Pacemaker interference by magnetic fields at power line frequencies

Human exposure to external 50/60-Hz electric and magnetic fields induces electric fields within the body. These induced fields can cause interference with implanted pacemakers. In the case of exposure to magnetic fields, the pacemaker leads are subject to induced electromotive forces, with current return paths being provided by the conducting body tissues. Modern computing resources used in conjunction with millimeter-scale human body conductivity models make numerical modeling a viable technique for examining any such interference. In this paper, an existing well-verified scalar-potential finite-difference frequency-domain code is modified to handle thin conducting wires embedded in the body. The effects of each wire can be included numerically by a simple modification to the existing code. Results are computed for two pacemaker lead insertion paths, terminating at either atrial or ventricular electrodes in the heart. Computations are performed for three orthogonal 60-Hz magnetic field orientations. Comparison with simplified estimates from Faraday's law applied directly to extracorporeal loops representing unipolar leads underscores problems associated with this simplified approach. Numerically estimated electromagnetic interference (EMI) levels under the worst case scenarios are about 40 microT for atrial electrodes, and 140 microT for ventricular electrodes. These methods could also be applied to studying EMI with other implanted devices such as cardiac defibrillators.     

Relation of emotion-related regulation to children's social competence: A longitudinal study.

The differential relations of children's emotion-related regulation (i.e., effortful control and impulsivity) to their personality resiliency, adult-rated popularity, and social competence were examined in children who were 4.5-7.9 years old and who were remeasured 2 years later. Parents and teachers reported on all constructs, and children's attentional persistence was observed. Structural equation modeling was used to test the mediating role of resiliency on the relations between regulation/control and popularity using two-wave longitudinal data. The results provide some evidence of the mediating role of resiliency in the relations between effortful control and popularity, provide some evidence of bidirectional effects, and also buttress the view that emotional regulation should be differentiated into effortful and reactive forms of control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measurements of density and viscosity of one- and two-phase fluids with torsional waveguides

The continuing need for in-situ measurements of physical properties of wastes contained within many high level radioactive waste tanks within the Hanford Site has initiated experimental and theoretical investigations of candidate measurement methods. This paper describes experiments performed with acoustic waveguide sensors. This technology has potential application at the Hanford Site for in-situ measurements of density, viscosity, and temperature of liquid wastes. Waveguides of both circular and rectangular geometry were used in these studies for determination of the densities and viscosities of various fluids. The flight time of a torsional pulse through the sensing region of the waveguide forms the measured quantity. The flight time depends on the velocity of the wave through the sensing region of the waveguide, and this velocity in turn depends upon the properties of the fluid in contact with the waveguide. We performed experiments with 15 different fluids, most of which were single-phase Newtonian fluids. However, three of the fluids were particle-liquid mixtures, and one of these Newtonian in behavior. Most of the wastes held in Hanford tanks contain high solids content. The results of our experiments showed that acoustic waveguides were well suited for measurements in most Newtonian fluids, in agreement with earlier research presented in the literature. However, results for two-phase Newtonian fluids containing particles indicate that, in our case, the waveguides responded primarily to the background fluid rather than the mixture. Very poor results were obtained with the non-Newtonian fluid. In addition, there was a class of fluids, which serve the community as viscosity standards, for which viscosities determined with torsional waveguides were in disagreement with viscosities obtained with standard viscometers.     

Clinical and theoretical implications of 5-HT2 and D2 receptor occupancy of clozapine, risperidone, and olanzapine in schizophrenia

OBJECTIVE: Dopamine D2 receptor occupancy measurements provide a valid predictor of antipsychotic response, extrapyramidal side effects, and elevation of prolactin levels. The new antipsychotics clozapine, risperidone, and olanzapine obtain antipsychotic response with few extrapyramidal side effects and little prolactin elevation. The purpose of this study was to compare the D2 and serotonin 5-HT2 receptor occupancies of these drugs in patients receiving multiple-dose, steady-state regimens. METHOD: Forty-four patients with schizophrenia (16 taking risperidone, 2-12 mg/day; 17 taking olanzapine, 5-60 mg/day; and 11 taking clozapine, 75-900 mg/day) had their D2 and 5-HT2 occupancies determined with the use of [11C]raclopride and [18F]setoperone, respectively, and positron emission tomography imaging. RESULTS: Clozapine showed a much lower D2 occupancy (16%-68%) than risperidone (63%-89%) and olanzapine (43%-89%). Risperidone and olanzapine gave equal D2 occupancies at doses of 5 and 20 mg/day, respectively. All three drugs showed greater 5-HT2 than D2 occupancy at all doses, although the difference was greatest for clozapine. CONCLUSIONS: Clozapine, at doses known to be effective in routine clinical settings, showed a D2 occupancy clearly lower than that of typical antipsychotics, while risperidone and olanzapine at their usual clinical doses gave the same level of D2 occupancy as low-dose typical antipsychotics. The results also suggest that some previous clinical comparisons of antipsychotics may have been confounded by different levels of D2 occupancy. Clinical comparisons of these drugs, matching for D2 occupancy, may provide a better measure of their true "atypicality" and will help in understanding the contribution of non-D2 receptors to antipsychotic effects.     

Prevention of type 2 diabetes

Type 2 diabetes is a major cause of morbidity and mortality resulting from its microangiopathic and macroangiopathic complications. Current approaches to its management and to the prevention of diabetic complications are difficult to implement effectively, and there is little evidence to date that these approaches are reducing the impact of this disease. The recognition that type 2 diabetes usually has a prolonged prediabetic phase raises the possibility that the emergence of hyperglycemia and the atherosclerotic complications associated with diabetes may be preventable by the institution of early treatment modalities. Sufficient data suggest that life-style modification or pharmacotherapy directed at improving insulin sensitivity or insulin secretion in subjects with impaired glucose tolerance may reduce progression to diabetes. Two long-term prospective, controlled trials have been initiated to test this hypothesis.     

GLUT4 and transferrin receptor are differentially sorted along the endocytic pathway in CHO cells

The trafficking of GLUT4, a facilitative glucose transporter, is examined in transfected CHO cells. In previous work, we expressed GLUT4 in neuroendocrine cells and fibroblasts and found that it was targeted to a population of small vesicles slightly larger than synaptic vesicles (Herman, G.A, F. Bonzelius, A.M. Cieutat, and R.B. Kelly. 1994. Proc. Natl. Acad. Sci. USA. 91: 12750-12754.). In this study, we demonstrate that at 37 degrees C, GLUT4-containing small vesicles (GSVs) are detected after cell surface radiolabeling of GLUT4 whereas uptake of radioiodinated human transferrin does not show appreciable accumulation within these small vesicles. Immunofluorescence microscopy experiments show that at 37 degrees C, cell surface-labeled GLUT4 as well as transferrin is internalized into peripheral and perinuclear structures. At 15 degrees C, endocytosis of GLUT4 continues to occur at a slowed rate, but whereas fluorescently labeled GLUT4 is seen to accumulate within large peripheral endosomes, no perinuclear structures are labeled, and no radiolabeled GSVs are detectable. Shifting cells to 37 degrees C after accumulating labeled GLUT4 at 15 degrees C results in the reappearance of GLUT4 in perinuclear structures and GSV reformation. Cytosol acidification or treatment with hypertonic media containing sucrose prevents the exit of GLUT4 from peripheral endosomes as well as GSV formation, suggesting that coat proteins may be involved in the endocytic trafficking of GLUT4. In contrast, at 15 degrees C, transferrin continues to traffic to perinuclear structures and overall labels structures similar in distribution to those observed at 37 degrees C. Furthermore, treatment with hypertonic media has no apparent effect on transferrin trafficking from peripheral endosomes. Double-labeling experiments after the internalization of both transferrin and surface-labeled GLUT4 show that GLUT4 accumulates within peripheral compartments that exclude the transferrin receptor (TfR) at both 15 degrees and 37 degrees C. Thus, GLUT4 is sorted differently from the transferrin receptor as evidenced by the targeting of each protein to distinct early endosomal compartments and by the formation of GSVs. These results suggest that the sorting of GLUT4 from TfR may occur primarily at the level of the plasma membrane into distinct endosomes and that the organization of the endocytic system in CHO cells more closely resembles that of neuroendocrine cells than previously appreciated.