Pathophysiological mechanisms of dominant and recessive KVLQT1 K+ channel mutations found in inherited cardiac arrhythmias

The inherited long QT syndrome (LQTS), characterized by a prolonged QT interval in the electrocardiogram and cardiac arrhythmia, is caused by mutations in at least four different genes, three of which have been identified and encode cardiac ion channels. The most common form of LQTS is due to mutations in the potassium channel gene KVLQT1, but their effects on associated currents are still unknown. Different mutations in KVLQT1 cause the dominant Romano-Ward (RW) syndrome and the recessive Jervell and Lange-Nielsen (JLN) syndrome, which, in addition to cardiac abnormalities, includes congenital deafness. Co- expression of KvLQT1 with the IsK protein elicits slowly activating potassium currents resembling the cardiac Iks current. We now show that IsK not only changes the kinetics of KvLQT1 currents, but also its ion selectivity. Several mutations found in RW, including a novel mutation (D222N) in the putative channel pore, abolish channel activity and reduce the activity of wild-type KvLQT1 by a dominant-negative mechanism. By contrast, a JLN mutation truncating the carboxyterminus of the KvLQT1 channel protein abolishes channel function without having a dominant-negative effect. This fully explains the different patterns of inheritance. Further, we identified a novel splice variant of the KVLQT1 gene, but could not achieve functional expression of this nor of a previously described heart-specific isoform.      

Safety for Human MR Scanners at 7T

After introduction of the first human 7 tesla (7T) system in 1999, 7T MR systems have been employed as one of the most advanced platforms for human MR research for more than 20 years. Currently, two 7T MR models are approved for clinical use in the U.S.A. The approval facilitated introduction of the 7T system, summing up to around 100 worldwide. The approval in Japan is much awaited. As a clinical MR scanner, the 7T MR system is drawing attention in terms of safety.Several large-sized studies on bioeffects have been reported for vertigo, dizziness, motion disturbances, nausea, and others. Such effects might also be found in MR workers and researchers. Frequency and severity of reported bioeffects will be presented and discussed, including their variances. The high resonance frequency and shorter RF wavelength of 7T increase the concern about the safety. Homogeneous RF pulse excitation is difficult even for the brain, and a multi-channel parallel transmit (pTx) system is considered mandatory. However, pTx may create a hot spot, which makes the estimation of specific absorption rate (SAR) to be difficult. The stronger magnetic field of 7T causes a large force of displacement and heating on metallic implants or devices, and the scan of patients with them should not be conducted at 7T. However, there are some opinions that such patients might be scanned even at 7T, if certain criteria are met. This article provides a brief review on the effect of the static magnetic field on humans (MR subjects, workers, and researchers) and neurons, in addition to scan sound, SAR, and metal implants and devices. Understanding and avoiding adverse effects will contribute to the reduction in safety risks and the prevention of incidents.     

Interleukin-5 is at 5q31 and is deleted in the 5q- syndrome

Human interleukin-5 (IL-5) is a selective eosinophilopoietic and eosinophil-activating growth hormone. By in situ hybridization this gene is mapped to chromosome 5q23.3 to 5q32. It is shown to be deleted in two patients with the 5q-syndrome and in one patient previously diagnosed with myelodysplasia whose condition had progressed to acute myeloblastic leukemia. The clustering of other genes involved in hematopoiesis (IL-3, granulocyte-macrophage colony-stimulating factor, feline sarcoma viral oncogene homolog, colony-stimulating factor 1) to the same region as IL-5 suggests a nonrandom localization and raises interesting questions concerning the evolution and regulation of these genes.     

Theophylline toxicity in a preterm infant: selected clinical aspects

A case of parent-induced theophylline toxicity in a preterm infant is described. Despite a theophylline level of 97 mcg/ml no clinical seizure activity was apparent. Pharmacokinetic data suggested that use of oral activated charcoal may have enhanced drug clearance. Further study is necessary before such therapy can be routinely advocated. Additional clinical features are discussed, including avoidance of dosing errors through careful instruction of all caretakers prior to discharge.     

Long-term Clinical Performance of Resin-Bonded Fixed Partial Dentures Placed in a Developing Country

Purpose This study assesses the clinical performance of 92 resin-bonded fixed partial dentures (FPDs) placed at four private practices in Karachi, Pakistan, between 1982 and 1991. Materials and Methods The distribution of the FPDs was 9 perforated, 45 electrolytically etched, and 38 silicoated. Twenty-five FPDs replaced anterior teeth and 67 replaced posterior teeth. There were 66 FPDs with single pontics and 26 with multiple pontics. The perforated designs used a restorative composite for cementation, whereas the electrolytically etched and silicoated designs used a composite luting cement. The observation periods for the perforated, electrolytically etched, and silicoated FPDs were 114,99, and 30 months respectively. Results During the evaluation period, 27 FPDs (29%) failed; of these, 4 were perforated, 18 were electrolytically etched, and 5 were silicoated. The mean (±SD) duration of the successful clinical service for all FPDs was 41 ± 26 months. The mean time to failure for the FPDs that did not survive was 35 ± 23 months. The silicoated FPDs tended to have early failure, as did the FPDs with multiple pontics and those in the mandibular arch. Anterior and posterior FPDs performed equally well. Conclusions These findings, in conjunction with those from Europe and North American, show that resin-bonded FPD technology is as successful in a developing country as in industrialized areas of the world.     

A prospective study of multiple needle biopsies versus a single open biopsy for testicular sperm extraction in men with non-obstructive azoospermia

Little is known about the efficacy and the factors affecting the outcome of fine needle aspiration biopsy of the testis for sperm retrieval in azoospermic men with defective spermatogenesis. A prospective study was designed to compare the efficacy of needle and open (window) testicular biopsies for testicular epididymal sperm extraction (TESE) in 35 consecutive men with azoospermia due to defective spermatogenesis undergoing testicular biopsy for intracytoplasmic injection of oocytes. Each of the consecutive 35 patients underwent TESE using a 19 gauge butterfly needle followed by a window (1-1.5 cm-sized incision) testicular biopsy in the same procedure. The extraction of spermatozoa into culture medium was compared with the assessment of testicular biopsies by histology, the mode of biopsy (needle or open biopsy) and the amount of tissue retrieved by either method. Testicular spermatozoa were retrieved in 22 (63%) who had an open testicular biopsy compared with five (14%) patients who had multiple needle biopsies, respectively; the difference was statistically significant. Open testicular biopsy retrieves more testicular tissue than needle biopsy. Needle testicular biopsy retrieved testicular spermatozoa in 50% of those with hypospermatogenesis, 10% with focal spermatogenesis and in no patients with maturation arrest or Sertoli cell-only pattern. In contrast, sperm retrieval was successful in 100%, 90% and 66% of those with respective histologies using open testicular biopsy. Other than bruising, for which they required no analgesia, none of the patients suffered any obvious complications associated with traditional testicular biopsy. We conclude that open testicular biopsy is more effective than needle biopsy for the retrieval of testicular spermatozoa in azoospermic men with defective spermatogenesis. The difference observed may be related to the amount of testicular tissue retrieved and to the influence of testicular histology.      

Enhancing patency,safety and cost effectiveness of catheters

Catheters are generally known to be the last resort for blood access in dialysis. Because of the many problems related to catheter use, catheters are banned from vascular access courses organized by professional societies and the development of catheters and catheter related equipment relies on a few interested medical doctors with limited knowledge of hydraulics and material science. Rather than accepting the need for catheters and the need for improving catheters and catheter related procedures, vascular access meetings typically begin and end with statements saying that the use of fistulas must be increased and catheters must be banned. Several small companies have developed new catheters and catheter related equipment, which potentially overcome many of the problems related to the use of catheters. The authors had the privilege of participating in one of these developments and report about basic features and clinical experience of the DIALOCK® blood access port and an antimicrobial catheter locking solution (CLS) which is used with conventional catheters as well as with the DIALOCK®.