Evaluating the impact of MEDLINE filters on evidence retrieval: study protocol

<p>Abstract</p> <p>Background</p> <p>Rather than searching the entire MEDLINE database, clinicians can perform searches on a filtered set of articles where relevant information is more likely to be found. Members of our team previously developed two types of MEDLINE filters. The 'methods' filters help identify clinical research of high methodological merit. The 'content' filters help identify articles in the discipline of renal medicine. We will now test the utility of these filters for physician MEDLINE searching.</p> <p>Hypothesis</p> <p>When a physician searches MEDLINE, we hypothesize the use of filters will increase the number of relevant articles retrieved (increase 'recall,' also called sensitivity) and decrease the number of non-relevant articles retrieved (increase 'precision,' also called positive predictive value), compared to the performance of a physician's search unaided by filters.</p> <p>Methods</p> <p>We will survey a random sample of 100 nephrologists in Canada to obtain the MEDLINE search that they would first perform themselves for a focused clinical question. Each question we provide to a nephrologist will be based on the topic of a recently published, well-conducted systematic review. We will examine the performance of a physician's unaided MEDLINE search. We will then apply a total of eight filter combinations to the search (filters used in isolation or in combination). We will calculate the recall and precision of each search. The filter combinations that most improve on unaided physician searches will be identified and characterized.</p> <p>Discussion</p> <p>If these filters improve search performance, physicians will be able to search MEDLINE for renal evidence more effectively, in less time, and with less frustration. Additionally, our methodology can be used as a proof of concept for the evaluation of search filters in other disciplines.</p

K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

<p>Abstract</p> <p>Background</p> <p>Lung epithelial Na⁺channels (ENaC) are regulated by cell Ca²⁺signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K⁺channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K⁺channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC) by up-regulating both apical and basolateral ion transport.</p> <p>Methods</p> <p>Verapamil-induced depression of heterologously expressed human αβγ ENaC in <it>Xenopus </it>oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441), and <it>in vivo </it>alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca²⁺signal in H441 cells was analyzed using Fluo 4AM.</p> <p>Results</p> <p>The rate of <it>in vivo </it>AFC was reduced significantly (40.6 ± 6.3% of control, <it>P </it>< 0.05, n = 12) in mice intratracheally administrated verapamil. K_Ca3.1(1-EBIO) and K_ATP(minoxidil) channel openers significantly recovered AFC. In addition to short-circuit current (Isc) in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca²⁺signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca²⁺in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, K_V(pyrithione-Na), K _Ca3.1(1-EBIO), and K_ATP(minoxidil) channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na⁺and K⁺transport pathways.</p> <p>Conclusions</p> <p>Our observations demonstrate that K⁺channel openers are capable of rescuing reduced vectorial Na⁺transport across lung epithelial cells with impaired Ca²⁺signal.</p

Regulation of epithelial sodium channels by cGMP/PKGII

Airway and alveolar fluid clearance is mainly governed by vectorial salt movement via apically located rate-limiting Na+ channels (ENaC) and basolateral Na+/K+-ATPases. ENaC is regulated by a spectrum of protein kinases, i.e. protein kinase A (PKA), C (PKC), and G (PKG). However, the molecular mechanisms for the regulation of ENaC by cGMP/PKG remain to be elucidated. In the present study, we studied the pharmacological responses of native epithelial Na+ channels in human Clara cells and human αβγδ ENaCs expressed in oocytes to cGMP. 8-pCPT-cGMP increased amiloride-sensitive short-circuit current (Isc) across H441 monolayers and heterologously expressed αβγδ ENaC activity in a dose-dependent manner. Similarly, 8-pCPT-cGMP (a PKGII activator) but not 8-Br-cGMP (a PKGI activator) increased amiloride-sensitive whole cell currents in H441 cells in the presence of CFTRinh-172 and diltiazem. In all cases, the cGMP-activated Na+ channel activity was inhibited by Rp-8-pCPT-cGMP, a specific PKGII inhibitor. This was substantiated by the evidence that PKGII was the sole isoform expressed in H441 cells at the protein level. Importantly, intratracheal instillation of 8-pCPT-cGMP in BALB/c mice increased amiloride-sensitive alveolar fluid clearance by ∼30%, consistent with the in vitro results. We therefore conclude that PKGII is an activator of lung epithelial Na+ channels, which may expedite the resolution of oedematous fluid in alveolar sacs

Vasotocin and vasopressin stimulation of the chloride secretion in the human bronchial epithelial cell line, 16HBE14o-

1. Effects of neuropeptides of the vasopressin family on Cl(−) secretion have not yet been reported in lung. Using the 16HBE14o- bronchial epithelial cell line, we investigated their action on Cl(−) secretion. 2. In symmetrical Cl(−) solutions, basolateral application of arginine vasotocin (AVT), oxytocin or isotocin induced a transient I(sc) stimulation (I(peak)), whereas arginine vasopressin (AVP) did not. The effects of different Cl(−) channel blockers and of a protein kinase C (PKC) inhibitor suggest that CFTR is involved in I(peak). The calcium-activated K(+) channel (SK4) and the Cl(−)/HCO(−)(3) exchanger favor the driving force for AVT-mediated Cl(−) secretion. The antagonists of V1a (SR49059)- and V1b (SSR149415)-receptors blocked I(peak), while SR121463B, a V2 receptor antagonist, did not. These results point to the stimulation of a V1-like receptor mediating I(peak) and presenting an efficacy order, AVT>oxytocin>isotocin≫AVP. 3. When a serosal to mucosal Cl(−) gradient was applied, AVT and AVP both stimulated I(sc) according to a biphasic profile, I(peak) being followed by a plateau phase (I(plateau)). The pharmacology of I(plateau) suggests that CFTR channels are involved and that Na(+)/K(+)/2Cl(−) is the only transporter associated with I(plateau). dDAVP, a V2 receptor agonist-induced I(plateau) with the same potency as AVP, suggesting the involvement of V2 receptors in the AVP-induced I(plateau). V2 receptors are present on both opposite membranes, while V1-like receptors are mainly expressed on the basolateral membranes. RT–PCR experiments show the expression of V1a, V1b, V2 and vasopressin-activated calcium-mobilizing (VACM) receptors mRNAs