Dynamic interneuron-principal cell interplay leads to a specific pattern of in vitro ictogenesis.

Ictal discharges induced by 4-aminopyridine in the in vitro rodent entorhinal cortex present with either low-voltage fast or sudden onset patterns. The role of interneurons in initiating low-voltage fast onset ictal discharges is well established but the processes leading to sudden onset ictal discharges remain unclear. We analysed here the participation of interneurons (n = 75) and principal cells (n = 13) in the sudden onset pattern by employing in vitro tetrode wire recordings in the entorhinal cortex of brain slices from Sprague-Dawley rats. Ictal discharges emerged from a background of frequently occurring interictal spikes that were associated to a specific interneuron/principal cell interplay. High rates of interneuron firing occurred 12 ms before interictal spike onset while principal cells fired later during low interneuron firing. In contrast, the onset of sudden ictal discharges was characterized by increased firing from principal cells 627 ms before ictal onset whereas interneurons increased their firing rates 161 ms before ictal onset. Our data show that sudden onset ictogenesis is associated with frequently occurring interictal spikes resting on the interplay between interneurons and principal cells while ictal discharges stem from enhanced principal cell firing leading to increased interneuron activity. These findings indicate that specific patterns of interactions between interneurons and principal cells shape interictal and ictal discharges with sudden onset in the rodent entorhinal cortex. We propose that specific neuronal interactions lead to the generation of distinct onset patterns in focal epileptic disorders.

Interneurons spark seizure-like activity in the entorhinal cortex.

Excessive neuronal synchronization is presumably involved in epileptiform synchronization. However, the respective roles played by interneurons (GABAergic) and principal (glutamatergic) cells during interictal and ictal discharges remain unclear. Here, we employed tetrode wire recordings to establish the involvement of these two cell types in 4-aminopyridine-induced interictal- and low-voltage fast (LVF) onset ictal-like discharges in the rat entorhinal cortex in an in vitro slice preparation. We recorded a total of 90 single units (69 putative interneurons, 17 putative principal and 4 unclassified cells) from 36 slices, and found that: (i) interneurons (66.7%) were more likely to fire during interictal discharges than principal cells (35.3%); (ii) interneuron activity increased shortly before LVF ictal onset, whereas principal cell activity did not change; (iii) interneurons and principal cells fired at high rates throughout the tonic phase of the ictal discharge; however, (iv) only interneurons showed phase-locked relationship with LVF activity at 5-15Hz during the tonic phase. Finally, the association of interneuron firing with interictal discharges was maintained during blockade of ionotropic glutamatergic transmission. Our findings demonstrate the prominent involvement of interneurons in interictal discharge generation and in the transition to LVF ictal activity in this in vitro model of epileptiform synchronization.

On the contribution of KCC2 and carbonic anhydrase to two types of in vitro interictal discharge.

GABAA receptor-mediated inhibition--which is due to Cl(-) and HCO3 (-) currents controlled by KCC2 and carbonic anhydrase activity, respectively--contributes to short- and long-lasting interictal events recorded from the CA3 region of hippocampus during application of 4-aminopyridine (4AP, 50 µM). Here, we employed field potential recordings in an in vitro brain slice preparation to establish the effects induced by the KCC2 blockers VU0240551 (10 µM) or bumetanide (50 µM) and by the carbonic anhydrase inhibitor acetazolamide (10 µM) on the two types of interictal events. We found that blocking KCC2 activity decreased the amplitude of the short-lasting events. In addition, this pharmacological procedure increased the interval of occurrence of the long-lasting events and reduced their amplitude. Blocking carbonic anhydrase activity with acetazolamide reduced the interval of occurrence and the duration of the short-lasting events while increasing their amplitude; acetazolamide also reduced the duration and amplitude of the long-lasting events. Finally, blocking either KCC2 or carbonic anhydrase activity increased the interval of occurrence of pharmacologically isolated synchronous GABAergic events and decreased their duration and amplitude. These data substantiate further the role of GABAA receptor-mediated signaling in driving neuronal populations toward hypersynchronous states presumably by increasing extracellular [K(+)].

KCC2 function modulates in vitro ictogenesis.

GABAA receptor-mediated inhibition is active and may contribute to epileptiform synchronization. The efficacy of inhibition relies on low levels of intracellular Cl(-), which are controlled by KCC2 activity. This evidence has led us to analyze with field potential recordings the effects induced by the KCC2 blockers VU0240551 (10 µM) or bumetanide (50 µM) and by the KCC2 enhancer CLP257 (100 µM) on the epileptiform discharges generated by piriform and entorhinal cortices (PC and EC, respectively) in an in vitro brain slice preparation. Ictal- and interictal-like discharges along with high-frequency oscillations (HFOs, ripples: 80-200 Hz, fast ripples: 250-500 Hz) were recorded from these two regions during application of 4-aminopyridine (4AP, 50 µM). Blocking KCC2 activity with either VU024055 or high doses of bumetanide abolished ictal discharge in both PC and EC; in addition, these experimental procedures decreased the interval of occurrence and duration of interictal discharges. In contrast, enhancing KCC2 activity with CLP257 increased ictal discharge duration in both regions. Finally, blocking KCC2 activity decreased the duration and amplitude of pharmacologically isolated synchronous GABAergic events whereas enhancing KCC2 activity led to an increase in their duration. Our data demonstrate that in vitro ictogenesis is abolished or facilitated by inhibiting or enhancing KCC2 activity, respectively. We propose that these effects may result from the reduction of GABAA receptor-dependent increases in extracellular K(+) that are known to rest on KCC2 function.

Continuous quality improvement in peritoneal dialysis: Your questions answered.

Peritoneal dialysis (PD) uptake around the globe has steadily increased over the last several decades as a viable alternative to haemodialysis. Continued success of this technique for patients is contingent on the application of continuous quality improvement (CQI) principles in PD practice which can improve patient outcomes and in turn lead to more successful PD programmes worldwide. In this installation of 'Your Questions Answered', we will outline an approach to quality improvement initiatives and examine the importance of CQI principles in PD practice. We will also highlight common pitfalls and provide strategies to identify potential targets for improvement within your PD programme.

The Feasibility of a Transitional Care Unit for Patients Newly Started on In-Center Hemodialysis: A Research Letter.

Background: Patients with end-stage kidney disease face high mortality and morbidity after dialysis initiation. Transitional care units (TCUs) are typically 4- to 8-week structured multidisciplinary programs targeted toward patients starting hemodialysis during this high-risk time in their care. The goals of such programs are to provide psychosocial support, provide dialysis modality education, and reduce risks of complications. Despite apparent benefits, the TCU model may be challenging to implement, and the effect on patient outcomes is unclear. Objective: To assess a newly created multidisciplinary TCUs' feasibility for patients newly started on hemodialysis. Design: Before-and-after study. Setting: Kingston Health Sciences Centre hemodialysis unit in Ontario, Canada. Patients: We considered all adult patients (age 18+) who initiated in-center maintenance hemodialysis eligible for the TCU program, although patients on infection control precautions and evening shifts were not able to receive TCU care due to staffing limitations. Measurements: We defined feasibility as eligible patients completing the TCU program in a timely fashion without additional need for space, no signal of harm, and without explicit concerns from TCU staff or patients at weekly meetings. Key outcomes at 6 months included mortality, proportion hospitalized, dialysis modality, vascular access, initiation of transplant workup, and code status. Methods: The TCU care consisted of 1:1 nursing and education until predefined clinical stability and dialysis decisions were satisfied. We compared outcomes among the pre-TCU cohort who initiated hemodialysis between June 2017 and May 2018, and TCU patients who initiated dialysis between June 2018 and March 2019. We summarized outcomes descriptively, along with unadjusted odds ratios (ORs) and 95% confidence intervals (CIs). Results: We included 115 pre-TCU patients and 109 post-TCU patients, of whom 49/109 (45%) entered and completed the TCU. The most common reasons for not participating in the TCU included evening hemodialysis shifts (18/60, 30%) or contact precautions (18/60, 30%). The TCU patients completed the program in a median of 35 (25-47) days. We observed no differences in mortality (9% vs 8%; OR = 0.93, 95% CI = 0.28-3.13) or proportion hospitalized (38% vs 39%; OR = 1.02, 95% CI = 0.51-2.03) between the pre-TCU cohort and TCU patients. There was also no difference in use of home dialysis (16% vs 10%; OR = 1.67, 95% CI = 0.64-4.39), non-catheter access (32% vs 25%; OR = 1.44, 95% CI = 0.69-2.98), initiation of transplant workup (14% vs 12%; OR 1.67; 95% CI = 0.64-4.39), and choosing "do not resuscitate" (DNR) orders (22% vs 19%; OR = 1.22, 95% CI = 0.54-2.77). There was no negative patient or staff feedback on the program. Limitations: Small sample size and potential for selection bias given inability to provide TCU care for patients on infection control precautions or evening shifts. Conclusions: The TCU accommodated a large number of patients, who completed the program in a timely fashion. The TCU model was determined to be feasible at our center. There was no difference in outcomes due to the small sample size. Future work at our center is required to expand the number of TCU dialysis chairs to evening shifts and evaluate the TCU model in prospective, controlled studies.

Contexte: Les patients atteints d'insuffisance rénale terminale (IRT) sont confrontés à des taux élevés de mortalité et de morbidité après l'initiation de la dialyse. De façon générale, les unités de soins transitoires (UST) sont des programmes multidisciplinaires structurés d'une durée de quatre à huit semaines pour les patients qui amorcent des traitements d'hémodialyse pendant cette période à haut risque de leur prise en charge. Les objectifs de ces programmes sont d'offrir un soutien psychosocial, de dispenser une formation sur les modalités de dialyse et de réduire les risques de complications. Malgré les avantages apparents, le modèle des UST peut être difficile à mettre en œuvre et son effet sur les résultats des patients n'est pas clair. Objectif: Examiner la faisabilité d'une UST multidisciplinaire nouvellement créée pour les patients qui amorcent des traitements d'hémodialyse. Type d'étude: Étude de type « avant-après ¼. Cadre: L'unité d'hémodialyse du Kingston Health Sciences Centre (KHSC) en Ontario (Canada). Sujets: Nous avons considéré que tous les patients adultes (18 ans et plus) qui avaient commencé des traitements d'hémodialyse d'entretien en centre étaient admissibles au programme d'UST, bien que les patients qui faisaient la dialyse de nuit ou qui faisaient l'objet de mesures de prévention contre les infections n'aient pas pu recevoir de soins d'UST en raison de limitations de personnel. Mesures: Nous avons défini la faisabilité selon que les patients admissibles terminaient le programme d'UST en temps opportun sans besoin supplémentaire d'espace, sans signe de préjudice et sans préoccupations explicites de leur part ou du personnel de l'UST lors des réunions hebdomadaires. Les principaux critères d'évaluation à 6 mois comprenaient la mortalité, la proportion d'hospitalisations, la modalité de dialyse, l'accès vasculaire, le début de l'évaluation à une transplantation et l'état de réanimation cardio-vasculaire. Méthodologie: Les soins d'UST consistaient en des soins infirmiers 1:1 et de l'éducation prodigués jusqu'à ce que la stabilité clinique prédéfinie et les décisions de dialyse soient satisfaites. Nous avons comparé les résultats de la cohorte pré-UST qui avaient commencé l'hémodialyse entre juin 2017 et mai 2018 avec ceux des patients UST qui avaient commencé la dialyse entre juin 2018 et mars 2019. Nous avons résumé les résultats de façon descriptive, accompagnés des rapports de cotes (RC) non corrigés et des intervalles de confiance (IC) à 95 %. Résultats: Nous avons inclus 115 patients pré-UST et 109 patients post-UST, desquels 45 % (49/109) ont complété le programme d'UST. Les raisons les plus couramment invoquées pour ne pas participer au programme d'UST comprenaient l'hémodialyse de nuit (18/60; 30 %) et les mesures de prévention de contact (18/60; 30 %). Les patients UST ont terminé le programme en un temps médian de 35 (25-47) jours. Nous n'avons observé aucune différence entre la cohorte pré-UST et les patients UST en ce qui concerne la mortalité (9 % c. 8 %; RC = 0,93; IC 95 % = 0,28-3,13) ou la proportion d'hospitalisations (38 % c. 39 %; RC = 1,02; IC 95 % = 0,51-2,03). Aucune différence non plus dans l'utilisation de la dialyse à domicile (16 % c. 10 %; RC = 1,67; IC 95 % = 0,64-4,39), l'accès sans cathéter (32 % c. 25 %; RC = 1,44; IC 95 % = 0,69-2,98), le début de l'évaluation à une greffe (14 % c. 12 %; RC = 1,67; IC 95 = 0,64-4,39) et le choix des ordonnances de « ne pas réanimer ¼ (NPR) (22 % c. 19 %; RC = 1,22; IC 95 % = 0,54-2,77). Le programme n'a reçu aucun commentaire négatif, ni des patients, ni du personnel. Limites: L'échantillon était faible et l'étude présente une possibilité de biais de sélection étant donné l'incapacité à fournir des soins d'UST aux patients faisant l'objet de mesures de prévention contre les infections ou qui suivaient leurs traitements de nuit. Conclusion: Le programme d'UST a accueilli un grand nombre de patients, et ceux-ci ont terminé le programme en temps opportun. Le modèle UST a été jugé réalisable à notre centre. Nous n'avons pas observé de différences dans les résultats en raison de la petite taille de l'échantillon. D'autres essais à notre centre sont nécessaires pour étendre les places en dialyse dans l'UST aux quarts de soir et pour évaluer le modèle UST dans des études prospectives et contrôlées.

Five Things to Know About Incremental Peritoneal Dialysis.

Incremental peritoneal dialysis (PD) offers patients newly starting dialysis less than the standard "full dose" of PD, reducing treatment burden and intrusiveness while minimizing symptoms of renal failure. Incremental PD is a cost-effective approach that has been associated with slower rates of decline in residual kidney function. This approach also produces less waste and in turn reduces environmental footprint compared to standard PD prescriptions. It also aligns with the International Society of Peritoneal Dialysis (ISPD) Practice Recommendations for high-quality, goal-oriented therapy. Awareness of incremental PD along with its advantages and limitations provides practitioners with the tools to provide more patient-centered dialysis prescriptions in appropriate populations.

La dialyse péritonéale (DP) incrémentale propose un traitement à une dose moindre que la « dose complète ¼ habituelle aux patients qui amorcent la dialyse; ce qui contribue à réduire le fardeau du traitement et à en limiter le caractère intrusif, tout en minimisant les symptômes de l'insuffisance rénale. La DP incrémentale est une approche qui présente un bon rapport coût/efficacité, en plus d'avoir été associée à un ralentissement du déclin de la fonction rénale résiduelle. Elle produit également moins de déchets que la DP standard, ce qui, par conséquent, réduit l'empreinte environnementale du traitement. Enfin, la DP incrémentale est conforme aux recommandations de pratique de l'International Society of Peritoneal Dialysis (ISPD) pour une thérapie de haute qualité axée sur les objectifs. La sensibilisation à la DP incrémentale, ainsi qu'à ses avantages et à ses limites, fournit aux praticiens les outils nécessaires pour prescrire une modalité de dialyse davantage centrée sur le patient dans les populations appropriées.

Rapid, direct fabrication of antireflection-coated microlens arrays by photoembossing.

Photoembossing is a rapid, low cost process to create surface relief structures in polymer thin films via a reaction/diffusion mechanism. It is demonstrated that this technique can be used to create a microlens array of which the focal length can be easily controlled by tuning the processing parameters. In addition, the technique is shown to be particularly interesting since it does not require any physical contact during the development of the microlens array. Additional coatings (e.g., a solution-processable antireflection coating) can therefore be applied prior to the development of the microlens array when the film is still flat. This stimulates the formation of films with a homogeneous thickness distribution and obviates the use of further postprocessing steps.

KCC2, epileptiform synchronization, and epileptic disorders.

The K+-Cl- co-transporter KCC2 is a neuron-specific, Cl- extruder that uses K+ gradient for maintaining low intracellular [Cl-]. It is indeed well established that sustaining an outwardly-directed electrochemical Cl- gradient across the neuronal membrane is fundamental for a proper function of postsynaptic GABAA receptor signaling. In particular, studies in the last two decades have shown that KCC2 activity is important to maintain a hyperpolarizing GABAergic neurotransmission. Conversely, low KCC2 activity should lead to depolarizing, and under specific conditions, excitatory GABAergic transmission. Not surprisingly given the critical role of KCC2 in regulating the inhibitory drive, alterations in its expression levels and activity are linked with epilepsy. Here, we will first summarize data regarding the role of KCC2 in epileptiform synchronization. Next, we will review evidence indicating that KCC2 expression and function are altered in chronic epileptic disorders, both in the developing and adult brain. We will also go through recent findings regarding the molecular mechanisms underlying the changes in KCC2 activity that occur following seizures. Finally, we will consider the modulation of KCC2 function as a potential, novel therapeutic target for the treatment of epileptic disorders.

Carbachol-induced network oscillations in an in vitro limbic system brain slice.

We employed simultaneous field potential recordings from CA3, subiculum and entorhinal cortex in an in vitro brain slice preparation to understand the involvement of these limbic areas in the generation of the field potential oscillations that are induced by bath application of the muscarinic receptor agonist carbachol. Regularly spaced oscillations that mainly presented at theta frequency range (5-12Hz) occurred synchronously in all three structures in the presence of carbachol. These oscillations, which disappeared when slices were perfused with pirenzepine or with glutamatergic receptor antagonists, were categorized as short (<4s) and long (>4s) with short events oscillating at higher frequencies than long events. Field oscillations were highly synchronized between regions and latency analysis revealed that they often initiated in the entorhinal cortex later than in the other two structures. Blocking GABAA receptors modified the activity patterns of both short and long oscillations and decreased their coherence in the theta frequency range. Finally, blocking KCC2 activity disclosed a pattern of recurrent short oscillations. Our results suggest that in the presence of carbachol both subiculum and CA3 most often drive theta generators in the entorhinal cortex and that these oscillations are influenced but not abolished by altering GABAA receptor signaling.

Carbonic anhydrase inhibition by acetazolamide reduces in vitro epileptiform synchronization.

Depolarizing GABAA receptor-mediated currents are contributed by HCO3(-) efflux, and play a role in initiating ictal-like epileptiform events in several cortical structures supporting the view that GABAA receptor signaling actively participates to epileptiform synchronization. We employed here field potential recordings to analyze the effects of the carbonic anhydrase inhibitor acetazolamide (10 µM) on the epileptiform activity generated in vitro by piriform and entorhinal cortices (PC and EC, respectively) during application of the K(+) channel blocker 4-aminopyridine (4AP, 50 µM). Under these experimental conditions ictal- and interictal-like discharges along with high-frequency oscillations (ripples: 80-200 Hz, fast ripples: 250-500 Hz) occurred in these two regions. In both PC and EC, acetazolamide: (i) reduced the duration and the interval of occurrence of ictal discharges along with the associated ripples and fast ripples; (ii) decreased the interval of occurrence of interictal discharges and the rates of associated fast ripples; and (iii) diminished the duration and amplitude of pharmacologically isolated GABAergic events while increasing their interval of occurrence. Our results indicate that acetazolamide effectively controls 4AP-induced epileptiform synchronization in PC and EC. We propose that this action may rest on decreased GABAA receptor-mediated HCO3(-) efflux leading to diminished depolarization of principal cells and, perhaps, of interneurons.

Limbic networks and epileptiform synchronization: the view from the experimental side.

In this review, we summarize findings obtained in acute and chronic epilepsy models and in particular experiments that have revealed how neuronal networks in the limbic system-which is closely involved in the pathophysiogenesis of mesial temporal lobe epilepsy (MTLE)-produce hypersynchronous discharges. MTLE is often associated with a typical pattern of brain damage known as mesial temporal sclerosis, and it is one of the most refractory forms of partial epilepsy in adults. Specifically, we will address the cellular and pharmacological features of abnormal electrographic events that, as in MTLE patients, can occur in in vivo and in vitro animal models; these include interictal and ictal discharges along with high-frequency oscillations. In addition, we will consider how different limbic structures made hyperexcitable by acute pharmacological manipulations interact during epileptiform discharge generation. We will also review the electrographic characteristics of two types of seizure onsets that are most commonly seen in human and experimental MTLE as well as in in vitro models of epileptiform synchronization. Finally, we will address the role played by neurosteroids in reducing epileptiform synchronization and in modulating epileptogenesis.