encephalopathy.

Patients with early infantile epileptic encephalopathy (EIEE) experience severe seizures and cognitive impairment and are at increased risk for sudden unexpected death in epilepsy (SUDEP). EIEE13 [Online Mendelian Inheritance in Man (OMIM) # 614558] is caused by de novo missense mutations in the voltage-gated sodium channel gene SCN8A Here, we investigated the neuronal phenotype of a mouse model expressing the gain-of-function SCN8A patient mutation, p.Asn1768Asp (Nav1.6-N1768D). Our results revealed regional and neuronal subtype specificity in the effects of the N1768D mutation. Acutely dissociated hippocampal neurons from Scn8aN1768D/+ mice showed increases in persistent sodium current (INa) density in CA1 pyramidal but not bipolar neurons. In CA3, INa,P was increased in both bipolar and pyramidal neurons. Measurement of action potential (AP) firing in Scn8aN1768D/+ pyramidal neurons in brain slices revealed early afterdepolarization (EAD)-like AP waveforms in CA1 but not in CA3 hippocampal or layer II/III neocortical neurons. The maximum spike frequency evoked by depolarizing current injections in Scn8aN1768D/+ CA1, but not CA3 or neocortical, pyramidal cells was significantly reduced compared with WT. Spontaneous firing was observed in subsets of neurons in CA1 and CA3, but not in the neocortex. The EAD-like waveforms of Scn8aN1768D/+ CA1 hippocampal neurons were blocked by tetrodotoxin, riluzole, and SN-6, implicating elevated persistent INa and reverse mode Na/Ca exchange in the mechanism of hyperexcitability. Our results demonstrate that Scn8a plays a vital role in neuronal excitability and provide insight into the mechanism and future treatment of epileptogenesis in EIEE13.