Different responses of human anti-HLA and anti-alphagal antibody to long-term intravenous immunoglobulin therapy

Concentrated human immunoglobulin (IVIG) has been administered intravenously in the treatment of autoimmune disorders and to reduce anti-HLA antibodies in highly sensitized patients awaiting organ transplantation. It has also been shown, in experimental animals, to prevent the hyperacute rejection of discordant xenografts, possibly by anticomplement activity. The aim of the present study was to assess the effect of IVIG therapy on both acquired anti-HLA antibodies and natural antigalactose alpha1-3 galactose (alphaGal) antibodies in five patients awaiting heart transplantation. Five patients placed on mechanical circulatory support who had developed high HLA panel-reactive antibodies (PRA) or in whom the percentage of PRA was increasing rapidly were treated weekly with 500 mg/kg IVIG, which contained 1% of anti-alphaGal IgG. Levels of PRA, anti-alphaGal IgG and IgM, and serum cytotoxicity to pig cells were measured before, during, and after therapy. PRA percentages in the five patients were initially 85%, 53%, 23%, 19% and 19% (mean 39%). Mean PRA fell by 66% after 3 months of therapy (to a mean PRA of 14%), and by 96% after 6 months therapy (to a mean PRA of 2%). Anti-alphaGal antibody levels and serum cytotoxicity to pig aortic endothelial cells did not change significantly. These results confirm the effectiveness of IVIG therapy in reducing PRA in HLA highly sensitized patients. It is likely that IVIG does not contain the relevant anti-HLA antibody, resulting in an accelerated catabolism of native alloantibodies. However, as IVIG contains a normal level of anti-alphaGal IgG, catabolism of anti-alphaGal IgG is not modified, as it is being continuously replaced. To achieve a decrease in the anti-alphaGal IgG level it would be necessary to use IVIG depleted of this antibody.

Measurement of thickness and density of thin structures by computed tomography: a simulation study

The limited spatial resolution of clinical CT systems causes difficulties in the measurement of the density and thickness of thin structures such as the vertebral cortical shell. We simulated the imaging process by convolving experimentally determined point spread functions with rectangular and Gaussian profiles, for various fields of view or pixel sizes and reconstruction kernels. The simulations successfully explained the reported overestimation of thickness and underestimation of density when imaging thin structures. Both effects are larger for Gaussian profiles. For the rectangular profiles, experimental estimates of thickness and density will only be accurate when the true thickness is greater than about 1.5 times (for the bone reconstruction kernel) or 2.0 times (for the standard kernel) the full width at half maximum of the point spread function (PSF) of the imaging system. For Gaussian profiles imaged by a system with a Gaussian PSF, there are straightforward analytical expressions for the overestimation of thickness and underestimation of density: and these are useful approximations to the simulations of Gaussian profiles with experimental (pseudo-Gaussian) PSFs. We have demonstrated that thresholding of the vertebral image cannot provide accurate estimates of cortical thickness and density because the appropriate threshold level requires foreknowledge of the cortical thickness. To circumvent such difficulties we suggest that the average value of the peak CT numbers measured along the medial axis of the cortical shell be adopted as an index of cortical shell strength, since its value depends on both the density and the thickness of the shell.

Cloning, tissue distribution, genomic organization, and functional characterization of NBC3, a new member of the sodium bicarbonate cotransporter family

Previous functional studies have demonstrated that muscle intracellular pH regulation is mediated by sodium-coupled bicarbonate transport, Na+/H+ exchange, and Cl-/bicarbonate exchange. We report the cloning, sequence analysis, tissue distribution, genomic organization, and functional analysis of a new member of the sodium bicarbonate cotransporter (NBC) family, NBC3, from human skeletal muscle. mNBC3 encodes a 1214-residue polypeptide with 12 putative membrane-spanning domains. The approximately 7.8-kilobase transcript is expressed uniquely in skeletal muscle and heart. The NBC3 gene (SLC4A7) spans approximately 80 kb and is composed of 25 coding exons and 24 introns that are flanked by typical splice donor and acceptor sequences. Expression of mNBC3 cRNA in Xenopus laevis oocytes demonstrated that the protein encodes a novel stilbene-insensitive 5-(N-ethyl-N-isopropyl)-amiloride-inhibitable sodium bicarbonate cotransporter.

The external urethral barrier for stress incontinence: a multicenter trial of safety and efficacy. Miniguard Investigators Group

OBJECTIVE

To assess the efficacy and safety of an external urethral barrier for the management of mild to moderate stress urinary incontinence in adult women.

METHODS

Four hundred eleven women with the symptom of stress urinary incontinence in 12 United States centers participated. Additional inclusion and exclusion criteria were applied before protocol device use, and ultimately 390 subjects began device use. Outcome measures for efficacy and safety were assessed. Efficacy was evaluated by the number of leakage episodes using a voiding diary, subjective urinary leakage severity, incontinence impact scores, and pad testing. Safety was evaluated by symptom assessment, urinalysis, urine culture, measurement of postvoid residual urine volume, vulvar cytology, vaginal culture, and (n = 81) cystometric testing.

RESULTS

Efficacy was indicated by statistically significant reductions in the number of leakage episodes, subjective leakage severity scores, incontinence impact scores, and pad-test loss during device use. The data also indicated that the device was safe, as evidenced by the lack of statistically significant changes in the percentage of subjects with urinary tract infections during device use or in postvoid residual urine volume and cystometric indices. Symptoms of vulvar irritation or lower urinary tract discomfort occurred in a small percentage of subjects but were generally transient, and only three women discontinued using the device.

CONCLUSION

The external urethral barrier appears to be a safe nonsurgical alternative to absorbent products for the management of mild to moderate stress urinary incontinence in adult women.

Azimilide decreases defibrillation voltage requirements and increases spatial organization during ventricular fibrillation

INTRODUCTION

Drugs with class III antiarrhythmic properties generally decrease defibrillation threshold (DFT). However, the concentration effect relation for this effect and drug effects on ventricular fibrillation (VF) itself are not well understood. The objectives of this study were to determine the effect of azimilide (NE-10064), a new class III agent, on DFT, and on spatial organization during VF.

METHODS

Defibrillation patch electrodes were sutured to the right and left ventricular epicardium in 12 open-chest anesthetized dogs. The delayed up-down algorithm was used to measure DFT and to estimate the shock strength (voltage) with a 50% probability of successful defibrillation (V50). The magnitude squared coherence (MSC), which measures the spatial relation in the frequency domain, was measured during VF between two unipolar epicardial electrodes 3 mm apart. The V50, MSC, electrophysiologic parameters, and plasma concentrations were determined before and after four cumulative i.v. doses of azimilide (2, 7, 17, and 30 mg/kg).

RESULTS

Azimilide elicited a dose dependent reduction of V50 and increase in MSC. Compared with baseline, azimilide lowered mean V50 by 2 +/- 9%, 10 +/- 18%, 11 +/- 14% and 19 +/- 5%, and increased MSC by 17 +/- 20%, 32 +/- 31%, 20 +/- 44% and 27 +/- 20% (p < 0.05 for dose effect) at 2, 7, 17 and 30 mg/kg, respectively. Mean increases in monophasic action potential duration at 90% repolarization (3-11%), ventricular effective refractory period (6-13%) at 400 msec paced cycle length, and VF cycle length (5-37%) (p < 0.01 for dose effect) were observed with the 4 increasing doses of azimilide, respectively.

CONCLUSION

Azimilide significantly decreases DFT and increases coherence in VF in a dose dependent manner.

Shop floor safety initiatives: the example of atmospheric testing in telecommunications cable vaults

Strategies for occupational safety and health campaigns often overlook the possibilities afforded by initiatives centered in the workplace itself, as opposed to those focused, for example, at the bargaining table or in the legislature. Workers themselves sometimes may be more cognizant and informed of immediate health and safety issues than are their union representatives, and may formulate innovative or unorthodox approaches to hazard remediation. Such approaches may in fact succeed despite ineffectual contract language or weak regulatory protection. This article examines a successful struggle by a small group of telecommunications technicians to get the employer to revise its obsolete procedures for atmospheric testing of unventilated, underground cable vaults. It demonstrates that increased consideration should be given to shopfloor actions and creative use of the grievance procedure as useful tools in the struggle for occupational safety and health.

The Canadian Registry of Atrial Fibrillation: a noninterventional follow-up of patients after the first diagnosis of atrial fibrillation

The Canadian Registry of Atrial Fibrillation (CARAF) is a nondirected, follow-up study of 1,086 patients who are enrolled at 6 centers across Canada at the time of initial electrocardiographically documented diagnosis of atrial fibrillation (AF). Enrollment commenced in 1991 with an intended 10-year follow-up. Comprehensive baseline data, including clinical history, laboratory, and echocardiographic variables were collected. The patients were treated by their own referring physicians and CARAF did not direct their care. Detailed follow-up was performed at 3 months, 1 year, then yearly, with echocardiograms repeated every 2 years. Several studies, which evaluated patient populations, predictors of events, and cardiac structure and functioning, have been performed and are ongoing. Thyroid function was evaluated at baseline, and, of 707 patients evaluated, only 6 patients were found to be hyperthyroid. Symptoms during AF were evaluated and a profile of the types of symptoms and the predictors of symptoms was compiled. Antiarrhythmic drug use is being followed. Sotalol and propafenone were the most commonly used medications, with the use of antiarrhythmic drugs increasing with recurrence of AF. The use of anticoagulants was assessed. The overall use of warfarin was relatively low, but its use increased dramatically with the presence of various risk factors including congestive heart failure, hypertension, and previous stroke. The one risk factor that did not result in increased use of warfarin was hypertension. Therefore, CARAF was able to identify that hypertension appears to be under-recognized and undertreated in its risk for thromboembolic events. CARAF is just now reaching maturity, with the majority of patients having > or=4 years of follow-up. Therefore, extensive investigations are currently under way that will evaluate the baseline characteristics and utilize these as predictors of recurrence of AF, progression to chronicity, and the occurrence of major events such as stroke and death. A very large cohort of patients with serial echocardiograms over 4 years will permit an understanding of the progression of structural and valvular disease. Therefore, CARAF offers a unique opportunity for comprehensive, nondirected follow-up of patients from their initial diagnosis of AF.

A double-blind placebo-controlled evaluation of the human electrophysiologic effects of zatebradine, a sinus node inhibitor

The purpose of this study was to evaluate the electrophysiologic effects of zatebradine, a sinus node inhibitor, in human subjects. Patients without structural heart disease were randomized to receive intravenous zatebradine (23 patients) or placebo (12 patients). Electrophysiologic measures were obtained at baseline and repeated at 40 and 70 min after drug administration. In the placebo group, there were no significant changes in any parameter over time. After zatebradine, sinus node function changed significantly at 40 min, with no further change at 70 min; sinus cycle length was prolonged by 16 and 17% (p < 0.001), and corrected sinus node recovery time was prolonged by 30 and 22% (p = 0.008). Similarly, atrioventricular node function changed significantly at 40 min, with no further change at 70 min; atrio-His interval was prolonged by 15 and 15% (p = 0.02), atrioventricular node effective refractory period was prolonged by 12 and 11% (p = 0.01), and Wenckebach cycle length was prolonged by 15 and 11% (p = 0.002). Atrial refractoriness, His-Purkinje conduction, ventricular refractoriness, and action-potential duration were not affected by zatebradine. Zatebradine, a sinus node inhibitor, alters the conduction and refractory properties of the human atrioventricular node, in addition to the expected effect on sinus node function.

Implantable defibrillators and/or amiodarone: alternatives or complementary therapies

Many patients with an implanted cardioverter defibrillator (ICD) also receive antiarrhythmic drug therapy. Although an expanding number of patients are receiving ICD therapy, many will not have received previous antiarrhythmic treatment. For patients with an ICD, infrequent arrhythmias and a low probability of inappropriate device discharges, no antiarrhythmic therapy is required. However, for those patients who require an antiarrhythmic drug, amiodarone is a reasonable first choice because of safety in patients with poor LV function. It may be particularly useful for patients with high density ventricular arrhythmias. However, the interactions between ICDs and antiarrhythmic therapy requires close monitoring in order that patient benefit can be optimised, and this review focuses on those interactions.

Molecular cloning, chromosomal localization, tissue distribution, and functional expression of the human pancreatic sodium bicarbonate cotransporter

We report the cloning, sequence analysis, tissue distribution, functional expression, and chromosomal localization of the human pancreatic sodium bicarbonate cotransport protein (pancreatic NBC (pNBC)). The transporter was identified by searching the human expressed sequence tag data base. An I.M.A.G.E. clone W39298 was identified, and a polymerase chain reaction probe was generated to screen a human pancreas cDNA library. pNBC encodes a 1079-residue polypeptide that differs at the N terminus from the recently cloned human sodium bicarbonate cotransporter isolated from kidney (kNBC) (Burnham, C. E., Amlal, H., Wang, Z., Shull, G. E., and Soleimani, M. (1997) J. Biol. Chem. 272, 19111-19114). Northern blot analysis using a probe specific for the N terminus of pNBC revealed an approximately 7.7-kilobase transcript expressed predominantly in pancreas, with less expression in kidney, brain, liver, prostate, colon, stomach, thyroid, and spinal chord. In contrast, a probe to the unique 5' region of kNBC detected an approximately 7.6-kilobase transcript only in the kidney. In situ hybridization studies in pancreas revealed expression in the acini and ductal cells. The gene was mapped to chromosome 4q21 using fluorescent in situ hybridization. Expression of pNBC in Xenopus laevis oocytes induced sodium bicarbonate cotransport. These data demonstrate that pNBC encodes the sodium bicarbonate cotransporter in the mammalian pancreas. pNBC is also expressed at a lower level in several other organs, whereas kNBC is expressed uniquely in kidney.

The effect of sinus node depression on heart rate variability in humans using zatebradine, a selective bradycardic agent

Zatebradine is a bradycardic agent with a selective effect on the pacemaker current in the sinus node. The effect of such drugs on heart rate variability is not known. Thirty-six patients without structural heart disease were randomly assigned to receive 10 mg of zatebradine i.v. (n = 24) or isotonic saline (n = 12). Heart rate variability (HRV) was recorded as power in the very low frequency (VLF, 0.003-0.040 Hz), low frequency (LF, 0.040-0.150 Hz), and high frequency (HF, 0.150-0.400 Hz) spectral bands as well as total power (TP, 0.003-0.400 Hz) during 5-min ECG acquisitions at baseline, 30, and 60 min following the start of the infusion. No change in heart rate variability was detected in the control group. Zatebradine significantly reduced heart rate variability at 60 min in all frequency bands: VLF (-12+/-4%, p<0.001), LF (-19+/-4%, p<0.001), and HF (-26+/-5%, p<0.001). The reduction in HRV following zatebradine is due to depression of sinus node response to all external stimuli and underscores the need for documentation of normal sinus node function in HRV research.

Peripheral blood mononuclear cells express mutated NCCT mRNA in Gitelman's syndrome: evidence for abnormal thiazide-sensitive NaCl cotransport

Genetic analysis has demonstrated complete linkage between the human thiazide-sensitive sodium chloride cotransporter gene (NCCT or TSC) and Gitelman's syndrome (GS). Several genomic NCCT mutations have been reported. This study was performed to determine whether peripheral blood mononuclear cells (PBMC) express NCCT mRNA and whether defective PBMC NaCl cotransport could be demonstrated in GS. PBMC were isolated from two brothers with GS, their parents, and healthy control subjects. Northern analysis revealed that NCCT mRNA is expressed in PBMC. The sequence of full-length NCCT cDNA amplified from normal PBMC was identical to human renal NCCT cDNA. Two different mutations were detected in the patients' NCCT cDNA (compound heterozygote). In cDNA derived from the patient's maternal allele, exon 24 was deleted, resulting in a premature stop codon (after amino acid 920). cDNA derived from the patient's paternal allele had an additional 119-bp insertion between exons 3 and 4, generating a premature stop codon (after amino acid 187). The patient's genomic DNA had a previously described 5' splice site mutation in intron 24, GGT --> GTT (maternal allele), and a new 3' splice site mutation in intron 3, CAG --> CAA (paternal allele), which resulted in the activation of a nearby cryptic splice site in intron 3. The latter mutation was not present in 300 normal chromosomes. To determine the functional significance of these findings, chlorothiazide-inhibitable 22Na uptake was measured in PBMC from control subjects, the parents, and the patients with GS in the presence of bumetanide. In control PBMC, chlorothiazide inhibited 22Na uptake by approximately 9%. PBMC from the two patients with GS failed to respond to chlorothiazide. These results demonstrate that PBMC can be used for mutational analysis of NCCT mRNA in patients with GS. Furthermore, functional evidence is provided that the underlying cause of GS is defective NCCT NaCl cotransport.

Axial heterogeneity of sodium-bicarbonate cotransporter expression in the rabbit proximal tubule

It is generally accepted that Na(HCO3)n cotransport is the most important mechanism mediating basolateral bicarbonate efflux in the early proximal tubule. The presence of basolateral Na(HCO3)n cotransport in the late proximal tubule (S3 segment) and in the juxtamedullary S1 and S2 segments has been controversial. The renal sodium-bicarbonate cotransporter (NBC) has been recently cloned from rat (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. J. Am. Soc. Nephrol. 7: 1259, 1996), salamander (M. F. Romero, M. A. Hediger, E. L. Boulpaep, and W. F. Boron. Nature 387: 409-413, 1997), and human (C. E. Burnham, H. Amlal, Z. Wang, G. E. Shull, and M. Soleimani. J. Biol. Chem. 272: 19111-19114, 1997). The localization of NBC in the kidney is unknown. The present study was designed to localize NBC mRNA expression in the rabbit proximal tubule. In situ hybridization studies were combined with functional studies of basolateral Na(HCO3)n cotransport in superficial and juxtamedullary S1, S2, and S3 segments of the rabbit proximal tubule. The results demonstrate that NBC mRNA is localized predominantly to the cortex, with less expression in the outer medulla. NBC expression was not detected in the inner medulla. The highest level of NBC mRNA is in the S1 proximal tubule. NBC is expressed at a low levels in the S3 segment, with intermediate expression in the S2 segment. In bicarbonate-buffered solutions, the rate of base efflux mediated by Na(HCO3)n cotransport followed a similar pattern in superficial and juxtamedullary proximal tubule segments, i.e., S1 > S2 > S3. The juxtamedullary S1 segment had the greatest rate of basolateral Na(HCO3)n cotransport and the highest level of NBC expression in the proximal tubule.

Autonomic correlates of antidepressant treatment using heart-rate variability analysis

OBJECTIVE

To assess the 24-hour temporal-domain heart-rate variability correlates of treatment with fluoxetine or doxepin for depression.

METHOD

A randomized evaluation of fluoxetine and doxepin measured a 50% change in the Hamilton Depression Rating Scale (HDRS) score as a response to therapy and was correlated with measures of standard deviation of the mean of all 5-minute segments of normal electrocardiographic R-R intervals (SDANN), standard deviation of all normal R-R intervals (SDNN), root mean square of successive differences in R-R intervals (r-MSSD), and percentage difference between adjacent normal R-R intervals that are greater than 50 msec (pNN50) from 24-hour electrocardiogram (ECG) tapes.

RESULTS

Ten out of 14 patients responded. Response was associated with an increase in SDANN of 17% (P < 0.05). Nonresponse was associated with a 17% decrease in SDANN and a 22% decrease in SDNN (both P < 0.05). No other measures correlated with therapeutic response. No heart-rate variability (HRV) differences between the 2 drug therapies were observed.

CONCLUSION

Twenty-four-hour HRV measures may be useful in assessing response to antidepressant therapy.

Aftereffects and sense of presence in virtual environments: formulation of a research and development agenda

This report represents a committee summary of the current state of knowledge regarding aftereffects and sense of presence in virtual environments (VEs). The work presented in this article, and the proposed research agenda, are the result of a special session that was set up in the framework of the Seventh International Conference on Human Computer Interaction. Recommendations were made by the committee regarding research needs in aftereffects and sense of presence, and, where possible, priorities were suggested. The research needs were structured in terms of the short, medium, and long term and, if followed, should lead toward the effective use of VE technology. The 2 most critical research issues identified were (a) standardization and use of measurement approaches for aftereffects and (b) identification and prioritization of sensorimotor discordances that drive aftereffects. Identification of aftereffects countermeasures (i.e., techniques to assist users in readily transitioning between the real and virtual worlds), reduction of system response latencies, and improvements in tracking technology were also thought to be of critical importance.

When pacemakers fail: an analysis of clinical presentation and risk in 120 patients with failed devices

Although pacemaker recalls are common, the optimal mechanism for risk assessment and triage of patients at risk for sudden loss of device system function is unknown. A retrospective chart review of 120 patients with factory proven failed devices was performed. Logistic regression analysis was used to determine clinical correlates of emergency room versus outpatient clinic presentation at time of device failure. Twenty-two patients (18%) presented to emergency and 98 (82%) to clinic. Sixty-three devices had no device output at the time of presentation. Multivariate logistic regression analysis revealed that antiarrhythmic drug use (odds ratio: 7.4, 95% CI: 2.0-28.0), atrioventricular nodal disease as an indication for pacing (odds ratio: 2.8, 95% CI: 1.2-3.0), and female gender (odds ratio: 2.2, 95% CI: 1.0-4.5) were the only significant correlates of emergency room presentations. Pacemaker dependency (escape heart rate < 40 beats/min) did not correlate with location of presentation even though no device output at the time of presentation was associated with emergency room presentation (odds ratio: 2.5, 95% CI: 1.1-5.8). Neither the presence of structural heart disease nor symptoms at the time of device implantation (syncope or presyncope) were correlated with location of presentation upon unexpected device failure. Although there were no deaths in the 120 failed devices studied, there were 26 deaths in the total group of 227 patients with recalled devices that could not be studied. Antiarrhythmic drug use, electrocardiographic pacing indication, and female gender may be more sensitive predictors of emergency room presentation and significant symptoms in the event of unanticipated pacemaker failure. The inability of any retrospective analysis to accurately assess mortality in the setting of pacemaker system failure underscores the need for prospective databases in recall situations.

Transcutaneous T wave shock: a universal method for ventricular fibrillation induction

Our objective was to develop a universal noninvasive method for VF induction. ICD implantation requires VF induction. Conventional rapid ventricular stimulation may fail to induce VF. Some ICDs can deliver low energy shocks on the T wave to induce VF. We hypothesized that an external dual chamber pacemaker and an external defibrillator could be configured to allow reliable VF induction with any ICD system. A surface ECG signal was delivered to the atrial channel of an external dual chamber DDD pacemaker. The 'AV' delay was adjusted so that the ventricular output of the pacemaker was delivered to an external defibrillator synchronized to deliver 5-50 J. Twenty-six patients at ICD implant or follow-up had VF induced in native rhythm (sinus rhythm or atrial fibrillation), or during a ventricular pacing train (3-8 beats at cycle length 500-880 ms). VF was successfully induced in 14 of 25 (56%) patients in native rhythm; and in 16 of 17 (94%) patients during pacing (P = 0.013). VF induction success rate was 36% in native rhythm (31/86 attempts) and 88% during pacing (69/78 attempts) (P < 0.001). The 'R' to shock interval was 269 +/- 31 ms in native rhythm and 257 +/- 48 ms during pacing. Energy delivered from the external defibrillator was 19 +/- 3 J in native rhythm and 21 +/- 6 J during pacing. We concluded that VF induction by synchronizing a small external shock to the T wave is a fast, effective way to reliably ensure arrhythmia induction with any ICD at implant or follow-up. This method is more successful during pacing than in sinus rhythm.