Effects of AFQ056 on language learning in fragile X syndrome

BACKGROUNDFXLEARN, the first-ever large multisite trial of effects of disease-targeted pharmacotherapy on learning, was designed to explore a paradigm for measuring effects of mechanism-targeted treatment in fragile X syndrome (FXS). In FXLEARN, the effects of metabotropic glutamate receptor type 5 (mGluR5) negative allosteric modulator (NAM) AFQ056 on language learning were evaluated in 3- to 6-year-old children with FXS, expected to have more learning plasticity than adults, for whom prior trials of mGluR5 NAMs have failed.METHODSAfter a 4-month single-blind placebo lead-in, participants were randomized 1:1 to AFQ056 or placebo, with 2 months of dose optimization to the maximum tolerated dose, then 6 months of treatment during which a language-learning intervention was implemented for both groups. The primary outcome was a centrally scored videotaped communication measure, the Weighted Communication Scale (WCS). Secondary outcomes were objective performance-based and parent-reported cognitive and language measures.RESULTSFXLEARN enrolled 110 participants, randomized 99, and had 91 who completed the placebo-controlled period. Although both groups made language progress and there were no safety issues, the change in WCS score during the placebo-controlled period was not significantly different between the AFQ056 and placebo-treated groups, nor were there any significant between-group differences in change in any secondary measures.CONCLUSIONDespite the large body of evidence supporting use of mGluR5 NAMs in animal models of FXS, this study suggests that this mechanism of action does not translate into benefit for the human FXS population and that better strategies are needed to determine which mechanisms will translate from preclinical models to humans in genetic neurodevelopmental disorders.TRIAL REGISTRATIONClincalTrials.gov NCT02920892.FUNDING SOURCESNeuroNEXT network NIH grants U01NS096767, U24NS107200, U24NS107209, U01NS077323, U24NS107183, U24NS107168, U24NS107128, U24NS107199, U24NS107198, U24NS107166, U10NS077368, U01NS077366, U24NS107205, U01NS077179, and U01NS077352; NIH grant P50HD103526; and Novartis IIT grant AFQ056X2201T for provision of AFQ056.

A Dynamic Balance between Neuronal Death and Clearance in an in Vitro Model of Acute Brain Injury

In in vitro models of acute brain injury, neuronal death may overwhelm the capacity for microglial phagocytosis, creating a queue of dying neurons awaiting clearance. Neurons undergoing programmed cell death are in this queue, and are the most visible and frequently quantified measure of neuronal death after injury. However, the size of this queue should be equally sensitive to changes in neuronal death and the rate of phagocytosis. Using rodent organotypic hippocampal slice cultures as a model of acute perinatal brain injury, serial imaging demonstrated that the capacity for microglial phagocytosis of dying neurons was overwhelmed for 2 weeks. Altering phagocytosis rates (e.g., by changing the number of microglia) dramatically changed the number of visibly dying neurons. Similar effects were generated when the visibility of dying neurons was altered by changing the membrane permeability for stains that label dying neurons. Canonically neuroprotective interventions, such as seizure blockade, and neurotoxic maneuvers, such as perinatal ethanol exposure, were mediated by effects on microglial activity and the membrane permeability of neurons undergoing programmed cell death. These canonically neuroprotective and neurotoxic interventions had either no or opposing effects on healthy surviving neurons identified by the ongoing expression of transgenic fluorescent proteins.SIGNIFICANCE STATEMENT In in vitro models of acute brain injury, microglial phagocytosis is overwhelmed by the number of dying cells. Under these conditions, the assumptions on which assays for neuroprotective and neurotoxic effects are based are no longer valid. Thus, longitudinal assays of healthy cells, such as serial assessment of the fluorescence emission of transgenically expressed proteins, provide more accurate estimates of cell death than do single-time point anatomic or biochemical assays of the number of dying neurons. More accurate estimates of death rates in vitro will increase the translatability of preclinical studies of neuroprotection and neurotoxicity.

A dynamic balance between neuronal death and clearance after acute brain injury

After acute brain injury, neuronal apoptosis may overwhelm the capacity for microglial phagocytosis, creating a queue of dying neurons awaiting clearance. The size of this queue should be equally sensitive to changes in neuronal death and the rate of phagocytosis. Using rodent organotypic hippocampal slice cultures as a model of acute perinatal brain injury, serial imaging demonstrated that the capacity for microglial phagocytosis of dying neurons was overwhelmed for two weeks. Altering phagocytosis rates, e.g. by changing the number of microglia, dramatically changed the number of visibly dying neurons. Similar effects were generated when the visibility of dying neurons was altered by changing the membrane permeability for vital stains. Canonically neuroprotective interventions such as seizure blockade and neurotoxic maneuvers such as perinatal ethanol exposure were mediated by effects on microglial activity and the membrane permeability of apoptotic neurons, and had either no or opposing effects on healthy surviving neurons.

Significance

After acute brain injury, microglial phagocytosis is overwhelmed by the number of dying cells. Under these conditions, the assumptions on which assays for neuroprotective and neurotoxic effects are based are no longer valid. Thus longitudinal assays of healthy cells, such as assessment of the fluorescence emission of transgenically-expressed proteins, provide more accurate estimates of cell death than do single-time-point anatomical or biochemical assays. More accurate estimates of death rates will increase the translatability of preclinical studies of neuroprotection and neurotoxicity.

Gene therapy for epilepsy

On-demand inhibition of neuronal activity reduced spontaneous seizures in mice

Risk and the Republican National Convention: Application of the Novel COVID-19 Operational Risk Assessment

The United States Centers for Disease Control and Prevention and the World Health Organization broadly categorize mass gathering events as high risk for amplification of coronavirus disease 2019 (COVID-19) spread in a community due to the nature of respiratory diseases and the transmission dynamics. However, various measures and modifications can be put in place to limit or reduce the risk of further spread of COVID-19 for the mass gathering. During this pandemic, the Johns Hopkins University Center for Health Security produced a risk assessment and mitigation tool for decision-makers to assess SARS-CoV-2 transmission risks that may arise as organizations and businesses hold mass gatherings or increase business operations: The JHU Operational Toolkit for Businesses Considering Reopening or Expanding Operations in COVID-19 (Toolkit). This article describes the deployment of a data-informed, risk-reduction strategy that protects local communities, preserves local health-care capacity, and supports democratic processes through the safe execution of the Republican National Convention in Charlotte, North Carolina. The successful use of the Toolkit and the lessons learned from this experience are applicable in a wide range of public health settings, including school reopening, expansion of public services, and even resumption of health-care delivery.

Robust, long-term video EEG monitoring in a porcine model of post-traumatic epilepsy

To date, post-traumatic epilepsy (PTE) research in large animal models has been limited. Recent advances in neocortical microscopy have made possible new insights into neocortical PTE. However, it is very difficult to engender convincing neocortical PTE in rodents. Thus, large animal models that develop neocortical PTE may provide useful insights that also can be more comparable to human patients. Because gyrencephalic species have prolonged latent periods, long-term video EEG recording is required. Here, we report a fully subcutaneous EEG implant with synchronized video in freely ambulatory swine for up to 13 months during epileptogenesis following bilateral cortical impact injuries or sham surgery The advantages of this system include the availability of a commercially available system that is simple to install, a low failure rate after surgery for EEG implantation, radiotelemetry that enables continuous monitoring of freely ambulating animals, excellent synchronization to video to EEG, and a robust signal to noise ratio. The disadvantages of this system in this species and age are the accretion of skull bone which entirely embedded a subset of skull screws and EEG electrodes, and the inability to rearrange the EEG electrode array. These disadvantages may be overcome by splicing a subdural electrode strip to the electrode leads so that skull growth is less likely to interfere with long-term signal capture and by placing two implants for a more extensive montage. This commercially available system in this bilateral cortical impact swine model may be useful to a wide range of investigators studying epileptogenesis in PTE.SignificancePost-traumatic epilepsy (PTE) is a cause of significant morbidity after traumatic brain injury (TBI) and is often drug-resistant. Robust, informative animal models would greatly facilitate PTE research. Ideally, this biofidelic model of PTE would utilize a species that approximates human brain anatomy, brain size, glial populations, and inflammatory pathways. An ideal model would also incorporate feasible methods for long-term video EEG recording required to quantify seizure activity. Here, we describe the first model of PTE in swine and describe a method for robust long-term video EEG monitoring for up to 13 months post-TBI. The relatively easy "out-of-the-box" radiotelemetry system and surgical techniques described here will be adaptable by a wide array of investigators studying the pathogenesis and treatment of PTE.

Government response to COVID-19: Gaps revealed

Drawing on the diverse perspectives of four emergency management professionals and a public administration academic, gaps revealed by our nation's response to the COVID-19 pandemic are discussed. These gaps range from political theory regarding our government system of federalism to fundamental questions around the public communication of risk management and the provision of mass shelter and care.

Antiepileptogenesis and disease modification: Progress, challenges, and the path forward-Report of the Preclinical Working Group of the 2018 NINDS-sponsored antiepileptogenesis and disease modification workshop

Epilepsy is one of the most common chronic brain diseases and is often associated with cognitive, behavioral, or other medical conditions. The need for therapies that would prevent, ameliorate, or cure epilepsy and the attendant comorbidities is a priority for both epilepsy research and public health. In 2018, the National Institute of Neurological Disease and Stroke (NINDS) convened a workshop titled “Accelerating the Development of Therapies for Antiepileptogenesis and Disease Modification” that brought together preclinical and clinical investigators and industry and regulatory bodies’ representatives to discuss and propose a roadmap to accelerate the development of antiepileptogenic (AEG) and disease‐modifying (DM) new therapies. This report provides a summary of the discussions and proposals of the Preclinical Science working group. Highlights of the progress of collaborative preclinical research projects on AEG/DM of ongoing research initiatives aiming to improve infrastructure and translation to clinical trials are presented. Opportunities and challenges of preclinical epilepsy research, vis‐à‐vis clinical research, were extensively discussed, as they pertain to modeling of specific epilepsy types across etiologies and ages, the utilization of preclinical models in AG/DM studies, and the strategies and study designs, as well as on matters pertaining to transparency, data sharing, and reporting research findings. A set of suggestions on research initiatives, infrastructure, workshops, advocacy, and opportunities for expanding the borders of epilepsy research were discussed and proposed as useful initiatives that could help create a roadmap to accelerate and optimize preclinical translational AEG/DM epilepsy research.

A perfect storm: The distribution of tissue damage depends on seizure duration, hemorrhage, and developmental stage in a gyrencephalic, multi-factorial, severe traumatic brain injury model

The pathophysiology of extensive cortical tissue destruction observed in hemispheric hypodensity, a severe type of brain injury observed in young children, is unknown. Here, we utilize our unique, large animal model of hemispheric hypodensity with multifactorial injuries and insults to understand the pathophysiology of this severe type of traumatic brain injury, testing the effect of different stages of development. Piglets developmentally similar to human infants (1 week old, “infants”) and toddlers (1 month old, “toddlers”) underwent injuries and insults scaled to brain volume: cortical impact, creation of mass effect, placement of a subdural hematoma, seizure induction, apnea, and hypoventilation or a sham injury while anesthetized with a seizure-permissive regimen. Piglets receiving model injuries required overnight intensive care. Hemispheres were evaluated for damage via histopathology. The pattern of damage was related to seizure duration and hemorrhage pattern in “toddlers” resulting in a unilateral hemispheric pattern of damage ipsilateral to the injuries with sparing of the deep brain regions and the contralateral hemisphere. While “infants” had the equivalent duration of seizures as “toddlers”, damage was less than “toddlers”, not correlated to seizure duration, and was bilateral and patchy as is often observed in human infants. Subdural hemorrhage was associate with adjacent focal subarachnoid hemorrhage. The percentage of the hemisphere covered with subarachnoid hemorrhage was positively correlated with damage in both developmental stages. In “infants”, hemorrhage over the cortex was associated with damage to the cortex with sparing of the deep gray matter regions; without hemorrhage, damage was directed to the hippocampus and the cortex was spared. “Infants” had lower neurologic scores than “toddlers”. This multifactorial model of severe brain injury caused unilateral, wide-spread destruction of the cortex in piglets developmentally similar to toddlers where both seizure duration and hemorrhage covering the brain were positively correlated to tissue destruction. Inherent developmental differences may affect how the brain responds to seizure, and thus, affects the extent and pattern of damage. Study into specifically how the “infant” brain is resistant to the effects of seizure is currently underway and may identify potential therapeutic targets that may reduce evolution of tissue damage after severe traumatic brain injury.

Development of a Model of Hemispheric Hypodensity ("Big Black Brain")

Subdural hematoma (SDH) is the most common finding after abusive head trauma (AHT). Hemispheric hypodensity (HH) is a radiological indicator of severe brain damage that encompasses multiple vascular territories, and may develop in the hemisphere(s) underlying the SDH. In some instances where the SDH is predominantly unilateral, the widespread damage is unilateral underlying the SDH. To date, no animal model has successfully replicated this pattern of injury. We combined escalating severities of the injuries and insults commonly associated with HH including SDH, impact, mass effect, seizures, apnea, and hypoventilation to create an experimental model of HH in piglets aged 1 week (comparable to human infants) to 1 month (comparable to human toddlers). Unilateral HH evolved over 24 h when kainic acid was applied ipsilateral to the SDH to induce seizures. Pathological examination revealed a hypoxic-ischemic injury-type pattern with vasogenic edema through much of the cortical ribbon with relative sparing of deep gray matter. The percentage of the hemisphere that was damaged was greater on the ipsilateral versus contralateral side and was positively correlated with SDH area and estimated seizure duration. Further studies are needed to parse out the pathophysiology of this injury and to determine if multiple injuries and insults act synergistically to induce a metabolic mismatch or if the mechanism of trauma induces severe seizures that drive this distinctive pattern of injury.

Transient ischemia facilitates neuronal chloride accumulation and severity of seizures

Objective

Preceding oxygen glucose deprivation (OGD) and ongoing seizures have both been reported to increase neuronal chloride concentration ([Cl⁻]_i), which may contribute to anticonvulsant failure by reversing the direction of chloride currents at inhibitory GABA_A synapses.

Methods

The effects of OGD on [Cl⁻]_i, seizure activity, and anticonvulsant efficacy were studied in a chronically epileptic in vitro preparation.

Results

Seizures initially increased during OGD, followed by suppression. On reperfusion, seizure frequency and [Cl⁻]_i progressively increased, and phenobarbital efficacy was reduced. Bumetanide (10 μmol/L) and furosemide (1 mmol/L) prevented or reduced the OGD induced [Cl⁻]_i increase. Phenobarbital efficacy was enhanced by bumetanide (10 μmol/L). Furosemide (1 mmol/L) suppressed recurrent seizures.

Interpretation

[Cl⁻]_i increases after OGD and is associated with worsened seizure activity, reduced efficacy of GABAergic anticonvulsants, and amelioration by antagonists of secondary chloride transport.

Standards for data acquisition and software-based analysis of in vivo electroencephalography recordings from animals. A TASK1-WG5 report of the AES/ILAE Translational Task Force of the ILAE

Electroencephalography (EEG)-the direct recording of the electrical activity of populations of neurons-is a tremendously important tool for diagnosing, treating, and researching epilepsy. Although standard procedures for recording and analyzing human EEG exist and are broadly accepted, there are no such standards for research in animal models of seizures and epilepsy-recording montages, acquisition systems, and processing algorithms may differ substantially among investigators and laboratories. The lack of standard procedures for acquiring and analyzing EEG from animal models of epilepsy hinders the interpretation of experimental results and reduces the ability of the scientific community to efficiently translate new experimental findings into clinical practice. Accordingly, the intention of this report is twofold: (1) to review current techniques for the collection and software-based analysis of neural field recordings in animal models of epilepsy, and (2) to offer pertinent standards and reporting guidelines for this research. Specifically, we review current techniques for signal acquisition, signal conditioning, signal processing, data storage, and data sharing, and include applicable recommendations to standardize collection and reporting. We close with a discussion of challenges and future opportunities, and include a supplemental report of currently available acquisition systems and analysis tools. This work represents a collaboration on behalf of the American Epilepsy Society/International League Against Epilepsy (AES/ILAE) Translational Task Force (TASK1-Workgroup 5), and is part of a larger effort to harmonize video-EEG interpretation and analysis methods across studies using in vivo and in vitro seizure and epilepsy models.

Chloride Dysregulation, Seizures, and Cerebral Edema: A Relationship with Therapeutic Potential

Pharmacoresistant seizures and cytotoxic cerebral edema are serious complications of ischemic and traumatic brain injury. Intraneuronal Cl^- concentration ([Cl^-]_i) regulation impacts on both cell volume homeostasis and Cl^--permeable GABA_A receptor-dependent membrane excitability. Understanding the pleiotropic molecular determinants of neuronal [Cl^-]_i - cytoplasmic impermeant anions, polyanionic extracellular matrix (ECM) glycoproteins, and plasmalemmal Cl^- transporters - could help the identification of novel anticonvulsive and neuroprotective targets. The cation/Cl^- cotransporters and ECM metalloproteinases may be particularly druggable targets for intervention. We establish here a paradigm that accounts for recent data regarding the complex regulatory mechanisms of neuronal [Cl^-]_i and how these mechanisms impact on neuronal volume and excitability. We propose approaches to modulate [Cl^-]_i that are relevant for two common clinical sequela of brain injury: edema and seizures.

Service users as collaborators in mental health research: less stick, more carrot

Involving service users in research improves its quality and relevance. Many research organizations funding and supporting research now ask researchers about involvement as part of their application process. Some researchers are facing challenges in taking forward involvement as the research infrastructure is not always facilitative. Researchers need greater reward and recognition for carrying out good quality involvement to encourage more effective processes.

Recognition of partially occluded and rotated images with a network of spiking neurons

In this paper, we introduce a novel system for recognition of partially occluded and rotated images. The system is based on a hierarchical network of integrate-and-fire spiking neurons with random synaptic connections and a novel organization process. The network generates integrated output sequences that are used for image classification. The proposed network is shown to provide satisfactory predictive performance given that the number of the recognition neurons and synaptic connections are adjusted to the size of the input image. Comparison of synaptic plasticity activity rule (SAPR) and spike timing dependant plasticity rules, which are used to learn connections between the spiking neurons, indicates that the former gives better results and thus the SAPR rule is used. Test results show that the proposed network performs better than a recognition system based on support vector machines.

Nicotinic α7 acetylcholine receptor-mediated currents are not modulated by the tryptophan metabolite kynurenic acid in adult hippocampal interneurons

The  tryptophan  metabolite,  kynurenic  acid (KYNA),  is  classically  known  to  be  an antagonist  of ionotropic glutamate receptors. Within the last decade several reports have been published suggesting that KYNA also blocks nicotinic acetylcholine receptors (nAChRs) containing the α7 subunit (α7*). Most of these reports involve either indirect measurements of KYNA effects on α7 nAChR function, or are reports of KYNA effects in complicated in vivo systems.  However, a recent report investigating KYNA interactions with α7 nAChRs failed to detect an interaction using direct measurements of α7 nAChRs function.  Further, it showed that a KYNA blockade of α7 nAChR stimulated GABA release (an indirect measure of α7 nAChR function) was not due to KYNA blockade of the α7 nAChRs. The current study measured the direct effects of KYNA on α7-containing nAChRs expressed on interneurons in the hilar and CA1 stratum radiatum regions of the mouse hippocampus and on interneurons in the CA1 region of the rat hippocampus.  Here we show that KYNA does not block α7* nACHRs using direct patch--clamp recording of α7 currents in adult brain slices.

The association between ambulance hospital turnaround times and patient acuity, destination hospital, and time of day

INTRODUCTION

The availability of ambulances to respond to emergency calls is related to their ability to return to service from the hospital. Extended hospital turnaround times decrease the number of available unit hours ambulances are deployed, which in turn can increase coverage costs or sacrifice coverage.

OBJECTIVE

To determine whether ambulance turnaround times were associated with patient acuity, destination hospital, and time of day.

METHODS

This retrospective analysis of ambulance hospital turnaround times utilized 12 months of data from a single, countywide, metropolitan emergency medical services (EMS) service. Turnaround time was defined as the interval between the time of ambulance arrival at the hospital and the time the ambulance became available to respond to another call. Independent variables included patient acuity (low [BLS nonemergency transport], medium [ALS care and nonemergency transport], and high [ALS care and emergency transport]), destination hospital (seven regional hospitals), and time of day (one-hour intervals). Data analysis consisted of descriptive statistics, t-tests, and linear regression.

RESULTS

Of the 61,094 patient transports, the mean turnaround time was 35.6 minutes (standard deviation [SD] = 16.5). Turnaround time was significantly associated with patient acuity (p < 0.001). High-acuity calls had a mean turnaround time of 52.5 minutes (SD = 21.5), whereas moderate-acuity and low-acuity calls had mean turnaround times of 42.0 minutes (SD = 16.4) and 32.5 minutes (SD = 14.4), respectively. A statistically significant relationship between destination hospital and turnaround time was found, with the differences in means ranging from 30 seconds to 8 minutes. Similarly, time of day was associated with turnaround time, with the longest turnaround times occurring between 0600 and 1500 hours.

CONCLUSION

This study demonstrated that patient acuity, destination hospital, and time of day were associated with variation in ambulance turnaround times. Research describing other system characteristics such as current emergency department census and patient handoff procedures may further demonstrate areas for improvement in HTAT. Results from this analysis may be used to inspire EMS administrators and EMS medical directors to start tracking these times to create a predictive model of EMS staffing needs.

Network mechanisms for fast ripple activity in epileptic tissue

Fast ripples are high-frequency, 250-600Hz field potential oscillations which can be recorded from hippocampal or neocortical structures. In the neocortex, fast ripples occur during both sensory information processing and under pathological, epileptic conditions. In the hippocampus and entorhinal cortex, fast ripples are exclusively associated with epilepsy and perhaps even mark the epileptogenic focus. In contrast to ripples, which regularly also occur in normal tissue and which are thought to reflect population spike bursts at 100-200Hz paced and synchronised by recurrent inhibition, the fast ripple frequency range exceeds the maximal firing frequency of most neurones. Hence, particularly in the hippocampus, fast ripples must emerge as a network phenomenon and cannot reflect the activity of single spiking neurones. In this review, current views on the mechanisms and processes underlying fast ripples are discussed.

The association between prehospital endotracheal intubation attempts and survival to hospital discharge among out-of-hospital cardiac arrest patients

OBJECTIVES

The benefit of prehospital endotracheal intubation (ETI) among individuals experiencing out-of-hospital cardiac arrest (OOHCA) has not been fully examined. The objective of this study was to determine if prehospital ETI attempts were associated with return of spontaneous circulation (ROSC) and survival to discharge among individuals experiencing OOHCA.

METHODS

This retrospective study included individuals who experienced a medical cardiac arrest between July 2006 and December 2008 and had resuscitation efforts initiated by paramedics from Mecklenburg County, North Carolina. Outcome variables were prehospital ROSC and survival to hospital discharge, while the primary independent variable was the number of prehospital ETI attempts.

RESULTS

There were 1,142 cardiac arrests included in the analytic data set. Prehospital ROSC occurred in 299 individuals (26.2%). When controlling for initial arrest rhythm and other confounding variables, individuals with no ETI attempted were 2.33 (95% confidence interval [CI] = 1.63 to 3.33) times more likely to have ROSC compared to those with one successful ETI attempt. Of the 299 individuals with prehospital ROSC, 118 (39.5%) were subsequently discharged alive from the hospital. Individuals having no ETI were 5.46 (95% CI = 3.36 to 8.90) times more likely to be discharged from the hospital alive compared to individuals with one successful ETI attempt.

CONCLUSIONS

Results from these analyses suggest a negative association between prehospital ETI attempts and survival from OOHCA. In this study, the individuals most likely to have prehospital ROSC and survival to hospital discharge were those who did not have a reported ETI attempt. Further comparative research should assess the potential causes of the demonstrated associations.

Altered neuronal chloride homeostasis and excitatory GABAergic signaling in human temporal lobe epilepsy

Cation-Chloride Cotransporters and GABAergic Innervation in the Human Epileptic Hippocampus. Munoz A, Mendez P, DeFelipe J, Alvarez-Leefmans FJ. Epilepsia 2007;48(4):663–673. Intracellular chloride concentration, [Cl]i, determines the polarity of GABAA-induced neuronal Cl currents. In neurons, [Cl]i is set by the activity of Na+, K+, 2Cl cotransporters (NKCC) such as NKCC1, which physiologically accumulate Cl in the cell, and Cl extruding K+, Cl cotransporters like KCC2. Alterations in the balance of NKCC1 and KCC2 activity may determine the switch from hyperpolarizing to depolarizing effects of GABA, reported in the subiculum of epileptic patients with hippocampal sclerosis. We studied the expression of NKCC (putative NKCC1) and KCC2 in human normal temporal neocortex by Western blot analysis and in normal and epileptic regions of the subiculum and the hippocampus proper using immunocytochemistry. Western blot analysis revealed NKCC and KCC2 proteins in adult human neocortical membranes similar to those in rat neocortex. NKCC and KCC2 immunolabeling of pyramidal and nonpyramidal cells was found in normal and epileptic hippocampal formation. In the transition between the subiculum with sclerotic regions of CA1, known to exhibit epileptogenic activity, double immunolabeling of NKCC and KCC2 revealed that approximately 20% of the NKCC-immunoreactive neurons do not express KCC2. In these same areas, some neurons were distinctly hyperinnervated by parvalbumin (PV) positive hypertrophic basket formations that innervated mostly neurons expressing NKCC (74%) and to a lesser extent NKCC-immunonegative neurons (26%). Hypertrophic basket formations also innervated KCC2-positive (76%) and -negative (24%) neurons. The data suggest that changes in the relative expression of NKCC1 and KCC2 in neurons having aberrant GABAergic hyperinnervation may contribute to epileptiform activity in the subicular regions adjacent to sclerotic areas of the hippocampus.

Perturbed Chloride Homeostasis and GABAergic Signaling in Human Temporal Lobe Epilepsy. Huberfeld G, Wittner L, Clemenceau S, Baulac M, Kaila K, Miles R, Rivera C. J Neurosci 2007;27(37):9866–9873. Changes in chloride (Cl-) homeostasis may be involved in the generation of some epileptic activities. In this study, we asked whether Cl- homeostasis, and thus GABAergic signaling, is altered in tissue from patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis. Slices prepared from this human tissue generated a spontaneous interictal-like activity that was initiated in the subiculum. Records from a minority of subicular pyramidal cells revealed depolarizing GABAA receptor-mediated postsynaptic events, indicating a perturbed Cl-homeostasis. We assessed possible contributions of changes in expression of the potassium–chloride cotransporter KCC2. Double in situ hybridization showed that mRNA for KCC2 was absent from 30% of CaMKII (calcium/calmodulin-dependent protein kinase II)-positive subicular pyramidal cells. Combining intracellular recordings with biocytin-filled electrodes and KCC2 immunochemistry, we observed that all cells that were hyperpolarized during interictal events were immunopositive for KCC2, whereas the majority of depolarized cells were immunonegative. Bumetanide, at doses that selectively block the chloride-importing potassium–sodium–chloride cotransporter NKCC1, produced a hyperpolarizing shift in GABAA reversal potentials and suppressed interictal activity. Changes in Cl- transporter expression thus contribute to human epileptiform activity, and molecules acting on these transporters may be useful antiepileptic drugs.

Effects of synaptic depression and recovery on synchronous network activity

SUMMARY

The output of an artificial neural network of spiking neurons linked by glutamatergic synapses subject to use-dependent depression was compared with physiologic data obtained from rat hippocampal area CA3 in vitro. The authors evaluated how network burst initiation and termination was affected by activity-dependent depression and recovery under a variety of experimental conditions including neuronal membrane depolarization, altered glutamate release probability, the strength of synaptic inhibition, and long-term potentiation and long-term depression of recurrent glutamatergic synapses. The results of computational experiments agreed with the in vitro data and support the idea that synaptic properties, including activity-dependent depression and recovery, play important roles in the timing and duration of spontaneous bursts of network activity. This validated network model is useful for experiments that are not feasible in vitro, and makes possible the investigation of two-dimensional aspects of burst propagation and termination.

High times for memory: cannabis disrupts temporal coordination among hippocampal neurons

Exogenous cannabinoid receptor agonists impair hippocampus-dependent learning and decrease the power of hippocampal electroencephalographic activity. A new paper shows that cannabinoids desynchronize neuronal assemblies without affecting average firing rates, and that this effect correlates with memory deficits in individuals.

A new synaptic plasticity rule for networks of spiking neurons

In this paper, we describe a new Synaptic Plasticity Activity Rule (SAPR) developed for use in networks of spiking neurons. Such networks can be used for simulations of physiological experiments as well as for other computations like image analysis. Most synaptic plasticity rules use artificially defined functions to modify synaptic connection strengths. In contrast, our rule makes use of the existing postsynaptic potential values to compute the value of adjustment. The network of spiking neurons we consider consists of excitatory and inhibitory neurons. Each neuron is implemented as an integrate-and-fire model that accurately mimics the behavior of biological neurons. To test performance of our new plasticity rule we designed a model of a biologically-inspired signal processing system, and used it for object detection in eye images of diabetic retinopathy patients, and lung images of cystic fibrosis patients. The results show that the network detects the edges of objects within an image, essentially segmenting it. Our ultimate goal, however, is not the development of an image segmentation tool that would be more efficient than nonbiological algorithms, but developing a physiologically correct neural network model that could be applied to a wide range of neurological experiments. We decided to validate the SAPR by using it in a network of spiking neurons for image segmentation because it is easy to visually assess the results. An important thing is that image segmentation is done in an entirely unsupervised way.

The use of radiotelemetry to evaluate electrographic seizures in rats with kainate-induced epilepsy

Temporal lobe epilepsy in humans is a chronic condition with a highly variable temporal evolution. Animal models of this disorder have been developed to recapitulate many of the characteristics seen in humans with temporal lobe epilepsy. These animal models generate chronic spontaneous electrographic and motor seizures with a progressive increase in frequency over many months. In order to understand the underlying cellular and molecular mechanisms driving epileptogenesis, a practical means for accurately assessing seizure progression over this extended time period must be devised. In this report, we describe the use of a three-channel radiotelemetry system to record spontaneous electrographic interictal "spikes" and seizure activity from the cortical surface and the two hippocampi. This approach has allowed continuous recording before, during, and several months after kainate-induced status epilepticus. The important advantages of this approach are the potential for long-term continuous electrographic recording with comparatively unrestricted behavior; the disadvantages include increased cost, surgical difficulty and lower frequency-response in the recordings.

Apoptotic DNA fragmentation is detected by a semi-quantitative ligation-mediated PCR of blunt DNA ends

Apoptosis is a form of programmed cell death (PCD) characterized by morphological changes and stereotypical DNA degradation described as a nucleosomal ;ladder'. However, nucleosomal ladders have only been clearly demonstrated in vertebrate tissues when large numbers of cells die in synchrony. Their absence may be explained by asynchronous death under physiological conditions, or by distinct molecular mechanisms. In this study, nucleosomal ladders were revealed by a ligation-mediated polymerase chain reaction (LMPCR), that amplifies DNA fragments with blunt, 5' phosphorylated ends. Numerous tissues from different organisms were examined which demonstrated that nucleosomal ladders (a) accompany physiological cell death in mammalian tissues where previously DNA fragmentation has not been detected; (b) are produced during invertebrate cell death; (c) are invariably generated via the production of blunt, 5' phosphorylated double strand breaks. These results suggest that PCD in multicellular organisms consistently involves apoptotic mechanisms and that the endonuclease activity is evolutionarily conserved.

Do interictal spikes drive epileptogenesis?

Interictal spikes are periodic, very brief bursts of neuronal activity that are observed in the electroencephalogram of patients with chronic epilepsy. These spikes are useful diagnostically, but we do not know why they are so strongly associated with the spontaneous seizures that characterize chronic epilepsy. Interictal spikes appear before the first spontaneous seizures in animal models of acquired epilepsy, and spikes are sufficient to induce long-term changes in synaptic connections between neurons. Thus, spikes may guide the development of the neuronal circuits that initiate spontaneous seizures. If so, then attempts to prevent or cure epilepsy may best be directed at spikes rather than seizures.

Pediatric injuries resulting from use of all-terrain vehicles

Annually, 20,000 children are injured while operating all-terrain vehicles (ATVs). The purpose of this paper was to review child-ATV injuries in Arkansas and identify any areas in need of further investigation. An analysis of emergency-medical-service transports was done for children 0-19 years who had ATV-related injuries in Arkansas from 1998 to 1999. Prehospital-reported child-ATV emergencies were identified, separated by county, and emergency encounter rates were calculated. Our results indicate that emergency medical services (EMS) transported 319 children in Arkansas from 1998 to 1999. ATV injury information is limited in Arkansas, but available data indicate high injury rates existed for many rural counties.

Expression of LIM protein genes Lmo1, Lmo2, and Lmo3 in adult mouse hippocampus and other forebrain regions: differential regulation by seizure activity

The LIM domain is a zinc-binding amino acid motif that characterizes various proteins which function in protein-protein interactions and transcriptional regulation. Expression patterns of several LIM protein genes are compatible with roles in vertebrate CNS development, but little is known about the expression, regulation, or function of LIM proteins in the mature CNS. Lmo1, Lmo2, and Lmo3 are LIM-only genes originally identified as putative oncogenes that have been implicated in the control of cell differentiation and are active during CNS development. Using in situ hybridization for mRNA and immunohistochemical detection of reporter protein expression in transgenic mice, we found that Lmo1, Lmo2, and Lmo3 show individually unique but partially overlapping patterns of expression in several regions of the adult mouse forebrain, including hippocampus, caudate putamen, medial habenula, thalamus, amygdala, olfactory bulb, hypothalamus, and cerebral cortex. In the hippocampal formation, Lmo1, Lmo2, and Lmo3 show different combinatorial patterns of expression levels in CA pyramidal and dentate granule neurons, and Lmo1 is present in topographically restricted subpopulations of astrocytes. Kainic acid-induced limbic seizures differentially regulated Lmo1, Lmo2, and Lmo3 mRNA levels in hippocampal pyramidal and granule neurons, such that Lmo1 mRNA increased, whereas Lmo2 and Lmo3 mRNAs decreased significantly, with maximal changes at 6 hr after seizure onset and return to baseline by 24 hr. These findings show that Lmo1, Lmo2, and Lmo3 continue to be expressed in the adult mammalian CNS in a cell type-specific manner, are differentially regulated by neuronal activity, and may thus be involved in cell phenotype-specific regulatory functions.

Alteration of GABAA receptor function following gene transfer of the CLC-2 chloride channel

The effect of GABAA receptor activation varies from inhibition to excitation depending on the state of the transmembrane anionic concentration gradient (delta anion). delta anion was genetically altered in cultured dorsal root ganglion neurons via adenoviral vector-mediated expression of ClC-2, a Cl- channel postulated to regulate the Cl- concentration in neurons in which GABAA receptor activation is predominantly inhibitory. ClC-2 expression was verified by the presence of the appropriate mRNA, protein, and membrane conductance. CIC-2 expression resulted in a large negative shift in the Cl- equilibrium potential (ECl) that attenuated the GABA-mediated membrane depolarization and prevented GABAA receptor-mediated action potentials. These results establish that gene transfer of transmembrane ion channels to neurons can be used to demonstrate their physiological function, and that delta anion can be genetically manipulated to alter the function of neuronal GABAA receptors in situ.

Widespread programmed cell death in proliferative and postmitotic regions of the fetal cerebral cortex

A key event in the development of the mammalian cerebral cortex is the generation of neuronal populations during embryonic life. Previous studies have revealed many details of cortical neuron development including cell birthdates, migration patterns and lineage relationships. Programmed cell death is a potentially important mechanism that could alter the numbers and types of developing cortical cells during these early embryonic phases. While programmed cell death has been documented in other parts of the embryonic central nervous system, its operation has not been previously reported in the embryonic cortex because of the lack of cell death markers and the difficulty in following the entire population of cortical cells. Here, we have investigated the spatial and temporal distribution of dying cells in the embryonic cortex using an in situ endlabelling technique called ‘ISEL+’ that identifies fragmented nuclear DNA in dying cells with increased sensitivity. The period encompassing murine cerebral cortical neurogenesis was examined, from embryonic days 10 through 18. Dying cells were rare at embryonic day 10, but by embryonic day 14, 70% of cortical cells were found to be dying. This number declined to 50% by embryonic day 18, and few dying cells were observed in the adult cerebral cortex. Surprisingly, while dying cells were observed throughout the cerebral cortical wall, the majority were found within zones of cell proliferation rather than in regions of postmitotic neurons. These observations suggest that multiple mechanisms may regulate programmed cell death in the developing cortex. Moreover, embryonic cell death could be an important factor enabling the selection of appropriate cortical cells before they complete their differentiation in postnatal life.

The role of an inwardly rectifying chloride conductance in postsynaptic inhibition

1. The relationship of the activation of a voltage-sensitive chloride conductance [GCl(V)] to the chloride transmembrane equilibrium potential (ECl) and the consequent role of this conductance in determining the effect of the gamma-aminobutyric acid-A (GABAA) receptor-mediated transmembrane chloride (Cl-) flux were investigated with the use of whole-cell recordings in the CA1 and dentate gyrus regions of adult rat hippocampal slice preparations. 2. GCl(V) was inwardly rectifying, with significant conductance only at membrane potentials more negative than ECl. For all tested neuronal Cl- concentrations, the activation of GCl(V) could be described by a Boltzman equation with an average half-activation voltage 15 mV negative to ECl, a slope factor of 14 mV, and a maximum conductance of 5 microS. There was no time-dependent inactivation of GCl(V). 3. GCl(V) was modulated by intracellular divalent cations. When magnesium was omitted from the electrode solution, the inward rectification of GCl(V) was unchanged, but the maximum amplitude of GCl(V) increased by a factor of 1.7. GCl(V) was blocked by bath application of 100 microM zinc (Zn2+), but not when 1-6 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) were present in the electrode solution. 4. GCl(V) was increased by 10 microM norepinephrine, and by activation of protein kinase A (PKA) with 1 mM 8-bromoadenosine cyclic monophosphate (8-Br cAMP). GCl(V) was blocked by activation of protein kinase C (PKC) with 10 microM phorbol 12,13-dibutyrate (PdBu) or 1-oleoyl-2-acetyl-sn-glycerol (OAG). 5. GCl(V) was present in all tested CA1 pyramidal neurons but no dentate gyrus neurons. In standard extracellular solution, the amplitude of GCl(V) was initially negligible but increased with recording time, suggesting that under normal conditions GCl(V) is blocked by an endogenous divalent cation or downregulated by PKC. 6. In current-clamp recordings, the steady-state resting membrane potential (RMP) diminished with Cl- loading, from -73 mV (4 mM electrode Cl-) to -27 mV (131 mM electrode Cl-). When GCl(V) was blocked with PdBu, there was no change in the RMP with Cl- loading. When electroneutral Cl- transport was blocked, voltage-clamp experiments using electrode Cl- concentrations of 4-131 mM demonstrated that ECl changed in parallel with the holding potential, but not when GCl(V) was blocked by PdBu.(ABSTRACT TRUNCATED AT 400 WORDS)

Death of developing septal cholinergic neurons following NGF withdrawal in vitro: protection by protein synthesis inhibition

Fetal septal neurons were grown in vitro under glass coverslips. This sandwich culture method significantly increased general neuronal survival, reduced glial proliferation, and permitted the removal of serum from the growth medium after 5 d in vitro. Thereafter, a simple, and completely defined, medium was used, and the effects of NGF, NGF withdrawal, and protein synthesis inhibition were examined on septal cholinergic neurons. NGF added to septal cultures at the time of plating resulted in a threefold increase in the number of cholinergic neurons seen at 14 d in vitro but had no effect on the survival of non-cholinergic cells. Cholinergic neurons identified by staining for AChE, ChAT, and p75NGFR could be maintained in serum-free, NGF-supplemented medium for over 40 d. When NGF was removed and NGF antibodies added to 14-d-old cultures, less than 30% of cholinergic neurons survived a further 4 d, but when NGF was similarly withdrawn from 35-d-old cultures, over 75% of cholinergic neurons survived. Reapplication of NGF after 3 but not after 12 or more hours of NGF withdrawal from 14-d-old cultures prevented the death of most cholinergic neurons. When NGF was withdrawn from 14-d-old cultures in the presence of the protein synthesis inhibitor cycloheximide, over 75% of the cholinergic neurons survived. These findings suggest that septal cholinergic neurons are dependent on NGF for survival only during a critical period of development and that growth factor-regulated developmental cell death may occur in CNS neurons by activation of programmed cell death requiring protein synthesis.

Transfection-mediated expression of human Hsp70i protects rat dorsal root ganglian neurones and glia from severe heat stress

Considerable evidence suggests that the expression of heat shock proteins prior to a toxic insult (e.g. ischaemia, excitoxins, heat) can confer protection to neurones and glia. It is not certain which hsp(s) are involved in conveying these neuroprotective effects. Here we show that calcium phosphate-mediated transfection of dorsal root ganglia with an EF-1 alpha promoter-hsp70i expression vector significantly increased the survival of neurones and glia exposed to a severe heat stress. These data suggest that overexpression of hsp70i plays an important role in protecting neurones and glia from the denaturing effects of severe thermal stress. Inducing the expression of specific hsps may lead to the development of novel treatment strategies for CNS diseases.

Enhancement of the excitatory actions of GABA by barbiturates and benzodiazepines

Whole cell recordings from hippocampal CA1 pyramidal neurons using electrode chloride concentrations of 12-80 mM demonstrated that the effect of synaptic activation of GABAA receptors was dependent on the transmembrane chloride gradient. When the chloride reversal potential was positive to action potential threshold, GABAA receptor activation was excitatory, and anticonvulsant barbiturates and benzodiazepines enhanced this excitation. Enhancement of GABAergic excitation of interneurons may contribute to the efficacy of these drugs, while enhancement of GABAergic excitation of principal neurons may be an important mechanism of failure, such as occurs in the treatment of neonatal seizures.

The role of N-methyl-d-aspartate-type glutamatergic neurotransmission in the photic induction of immediate-early gene expression in the suprachiasmatic nuclei of the Syrian hamster

Abstract This study investigated the role of N-methyl-D-aspartate (NMDA)-type glutamatergic neurotransmission in mediating the photic induction of immediate-early gene expression in the Suprachiasmatic nucleus (SCN) of the Syrian hamster. Activation of c-fos, c-jun and egr-1 was assessed by immunocytochemical detection of their protein products. To characterize the circadian basis to the inductive effects of light, hamsters were allowed to free-run in constant dim red light and received a 1 h light pulse at different circadian phases relative to activity onset (defined as CT 12). In control animals which did not receive light pulses, c-fos and egr-1 expression was absent or restricted to a small area of the dorsolateral region of the SCN, and expression of c-jun could not be detected in the SCN. In hamsters killed after presentation of a light pulse at either CT 14 or CT 20, there was a marked increase in c-fos and egr-1 immunoreactivities throughout the ventrolateral division of the SCN. In contrast, light pulses given at CT4 or CT 8 failed to activate immediate-early gene expression. Light pulses did not induce c-jun immunoreactivity at any circadian phase tested. Staining for c-fos was maximal 1 h after the start of the light pulse and had started to decline by 2 h. At this later time, c-jun expression was still undetectable. To compare the distribution of retinal afferents with that of c-fos induction, hamsters held on a light schedule of 16 h light: 8 h dark received an intraocular injection of cholera toxin-horseradish peroxidase conjugate 3 days before exposure to a 1 h light pulse given 2 h after lights off. Comparison of adjacent sections processed for c-fos immunoreactivity or for cholera toxin-horseradish peroxidase revealed that light-induced c-fos expression was precisely restricted to retinal terminal fields in the SCN. Light pulses also induced c-fos expression in the retinoreceptive ventral lateral geniculate nucleus and intergeniculate leaflet but not in the retinal fields of the dorsal lateral geniculate nucleus, indicating that the expression of cfos in response to light is spatially specific. The aim of the subsequent experiments was to investigate the role of NMDA-type glutamatergic neurotransmission in mediating the effects of light on c-fos expression in the SCN. To determine whether NMDA had the potential to activate c-fos expression in the SCN, hamsters were infused with 2.5 nmol NMDA or vehicle via an intracerebroventricular (icv) cannula positioned adjacent to the nuclei. In contrast to the effects of light, icv NMDA activated c-fos expression at both CT8 and CT 14. The distribution of immunoreactivity was more widespread than that observed after light, extending throughout the SCN and adjacent hypothalamus. To test whether NMDA receptors had a physiological role in the photic response, hamsters were treated systemically with the non-competitive NMDA antagonist MK801 (dose range 0.6 to 6.0 mg/kg body wt, ip) or vehicle prior to exposure to a 1 h light pulse given at CT 14 or CT 20. Expression of c-fos was still detectable in the dorsolateral SCN but MK801 blocked expression in the ventral portion of the retinoreceptive zone of the SCN. MK801 (10 or 100 nmol) delivered centrally (icv) also prevented light-induced c-fos expression in the ventral region of the SCN bordering the optic chiasm, though staining again persisted in the dorsolateral region. The induction of c-fos by icv NMDA, and the partial blockade of light-induced c-fos expression by the antagonist MK801, are consistent with the hypothesis that glutamate mediates the effects of light on SCN activity. However, the persistent photic induction of c-fos expression in a subfield of retinal afferents following treatment with MK801 suggests that other, non-NMDA-type mechanisms may contribute to photic entrainment.

Somatosensory dysfunction in cystic fibrosis

Posterior tibial somatosensory evoked potentials were obtained in a group of cystic fibrosis patients and age-matched controls. A small but significant delay of the lumbar potential and larger delays of the early scalp potentials were observed. These findings are consistent with earlier pathological studies demonstrating involvement of the somatosensory system in cystic fibrosis.

The human fetal auditory evoked potential

The brain-stem auditory evoked potential (BAEP), a sensitive test of the functional status of the neonatal brain, has not been studied in utero since no practical technique for human fetal recording is available. We have developed a simple recording technique which allows continuous monitoring of the fetal AEP during labor. Waves I, III and V of the fetal brain-stem AEP have been consistently identified. Wave form morphology, interpeak latencies, and latency-intensity relations are similar to postnatal recordings. Middle latency potentials have also been recorded, with wave forms that correspond to the neonatal middle latency AEP.

Development of separation fluoroimmunoassays for bendazac and 5-hydroxy bendazac

Two distinct separation fluoroimmunoassays were developed to determine serum levels of bendazac and its main metabolite 5-hydroxy bendazac for use in early pharmacokinetic studies and for long-term therapeutic drug monitoring should this prove necessary. In both assays fluorescein-labeled analyte was used as tracer and the antibodies were coupled to magnetizable particles. The use of a magnetizable solid phase enabled a simple and rapid separation step and thus a high sample throughput. There was no crossreactivity between the drug and its metabolite in either assay, indicating that highly specific antibodies had been produced. The results from both assays correlated well with serum levels determined by a high performance liquid chromatography method.