Determining how a particular neuron, or population of neurons, encodes information in their spike trains is not a trivial problem, because multiple coding schemes exist and are not necessarily ...mutually exclusive. Coding schemes generally fall into one of two broad categories, which we refer to as rate and temporal coding. In rate coding schemes, information is encoded in the variations of the average firing rate of the spike train. In contrast, in temporal coding schemes, information is encoded in the specific timing of the individual spikes that comprise the train. Here, we describe a method for testing the presence of temporal encoding of information. Suppose that a set of original spike trains is given. First, surrogate spike trains are generated by randomizing each of the original spike trains subject to the following constraints: the local average firing rate is approximately preserved, while the overall average firing rate and the distribution of primary interspike intervals are perfectly preserved. These constraints ensure that any rate coding of information present in the original spike trains is preserved in the members of the surrogate population. The null-hypothesis is rejected when additional information is found to be present in the original spike trains, implying that temporal coding is present. The method is validated using artificial data, and then demonstrated using real neuronal data.
Proliferative vitreoretinopathy (PVR) is a metaplasia in the vitreous of the eye manifested by the transformation of retinal pigment epithelial (RPE) cells and the development of contracting ...epiretinal membranes (ERM), which lead to retinal detachment and vision loss. While TGFβ1 and TNFα have been associated with PVR, here we show that these cytokines act synergistically to induce an aggressive contraction phenotype on adult human (ah)RPE. Connected RPE detach upon contraction and form motile membranes that recruit more cells. TGFβ1 and TNFα (TNT)-induced contracting membranes uniquely express muscle and extracellular rearrangement genes. Whole transcriptome RNA sequencing of patient-dissected PVR membranes showed activation of the p38-MAPK signaling pathway. Inhibition of p38 during TNT treatment blocks ahRPE transformation and membrane contraction. Furthermore, TNT-induced membrane contractility can be reversed by p38 inhibition after induction. Therefore, targeting the p38-MAPK pathway may have therapeutic benefits for patients with PVR even after the onset of contracting ERMs.
For effective treatment, induced pluripotent stem cell (iPSC)‐retinal pigment epithelium (RPE) must recapitulate the physiology of native human RPE cells. A set of physiologically relevant functional ...assays that assess the polarized functional activity and maturation state of the intact RPE monolayer is provided. The study data show that donor‐to‐donor variability exceeds the tissue‐to‐tissue variability for a given donor and provides, for the first time, criteria necessary to identify iPSC‐RPE cells most suitable for clinical application.
Acknowledgements
Induced pluripotent stem cells (iPSCs) can be efficiently differentiated into retinal pigment epithelium (RPE), offering the possibility of autologous cell replacement therapy for retinal degeneration stemming from RPE loss. The generation and maintenance of epithelial apical‐basolateral polarity is fundamental for iPSC‐derived RPE (iPSC‐RPE) to recapitulate native RPE structure and function. Presently, no criteria have been established to determine clonal or donor based heterogeneity in the polarization and maturation state of iPSC‐RPE. We provide an unbiased structural, molecular, and physiological evaluation of 15 iPSC‐RPE that have been derived from distinct tissues from several different donors. We assessed the intact RPE monolayer in terms of an ATP‐dependent signaling pathway that drives critical aspects of RPE function, including calcium and electrophysiological responses, as well as steady‐state fluid transport. These responses have key in vivo counterparts that together help determine the homeostasis of the distal retina. We characterized the donor and clonal variation and found that iPSC‐RPE function was more significantly affected by the genetic differences between different donors than the epigenetic differences associated with different starting tissues. This study provides a reference dataset to authenticate genetically diverse iPSC‐RPE derived for clinical applications.
The retinal pigment epithelium (RPE) is essential for maintaining visual function. RPE derived from human induced pluripotent stem cells (iPSC‐RPE) offer a promising cell‐based transplantation therapy for slowing or rescuing RPE‐induced visual function loss. For effective treatment, iPSC‐RPE must recapitulate the physiology of native human RPE. A set of physiologically relevant functional assays are provided that assess the polarized functional activity and maturation state of the intact RPE monolayer. The present data show that donor‐to‐donor variability exceeds the tissue‐to‐tissue variability for a given donor and provides, for the first time, criteria necessary to identify iPSC‐RPE most suitable for clinical application.
The olivocerebellar system is capable of generating synchronous and rhythmic discharges thought to be involved in the precise timing of movement sequences (Llinás 1991). Implicated in olivocerebellar ...system function is its effects on cerebellar nuclei (CN), which receives input from the inferior olive (IO) and cerebellar cortex and is the proposed locus through which the olivocerebellar system influences motor coordination. IO neurons are electrotonically coupled via gap junctions, which are hypothesized to be the essential neuronal machinery by which rhythmic and synchronous patterns of activity are generated in the olivocerebellar system. However, while in vitro slice studies have demonstrated electrotonic coupling of IO neurons (Llinás and Yarom 1981a), and in vivo studies have demonstrated that rhythmic and synchronous complex spike (CS) activity persists following the blockade of glutamatergic and GABAergic olivary afferents (Llinás and Sasaki 1989; Lang, Sugihara et al. 1996; Lang 2001; Lang 2002), no definitive proof that gap junctions are responsible exists. The experiments of this proposal directly test the importance of gap junctions in the functioning of the olivocerebellar system and its impact on CN firing. By the use of extracellular single-unit multielectrode recordings of Purkinje cell CS in tandem with single unit cerebellar nuclear recordings and intra-olivary drug injections we have determined the following: (1) olivocerebellar synchrony and rhythmicity are generated by electrical coupling through dendro-dendritic gap junctions in the IO; (2) IO leak conductances are capable of modulating both the CS synchrony and rhythmicity patterns; (3) CS synchrony and rhythmicity are temporally related to CN burst transitions and the olivocerebellar activity likely drives this relationship.
Recommended treatment for travelers' diarrhea includes the combination of an antibiotic, usually a fluoroquinolone or azithromycin, and loperamide for rapid resolution of symptoms. However, adverse ...events, postdose nausea with high-dose azithromycin, effectiveness of single-dose rifaximin, and emerging resistance to front-line agents are evidence gaps underlying current recommendations.
A randomized, double-blind trial was conducted in 4 countries (Afghanistan, Djibouti, Kenya, and Honduras) between September 2012 and July 2015. US and UK service members with acute watery diarrhea were randomized and received single-dose azithromycin (500 mg; 106 persons), levofloxacin (500 mg; 111 persons), or rifaximin (1650 mg; 107 persons), in combination with loperamide (labeled dosing). The efficacy outcomes included clinical cure at 24 hours and time to last unformed stool.
Clinical cure at 24 hours occurred in 81.4%, 78.3%, and 74.8% of the levofloxacin, azithromycin, and rifaximin arms, respectively. Compared with levofloxacin, azithromycin was not inferior (P = .01). Noninferiority could not be shown with rifaximin (P = .07). At 48 and 72 hours, efficacy among regimens was equivalent (approximately 91% at 48 and 96% at 72 hours). The median time to last unformed stool did not differ between treatment arms (azithromycin, 3.8 hours; levofloxacin, 6.4 hours; rifaximin, 5.6 hours). Treatment failures were uncommon (3.8%, 4.4%, and 1.9% in azithromycin, levofloxacin, and rifaximin arms, respectively) (P = .55). There were no differences between treatment arms with postdose nausea, vomiting, or other adverse events.
Single-dose azithromycin, levofloxacin, and rifaximin with loperamide were comparable for treatment of acute watery diarrhea.
NCT01618591.
The channels mediating most of the somatodendritic A-type K+ current in neurons are thought to be ternary complexes of Kv4 pore-forming subunits and two types of auxiliary subunits, the K+ channel ...interacting proteins (KChIPs) and dipeptidyl-peptidase-like (DPPL) proteins. The channels expressed in heterologous expression systems by mixtures of Kv4.2, KChIP1 and DPP6-S resemble in many properties the A-type current in hippocampal CA1 pyramidal neurons and cerebellar granule cells, neurons with prominent A-type K+ currents. However, the native currents have faster kinetics. Moreover, the A-type currents in neurons in intermediary layers of the superior colliculus have even faster inactivating rates. We have characterized a new DPP6 spliced isoform, DPP6-E, that produces in heterologous cells ternary Kv4 channels with very fast kinetics. DPP6-E is selectively expressed in a few neuronal populations in brain including cerebellar granule neurons, hippocampal pyramidal cells and neurons in intermediary layers of the superior colliculus. The effects of DPP6-E explain past discrepancies between reconstituted and native Kv4 channels in some neurons, and contributes to the diversity of A-type K+ currents in neurons.
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