•The block inception time for kiloHertz frequency alternating current nerve block has not been measured previously.•A novel method was created to extract the block inception time from muscle force ...measurements.•The block inception time was found to be on average 5 ms to 10 ms, with the most rapid inception being 2.5 ms to 5 ms.•Block inception times for KHFAC nerve block were significant more rapid than previously estimated.
Kilohertz frequency alternating currents (KHFAC) produce rapid nerve conduction block of mammalian peripheral nerves and have potential clinical applications in reducing nerve hyperactivity. However, there are no experimental measurements of the block inception time (BIT) for the complete block of mammalian motor axons, i.e. the time from the start of delivery of the KHFAC to the axons reaching a fully blocked state.
A “counted cycles” method (CCM) was designed to exploit characteristics of the onset response, which is typical of KHFAC block, to measure the BIT with a millisecond time resolution. Randomized and repeated experiments were conducted in an in-vivo rodent model, using trains of KHFAC over a range of complete cycle counts at three frequencies (10, 20, and 40 kHz).
Complete motor nerve conduction block was obtained in the rat sciatic nerve (N = 4) with an average BIT range of 5 ms–10 ms. The fastest BIT measured was 2.5 ms–5 ms. There was no statistical difference between the block inception times for the three frequencies tested.
There are no comparable methods to measure the KHFAC BIT.
The KHFAC BIT is faster than previously estimated. KHFAC motor nerve block is established in milliseconds. These results may assist in the design of methods to eliminate the onset response produced by KHFAC nerve block.
Drug Mode of Action and hERG‐Related Safety
Introduction
Since the discovery of the link that exists between drug‐induced hERG inhibition and Torsade de Pointes (TdP), extreme attention has been ...given to avoid new drugs inhibiting this channel. hERG inhibition is routinely screened for in new drugs and, typically, IC50 values are compared to projected plasma concentrations to define a safety margin.
Methods and Results
We aimed to show that drugs with similar hERG potency are not uniformly pro‐arrhythmic—this depends on the drug binding kinetics and mode of action (trapped or not) rather than the IC50 value only. We used a mathematical model of hERG and its related encoded current IKr to simulate drug binding in different configurations. Expression systems mimicking the screening process were first investigated. hERG model was then incorporated into a canine action potential (AP) and tissue model to study the impact of drug binding configurations on AP and pseudo‐ECG (QT interval prolongation). Our data show that: (1) trapped and not trapped configurations and different binding kinetics could be identified during hERG screening; (2) slow binding, not trapped drugs, induced less AP prolongation and minimal QT interval prolongation (4.7%) at a concentration equal to the IC50 whereas maximal pro‐arrhythmic risk was observed for trapped drugs at the same concentration (QT interval prolongation, 23.1%).
Conclusion
Our study demonstrates the need for screening for hERG binding configurations rather than potency alone. It also demonstrates the potential link between hERG, drug mode of action and TdP, and the need to question the current regulatory guidance.
Cell lines expressing ion channels (IC) and the advent of plate-based electrophysiology device have enabled a molecular understanding of the action potential (AP) as a means of early QT assessment. ...We sought to develop an in silico AP (isAP) model that provides an assessment of the effect of a compound on the myocyte AP duration (APD) using concentration-effect curve data from a panel of five ICs (hNav1.5, hCav1.2, hKv4.3/hKChIP2.2, hKv7.1/hminK, hKv11.1). A test set of 53 compounds was selected to cover a range of selective and mixed IC modulators that were tested for their effects on optically measured APD. A threshold of >10% change in APD at 90% repolarization (APD(90)) was used to signify an effect at the top test concentration. To capture the variations observed in left ventricular midmyocardial myocyte APD data from 19 different dogs, the isAP model was calibrated to produce an ensemble of 19 model variants that could capture the shape and form of the APs and also quantitatively replicate dofetilide- and diltiazem-induced APD(90) changes. Provided with IC panel data only, the isAP model was then used, blinded, to predict APD(90) changes greater than 10%. At a simulated concentration of 30 μM and based on a criterion that six of the variants had to agree, isAP prediction was scored as showing greater than 80% predictivity of compound activity. Thus, early in drug discovery, the isAP model allows integrating separate IC data and is amenable to the throughput required for use as a virtual screen.
New Findings
What is the central question of this study?
Type 2 diabetes is associated with a higher rate of ventricular arrhythmias compared with the non‐diabetic population, but the associated ...myocardial gene expression changes are unknown; furthermore, it is also unknown whether any changes are attributable to chronic hyperglycaemia or are a consequence of structural changes.
What is the main finding and its importance?
We found downregulation of left ventricular ERG gene expression and increased NCX1 gene expression in humans with type 2 diabetes compared with control patients with comparable left ventricular hypertrophy and possible myocardial fibrosis. This was associated with QT interval prolongation. Diabetes and associated chronic hyperglycaemia may therefore promote ventricular arrhythmogenesis independently of structural changes.
Type 2 diabetes is associated with a higher rate of ventricular arrhythmias, and this is hypothesized to be independent of coronary artery disease or hypertension. To investigate further, we compared changes in left ventricular myocardial gene expression in type 2 diabetes patients with patients in a control group with left ventricular hypertrophy. Nine control patients and seven patients with type 2 diabetes with aortic stenosis undergoing aortic valve replacement had standard ECGs, signal‐averaged ECGs and echocardiograms before surgery. During surgery, a left ventricular biopsy was taken, and mRNA expressions for genes relevant to the cardiac action potential were estimated by RT‐PCR. Mathematical modelling of the action potential and calcium transient was undertaken using the O'Hara–Rudy model using scaled changes in gene expression. Echocardiography revealed similar values for left ventricular size, filling pressures and ejection fraction between groups. No difference was seen in positive signal‐averaged ECGs between groups, but the standard ECG demonstrated a prolonged QT interval in the diabetes group. Gene expression of KCNH2 and KCNJ3 were lower in the diabetes group, whereas KCNJ2, KCNJ5 and SLC8A1 expression were higher. Modelling suggested that these changes would lead to prolongation of the action potential duration with generation of early after‐depolarizations secondary to a reduction in density of the rapid delayed rectifier K+ current and increased Na+–Ca2+ exchange current. These data suggest that diabetes leads to pro‐arrythmogenic changes in myocardial gene expression independently of left ventricular hypertrophy or fibrosis in an elderly population.
To present final, 2-year data from randomized comparison of an expanded polytetrafluoroethylene stent graft (SG) and percutaneous transluminal angioplasty (PTA) for treatment of arteriovenous graft ...(AVG) anastomotic stenoses.
A 28-site, prospective, controlled US study enrolled 270 patients with malfunctioning AVG anastomotic stenoses of ≥ 50%; 138 patients underwent SG placement, and 132 underwent PTA alone. Follow-up imaging and intervention were event-driven.
The study was completed by 191 patients (97 SG, 94 PTA). Five patients were lost to follow-up or withdrew; 74 patients died during the study (38 SG, 36 PTA). At 12 months, treatment area primary patency (TAPP) was SG 47.6% versus PTA 24.8% (P < .001), access circuit primary patency (ACPP) was SG 24% versus PTA 11% (P = .007), and index of patency function (IPF) was SG 5.2 months/intervention ± 4.1 versus PTA 4.4 months/intervention ± 3.5 (P = .009). At 24 months, TAPP was SG 26.9% versus PTA 13.5% (P < .001), ACPP was SG 9.5% versus PTA 5.5% (P = .01), and IPF was SG 7.1 months/intervention ± 7.0 versus PTA 5.3 months/intervention ± 5.2; estimated number of reinterventions before graft abandonment was 3.4 for SG patients versus 4.3 for PTA patients. There were no significant differences in adverse events (P > .05) except for restenosis requiring reintervention rates of 82.6% in PTA patients versus 63.0% in SG patients (P < .001).
At 2 years, SG use provided a sustained, greater than 2-fold advantage over PTA in treatment area and overall access patency. Time to subsequent intervention was longer in the SG group.
Epidural glucocorticoid injections are widely used to treat symptoms of lumbar spinal stenosis, a common cause of pain and disability in older adults. However, rigorous data are lacking regarding the ...effectiveness and safety of these injections.
In a double-blind, multisite trial, we randomly assigned 400 patients who had lumbar central spinal stenosis and moderate-to-severe leg pain and disability to receive epidural injections of glucocorticoids plus lidocaine or lidocaine alone. The patients received one or two injections before the primary outcome evaluation, performed 6 weeks after randomization and the first injection. The primary outcomes were the score on the Roland-Morris Disability Questionnaire (RMDQ, in which scores range from 0 to 24, with higher scores indicating greater physical disability) and the rating of the intensity of leg pain (on a scale from 0 to 10, with 0 indicating no pain and 10 indicating "pain as bad as you can imagine").
At 6 weeks, there were no significant between-group differences in the RMDQ score (adjusted difference in the average treatment effect between the glucocorticoid-lidocaine group and the lidocaine-alone group, -1.0 points; 95% confidence interval CI, -2.1 to 0.1; P=0.07) or the intensity of leg pain (adjusted difference in the average treatment effect, -0.2 points; 95% CI, -0.8 to 0.4; P=0.48). A prespecified secondary subgroup analysis with stratification according to type of injection (interlaminar vs. transforaminal) likewise showed no significant differences at 6 weeks.
In the treatment of lumbar spinal stenosis, epidural injection of glucocorticoids plus lidocaine offered minimal or no short-term benefit as compared with epidural injection of lidocaine alone. (Funded by the Agency for Healthcare Research and Quality; ClinicalTrials.gov number, NCT01238536.).
Abstract
Background and purpose
Heart failure (HF) is characterised by generalised dysfunction of the cardiac conduction system (CCS). Ion channel and structural remodelling in the CCS have been ...widely demonstrated in animal models of cardiovascular disease. As Purkinje fibres (PFs) are minute strands of tissue, little is known about their ultrastructure and remodelling in disease. Furthermore, given the role for microRNAs (miRs) in CCS molecular remodelling, we aimed to develop a tissue specific method for delivering therapeutic transgenes, such as miR sponges.
Methods
New Zealand rabbits were used for PF ultrastructural studies. HF was induced via pressure and volume overload. Free running PFs were processed for serial block face scanning electron microscopy (SBF-SEM). Manual contrast-based segmentation techniques were used on IMOD software to determine the 3D cellular ultrastructure. To target transgene expression to the CCS, adenoviral plasmids were cloned expressing a GFP reporter gene. GFP transcription was placed under control of the KCNE1 promoter, a K+ channel subunit expressed throughout the CCS, or the HCN4 promoter, a key pacemaker ion channel, to target the sinus node. The strong ubiquitous cytomegalovirus (CMV) promoter was used as a positive control. Adenovirus was produced using via transfection into the 293A cell line for viral packaging and amplification.
Results
Purkinje cells (PCs) formed a central core within PFs, encapsulated by an extensive collagen matrix. PCs were uninucleated and spindle shaped with an irregular membrane. Gap junctions were abundant and distributed along the lateral surface of cells, and there was a trend towards decreased expression in HF (p=0.0526, n=3 cells analysed per group). Hypertrophy and nuclear membrane breakdown were evident in HF PCs, the latter facilitating mitochondrial entry.
Using the CMV-GFP adenoviral construct, abundant GFP expression was conferred in ex vivo sinus node tissue, isolated sinus node myocytes, and neonatal ventricular rat cardiomyocytes (NRCMs). The KCNE1 promoter conferred relatively high GFP expression in NRCMs, greater than that from the HCN4 promoter. In isolated sinus node myocytes, the HCN4 promoter conferred greater transgene expression than in NRCMs. In ex vivo sinus node tissue, only the CMV construct was capable of driving significant GFP expression. Notably, expression was largely confined to the sinus node, with only sparse expression detected in the surrounding atrial muscle.
Conclusions
SBF-SEM revealed ultrastructure of free running PFs in situ, and uncovered novel structural changes in HF that are likely to be pro-arrhythmic. Preliminary data suggest that 1.2 kb and 0.8 kb fragments of the HCN4 promoter are capable of driving sinus node specific transgene expression. Further tests are warranted to confirm the utility of these promoters to express therapeutic transgenes, such as miR sponges to competitively inhibit miR activity in vitro and in vivo.
Acknowledgement/Funding
The British Heart Foundation
The Humira in Ocular Inflammations Taper (HOT) Study Pichi, Francesco; Smith, Scott D.; Goldstein, Debra A. ...
American journal of ophthalmology,
February 2024, 2024-Feb, 2024-02-00, 20240201, Letnik:
258
Journal Article
Recenzirano
To assess factors that impact the risk of relapse in patients with noninfectious uveitis (NIU) who undergo adalimumab tapering after achieving remission.
Retrospective study.
In this multicenter ...study, patients with NIU were treated with adalimumab and subsequently tapered. Patient demographics, type of NIU, onset and duration of disease, the period of inactivity before tapering adalimumab, and the tapering schedule were collected. The primary outcome measures were independent predictors of the rate of uveitis recurrence after adalimumab tapering.
Three hundred twenty-eight patients were included (54.6% female) with a mean age of 34.3 years. The mean time between disease onset and initiation of adalimumab therapy was 35.2 ± 70.1 weeks. Adalimumab tapering was commenced after a mean of 100.8 ± 69.7 weeks of inactivity. Recurrence was observed in 39.6% of patients at a mean of 44.7 ± 61.7 weeks. Patients who experienced recurrence were significantly younger than those without recurrence (mean 29.4 years vs 37.5 years, P = .0005), and the rate of recurrence was significantly higher in younger subjects (hazard ratio HR = 0.88 per decade of increasing age, P = .01). The lowest rate of recurrence was among Asian subjects. A faster adalimumab taper was associated with an increased recurrence rate (HR = 1.23 per unit increase in speed, P < .0005). Conversely, a more extended period of remission before tapering was associated with a lower rate of recurrence (HR = 0.97 per 10-weeks longer period of inactivity, P = .04).
When tapering adalimumab, factors that should be considered include patient age, race, and duration of disease remission on adalimumab. A slow tapering schedule is advisable.
In most exposed individuals, hepatitis C virus (HCV) establishes a chronic infection; this long-term infection in turn contributes to the development of liver diseases such as cirrhosis and ...hepatocellular carcinoma. The role of antibodies directed against HCV in disease progression is poorly understood. Neutralizing antibodies (nAbs) can prevent HCV infection in vitro and in animal models. However, the effects of nAbs on an established HCV infection are unclear. We demonstrate that three broadly nAbs-AR3A, AR3B, and AR4A-delivered with adeno-associated viral vectors can confer protection against viral challenge in humanized mice. Furthermore, we provide evidence that nAbs can abrogate an ongoing HCV infection in primary hepatocyte cultures and in a human liver chimeric mouse model. These results showcase a therapeutic approach to interfere with HCV infection by exploiting a previously unappreciated need for HCV to continuously infect new hepatocytes to sustain a chronic infection.
Abstract
Background
Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by chronic obstruction of major pulmonary arteries with organized thrombi and is classified as pre-capillary ...pulmonary hypertension (PH) by the current hemodynamic definition of the guidelines. However, clinical risk factors for PH due to left heart disease including features of the metabolic syndrome, left-sided valvular heart disease and stable ischemic heart disease can be frequently observed in patients with CTEPH. The aim of this study was to investigate the prevalence, mechanisms and prognostic implications of elevated left ventricular filling pressures (LVFP) in patients with CTEPH.
Methods
394 consecutive CTEPH patients undergoing a first diagnostic right and left heart catheterization were included in this study. mPAWP and LVEDP were utilized for assessment of LVFP. Two cutoffs were applied to identify patients with elevated LVFP: (1) mPAWP and/or LVEDP >15 mmHg as recommended by the current PH guidelines and (2) mPAWP and/or LVEDP >11 mmHg, which is the upper limit of normal in healthy subjects. Clinical and echocardiographic features as well as long-term mortality data were assessed.
Results
LVFP was >15 mmHg in 41 (10.4%) and >11 mmHg in 155 patients (39.3%). Univariable logistic regression analysis identified age, body mass index, systemic hypertension, diabetes, atrial fibrillation, mitral regurgitation and left atrial volume as significant clinical predictors of elevated LVFP. Systemic hypertension, atrial fibrillation, mitral regurgitation and left atrial volume remained independent determinants of LVFP in adjusted analysis. LVFP >11 mmHg was associated with worse long-term survival (p-logrank = 0.020).
Conclusions
Elevated LVFP is common in patients with CTEPH at the time of diagnosis. Elevated LVFP in CTEPH appears to be due to comorbid left heart disease. CTEPH patients with LVFP >11 mmHg have worse outcomes.
Funding Acknowledgement
Type of funding sources: None.
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