Abstract: The aim of this work was to study the exposure to magnetic fields of children living at different distances from a power line and to evaluate how well theoretical calculations compared with actual exposure. Personal exposure instruments were carried for 24 h by 65 schoolchildren living 28-325 m from a 300 kV transmission line; the current load was 200-700 A. About half of the children attended a school far from the power line, whereas the other half attended a school located about 25 m from the line. Exposure to magnetic fields was analyzed for three categories of location: at home, at school, and at all other places. Time spent in bed was analyzed separately. The results indicated that children who lived close to a power line had a higher magnetic field exposure than other children. The power line was the most important source of exposure when the magnetic field due to the line was greater than about 0.2 microT. Exposure at school influenced the 24 h time-weighted average results considerably in those cases where the distance between home and power line was very different from the distance between school and power line. The calculated magnetic field, based on line configuration, current load, and distance between home and power line, corresponded reasonably well with the measured field. However, the correlation depends on whether home only or 24 h exposure is used in the analysis and on which school the children attended. The calculated magnetic field seems to be a reasonably good predictor of actual exposure and could be used in epidemiological studies, at least in Norway, where the electrical system normally results in less ground current than in most other countries.

Abstract: The second messenger 3':5'-cyclic adenosine monophosphate (cAMP) inhibits the proliferation of human B lymphocytes. In lymphoid malignancies, cAMP levels or the number of beta 2-adrenergic receptors seem to be decreased. In order to explore this phenomenon further, the function of the beta 2-adrenergic receptor complex was examined in mononuclear leucocytes (MNLs) from patients with B-cell chronic lymphocytic leukaemia (CLL). Peripheral blood MNLs from 25 CLL patients (16 male, nine female: aged 62 +/- 9 years) and 10 healthy volunteers (seven male, three female; aged 47 +/- 19 years) were used. The binding characteristics of beta 2-adrenergic receptors (beta 2-AR) on MNLs were determined by radioligand binding assays with [125I]-cyanopindolol ([125I]-CYP). The number of high-affinity binding sites for [125I]-CYP was significantly lower in CLL patients (313 +/- 300 sites per cell; mean +/- SD) than in control subjects (1479 +/- 1268 sites per cell). Moreover, the density of beta 2-AR decreased with disease progression, from Binet stage A (371 +/- 236, n = 13) to B (236 +/- 136, n = 7) and C (141 +/- 59, n = 5) (P < 0.05; Kruskal-Wallis analysis). Functional analyses of the beta 2-AR complex were performed by measuring the cellular cAMP content of MNLs in response to different stimulators. The cAMP production of MNLs upon isoprenaline stimulation (ISO; 10 min, 10(-4) mol L-1) was slightly lower in CLL patients (12.5 +/- 7.04 pmol 10(-6) cells) than in control subjects (15.91 +/- 10.08 pmol 10(-6) cells), and decreased with CLL progression (stage A 14 +/- 7; stage B 13.66 +/- 3.91; stage C 3.07 +/- 0.79 pmol 10(-6) cells). In contrast, cAMP accumulation in response to cholera toxin (CHO; 10(-4) gml-1, 120 min) was not different in control subjects (70.07 +/- 31.30 pmol 10(-6) cells) and CLL patients (stage A 95.24 +/- 123.07, stage B 70.76 +/- 57.37, stage C 33.21 +/- 33.73 pmol 10(-6) cells). When stimulated with forskolin (100 mumol L-1, 15 min), control MNLs produced about ten-fold more cAMP than CLL MNLs (188.56 +/- 92.53 vs. 17.88 +/- 10.32 pmol 10(-6) cells); this response was not stage dependent. Taken together, the results show that the beta 2-AR transmembrane signalling is impaired in CLL patients. The correlation of some beta 2-AR signalling defects with disease progression suggests that they may contribute to the disease progression of CLL patients.

Abstract: Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature, across the frequency range, demonstrating that good agreement was achieved between measurements using the three pieces of equipment. Moreover, the measured values fall well within the body of corresponding literature data.