A novel family of sugar-specific phosphodiesterases that remove zwitterionic modifications of GlcNAc.

The zwitterions phosphorylcholine (PC) and phosphoethanolamine (PE) are often found esterified to certain sugars in polysaccharides and glycoconjugates in a wide range of biological species. One such modification involves PC attachment to the 6-carbon of N-acetylglucosamine (GlcNAc-6-PC) in N-glycans and glycosphingolipids (GSLs) of parasitic nematodes, a modification that helps the parasite evade host immunity. Knowledge of enzymes involved in the synthesis and degradation of PC and PE modifications is limited. More detailed studies on such enzymes would contribute to a better understanding of the function of PC modifications and have potential application in the structural analysis of zwitterion-modified glycans. In this study, we used functional metagenomic screening to identify phosphodiesterases encoded in a human fecal DNA fosmid library that remove PC from GlcNAc-6-PC. A novel bacterial phosphodiesterase was identified and biochemically characterized. This enzyme (termed GlcNAc-PDase) shows remarkable substrate preference for GlcNAc-6-PC and GlcNAc-6-PE, with little or no activity on other zwitterion-modified hexoses. The identified GlcNAc-PDase protein sequence is a member of the large endonuclease/exonuclease/phosphatase superfamily where it defines a distinct subfamily of related sequences of previously unknown function, mostly from Clostridium bacteria species. Finally, we demonstrate use of GlcNAc-PDase to confirm the presence of GlcNAc-6-PC in N-glycans and GSLs of the parasitic nematode Brugia malayi in a glycoanalytical workflow.

Enhanced expression and purification of nucleotide-specific ribonucleases MC1 and Cusativin.

Combinations of ribonucleases (RNases) are commonly used to digest RNA into oligoribonucleotide fragments prior to liquid chromatography-mass spectrometry (LC-MS) analysis. The distribution of the RNase target sequences or nucleobase sites within an RNA molecule is critical for achieving a high mapping coverage. Cusativin and MC1 are nucleotide-specific endoribonucleases encoded in the cucumber and bitter melon genomes, respectively. Their high specificity for cytidine (Cusativin) and uridine (MC1) make them ideal molecular biology tools for RNA modification mapping. However, heterogenous recombinant expression of either enzyme has been challenging because of their high toxicity to expression hosts and the requirement of posttranslational modifications. Here, we present two highly efficient and time-saving protocols that overcome these hurdles and enhance the expression and purification of these RNases. We first purified MC1 and Cusativin from bacteria by expressing and shuttling both enzymes to the periplasm as MBP-fusion proteins in T7 Express lysY/IqE. coli strain at low temperature. The RNases were enriched using amylose affinity chromatography, followed by a subsequent purification via a C-terminal 6xHIS tag. This fast, two-step purification allows for the purification of highly active recombinant RNases significantly surpassing yields reported in previous studies. In addition, we expressed and purified a Cusativin-CBD fusion enzyme in P. pastoris using chitin magnetic beads. Both Cusativin variants exhibited a similar sequence preference, suggesting that neither posttranslational modifications nor the epitope-tags have a substantial effect on the sequence specificity of the enzyme.

Combining functional metagenomics and glycoanalytics to identify enzymes that facilitate structural characterization of sulfated N-glycans.

BACKGROUND: Sulfate modification of N-glycans is important for several biological functions such as clearance of pituitary hormones or immunoregulation. Yet, the prevalence of this N-glycan modification and its functions remain largely unexplored. Characterization of N-glycans bearing sulfate modifications is hampered in part by a lack of enzymes that enable site-specific detection of N-glycan sulfation. In this study, we used functional metagenomic screening to identify enzymes that act upon sulfated N-acetylglucosamine (GlcNAc). Using multiplexed capillary gel electrophoresis with laser-induced fluorescence detection (xCGE-LIF) -based glycoanalysis we proved their ability to act upon GlcNAc-6-SO4 on N-glycans. RESULTS: Our screen identified a sugar-specific sulfatase that specifically removes sulfate from GlcNAc-6-SO4 when it is in a terminal position on an N-glycan. Additionally, in the absence of calcium, this sulfatase binds to the sulfated glycan but does not remove the sulfate group, suggesting it could be used for selective isolation of sulfated N-glycans. Further, we describe isolation of a sulfate-dependent hexosaminidase that removes intact GlcNAc-6-SO4 (but not asulfated GlcNAc) from a terminal position on N-glycans. Finally, the use of these enzymes to detect the presence of sulfated N-glycans by xCGE-LIF is demonstrated. CONCLUSION: The present study demonstrates the feasibility of using functional metagenomic screening combined with glycoanalytics to discover enzymes that act upon chemical modifications of glycans. The discovered enzymes represent new specificities that can help resolve the presence of GlcNAc-6-SO4 in N-glycan structural analyses.

Functional metagenomics identifies an exosialidase with an inverting catalytic mechanism that defines a new glycoside hydrolase family (GH156).

Exosialidases are glycoside hydrolases that remove a single terminal sialic acid residue from oligosaccharides. They are widely distributed in biology, having been found in prokaryotes, eukaryotes, and certain viruses. Most characterized prokaryotic sialidases are from organisms that are pathogenic or commensal with mammals. However, in this study, we used functional metagenomic screening to seek microbial sialidases encoded by environmental DNA isolated from an extreme ecological niche, a thermal spring. Using recombinant expression of potential exosialidase candidates and a fluorogenic sialidase substrate, we discovered an exosialidase having no homology to known sialidases. Phylogenetic analysis indicated that this protein is a member of a small family of bacterial proteins of previously unknown function. Proton NMR revealed that this enzyme functions via an inverting catalytic mechanism, a biochemical property that is distinct from those of known exosialidases. This unique inverting exosialidase defines a new CAZy glycoside hydrolase family we have designated GH156.

Prolonged action potential duration and dynamic transmural action potential duration heterogeneity underlie vulnerability to ventricular tachycardia in patients undergoing ventricular tachycardia ablation.

AIMS: Differences of action potential duration (APD) in regions of myocardial scar and their borderzones are poorly defined in the intact human heart. Heterogeneities in APD may play an important role in the generation of ventricular tachycardia (VT) by creating regions of functional block. We aimed to investigate the transmural and planar differences of APD in patients admitted for VT ablation. METHODS AND RESULTS: Six patients (median age 53 years, five male); (median ejection fraction 35%), were studied. Endocardial (Endo) and epicardial (Epi) 3D electroanatomic mapping was performed. A bipolar voltage of <0.5 mV was defined as dense scar, 0.5-1.5 mV as scar borderzone, and >1.5 mV as normal. Decapolar catheters were positioned transmurally across the scar borderzone to assess differences of APD and repolarization time (RT) during restitution pacing from Endo and Epi. Epi APD was 173 ms in normal tissue vs. 187 ms at scar borderzone and 210 ms in dense scar (P < 0.001). Endocardial APD was 210 ms in normal tissue vs. 222 ms in the scar borderzone and 238 ms in dense scar (P < 0.01). This resulted in significant transmural RT dispersion (ΔRT 22 ms across dense transmural scar vs. 5 ms in normal transmural tissue, P < 0.001), dependent on the scar characteristics in the Endo and Epi, and the pacing site. CONCLUSION: Areas of myocardial scar have prolonged APD compared with normal tissue. Heterogeneity of regional transmural and planar APD result in localized dispersion of repolarization, which may play an important role in initiating VT.

C-C Motif Chemokine 5 Attenuates Angiotensin II-Dependent Kidney Injury by Limiting Renal Macrophage Infiltration.

Inappropriate activation of the renin angiotensin system (RAS) is a key contributor to the pathogenesis of essential hypertension. During RAS activation, infiltration of immune cells into the kidney exacerbates hypertension and renal injury. However, the mechanisms underpinning the accumulation of mononuclear cells in the kidney after RAS stimulation remain unclear. C-C motif chemokine 5 (CCL5) drives recruitment of macrophages and T lymphocytes into injured tissues, and we have found that RAS activation induces CCL5 expression in the kidney during the pathogenesis of hypertension and renal fibrosis. We therefore evaluated the contribution of CCL5 to renal damage and fibrosis in hypertensive and normotensive models of RAS stimulation. Surprisingly, during angiotensin II-induced hypertension, CCL5-deficient (knockout, KO) mice exhibited markedly augmented kidney damage, macrophage infiltration, and expression of proinflammatory macrophage cytokines compared with wild-type controls. When subjected to the normotensive unilateral ureteral obstruction model of endogenous RAS activation, CCL5 KO mice similarly developed more severe renal fibrosis and greater accumulation of macrophages in the kidney, congruent with enhanced renal expression of the macrophage chemokine CCL2. In turn, pharmacologic inhibition of CCL2 abrogated the differences between CCL5 KO and wild-type mice in kidney fibrosis and macrophage infiltration after unilateral ureteral obstruction. These data indicate that CCL5 paradoxically limits macrophage accumulation in the injured kidney during RAS activation by constraining the proinflammatory actions of CCL2.

Noninvasive proteome analysis of psoriatic stratum corneum reflects pathophysiological pathways and is useful for drug profiling.

BACKGROUND: Protein expression is disturbed in the psoriatic stratum corneum (SC). Noninvasive methods for the description of pathophysiological changes and drug profiling in psoriasis are desirable. OBJECTIVES: Undertake large-scale noninvasive protein expression studies in psoriatic SC to identify biomarkers of pathophysiological processes and use them for drug profiling. METHODS: Psoriatic SC was harvested through repetitive tape-stripping. Nonlesional and lesional SC, as well as vehicle-treated and drug-treated lesional SC samples were collected. Protein extracts from nonlesional and lesional skin biopsies were used for comparison. Calcipotriol-betamethasone (CB) was used as a reference medication. Proteins extracted from pooled tape strips were quantified using mass spectrometry (MS), Western blotting, enzyme-linked immunosorbent assay and Luminex technologies. RESULTS: MS-based methods identified 140 proteins differentially expressed in psoriatic SC. Epidermis development, glycolysis, regulation of apoptosis, cytoskeleton organization and peptide cross-linking were modulated, all reflecting perturbed epidermal differentiation. Using antibody-based techniques, increased levels of sICAM1, of CXCL1- and CXCL8-attracting neutrophils, of CXCL10- and CCL4-attracting T helper (Th) 1 cells, and of CCL2- and CCL4-attracting monocytes and dendritic cells were observed. Quantification of the Th1 and Th17 markers tumour necrosis factor, interleukin (IL) 12B, IL17A and IL17F in lesional SC was successful, while the Th2 cytokines IL4, IL5 and IL13, not involved in the disease process, were not detected. The pruritic cytokine IL31 was detected in lesional SC. CXCL1, CXCL8, CXCL10 and sICAM were used to investigate disease remission, ranking three topical treatments according to their known clinical efficacy. CONCLUSIONS: Protein biomarker quantification in psoriatic SC detects key pathophysiological mechanisms and enables noninvasive drug profiling in translational medicine settings.

Safety and mid-term outcome of catheter ablation of ventricular tachycardia in octogenarians.

AIMS: Radiofrequency (RF) catheter ablation (CA) is superior to standard medical therapy in controlling recurrent ventricular tachycardia (VT). The majority of procedures have been performed in a middle-aged population. The outcome of VT ablation in the elderly has not been described. METHODS AND RESULTS: We retrospectively studied the outcome and safety of CA of VT in octogenarians performed in four European centres. The population consisted of patients presenting with recurrent VT refractory to medical therapy. Patients aged over 80 years were compared with younger patients undergoing CA. Clinical characteristics, procedural data, complications, and outcomes were examined. Implantable cardioverter-defibrillator (ICD) therapy data were collected. A total of 54 consecutive octogenarian patients underwent RF CA of VT and represented the study group (42 males, age 82.8 ± 2.7 years) compared with a control group of 104 younger patients (85 males, age 66.7 ± 8.9 years). Mean follow-up was 33 ± 48 months. Implantable cardioverter-defibrillators were present in 81 and 86% of patients, respectively (P = 0.93). Left ventricular ejection fraction was 29% ± 8.2 in octogenarians vs. 34% ± 10.2 in the younger group (P < 0.01). More major complications occurred in octogenarians (18 vs. 2%, P < 0.01). During follow-up, there were more ICD shocks in the octogenarians (28 vs. 15%, P < 0.01). The Kaplan-Meier curve of survival after VT ablation confirms comparable survival rates at 1 year, but the elderly have poor survival in the mid-term. Survival in the elderly post VT ablation is comparable with that in an age-matched cohort with ICDs but no VT storm. CONCLUSION: Octogenarians undergoing CA of VT have more risk factors, higher risk of complications and ICD shocks, but demonstrate comparable short-term survival rates.

Competing Actions of Type 1 Angiotensin II Receptors Expressed on T Lymphocytes and Kidney Epithelium during Cisplatin-Induced AKI.

Inappropriate activation of the renin-angiotensin system (RAS) contributes to many CKDs. However, the role of the RAS in modulating AKI requires elucidation, particularly because stimulating type 1 angiotensin II (AT1) receptors in the kidney or circulating inflammatory cells can have opposing effects on the generation of inflammatory mediators that underpin the pathogenesis of AKI. For example, TNF-α is a fundamental driver of cisplatin nephrotoxicity, and generation of TNF-α is suppressed or enhanced by AT1 receptor signaling in T lymphocytes or the distal nephron, respectively. In this study, cell tracking experiments with CD4-Cre mT/mG reporter mice revealed robust infiltration of T lymphocytes into the kidney after cisplatin injection. Notably, knockout of AT1 receptors on T lymphocytes exacerbated the severity of cisplatin-induced AKI and enhanced the cisplatin-induced increase in TNF-α levels locally within the kidney and in the systemic circulation. In contrast, knockout of AT1 receptors on kidney epithelial cells ameliorated the severity of AKI and suppressed local and systemic TNF-α production induced by cisplatin. Finally, disrupting TNF-α production specifically within the renal tubular epithelium attenuated the AKI and the increase in circulating TNF-α levels induced by cisplatin. These results illustrate discrepant tissue-specific effects of RAS stimulation on cisplatin nephrotoxicity and raise the concern that inflammatory mediators produced by renal parenchymal cells may influence the function of remote organs by altering systemic cytokine levels. Our findings suggest selective inhibition of AT1 receptors within the nephron as a promising intervention for protecting patients from cisplatin-induced nephrotoxicity.

Experimental inhibition of porcupine-mediated Wnt O-acylation attenuates kidney fibrosis.

Activated Wnt signaling is critical in the pathogenesis of renal fibrosis, a final common pathway for most forms of chronic kidney disease. Therapeutic intervention by inhibition of individual Wnts or downstream Wnt/ß-catenin signaling has been proposed, but these approaches do not interrupt the functions of all Wnts nor block non-canonical Wnt signaling pathways. Alternatively, an orally bioavailable small molecule, Wnt-C59, blocks the catalytic activity of the Wnt-acyl transferase porcupine, and thereby prevents secretion of all Wnt isoforms. We found that inhibiting porcupine dramatically attenuates kidney fibrosis in the murine unilateral ureteral obstruction model. Wnt-C59 treatment similarly blunts collagen mRNA expression in the obstructed kidney. Consistent with its actions to broadly arrest Wnt signaling, porcupine inhibition reduces expression of Wnt target genes and bolsters nuclear exclusion of ß-catenin in the kidney following ureteral obstruction. Importantly, prevention of Wnt secretion by Wnt-C59 blunts expression of inflammatory cytokines in the obstructed kidney that otherwise provoke a positive feedback loop of Wnt expression in collagen-producing fibroblasts and epithelial cells. Thus, therapeutic targeting of porcupine abrogates kidney fibrosis not only by overcoming the redundancy of individual Wnt isoforms but also by preventing upstream cytokine-induced Wnt generation. These findings reveal a novel therapeutic maneuver to protect the kidney from fibrosis by interrupting a pathogenic crosstalk loop between locally generated inflammatory cytokines and the Wnt/ß-catenin signaling pathway.

Use of a contact force-sensing ablation catheter with advanced catheter location significantly reduces fluoroscopy time and radiation dose in catheter ablation of atrial fibrillation.

AIMS: The aim of this study was to evaluate the 'real-world' impact of a novel contact force (CF)-sensing (SmartTouch™, Biosense Webster, Diamond Bar, CA, USA) catheter coupled with an advanced catheter location (ACL) system on fluoroscopy time and fluoroscopy dose during atrial fibrillation (AF) ablation. METHODS AND RESULTS: This was a retrospective observational cohort study of prospectively collected data of 1515 consecutive patients undergoing paroxysmal AF (PAF) and persistent AF (PerAF) ablation at a single institution between 2009 and 2014. Patients undergoing AF ablation with the SmartTouch catheter and the ACL system (SmartTouch group, n = 510) were compared with those undergoing AF ablation without this technology (control group, n = 1005). The primary outcomes were total fluoroscopy time (min) and fluoroscopy dose as measured by the dose-area product (mGy cm(2)). Secondary endpoints included total procedure time, total ablation time, and major cardiac complications (tamponade, pericardial effusion, and urgent cardiac surgery). The SmartTouch group had significantly lower fluoroscopy times (9.5 vs. 41 min, P < 0.001), radiation doses (1044 vs. 3571 mGy cm(2), P < 0.001), and shorter procedural time (195 vs. 240 min, P < 0.001) when compared with the control group. This was statistically significant for both PAF and PerAF ablations and for both de novo and redo AF procedures. After a learning curve, a median fluoroscopy time of 3.5 min (interquartile range 6) for all AF ablations was achieved. There was no difference in the rate of cardiac complications (∼ 1.5%). CONCLUSION: SmartTouch™ CF-sensing catheter use with ACL™ during AF ablation significantly reduces fluoroscopy times by 77%, radiation dose by 71%, and procedural time by 19% but does not improve overall safety or the risk of cardiac complications.

Factors affecting catheter contact in the human left atrium and their impact on ablation efficacy.

INTRODUCTION: Preclinical work suggests factors including catheter orientation and contact consistency during individual radiofrequency ablations influence lesion size. Our aim was to investigate factors affecting catheter contact in the left atrium (LA) and their effects on ablation. METHODS AND RESULTS: A total of 2,298 8-second static LA mapping points were studied in 30 patients undergoing ablation for AF (16 in AF, 14 sinus rhythm [SR], 18 remote robotic navigation [RRN] procedures) using a contact force (CF) sensing catheter. CF variability (CFV: difference between 20 Hz-sampled CF waveform mean peak and trough) increased with mean CF, Spearman's ρ = 0.6, P < 0.005. Catheter drift correlated weakly with CF (Pearson's correlation -0.06, P = 0.005). CFV was higher in SR than AF and with RRN (P < 0.001). In AF, there was less catheter drift for RRN than manual navigation points but the converse was true in SR. In 747 static 30 second LA ablations, the influence of contact parameters on ablation efficacy was compared by multivariate analysis of impedance drop during ablation: a lesser drop suggesting reduced efficacy. For a given force time integral (FTI), increased CFV (>5 g) and locational drift (>3.5 mm), perpendicular contact, SR and RRN usage were associated with a lesser impedance drop with ablation (P < 0.005 for each), suggesting reduced efficacy. CONCLUSIONS: Beyond the FTI, the quality of catheter contact influences ablation efficacy, and clinical catheter contact is affected by multiple factors, including the atrial rhythm and catheter navigation mode. Maximal efficacy is provided by parallel contact with CFV ≤5 g, catheter drift ≤3.5 mm, and manual navigation.

A novel role for type 1 angiotensin receptors on T lymphocytes to limit target organ damage in hypertension.

RATIONALE: Human clinical trials using type 1 angiotensin (AT(1)) receptor antagonists indicate that angiotensin II is a critical mediator of cardiovascular and renal disease. However, recent studies have suggested that individual tissue pools of AT(1) receptors may have divergent effects on target organ damage in hypertension. OBJECTIVE: We examined the role of AT(1) receptors on T lymphocytes in the pathogenesis of hypertension and its complications. METHODS AND RESULTS: Deficiency of AT(1) receptors on T cells potentiated kidney injury during hypertension with exaggerated renal expression of chemokines and enhanced accumulation of T cells in the kidney. Kidneys and purified CD4(+) T cells from "T cell knockout" mice lacking AT(1) receptors on T lymphocytes had augmented expression of Th1-associated cytokines including interferon-γ and tumor necrosis factor-α. Within T lymphocytes, the transcription factors T-bet and GATA-3 promote differentiation toward the Th1 and Th2 lineages, respectively, and AT(1) receptor-deficient CD4(+) T cells had enhanced T-bet/GATA-3 expression ratios favoring induction of the Th1 response. Inversely, mice that were unable to mount a Th1 response due to T-bet deficiency were protected from kidney injury in our hypertension model. CONCLUSIONS: The current studies identify an unexpected role for AT(1) receptors on T lymphocytes to protect the kidney in the setting of hypertension by favorably modulating CD4(+) T helper cell differentiation.

Assessment of adequate safety margin using single coupling interval-upper limit of vulnerability test.

PURPOSE: Upper limit of vulnerability (ULV) testing using T-wave scanning shocks at multiple coupling intervals correlates well with defibrillation threshold (DFT), but remains underutilized in clinical practice. We measured DFT and ULV at a single coupling interval (SCI), with the aim to identify adequate safety margin at a coupling interval that correlates best with DFT. METHODS: Consecutive patients undergoing implantable cardioverter defibrillator implantation underwent simultaneous SCI-ULV and DFT assessment. Following a drive train of 400 ms, a T-wave-coupled shock was delivered. To minimize shocks, patients were randomized to programmed shock at 20 ms before peak (Group I), at peak (Group II), or 20 ms after peak (Group III) of T wave. An initial T-wave test shock at 9 J was followed by ±2 J shocks, until SCI-ULV was ascertained. Device rescue shocks were programmed at test shock +2 J and +4 J shocks followed by external rescue shock. RESULTS: There were 200 patients: 66 patients in Group I, 67 patients each in Groups II and III; mean age was 68.9 ± 12.4 years; 75% of patients men, 66% with ischemic heart disease and mean ejection fraction of 27.1 ± 7.1%. Overall, the mean number of ventricular fibrillation induction was 1.39 ± 0.8, mean SCI-ULV energy was 7.97 ± 3.39 J, and mean DFT was 8.68 ± 3.19 J. The correlation between SCI-ULV and DFT improved from Group I to Group III and was best in Group III (r(2) = 0.689). There were no major adverse events. CONCLUSIONS: SCI-ULV measured 20 ms after the peak of the T wave correlates well with DFT for assessment of adequate safety margin.

Distal Ventricular Pacing for Drug-Refractory Mid-Cavity Obstructive Hypertrophic Cardiomyopathy: A Randomized, Placebo-Controlled Trial of Personalized Pacing.

BACKGROUND: Patients with refractory, symptomatic left ventricular (LV) mid-cavity obstructive (LVMCO) hypertrophic cardiomyopathy have few therapeutic options. Right ventricular pacing is associated with modest hemodynamic and symptomatic improvement, and LV pacing pilot data suggest therapeutic potential. We hypothesized that site-specific pacing would reduce LVMCO gradients and improve symptoms. METHODS: Patients with symptomatic-drug-refractory LVMCO were recruited for a randomized, blinded trial of personalized prescription of pacing (PPoP). Multiple LV and apical right ventricular pacing sites were assessed during an invasive hemodynamic study of multisite pacing. Patient-specific pacing-site and atrioventricular delays, defining PPoP, were selected on the basis of LVMCO gradient reduction and acceptable pacing parameters. Patients were randomized to 6 months of active PPoP or backup pacing in a crossover design. The primary outcome examined invasive gradient change with best-site pacing. Secondary outcomes assessed quality of life and exercise following randomization to PPoP. RESULTS: A total of 17 patients were recruited; 16 of whom met primary end points. Baseline New York Heart Association was 3±0.6, despite optimal medical therapy. Hemodynamic effects were assessed during pacing at the right ventricular apex and at a mean of 8 LV sites. The gradients in all 16 patients fell with pacing, with maximum gradient reduction achieved via LV pacing in 14 (88%) patients and right ventricular apex in 2. The mean baseline gradient of 80±29 mm Hg fell to 31±21 mm Hg with best-site pacing, a 60% reduction (P<0.0001). One cardiac vein perforation occurred in 1 case, and 15 subjects entered crossover; 2 withdrawals occurred during crossover. Of the 13 completing crossover, 9 (69%) chose active pacing in PPoP configuration as preferred setting. PPoP was associated with improved 6-minute walking test performance (328.5±99.9 versus 285.8±105.5 m; P=0.018); other outcome measures also indicated benefit with PPoP. CONCLUSIONS: In a randomized placebo-controlled trial, PPoP reduces obstruction and improves exercise performance in severely symptomatic patients with LVMCO. REGISTRATION: URL: https://clinicaltrials.gov/study; Unique Identifier: NCT03450252.

Role of vaptans in the management of hyponatremia.

Hyponatremia, the most commonly encountered electrolyte abnormality, affects as many as 30% of hospitalized patients. It is a powerful predictor of poor outcomes, especially in patients with congestive heart failure or cirrhosis. The failure to excrete electrolyte-free water that results from persistent secretion of antidiuretic hormone despite low serum osmolality usually underlies the development of hyponatremia. Treatment depends on several factors, including the cause, overall volume status of the patient, severity of hyponatremic symptoms, and duration of hyponatremia at presentation. This review focuses on the role of the vasopressin receptor antagonists, or vaptans, in the treatment of hyponatremia. These recently introduced agents have the unique ability to induce an aquaresis, the excretion of electrolyte-free water without accompanying solutes. After a brief historical perspective and discussion of pharmacologic characteristics of vaptans, we review the accumulated experience with vaptans for the treatment of hyponatremia. Vaptans have been shown to increase serum sodium concentrations in patients with euvolemic or hypervolemic hyponatremia in a reproducible manner, but their safe use requires full understanding of their indications and contraindications.

The AMP deaminase of the mollusk Helix pomatia is an unexpected member of the adenosine deaminase-related growth factor (ADGF) family.

We report here the first occurrence of an adenosine deaminase-related growth factor (ADGF) that deaminates adenosine 5' monophosphate (AMP) in preference to adenosine. The ADGFs are a group of secreted deaminases found throughout the animal kingdom that affect the extracellular concentration of adenosine by converting it to inosine. The AMP deaminase studied here was first isolated and biochemically characterized from the roman snail Helix pomatia in 1983. Determination of the amino acid sequence of the AMP deaminase enabled sequence comparisons to protein databases and revealed it as a member of the ADGF family. Cloning and expression of its cDNA in Pichia pastoris allowed the comparison of the biochemical characteristics of the native and recombinant forms of the enzyme and confirmed they correspond to the previously reported activity. Uncharacteristically, the H. pomatia AMP deaminase was determined to be dissimilar to the AMP deaminase family by sequence comparison while demonstrating similarity to the ADGFs despite having AMP as its preferred substrate rather than adenosine.

A Comparative Study on Therapeutic Efficacy of Autologous Platelet-rich Plasma, Autologous Platelet-rich Fibrin Matrix, Recombinant Human Epidermal Growth Factor, and Collagen Particles in Nonhealing Leg Ulcers.

Background: Nonhealing leg ulcers are challenging to manage and cause significant patient morbidity. To promote healing, newer techniques focus on delivering/enhancing dermal matrix components. Aim: The aim of this study was to compare the therapeutic efficacy of autologous platelet-rich plasma (PRP), autologous platelet-rich fibrin matrix (PRFM), recombinant human epidermal growth factor (rhEGF), and collagen particles in treating nonhealing leg ulcers. Materials and Methods: Open, randomized prospective study was conducted in a single tertiary center over 2 years where after fulfilling the criteria, randomization was done into four groups. Group A: Autologous PRP (double spin, manual method, weekly); Group B: Autologous PRFM (weekly); Group C: rhEGF (daily application); and Group D: Collagen particles (weekly) along with cleansing, debris removal, and wound dressing. Treatment endpoints were complete healing/6 months of treatment, whichever was earlier. Follow-up was done two weekly by clinical assessment, photographs, and measurement of the ulcer area. Epi info 7 software was used for statistical analysis. Results: A total of 48 patients completed the study, 12 in each group, with mean age: 42.37 ± 4.56 years and male-to-female ratio 2.6:1. Underlying etiology was varicosities (43.75%), traumatic (25%), diabetes (22.91%), and leprosy (8.34%). At baseline, all groups were comparable in terms of patient and ulcer characteristics. Complete healing was seen in 79.17% at the end of 12 weeks: 91.67% of patients from Groups A and B each, and 66.67% from Groups C and D each. The mean time to complete healing was 6.9 ± 2.5 weeks, the least in Group B (4.73 ± 2.3 weeks). Differences between excellent (≥75%) ulcer healing across all groups were statistically significant at the end of 8 weeks where Group B showed maximum improvement. No major adverse events were seen. Conclusion: PRFM resulted in relatively faster ulcer healing compared with other modalities.

Atrioventricular nodal ablation is an effective management strategy for atrial fibrillation in patients with hypertrophic cardiomyopathy.

BACKGROUND: Atrial fibrillation (AF) is common in patients with hypertrophic cardiomyopathy (HCM) and can be challenging to manage. Atrioventricular nodal (AVN) ablation may be an effective management strategy for AF in these patients. OBJECTIVE: The purpose of this study was to assess the efficacy of AVN ablation in HCM patients who have failed medical therapy and/or catheter ablation for AF. METHODS: A multicenter study with retrospective analysis of a prospectively collated HCM registry was performed. AVN ablation patients were identified. Baseline characteristics and device and procedural indications were collected. Symptoms defined by New York Heart Association and European Heart Rhythm Association classification and echocardiographic findings during follow-up were assessed. RESULTS: Fifty-nine patients were included in the study. Indications for AVN ablation were 6 (10.2%) inappropriate implantable cardioverter-defibrillator shock, 35 (59.3%) ineffective rate control, and 18 (30.5%) to regularize rhythm for symptom improvement. During post-AVN ablation follow-up of 79.4 ± 61.1 months, left ventricular ejection fraction (LVEF) remained stable (pre-LVEF 48.9% ± 12.6% vs post-LVEF 50.1% ± 10.1%; P = .29), even in those without a cardiac resynchronization therapy (CRT) device (pre-LVEF 54.3% ± 8.0% vs post-LVEF 53.8% ± 8.0%; P = .65). Forty-nine patients (83.1%) reported an improvement in symptoms regardless of AF type (17/21 [81.0%] paroxysmal vs 32/38 [84.2%] persistent; P = 1.00), presence of baseline left ventricular impairment (22/26 [84.6%] LVEF ≤50% vs 27/33 [81.8%] LVEF ≥50%; P = 1.00) or CRT device (27/32 [84.4%] CRT vs 22/27 [81.5%] no CRT; P = 1.00). Symptoms improved in 16 patients (89.0%) who underwent AVN ablation to regularize rhythm. CONCLUSION: AVN ablation improved symptoms without impacting left ventricular function in the majority of patients. The data suggest that AVN ablation is an effective and safe management approach for AF in HCM and should be further evaluated in larger prospective studies.