Reliability of Coated Wire Defibrillation Leads

A higher rate of complications and need for reoperation has been identified with epicardial and endocardial defibrillator systems. Improved reliability may be achieved with alternate designs that use coated wire and coated coil conductors. Six-year reliability in the 98% range is reported for one bipolar design, the Sulzer Intermedics Intervene® lead.     

Detection of a Retention Wire Fracture in An Asymptomatic Patient 18 Years after Implantation

An asymptomatic patient with a Teletronics Accufix atrial lead (Teletronics, Englewood, CO, USA) presented for an annual fluoroscopic examination. The examination revealed a retention wire fracture, which occurred 18 years after the initial implantation. Annual fluoroscopic examination of these leads should still be performed. (PACE 2010; 33:246–247)     

ALTERED DRUG RESISTANCE AND RECOVERY FROM PARALYSIS IN DROSOPHILA MELANOGASTER WITH A DEFICIENT HISTAMINE-GATED CHLORIDE CHANNEL

The recent identification and characterization of two genes, encoding histamine-gated chloride channel subunits from Drosophila melanogaster , has confirmed that histamine is a major neurotransmitter in the fruitfly. One of the cloned genes, hclA (synonyms: HisCl - &#102 1 ; HisCl2 ), corresponds to ort ( ora transientless ), mutationsin which affect synaptic transmission in the Drosophila visual system. We identified a mutational change (a null mutation) in the genomic and RNA copies of hclA derived from mutants carrying the ort 1 allele. This correlates with new phenotypes observed in the mutant strain. We found hypersensitivity to the avermectin neurotoxins in both the ort 1 adult flies and third instar larvae compared to Oregon R wild-type animals. On the other hand, the mutation makes both male and female adult flies more resistant to treatment with diethyl ether, and the animals show substantially prolonged recovery from paralysis after diethylether anaesthesia, as well as from paralysis after mechanical shock, as revealed by the bang sensitivity test. Altogether, our data give direct evidence that in vivo a HCLA subunit-containing receptor has a distinct role in the neurotoxic action of the avermectins. They also provide new evidence for a function in the response to diethylether anaesthesia and, moreover, that HCLA function is not limited to the visual system.     

Myotropic Peptides in Drosophila Melanogaster And The Genes That Encode Them

Myotropic peptides are structurally dissimilar; thus, they comprise different families. The cellular expressions of myotropins suggest they act as hormones, transmitters, and modulators of numerous biological processes. Drosophila melanogaster allatostatin (AST), FMRFamide-containing, dromyosuppressin (DMS), and drosulfakinin (DSK) peptides represent four different myotropin families. A different gene encodes each of these four myotropin families. D. melanogaster AST, FMRFamide-containing, DMS, and DSK peptides are present in neural and gut tissue, but are not all expressed in the same cells. These four families of myotropins affect spontaneous contractions of gut, heart, and/or reproductive tissue, but their effects are dissimilar in magnitude and time course. Based on their structures, genes, distributions, and activities, the synthesis and release of these D. melanogaster myotropins are likely governed by different sensory inputs and regulatory mechanisms. The differences in structures, precursors, cellular expressions, and activities are consistent with the conclusion that they do not play redundant roles in their effects on the frequency of muscle contractions. Orthologs of these D. melanogaster myotropins exist in other animal species; thus, research on the mechanisms involved in their production and processing, functions, and signaling may be widely applicable. Here, we review research on D. melanogaster AST, FMRFamide-containing, myosuppressin, and sulfakinin peptides.     

Nitric Oxide Mediates C5a-Induced Vasodilation in the Small Intestine

Objective: This study was designed to investigate the microvascular responses of the small intestine to complement C5a and to define the role of nitric oxide in the C5a-induced response. Methods: Male Sprague–Dawley rats were anesthetized with pentobarbital, and a loop of small intestine was exteriorized and suffused with Krebs solution. The diameters of large and small arterioles of the small intestinal wall were measured with in vivo videomicroscopy following the application of experimental mediators. Four 1-hr C5a dose-response trials were performed (10^?14 M, 10^?12 M, 10^?10 M, and 10^?8 M). Then, we completed acetylcholine dose-response curves with and without N^ω-nitro-L-arginine (N-Arg) to document the adequacy of nitric oxide synthase inhibition. The microvascular response to the topical application of C5a (10^?12 M) was recorded in the presence of 2 × 10^?4 M N-Arg. Additionally, experiments of C5a-induced response with N-Arg were repeated in the presence of L-arginine (L-Arg; the precursor of nitric oxide synthesis) or with systemic administration of superoxide dismutase (SOD). Results: (1) C5a induces a dose-dependent vasodilation in the small intestine, and the maximal vasodilation occurs in A3 arterioles at C5a concentration of 10^?12 M; (2) N-Arg inhibits the Ach-induced vasodilation in the rat small intestine; and (3) L-Arg or SOD partially reverses the inhibitory effect of N-Arg. Conclusions: Nitric oxide mediates the C5a-induced vasodilation in small intestinal microvessels. Superoxide is, at least partially, responsible for the vasoconstrictor response to C5a in the presence of N-Arg.     

Nonthoracotomy Implantation of Cardioverter Defibrillators: Preliminary Experience with a Defibrillation Lead Placed at the Right Ventricular Outflow Tract

Although morbidity and mortality associated with defibrillator implantation using a nonthoracotomy approach have decreased as compared with a thoracotomy approach, dfifihrillation thresholds have been higher and fewer patients satisfied implan t criteria. It may be possible to improve on the success of nonthoracotomy defibrillator implantation by the placement of a right ventricular (HV) outflow defibrillation lead. Implnntable car-dioverter defibrillator implantation data of 30 consecutive patients with clinical VT or VF were reviewed. Three defibrillation leads were routinely used. When either pacing threshold at the RV apex ivas inadequate (n - 2) or 18-J shocks were not successful in terminating VF in 3 of 4 trials (n = 8). the RV apex lead was positioned to the HV outflow tract attaching to the septum. Defibrillation testing was first performed with the RV apex lead in combination with CS, SVC. and/or subcutaneous leads. Twenty patients satisfied implant criteria with a defibrillation threshold of 13.5 ± 3.6 J. In 7 of the 10 patients, whose RV lead was repositioned to the RV outflow tract, this lead in combination with SVC, CS, or subcutaneous leads produced successful defibrillation at < 18 J or in 3 of 4 trials. This approach improved the overall success of nonthoracotomy implantation of defibrillators from 69% to 90%, After a follow-up of 27 ± 6 months, there was no dislodgment of the HV outflow tract defibrillation leads. Conclusions: This article reports the preliminary observation that placement of defibrillation leads to the RV outflow tract in humans was possible and without dislodgment. RV outflow tract offers an alternative for placement of defibrillation leads, which may improve on the success of nonthoracotomy defibrillator implantation.     

Diaphragm Pacing with a Quadripolar Phrenic Nerve Electrode: An International Study

We sought to determine the international experience with the quadripolar diaphragm pacer system and to test two hypotheses: the incidence of pacer complications would be (1) increased among pediatric as compared to adult patients; and (2) highest among active pediatric patients with idiopathic congenital central hypoventilation syndrome (CCHS). Data were collected via a questionnaire coupled with the Atrotech Registry data for a total of 64 patients (35 children and 29 adults) from 14 countries. Thoracic implantation of electrodes and bilateral pacer use each occurred in 94% of all subjects. Tetraplegic (vs pediatric CCHS) patients were more typically paced 24 hours/day (P = 0.001). Pacing duration averaged 2.0 ± 1.0 years among children and 2.2 ± 1.1 years among adults. Infections occurred among 2.9% of surgical procedures, all in pediatric CCHS patients (vs pediatric tetraplegic patients, P = 0.01). The incidence of mechanical trauma was 3.8%, without significant differences among patient groups. The incidence of presumed electrode and receiver failure were 3.1% and 5.9%, respectively, with internal component failure greater among pediatric CCHS than pediatric tetraplegic patients (P < 0.01). Intermittent or absent function of 0–4 electrode combinations occurred among 19% of all patients, with increased frequency among pediatric CCHS than pediatric tetraplegic patients (P < 0.03). Complication- free successful pacing occurred in 60% of pediatric and 52% of adult patients. In all, 94 % of the pediatric and 86% of the adult patients paced successfully after the necessary intervention. Although pacer complications were not increased among pediatric as compared to adult patients, the incidence of complications was highest among the active pediatric patients with CCHS. Longitudinal study of these patients will provide invaluable information for modification and improvement of the quadripolar system.     

Increased expression of urokinase-type plasminogen activator in colorectal carcinoma and in adenomatous polyps

Human plasminogen activators (HPA) comprise the tissue type produced mainly by endothelial cells of 66 000 molecular weight (MW) which is principally involved in fibrinolysis (HPA66) and the urokinase type of 52 000 MW (HPA52) which is implicated in the invasion process of malignancy. The purpose of this study was to elucidate the pattern of HPA expression in histologically normal colonic mucosa, sporadic polyps, polyposis coli polyps, and in colon cancer tissue, to determine whether the expression of HPA52 is a correlate of neoplastic transformation of colonic epithelial cells. Homogenates of colonoscopic biopsies and resected colon tissue were subjected to polyacrylamide gel electrophoresis and the HPA activity was detected by a fibrin overlay gel. In histologically normal mucosal biopsies from non-cancer-bearing colons and in uninvolved mucosa from cancer-bearing colons, only HPA66 was detected. By contrast, all 19 colon cancer specimens expressed HPA52 and 16 of these also showed HPA66 activity. Two of three colon cancer cell lines showed HPA52 activity, but none expressed HPA66. HPA52 activity was observed in 17 of 20 adenomatous polyps, all of which displayed HPA66 activity. No correlation was found between polyp size, degree of epithelial dysplasia or the type of polyp architecture, and the semiquantitative estimates of HPA52 activity as judged by the areas of fibrinolysis generated.
This study of HPA52 in the colon epithelial neoplasms comprising adenomatous polyps, colon cancer tissue and colon cancer cell lines suggests that the transformation of the colon epithelial cell correlates with increased expression of HPA52, an enzyme that has been implicated in the invasive process of malignancy.