ResearchPad - 6 https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Shunting Inhibition Improves Synchronization in Heterogeneous Inhibitory Interneuronal Networks with Type 1 Excitability Whereas Hyperpolarizing Inhibition Is Better for Type 2 Excitability]]> https://www.researchpad.co/article/elastic_article_10610 All-to-all homogeneous networks of inhibitory neurons synchronize completely under the right conditions; however, many modeling studies have shown that biological levels of heterogeneity disrupt synchrony. Our fundamental scientific question is “how can neurons maintain partial synchrony in the presence of heterogeneity and noise?” A particular subset of strongly interconnected interneurons, the PV+ fast-spiking (FS) basket neurons, are strongly implicated in γ oscillations and in phase locking of nested γ oscillations to theta. Their excitability type apparently varies between brain regions: in CA1 and the dentate gyrus they have type 1 excitability, meaning that they can fire arbitrarily slowly, whereas in the striatum and cortex they have type 2 excitability, meaning that there is a frequency thresh old below which they cannot sustain repetitive firing. We constrained the models to study the effect of excitability type (more precisely bifurcation type) in isolation from all other factors. We use sparsely connected, heterogeneous, noisy networks with synaptic delays to show that synchronization properties, namely the resistance to suppression and the strength of theta phase to γ amplitude coupling, are strongly dependent on the pairing of excitability type with the type of inhibition. Shunting inhibition performs better for type 1 and hyperpolarizing inhibition for type 2. γ Oscillations and their nesting within theta oscillations are thought to subserve cognitive functions like memory encoding and recall; therefore, it is important to understand the contribution of intrinsic properties to these rhythms.

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<![CDATA[Biophysical Basis of Alpha Rhythm Disruption in Alzheimer’s Disease]]> https://www.researchpad.co/article/elastic_article_8069 Occipital alpha is a prominent rhythm (∼10 Hz) detected in electroencephalography (EEG) during wakeful relaxation with closed eyes. The rhythm is generated by a subclass of thalamic pacemaker cells that burst at the alpha frequency, orchestrated by the interplay of hyperpolarization-activated cyclic nucleotide-gated channels (HCN) and calcium channels in response to elevated levels of ambient acetylcholine (ACh). These oscillations are known to have a lower peak frequency and coherence in the early stages of Alzheimer’s disease (AD). Interestingly, calcium signaling, HCN channel expression and ACh signaling, crucial for orchestrating the alpha rhythm, are also known to be aberrational in AD. In a biophysically detailed network model of the thalamic circuit, we investigate the changes in molecular signaling and the causal relationships between them that lead to a disrupted thalamic alpha in AD. Our simulations show that lowered HCN expression leads to a slower thalamic alpha, which can be rescued by increasing ACh levels, a common therapeutic target of AD drugs. However, this rescue is possible only over a limited range of reduced HCN expression. The model predicts that lowered HCN expression can modify the network activity in the thalamic circuit leading to increased GABA release in the thalamus and disrupt the calcium homeostasis. The changes in calcium signaling make the network more susceptible to noise, causing a loss in rhythmic activity. Based on our results, we propose that reduced frequency and coherence of the occipital alpha rhythm seen in AD may result from downregulated HCN expression, rather than modified cholinergic signaling.

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<![CDATA[Chronic Activation of Gp1 mGluRs Leads to Distinct Refinement of Neural Network Activity through Non-Canonical p53 and Akt Signaling]]> https://www.researchpad.co/article/elastic_article_8065 Group 1 metabotropic glutamate receptors (Gp1 mGluRs), including mGluR1 and mGluR5, are critical regulators for neuronal and synaptic plasticity. Dysregulated Gp1 mGluR signaling is observed with various neurologic disorders, including Alzheimer’s disease, Parkinson’s disease, epilepsy, and autism spectrum disorders (ASDs). It is well established that acute activation of Gp1 mGluRs leads to elevation of neuronal intrinsic excitability and long-term synaptic depression. However, it remains unknown how chronic activation of Gp1 mGluRs can affect neural activity and what molecular mechanisms might be involved. In the current study, we employed a multielectrode array (MEA) recording system to evaluate neural network activity of primary mouse cortical neuron cultures. We demonstrated that chronic activation of Gp1 mGluRs leads to elevation of spontaneous spike frequency while burst activity and cross-electrode synchronization are maintained at the baseline. We further showed that these neural network properties are achieved through proteasomal degradation of Akt that is dependent on the tumor suppressor p53. Genetically knocking down p53 disrupts the elevation of spontaneous spike frequency and alters the burst activity and cross-electrode synchronization following chronic activation of Gp1 mGluRs. Importantly, these deficits can be restored by pharmacologically inhibiting Akt to mimic inactivation of Akt mediated by p53. Together, our findings reveal the effects of chronic activation of Gp1 mGluRs on neural network activity and identify a unique signaling pathway involving p53 and Akt for these effects. Our data can provide insights into constitutively active Gp1 mGluR signaling observed in many neurologic and psychiatric disorders.

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<![CDATA[Loop-closure kinetics reveal a stable, right-handed DNA intermediate in Cre recombination]]> https://www.researchpad.co/article/Ne49459d2-72dd-414a-b18a-72723f144fa7 In Cre site-specific recombination, the synaptic intermediate is a recombinase homotetramer containing a pair of loxP DNA target sites. The enzyme system's strand-exchange mechanism proceeds via a Holliday-junction (HJ) intermediate; however, the geometry of DNA segments in the synapse has remained highly controversial. In particular, all crystallographic structures are consistent with an achiral, planar Holliday-junction (HJ) structure, whereas topological assays based on Cre-mediated knotting of plasmid DNAs are consistent with a right-handed chiral junction. We use the kinetics of loop closure involving closely spaced (131–151 bp) loxP sites to investigate the in-aqueo ensemble of conformations for the longest-lived looped DNA intermediate. Fitting the experimental site-spacing dependence of the loop-closure probability, J, to a statistical-mechanical theory of DNA looping provides evidence for substantial out-of-plane HJ distortion, which unequivocally stands in contrast to the square-planar intermediate geometry from Cre-loxP crystal structures and those of other int-superfamily recombinases. J measurements for an HJ-isomerization-deficient Cre mutant suggest that the apparent geometry of the wild-type complex is consistent with temporal averaging of right-handed and achiral structures. Our approach connects the static pictures provided by crystal structures and the natural dynamics of macromolecules in solution, thus advancing a more comprehensive dynamic analysis of large nucleoprotein structures and their mechanisms.

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<![CDATA[Propagating Activity in Neocortex, Mediated by Gap Junctions and Modulated by Extracellular Potassium]]> https://www.researchpad.co/article/N979ce65e-e257-454f-9667-068464737f71

Abstract

Parvalbumin-expressing interneurons in cortical networks are coupled by gap junctions, forming a syncytium that supports propagating epileptiform discharges, induced by 4-aminopyridine. It remains unclear, however, whether these propagating events occur under more natural states, without pharmacological blockade. In particular, we investigated whether propagation also happens when extracellular K+ rises, as is known to occur following intense network activity, such as during seizures. We examined how increasing [K+]o affects the likelihood of propagating activity away from a site of focal (200–400 μm) optogenetic activation of parvalbumin-expressing interneurons. Activity was recorded using a linear 16-electrode array placed along layer V of primary visual cortex. At baseline levels of [K+]o (3.5 mm), induced activity was recorded only within the illuminated area. However, when [K+]o was increased above a threshold level (50th percentile = 8.0 mm; interquartile range = 7.5–9.5 mm), time-locked, fast-spiking unit activity, indicative of parvalbumin-expressing interneuron firing, was also recorded outside the illuminated area, propagating at 59.1 mm/s. The propagating unit activity was unaffected by blockade of GABAergic synaptic transmission, but it was modulated by glutamatergic blockers, and was reduced, and in most cases prevented altogether, by pharmacological blockade of gap junctions, achieved by any of the following three different drugs: quinine, mefloquine, or carbenoxolone. Washout of quinine rapidly re-established the pattern of propagating activity. Computer simulations show qualitative differences between propagating discharges in high [K+]o and 4-aminopyridine, arising from differences in the electrotonic effects of these two manipulations. These interneuronal syncytial interactions are likely to affect the complex electrographic dynamics of seizures, once [K+]o is raised above this threshold level.

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<![CDATA[Prospective Biomarker Study in Advanced RAS Wild‐Type Colorectal Cancer: POSIBA Trial (GEMCAD 10‐02)]]> https://www.researchpad.co/article/Nfdc2f8a5-e695-4ecf-80f1-840c9a2dcf74

This articles compares the capacity of several biomarkers (BRAF mutation, PIK3CA mutation/PTEN loss and DP phenotype) to predict 12‐month progression‐free survival and compares it with that of clinical variables

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<![CDATA[The McCAVE Trial: Vanucizumab plus mFOLFOX‐6 Versus Bevacizumab plus mFOLFOX‐6 in Patients with Previously Untreated Metastatic Colorectal Carcinoma (mCRC)]]> https://www.researchpad.co/article/Nea8b4647-34da-4b60-815c-303ebbb07b55

Abstract

Background

Bevacizumab, a VEGF‐A inhibitor, in combination with chemotherapy, has proven to increase progression‐free survival (PFS) and overall survival in multiple lines of therapy of metastatic colorectal cancer (mCRC). The angiogenic factor angiopoetin‐2 (Ang‐2) is associated with poor prognosis in many cancers, including mCRC. Preclinical models demonstrate improved activity when inhibiting both VEGF‐A and Ang‐2, suggesting that the dual VEGF‐A and Ang‐2 blocker vanucizumab (RO5520985 or RG‐7221) may improve clinical outcomes. This phase II trial evaluated the efficacy of vanucizumab plus modified (m)FOLFOX‐6 (folinic acid (leucovorin), fluorouracil (5‐FU) and oxaliplatin) versus bevacizumab/mFOLFOX‐6 for first‐line mCRC.

Patients and Methods

All patients received mFOLFOX‐6 and were randomized 1:1 to also receive vanucizumab 2,000 mg or bevacizumab 5 mg/kg every other week. Oxaliplatin was given for eight cycles; other agents were continued until disease progression or unacceptable toxicity for a maximum of 24 months. The primary endpoint was investigator‐assessed PFS.

Results

One hundred eighty‐nine patients were randomized (vanucizumab, n = 94; bevacizumab, n = 95). The number of PFS events was comparable (vanucizumab, n = 39; bevacizumab, n = 43). The hazard ratio was 1.00 (95% confidence interval, 0.64–1.58; p = .98) in a stratified analysis based on number of metastatic sites and region. Objective response rate was 52.1% and 57.9% in the vanucizumab and bevacizumab arm, respectively. Baseline plasma Ang‐2 levels were prognostic in both arms but not predictive for treatment effects on PFS of vanucizumab. The incidence of adverse events of grade ≥3 was similar between treatment arms (83.9% vs. 82.1%); gastrointestinal perforations (10.8% vs. 8.4%) exceeded previously reported rates in this setting. Hypertension and peripheral edema were more frequent in the vanucizumab arm.

Conclusion

Vanucizumab/mFOLFOX‐6 did not improve PFS and was associated with increased rates of antiangiogenic toxicity compared with bevacizumab/mFOLFOX‐6. Our results suggest that Ang‐2 is not a relevant therapeutic target in first‐line mCRC.

Implications for Practice

This randomized phase II study demonstrates that additional angiopoietin‐2 (Ang‐2) inhibition does not result in superior benefit over anti–VEGF‐A blockade alone when each added to standard chemotherapy. Moreover, the performed pharmacokinetic and pharmacodynamic analysis revealed that vanucizumab was bioavailable and affected its intended target, thereby strongly suggesting that Ang‐2 is not a relevant therapeutic target in the clinical setting of treatment‐naïve metastatic colorectal cancer. As a result, the further clinical development of the dual VEGF‐A and Ang‐2 inhibitor vanucizumab was discontinued.

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<![CDATA[An evidence-based framework for priority clinical research questions for COVID-19]]> https://www.researchpad.co/article/Ncb49dde6-2ee2-4711-a175-2e4d0f8f9ab7

Background

On 31 December, 2019, the World Health Organization China Country Office was informed of cases of pneumonia of unknown aetiology. Since then, there have been over 75 000 cases globally of the 2019 novel coronavirus (COVID-19), 2000 deaths, and over 14 000 cases recovered. Outbreaks of novel agents represent opportunities for clinical research to inform real-time public health action. In 2018, we conducted a systematic review to identify priority research questions for Severe Acute Respiratory Syndrome-related coronavirus (SARS-CoV) and Middle East Respiratory Syndrome-related coronavirus (MERS-CoV). Here, we review information available on COVID-19 and provide an evidenced-based framework for priority clinical research in the current outbreak.

Methods

Three bibliographic databases were searched to identify clinical studies published on SARS-CoV and MERS-CoV in the outbreak setting. Studies were grouped thematically according to clinical research questions addressed. In February 2020, available information on COVID19 was reviewed and compared to the results of the SARS-CoV and MERS-CoV systematic review.

Results

From the research objectives for SARS-CoV and MERS-CoV, ten themes in the literature were identified: Clinical characterisation, prognosis, diagnosis, clinical management, viral pathogenesis, epidemiological characterisation, infection prevention and control/transmission, susceptibility, psychosocial, and aetiology. For COVID19, some information on clinical presentation, diagnostic testing, and aetiology is available but many clinical research gaps have yet to be filled.

Conclusions

Based on a systematic review of other severe coronaviruses, we summarise the state of clinical research for COVID-19, highlight the research gaps, and provide recommendations for the implementation of standardised protocols. Data based on internationally standardised protocols will inform clinical practice real-time.

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<![CDATA[When will the battle against novel coronavirus end in Wuhan: A SEIR modeling analysis]]> https://www.researchpad.co/article/N28fb7c6f-7d56-4d59-8d81-6666e3330410

Background

Recent outbreak of 2019-nCoV in Wuhan raised serious public health concerns. By February 15, 2020 in Wuhan, the total number of confirmed infection cases has reached 37 914, and the number of deaths has reached 1123, accounting for 56.9% of the total confirmed cases and 73.7% of the total deaths in China. People are eager to know when the epidemic will be completely controlled and when people's work and life will be on the right track.

Method

In this study we analyzed the epidemic dynamics and trend of 2019-nCoV in Wuhan by using the data after the closure of Wuhan city till February 12, 2020 based on the SEIR modeling method.

Results

The optimal parameters were estimated as R0 = 1.44 (interquartile range: 1.40-1.47), TI = 14 (interquartile range = 14-14) and TE = 3.0 (interquartile range = 2.8-3.1). Based on these parameters, the number of infected individuals in Wuhan city may reach the peak around February 19 at about 47 000 people. Once entering March, the epidemic would gradually decline, and end around the late March. It is worth noting that the above prediction is based on the assumption that the number of susceptible population N = 200 000 will not increase. If the epidemic situation is not properly controlled, the peak of infected number can be further increased and the peak time will be a little postponed. It was expected that the epidemic would subside in early March, and disappear gradually towards the late March.

Conclusions

The epidemic situation of 2019-nCoV in Wuhan was effectively controlled after the closure of the city, and the disease transmission index also decreased significantly. It is expected that the peak of epidemic situation would be reached in late February and end in March.

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<![CDATA[Extraretinal Spike Normalization in Retinal Ganglion Cell Axons]]> https://www.researchpad.co/article/N92f187e4-0ba5-480d-a35a-41421c5a2bec

Abstract

Spike conduction velocity characteristically differs between myelinated and unmyelinated axons. Here we test whether spikes of myelinated and unmyelinated paths differ in other respects by measuring rat retinal ganglion cell (RGC) spike duration in the intraretinal, unmyelinated nerve fiber layer and the extraretinal, myelinated optic nerve and optic chiasm. We find that rapid spike firing and illumination broaden spikes in intraretinal axons but not in extraretinal axons. RGC axons thus initiate spikes intraretinally and normalize spike duration extraretinally. Additionally, we analyze spikes that were recorded in a previous study of rhesus macaque retinogeniculate transmission and find that rapid spike firing does not broaden spikes in optic tract. The spike normalization we find reduces the number of spike properties that can change during RGC light responses. However, this is not because identical spikes fire in all axons. Instead, our recordings show that different subtypes of RGC generate axonal spikes of different durations and that the differences resemble spike duration increases that alter neurotransmitter release from other neurons. Moreover, previous studies have shown that RGC spikes of shorter duration can fire at higher maximum frequencies. These properties should facilitate signal transfer by different mechanisms at RGC synapses onto subcortical target neurons.

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<![CDATA[Basic principles of the genetic code extension]]> https://www.researchpad.co/article/Nc5ec4642-2c29-40a2-b157-238efe1c4a2d

Compounds including non-canonical amino acids (ncAAs) or other artificially designed molecules can find a lot of applications in medicine, industry and biotechnology. They can be produced thanks to the modification or extension of the standard genetic code (SGC). Such peptides or proteins including the ncAAs can be constantly delivered in a stable way by organisms with the customized genetic code. Among several methods of engineering the code, using non-canonical base pairs is especially promising, because it enables generating many new codons, which can be used to encode any new amino acid. Since even one pair of new bases can extend the SGC up to 216 codons generated by a six-letter nucleotide alphabet, the extension of the SGC can be achieved in many ways. Here, we proposed a stepwise procedure of the SGC extension with one pair of non-canonical bases to minimize the consequences of point mutations. We reported relationships between codons in the framework of graph theory. All 216 codons were represented as nodes of the graph, whereas its edges were induced by all possible single nucleotide mutations occurring between codons. Therefore, every set of canonical and newly added codons induces a specific subgraph. We characterized the properties of the induced subgraphs generated by selected sets of codons. Thanks to that, we were able to describe a procedure for incremental addition of the set of meaningful codons up to the full coding system consisting of three pairs of bases. The procedure of gradual extension of the SGC makes the whole system robust to changing genetic information due to mutations and is compatible with the views assuming that codons and amino acids were added successively to the primordial SGC, which evolved minimizing harmful consequences of mutations or mistranslations of encoded proteins.

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<![CDATA[The impact of perceived risk, screening eligibility and worry on preference for lung cancer screening: a cross-sectional survey]]> https://www.researchpad.co/article/Nfa3d397e-5f18-4c5d-b6fe-853741d7b391

Lung cancer screening is effective at reducing lung cancer deaths when individuals at greatest risk are screened. Recruitment initiatives target all current and former smokers, of whom only some are eligible for screening, potentially leading to discordance between screening preference and eligibility in ineligible individuals. The objective of the present study was to identify factors associated with preference for screening among ever-smokers.

Ever-smokers aged 55–80 years attending outpatient clinics at three Australian hospitals were invited. The survey recorded: 1) demographics; 2) objective lung cancer risk and screening eligibility using the Prostate Lung Colon Ovarian 2012 risk model; and 3) perceived lung cancer risk, worry about and seriousness of lung cancer using a validated questionnaire. Multivariable ordinal logistic regression identified predictors of screening preference.

The survey was completed by 283 individuals (response rate 27%). Preference for screening was high (72%) with no significant difference between low-dose computed tomography screening-eligible and -ineligible individuals (77% versus 68%, p=0.11). Worry about lung cancer (adjusted-proportional odds ratio (adj-OR) 1.31, 95% CI 1.08–1.58; p=0.007) and perceived seriousness of lung cancer (adj-OR 1.31, 95% CI 1.05–1.64; p=0.02) were associated with higher preference for lung cancer screening while screening eligibility was not. The concept of “early detection” was the most important driver to have screening while practical obstacles like difficulty travelling to the scan or taking time off work were the least important barriers to screening.

Most current or former smokers prefer to undergo screening. Worry about lung cancer and perceived seriousness of the diagnosis are more important drivers for screening preference than eligibility status.

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<![CDATA[Relationship between pneumonitis induced by immune checkpoint inhibitors and the underlying parenchymal status: a retrospective study]]> https://www.researchpad.co/article/Nc37a7aa3-4d2f-449b-9abe-9a659eea3349

In patients with primary or secondary lung tumour treated with immune checkpoint inhibitors, immune-related pneumonitis is a rare adverse event but may evolve to respiratory failure. Prompt management is required and usually consists of treatment interruption and immunosuppressive drug administration. The aim of this study was to evaluate relationships between immune-related pneumonitis and pre-existing parenchymal status, especially tumour location and history of chest radiotherapy.

Computed tomography (CT) scans of patients with immune-related pneumonitis were retrospectively reviewed. Pattern, distribution and extent of pneumonitis were assessed in six lung regions. In patients who received radiotherapy, the extent of pneumonitis was evaluated according to the radiation field.

Among 253 patients treated with immunotherapy, 15 cases of immune-related pneumonitis were identified. 10 had previous or concomitant chest radiotherapy in addition to immunotherapy. At CT scan, 29 (33%) out of 88 regions encompassed the primary tumour (n=4), a lung metastasis (n=4) and/or radiation fields (n=21). A significantly higher prevalence of parenchymal involvement by immune-related pneumonitis occurred within areas of primary or metastatic malignancy and/or radiation field (97%) as compared to other areas (3%, p=0.009). Lung regions affected by the primary tumour, metastasis or radiotherapy had a higher probability of immune-related pneumonitis than others (OR 10.8, p=0.024). An organising pneumonia (OP) pattern was more frequent after radiotherapy (70% versus 0%, p=0.024), whereas nonspecific interstitial pneumonia features were more commonly seen in radiotherapy-naive patients (100% versus 10%, p=0.002).

In patients with primary or secondary lung tumour treated with immune checkpoint inhibitors, immune-related pneumonitis is preferentially located within lung areas involved by tumour and/or radiation fields.

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<![CDATA[Improving lung cancer diagnosis by combining exhaled-breath data and clinical parameters]]> https://www.researchpad.co/article/Nb8d7f983-c517-46a7-b965-58a43503eb4a

Introduction

Exhaled-breath analysis of volatile organic compounds could detect lung cancer earlier, possibly leading to improved outcomes. Combining exhaled-breath data with clinical parameters may improve lung cancer diagnosis.

Methods

Based on data from a previous multi-centre study, this article reports additional analyses. 138 subjects with non-small cell lung cancer (NSCLC) and 143 controls without NSCLC breathed into the Aeonose. The diagnostic accuracy, presented as area under the receiver operating characteristic curve (AUC-ROC), of the Aeonose itself was compared with 1) performing a multivariate logistic regression analysis of the distinct clinical parameters obtained, and 2) using this clinical information beforehand in the training process of the artificial neural network (ANN) for the breath analysis.

Results

NSCLC patients (mean±sd age 67.1±9.1 years, 58% male) were compared with controls (62.1±7.0 years, 40.6% male). The AUC-ROC of the classification value of the Aeonose itself was 0.75 (95% CI 0.69–0.81). Adding age, number of pack-years and presence of COPD to this value in a multivariate regression analysis resulted in an improved performance with an AUC-ROC of 0.86 (95% CI 0.81–0.90). Adding these clinical variables beforehand to the ANN for classifying the breath print also led to an improved performance with an AUC-ROC of 0.84 (95% CI 0.79–0.89).

Conclusions

Adding readily available clinical information to the classification value of exhaled-breath analysis with the Aeonose, either post hoc in a multivariate regression analysis or a priori to the ANN, significantly improves the diagnostic accuracy to detect the presence or absence of lung cancer.

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<![CDATA[Lung cancer incidence and mortality with extended follow-up in the National LungScreening Trial]]> https://www.researchpad.co/article/N0b0bde67-6ac6-4eb0-9c68-799abe71e7ab

Since lung cancer (LC) is still the leading cause of cancer deaths worldwide [1], early detection through screening represents an important opportunity to improve LC survival and is a priority area for cancer care. The National Lung Screening Trial (NLST) aimed to compare low-dose helical computed tomography (LDCT) with chest radiography in LC screening of current or former heavy smokers. The trial found a relative reduction in mortality from LC of 20% in those who had undergone LDCT screening. LC screening has regained prominence in the thoracic oncology literature with the completion of NELSON and other European trials, which support the role of LC screening in achieving early diagnosis and reducing mortality. A growing number of implementation pilots are providing an impetus towards organised, national programmes for LC screening, which are in need of long-term follow-up data such as those presented in this study.

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<![CDATA[Lung cancer: keep your mind open – it's not always the usualsuspects!]]> https://www.researchpad.co/article/Na3b3e76b-952c-416a-8c1a-b87a051a59bd

Some years ago, I entered a completely unfamiliar world. This was a landscape that clinicians deal with every day but for the individual suspected of having lung cancer, it can appear hostile and scary, often misrepresented by outdated imagery, information and television portrayal. Lung cancer is not awash with celebrities admitting to having it or grand fundraising campaigns like other conditions. Despite many changes in the treatment landscape, it's still generally much more stigmatised than other cancers.

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<![CDATA[Overdiagnosis of lung cancer with low-dose computed tomography screening: meta-analysis of the randomised clinical trials]]> https://www.researchpad.co/article/Nae9fbcf7-35f1-4a13-b3e2-17e2f5fccc43

In low-dose computed tomography (LDCT) screening for lung cancer, all three main conditions for overdiagnosis in cancer screening are present: 1) a reservoir of slowly or nongrowing lung cancer exists; 2) LDCT is a high-resolution imaging technology with the potential to identify this reservoir; and 3) eligible screening participants have a high risk of dying from causes other than lung cancer. The degree of overdiagnosis in cancer screening is most validly estimated in high-quality randomised controlled trials (RCTs), with enough follow-up time after the end of screening to avoid lead-time bias and without contamination of the control group.

Nine RCTs investigating LDCT screening were identified. Two RCTs were excluded because lung cancer incidence after the end of screening was not published. Two other RCTs using active comparators were also excluded. Therefore, five RCTs were included: two trials were at low risk of bias, two of some concern and one at high risk of bias. In a meta-analysis of the two low risk of bias RCTs including 8156 healthy current or former smokers, 49% of the screen-detected cancers were overdiagnosed. There is uncertainty about this substantial degree of overdiagnosis due to unexplained heterogeneity and low precision of the summed estimate across the two trials.

Key points

  • Nine randomised controlled trials (RCTs) on low-dose computed tomography screening were identified; five were included for meta-analysis but only two of those were at low risk of bias.

  • In a meta-analysis of recent low risk of bias RCTs including 8156 healthy current or former smokers from developed countries, we found that 49% of the screen-detected cancers may be overdiagnosed.

  • There is uncertainty about the degree of overdiagnosis in lung cancer screening due to unexplained heterogeneity and low precision of the point estimate.

  • If only high-quality RCTs are included in the meta-analysis, the degree of overdiagnosis is substantial.

Educational aims

  • To appreciate that low-dose computed tomography screening for lung cancer meets all three main conditions for overdiagnosis in cancer screening: a reservoir of indolent cancers exists in the population; the screening test is able to “tap” this reservoir by detecting biologically indolent cancers as well as biologically important cancers; and the population being screened is characterised by a relatively high competing risk of death from other causes

  • To learn about biases that might affect the estimates of overdiagnosis in randomised controlled trials in cancer screening

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<![CDATA[Proportional Downscaling of Glutamatergic Release Sites by the General Anesthetic Propofol at Drosophila Motor Nerve Terminals]]> https://www.researchpad.co/article/Nc0336880-ed08-4635-a960-a7179c1caa22

Visual Abstract

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<![CDATA[LRIT3 is Required for Nyctalopin Expression and Normal ON and OFF Pathway Signaling in the Retina]]> https://www.researchpad.co/article/N29e0abcc-45e2-43a7-9998-c68ab13e737d

Abstract

The first retinal synapse, photoreceptor→bipolar cell (BC), is both anatomically and functionally complex. Within the same synaptic region, a change in presynaptic glutamate release is sensed by both ON BCs (DBCs) via the metabotropic glutamate receptor 6 (mGluR6), and OFF BCs (HBCs) via ionotropic glutamate receptors to establish parallel signaling pathways that preferentially encode light increments (ON) or decrements (OFF), respectively. The synaptic structural organization of ON and OFF-type BCs at the photoreceptor terminal differs. DBCs make an invaginating synapse that contains a diverse but incompletely understood complex of interacting proteins (signalplex). HBCs make primarily flat contacts that contain an apparent different set of proteins that is equally uncharacterized. LRIT3 is a synaptic protein known to be essential for ON pathway visual function. In both male and female mice, we demonstrate that LRIT3 interacts with and is required for expression of nyctalopin, and thus TRPM1 at all DBC dendritic tips, but DBC signalplex components are not required for LRIT3 expression. Using whole-cell and multielectrode array (MEA) electrophysiology and glutamate imaging, we demonstrate that the loss of LRIT3 impacts both ON and OFF signaling pathway function. Without LRIT3, excitatory input to type 1 BCs is reduced, as are the visually evoked responses of many OFF retinal ganglion cells (RGCs). We conclude that the absence of LRIT3 expression disrupts excitatory input to OFF BCs and, thus disrupts the normal function of OFF RGCs.

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<![CDATA[Hsc70 Ameliorates the Vesicle Recycling Defects Caused by Excess α-Synuclein at Synapses]]> https://www.researchpad.co/article/Ne2ad10e1-59b4-428a-995d-887e5ac15bd1

α-Synuclein overexpression and aggregation are linked to Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and several other neurodegenerative disorders. In addition to effects in the cell body, α-synuclein accumulation occurs at presynapses where the protein is normally localized. While it is generally agreed that excess α-synuclein impairs synaptic vesicle trafficking, the underlying mechanisms are unknown.

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