Consensus Paper: Language and the Cerebellum: an Ongoing Enigma

In less than three decades, the concept “cerebellar neurocognition” has evolved from a mere afterthought to an entirely new and multifaceted area of neuroscientific research. A close interplay between three main strands of contemporary neuroscience induced a substantial modification of the traditional view of the cerebellum as a mere coordinator of autonomic and somatic motor functions. Indeed, the wealth of current evidence derived from detailed neuroanatomical investigations, functional neuroimaging studies with healthy subjects and patients and in-depth neuropsychological assessment of patients with cerebellar disorders shows that the cerebellum has a cardinal role to play in affective regulation, cognitive processing, and linguistic function. Although considerable progress has been made in models of cerebellar function, controversy remains regarding the exact role of the “linguistic cerebellum” in a broad variety of nonmotor language processes. This consensus paper brings together a range of different viewpoints and opinions regarding the contribution of the cerebellum to language function. Recent developments and insights in the nonmotor modulatory role of the cerebellum in language and some related disorders will be discussed. The role of the cerebellum in speech and language perception, in motor speech planning including apraxia of speech, in verbal working memory, in phonological and semantic verbal fluency, in syntax processing, in the dynamics of language production, in reading and in writing will be addressed. In addition, the functional topography of the linguistic cerebellum and the contribution of the deep nuclei to linguistic function will be briefly discussed. As such, a framework for debate and discussion will be offered in this consensus paper.     

Novel Tools to Improve Patient Selection and Monitoring on Active Surveillance for Low-risk Prostate Cancer: A Systematic Review

Context

Active surveillance (AS) is an alternative to initial radical treatment of low-risk prostate cancer (PCa). Current criteria for selection and follow-up incorrectly exclude some patients eligible for AS and misclassify some who actually harbour significant disease. Better prediction of cancer behaviour at diagnosis would allow less strict monitoring and may improve acceptance of AS.

Objective

To review and critically analyse the literature on the value of novel clinical tools for patient selection and monitoring on AS.

Evidence acquisition

A comprehensive search of the PubMed database until July 10, 2013, was performed according to Preferred Reporting Items for Systematic Reviews and Meta-analysis statement guidelines. Studies assessing novel markers and diagnostics for patient selection for AS and follow-up during AS were included. Studies analysing only classic clinical parameters used in current protocols (prostate-specific antigen, prostate volume, number of (positive) prostate biopsies, percentage malignant tissue, Gleason score) were excluded. This review focuses only on the AS setting and not on predicting insignificant disease in general.

Evidence synthesis

Of 787 studies on AS, 30 were included in this review: 14 on magnetic resonance imaging (MRI), 5 on serum markers, 5 on urinary markers, 4 on histopathology markers, and 2 on germline genetic markers. Several of these markers improve the prediction of tumour volume, tumour grade, or time to active treatment. MRI has a high specificity for low-risk PCa; new serum markers are associated with unfavourable disease. In none of the studies was the new marker used as the primary decision tool. Long-term outcome measures such as mortality were not assessed. The definition of indolent PCa is disputable.

Conclusions

Imaging and serum markers may improve future patient selection for AS and follow-up during AS. Prospective studies should aim to further evaluate the clinical utility of these new markers with respect to longer term outcomes of AS.

Patient summary

We searched the literature for articles reporting new ways to safely monitor low-risk prostate cancer for patients who have not had radical treatment. We found 30 articles. The most promising tools appear to be magnetic resonance imaging scans and various new blood markers. These may be used in the future within active surveillance regimens.     

Multiple Genes of the Renin-Angiotensin System Are Novel Targets of Wnt/β-Catenin Signaling

Activation of the renin-angiotensin system (RAS) plays an essential role in the pathogenesis of CKD and cardiovascular disease. However, current anti-RAS therapy only has limited efficacy, partly because of compensatory upregulation of renin expression. Therefore, a treatment strategy to simultaneously target multiple RAS genes is necessary to achieve greater efficacy. By bioinformatics analyses, we discovered that the promoter regions of all RAS genes contained putative T-cell factor (TCF)/lymphoid enhancer factor (LEF)-binding sites, and β-catenin induced the binding of LEF-1 to these sites in kidney tubular cells. Overexpression of either β-catenin or different Wnt ligands induced the expression of all RAS genes. Conversely, a small-molecule β-catenin inhibitor ICG-001 abolished RAS induction. In a mouse model of nephropathy induced by adriamycin, either transient therapy or late administration of ICG-001 abolished established proteinuria and kidney lesions. ICG-001 inhibited renal expression of multiple RAS genes in vivo and abolished the expression of other Wnt/β-catenin target genes. Moreover, ICG-001 therapy restored expression of nephrin, podocin, and Wilms’ tumor 1, attenuated interstitial myofibroblast activation, repressed matrix expression, and inhibited renal inflammation and fibrosis. Collectively, these studies identify all RAS genes as novel downstream targets of Wnt/β-catenin. Our results indicate that blockade of Wnt/β-catenin signaling can simultaneously repress multiple RAS genes, thereby leading to the reversal of established proteinuria and kidney injury.     

Improving integrated team working to support people to die in the place of their choice

Dying in a place of one's choice is considered to be a quantifiable measure of the effectiveness of end of life services in primary care. Although most people say they would prefer to die in their own home, very few actually do so. This article looks at how a team of community nurses and GPs changed their practice by using recognised end of life care tools. These helped practitioners in supporting adults with terminal illnesses to die in a place of their choice. A subsequent audit of patients' actual place of death against their preferred place demonstrates how working in more integrated ways has helped.     

Impact of Ciprofloxacin and Clindamycin Administration on Gram-Negative Bacteria Isolated from Healthy Volunteers and Characterization of the Resistance Genes They Harbor

The aim of this study was to assess the impact of ciprofloxacin, clindamycin, and placebo administration on culturable Gram-negative isolates and the antibiotic resistance genes they harbor. Saliva and fecal samples were collected from healthy human volunteers before and at intervals, up to 1 year after antibiotic administration. Samples were plated on selective and nonselective media to monitor changes in different colony types or bacterial species. Following ciprofloxacin administration, there was a decrease of Escherichia coli in feces and after clindamycin administration a decrease of Bacteroides in feces and Leptotrichia in saliva, which all returned to pretreatment levels within 1 to 4 months. Ciprofloxacin administration also resulted in an increase in ciprofloxacin-resistant Veillonella in saliva, which persisted for 12 months. Additionally, 949 aerobic and anaerobic isolates purified from ciprofloxacin- and clindamycin-containing plates were screened for the presence of resistance genes. Resistance gene carriage was widespread in isolates from all three treatment groups, and no association was observed between genes and antibiotic administration. Although the anaerobic component of the microbiota was not a major reservoir of aerobe-associated antimicrobial resistance (AMR) genes, we detected the sulfonamide resistance gene sul2 in anaerobic isolates. The longitudinal nature of the study allowed identification of distinct Escherichia coli clones harboring multiple resistance genes, including one carrying an extended-spectrum β-lactamase bla_CTX-M group 9 gene, which persisted in the gut for up to 4 months. This study provided insight into the effects of antibiotic administration on healthy microbiota and the diversity of resistance genes harbored therein.     

Voltage-sensor movements in the Eag Kv channel under an applied electric field

Voltage-dependent ion channels regulate the opening of their pores by sensing the membrane voltage. This process underlies the propagation of action potentials and other forms of electrical activity in cells. The voltage dependence of these channels is governed by the transmembrane displacement of the positive charged S4 helix within their voltage-sensor domains. We use cryo-electron microscopy to visualize this movement in the mammalian Eag voltage-dependent potassium channel in lipid membrane vesicles with a voltage difference across the membrane. Multiple structural configurations show that the applied electric field displaces S4 toward the cytoplasm by two helical turns, resulting in an extended interfacial helix near the inner membrane leaflet. The position of S4 in this down conformation is sterically incompatible with an open pore, thus explaining how movement of the voltage sensor at hyperpolarizing membrane voltages locks the pore shut in this kind of voltage-dependent K⁺ (K_v) channel. The structures solved in lipid bilayer vesicles detail the intricate interplay between K_v channels and membranes, from showing how arginines are stabilized deep within the membrane and near phospholipid headgroups, to demonstrating how the channel reshapes the inner leaflet of the membrane itself.

In voltage-dependent ion channels, the transmembrane voltage determines whether the pore opens. At the same time, the flow of ions through the open pore alters the membrane voltage by charging the membrane capacitance. This recursive regulation of ion channel activity by membrane voltage is the fundamental process at the heart of cellular electricity. As described by Hodgkin and Huxley (1), voltage-dependent membrane permeability to Na⁺ and K⁺ (ion channels as molecular entities had not yet been discovered) generates the action potential, which is by far the most rapid form of information transfer across long distances in cells. Voltage-dependent ion channels underlie many other aspects of cell signaling as well, including the initiation of muscle contraction by voltage-dependent Ca²⁺ channels (2, 3) and the control of cardiac and neuronal pacemaker frequency by the hyperpolarization-activated cyclic nucleotide–gated (HCN) channel (4, 5).Voltage-dependent ion channels contain structural domains called voltage sensors that control pore opening by membrane voltage. Whether in K⁺, Na⁺, Ca²⁺, or cation channels like HCN channels or transient receptor potential (TRP) channels, voltage sensors have a conserved structure comprising four transmembrane helices, named S1, S2, S3, and S4 (3, 6, 7). The fourth helix, S4, contains repeats of the amino acid triplet (RXX)_n, where R stands for arginine, sometimes substituted by lysine, X for hydrophobic amino acid, and n varies widely among different channels. At the center of voltage sensors, inside the membrane’s interior, a constellation of negative charged amino acids, aspartate or glutamate, and a phenylalanine residue forms a gating-charge transfer center that stabilizes the positive charged side chains of arginine and lysine as they cross the membrane (8, 9). In some voltage sensors, S4 undergoes a transition from an α to a 3₁₀ helix to direct the arginine and lysine side chains of S4 into the gating-charge transfer center (8–11). The displacement of S4 across the membrane is detectable as a nonlinear capacitive current, called gating current in electrophysiology experiments (9, 12), and is ultimately responsible for voltage control of a voltage-dependent ion channel’s pore.So far, voltage-dependent ion channel structures have been determined in crystals, detergent micelles, or nanodiscs without a voltage difference across them (8, 13–19). Under such conditions, most voltage sensors adopt a depolarized conformation, which is expected in a membrane at 0 mV. Chemical cross links, metal affinity bridges, mutations, and toxins have been used to capture or stabilize voltage sensors in conformations thought to mimic the hyperpolarized (i.e., negative voltage inside) condition (10, 11, 20–23). Here, we present a cryo-electron microscopy (cryo-EM) analysis of the mammalian Eag voltage-dependent K⁺ (K_v) channel in lipid membrane vesicles with a voltage generated across the membrane using K⁺ ion gradients in the presence of valinomycin. Doing so allows us to not only visualize how the voltage sensors respond to the applied electric field but also to see how the lipid membrane near the channel, which is intimately tied to the function of voltage-dependent ion channels, is reshaped by these conformational changes.