Magnetogenetic cell activation using endogenous ferritin.

The ability to precisely control the activity of defined cell populations enables studies of their physiological roles and may provide therapeutic applications. While prior studies have shown that magnetic activation of ferritin-tagged ion channels allows cell-specific modulation of cellular activity, the large size of the constructs made the use of adeno-associated virus, AAV, the vector of choice for gene therapy, impractical. In addition, simple means for generating magnetic fields of sufficient strength have been lacking. Toward these ends, we first generated a novel anti-ferritin nanobody that when fused to transient receptor potential cation channel subfamily V member 1, TRPV1, enables direct binding of the channel to endogenous ferritin in mouse and human cells. This smaller construct can be delivered in a single AAV and we validated that it robustly enables magnetically induced cell activation in vitro . In parallel, we developed a simple benchtop electromagnet capable of gating the nanobody-tagged channel in vivo . Finally, we showed that delivering these new constructs by AAV to pancreatic beta cells in combination with the benchtop magnetic field delivery stimulates glucose-stimulated insulin release to improve glucose tolerance in mice in vivo . Together, the novel anti-ferritin nanobody, nanobody-TRPV1 construct and new hardware advance the utility of magnetogenetics in animals and potentially humans.

Crystallization in one-step solution deposition of perovskite films: Upward or downward?

Despite the fast progress of perovskite photovoltaic performances, understanding the crystallization and growth of perovskite films is still lagging. One unanswered fundamental question is whether the perovskite films are grown from top (air side) to bottom (substrate side) or from bottom to top despite 10 years of development. Here, by using grazing incidence x-ray diffraction and morphology characterizations, we unveil that the perovskite films prepared by one-step solution processes, including antisolvent-assisted spin coating and blade coating, follow the downward growth from intermediate phase during thermal annealing. Such a top-to-bottom downward growth is initialized by the evaporation of residual solvent from the top surface of "wet" films and is less sensitive to perovskite compositions and the wettability of underlying substrates. Addressing this fundamental question is important to understand the heterogeneity of perovskite films along the vertical direction, which markedly affects the efficiency and stability of perovskite solar cells.

Reverse-Surge Planning During the COVID-19 Pandemic: A Cautionary Ramp-up for the Otolaryngologist.

As the coronavirus disease 2019 (COVID-19) pandemic continues to evolve through the United States and other countries, differing rates of progression and decline are occurring based on varied population densities. While some health systems are reaching a steady state of new patient cases, others are seeing a leveling off or decline, allowing for restoration of normal practices. This "reverse-surge" planning and implementation process is a colossal undertaking for health systems trying to reacquire patient access and financial stability while preserving necessary resources and maintaining precautions for another potential surge. For the otolaryngologist, reverse-surge planning involves additional workflow adjustments in the outpatient and operating room settings given the abundance of COVID-19 virus in the upper aerodigestive tract. As the reverse-surge best practices are still under development, open communication between otolaryngology colleagues and health system leadership is paramount to optimize efficiency and maintain an adequate measure of safety for patients and our health care teams.

The Role of Trauma and Stressful Life Events among Individuals at Clinical High Risk for Psychosis: A Review.

The experience of childhood trauma (CT) and stressful life events (SLEs) is associated with subsequent development of a variety of mental health conditions, including psychotic illness. Recent research identifying adolescents and young adults at clinical high risk (CHR) for psychosis allows for prospective evaluation of the impact of trauma and adverse life events on psychosis onset and other outcomes, addressing etiological questions that cannot be answered in studies of fully psychotic or non-clinical populations. This article provides a comprehensive review of the current emerging literature on trauma and adverse life events in the CHR population. Up to 80% of CHR youth endorse a lifetime history of childhood traumatic events and victimization (e.g., bullying). Several studies have shown that the experience of CT predicts psychosis onset among CHR individuals, while the literature on the influence of recent SLEs (e.g., death of a loved one) remains inconclusive. Multiple models have been proposed to explain the link between trauma and psychosis, including the stress-vulnerability and stress-sensitivity hypotheses, with emphases on both cognitive processes and neurobiological mechanisms (e.g., the hypothalamic-pituitary-adrenal axis). Despite the preponderance of CHR individuals who endorse either CT or SLEs, no clinical trials have been conducted evaluating interventions for trauma in CHR youth to date. Furthermore, the current process of formal identification and assessment of trauma, SLEs, and their impact on CHR youth is inconsistent in research and clinical practice. Recommendations for improving trauma assessment, treatment, and future research directions in the CHR field are provided.

Bidirectional electromagnetic control of the hypothalamus regulates feeding and metabolism.

Targeted, temporally regulated neural modulation is invaluable in determining the physiological roles of specific neural populations or circuits. Here we describe a system for non-invasive, temporal activation or inhibition of neuronal activity in vivo and its use to study central nervous system control of glucose homeostasis and feeding in mice. We are able to induce neuronal activation remotely using radio waves or magnetic fields via Cre-dependent expression of a GFP-tagged ferritin fusion protein tethered to the cation-conducting transient receptor potential vanilloid 1 (TRPV1) by a camelid anti-GFP antibody (anti-GFP-TRPV1). Neuronal inhibition via the same stimuli is achieved by mutating the TRPV1 pore, rendering the channel chloride-permeable. These constructs were targeted to glucose-sensing neurons in the ventromedial hypothalamus in glucokinase-Cre mice, which express Cre in glucose-sensing neurons. Acute activation of glucose-sensing neurons in this region increases plasma glucose and glucagon, lowers insulin levels and stimulates feeding, while inhibition reduces blood glucose, raises insulin levels and suppresses feeding. These results suggest that pancreatic hormones function as an effector mechanism of central nervous system circuits controlling blood glucose and behaviour. The method we employ obviates the need for permanent implants and could potentially be applied to study other neural processes or used to regulate other, even dispersed, cell types.

Spectroscopy and control of near-surface defects in conductive thin film ZnO.

The electronic structure of inorganic semiconductor interfaces functionalized with extended π-conjugated organic molecules can be strongly influenced by localized gap states or point defects, often present at low concentrations and hard to identify spectroscopically. At the same time, in transparent conductive oxides such as ZnO, the presence of these gap states conveys the desirable high conductivity necessary for function as electron-selective interlayer or electron collection electrode in organic optoelectronic devices. Here, we report on the direct spectroscopic detection of a donor state within the band gap of highly conductive zinc oxide by two-photon photoemission spectroscopy. We show that adsorption of the prototypical organic acceptor C60 quenches this state by ground-state charge transfer, with immediate consequences on the interfacial energy level alignment. Comparison with computational results suggests the identity of the gap state as a near-surface-confined oxygen vacancy.

Hybridization-Induced Carrier Localization at the C60 /ZnO Interface.

Electronic coupling and ground-state charge transfer at the C60 /ZnO hybrid interface is shown to localize carriers in the C60 phase. This effect, revealed by resonant X-ray photoemission, arises from interfacial hybridization between C60 and ZnO. Such localization at carrier-selective electrodes and interlayers may lead to severely reduced carrier harvesting efficiencies and increased recombination rates in organic electronic devices.

Hypothalamic Amylin Acts in Concert with Leptin to Regulate Food Intake.

In this report we evaluated the functions of hypothalamic amylin in vivo and in vitro. Profiling of hypothalamic neurons revealed that islet amyloid polypeptide (Iapp, precursor to amylin) is expressed in neurons in the lateral hypothalamus, arcuate nucleus, medial preoptic area, and elsewhere. Hypothalamic expression of lapp is markedly decreased in ob/ob mice and normalized by exogenous leptin. In slices, amylin and leptin had similar electrophysiologic effects on lateral hypothalamic leptin receptor ObRb-expressing neurons, while the amylin antagonist AC187 inhibited their activity and blunted the effect of leptin. Finally, i.c.v. infusion of AC187 acutely reduced the anorectic effects of leptin. These data show that hypothalamic amylin is transcriptionally regulated by leptin, that it can act directly on ObRb neurons in concert with leptin, and that it regulates feeding. These findings provide a potential mechanism for the increased efficacy of a metreleptin/pramlintide combination therapy for obesity.

Disrupted Attosecond Charge Carrier Delocalization at a Hybrid Organic/Inorganic Semiconductor Interface.

Despite significant interest in hybrid organic/inorganic semiconductor interfaces, little is known regarding the fate of charge carriers at metal oxide interfaces, particularly on ultrafast time scales. Using core-hole clock spectroscopy, we investigate the ultrafast charge carrier dynamics of conductive ZnO films at a hybrid interface with an organic semiconductor. The adsorption of C60 on the ZnO surface strongly suppresses the ultrafast carrier delocalization and increases the charge carrier residence time from 400 attoseconds to nearly 30 fs. Here, we show that a new hybridized interfacial density of states with substantial molecular character is formed, fundamentally altering the observed carrier dynamics. The remarkable change in the dynamics sheds light on the fate of carriers at hybrid organic/inorganic semiconductor interfaces relevant to organic optoelectronics and provides for the first time an atomistic picture of the electronically perturbed near-interface region of a metal oxide.

Profiling of Glucose-Sensing Neurons Reveals that GHRH Neurons Are Activated by Hypoglycemia.

Comprehensive transcriptional profiling of glucose-sensing neurons is challenging because of low expression levels of glucokinase (Gck) and other key proteins that transduce a glucose signal. To overcome this, we generated and validated transgenic mice with a neuronal/endocrine-specific Gck promoter driving cre expression and mated them to mice with cre-dependent expression of an EGFP-tagged ribosomal protein construct (EEF1A1-LSL.EGFPL10) that can be used to map and profile cells. We found significant Gck expression in hypothalamic and limbic regions in cells that are activated following administration of glucose or 2-deoxyglucose. Transcriptional profiling from Gck-cre/EEF1A1-LSL.EGFPL10 mice enriched known and previously unknown glucose-sensing populations including neurons expressing growth hormone releasing hormone (GHRH). Electrophysiological recordings show that hypoglycemia activates GHRH neurons, suggesting a mechanistic link between hypoglycemia and growth hormone release. These studies provide a means for mapping glucose-sensitive neurons and for generating transcriptional profiles from other cell types expressing cre in a cell-specific manner.

Resonance and localization effects at a dipolar organic semiconductor interface.

The image state manifold of the dipolar organic semiconductor vanadyl naphthalocyanine (VONc) on highly oriented pyrolytic graphite is investigated by angle-resolved two-photon photoemission (AR-TPPE) spectroscopy in the 0-1 monolayer regimes. Interfacial charge-transfer from the image potential state of clean graphite populates a near-resonant VONc anion level, identifiable by the graphite image potential state by its distinct momentum dispersion obtained from AR-TPPE. This affinity level is subject to depolarization by the neighboring molecules, resulting in stabilization of this state with coverage. Near a coverage of one monolayer, a hybrid image potential/anion state is also formed, showing progressive localization with coverage. Intensities for all these features develop rather differently with molecular coverage, pointing towards the different types of charge-transfer interactions at play at this interface.

Synaptic mGluR activation drives plasticity of calcium-permeable AMPA receptors.

In contrast with conventional NMDA receptor-dependent synaptic plasticity, the synaptic events controlling the plasticity of GluR2-lacking Ca(2+)-permeable AMPA receptors (CP-AMPARs) remain unclear. At parallel fiber synapses onto cerebellar stellate cells, Ca(2+) influx through AMPARs triggers a switch in AMPAR subunit composition, resulting in loss of Ca(2+) permeabilty. Paradoxically, synaptically induced depolarization will suppress this Ca(2+) entry by promoting polyamine block of CP-AMPARs. We therefore examined other mechanisms that may control this receptor regulation under physiological conditions. We found that activation of both mGluRs and CP-AMPARs is necessary and sufficient to drive an AMPAR subunit switch and that by enhancing mGluR activity, GABA(B)R activation promotes this plasticity. Furthermore, we found that mGluRs and GABA(B)Rs are tonically activated, thus setting the basal tone for EPSC amplitude and rectification. Regulation by both excitatory and inhibitory inputs provides an unexpected mechanism that determines the potential of these synapses to show dynamic changes in AMPAR Ca(2+) permeability.

Stargazin attenuates intracellular polyamine block of calcium-permeable AMPA receptors.

Endogenous polyamines profoundly affect the activity of various ion channels, including that of calcium-permeable AMPA-type glutamate receptors (CP-AMPARs). Here we show that stargazin, a transmembrane AMPAR regulatory protein (TARP) known to influence transport, gating and desensitization of AMPARs, greatly reduces block of CP-AMPARs by intracellular polyamines. By decreasing CP-AMPAR affinity for cytoplasmic polyamines, stargazin enhances the charge transfer following single glutamate applications and eliminates the frequency-dependent facilitation seen with repeated applications. In cerebellar stellate cells, which express both synaptic CP-AMPARs and stargazin, we found that the rectification and unitary conductance of channels underlying excitatory postsynaptic currents were matched by those of recombinant AMPARs only when the latter were associated with stargazin. Taken together, our observations establish modulatory actions of stargazin that are specific to CP-AMPARs, and suggest that during synaptic transmission the activity of such receptors, and thus calcium influx, is fundamentally changed by TARPs.

Regulation of Ca2+-permeable AMPA receptors: synaptic plasticity and beyond.

AMPA-type glutamate receptors (AMPARs) mediate most fast excitatory synaptic transmission in the brain. Diversity in excitatory signalling arises, in part, from functional differences among AMPAR subtypes. Although the rapid insertion or deletion of AMPARs is recognised as important for the expression of conventional forms of long-term synaptic plasticity--triggered, for example, by Ca2+ entry through NMDA-type glutamate receptors--only recently has attention focused on novel forms of plasticity that are regulated by, or alter the expression of, Ca2+-permeable AMPARs. The dynamic regulation of these receptors is important for normal synaptic function and in disease states.