Search

The present study investigated the effects of microwave (MW) radiation applied under a sublethal temperature on Escherichia coli. The experiments were conducted at a frequency of 18 GHz and at a temperature below 40°C to avoid the thermal degradation of bacterial cells during exposure. The absorbed power was calculated to be 1,500 kW/m(3), and the electric field was determined to be 300 V/m. Both values were theoretically confirmed using CST Microwave Studio 3D Electromagnetic Simulation Software. As a negative control, E. coli cells were also thermally heated to temperatures up to 40°C using Peltier plate heating. Scanning electron microscopy (SEM) analysis performed immediately after MW exposure revealed that the E. coli cells exhibited a cell morphology significantly different from that of the negative controls. This MW effect, however, appeared to be temporary, as following a further 10-min elapsed period, the cell morphology appeared to revert to a state that was identical to that of the untreated controls. Confocal laser scanning microscopy (CLSM) revealed that fluorescein isothiocyanate (FITC)-conjugated dextran (150 kDa) was taken up by the MW-treated cells, suggesting that pores had formed within the cell membrane. Cell viability experiments revealed that the MW treatment was not bactericidal, since 88% of the cells were recovered after radiation. It is proposed that one of the effects of exposing E. coli cells to MW radiation under sublethal temperature conditions is that the cell surface undergoes a modification that is electrokinetic in nature, resulting in a reversible MW-induced poration of the cell membrane.

This is the first of two articles addressing the most appropriate crossover frequency at which incident power flux density (S(inc)) replaces the spatial peak value of the specific energy absorption rate (SAR) averaged over 1 or 10 g (i.e., peak 1 or 10 g SAR) as the basic restriction for protecting against radiofrequency (RF) heating effects in the 1-10 GHz range. Our general approach has been to compare the degree of correlation between these basic restrictions and the peak induced tissue temperature rise (DeltaT) for a representative range of population/exposure scenarios. In this article we particularly address the effect of human population diversity in the thickness of body tissue layers at eight different sites of the body. We used a Monte Carlo approach to specify 32000 models (400 models for each of 8 body sites for 10 frequencies) which were representative of tissue thicknesses for age (18-74 years) and sex at the eight body sites. Histogram distributions of S(inc) and peak 1 and 10 g SAR corresponding to a peak 1 degrees C temperature rise were obtained from RF and thermal analyses of 1D multiplanar models exposed to a normally incident plane wave ranging from 1 to 10 GHz in thermo-neutral environmental conditions. Examination of the distribution spread of the histograms indicated that peak SAR was a better predictor of peak tissue temperature rise across the entire 1-10 GHz frequency range than S(inc), as indicated by the smaller spread in its histogram distributions, and that peak 10 g SAR was a slightly better predictor than peak 1 g SAR. However, this result must be weighed against partly conflicting indications from complex body modeling in the second article of this series, which incorporates near-field effects and the influence of complex body geometries., (2010 Wiley-Liss, Inc.)

The effects of exposure to radiofrequency electromagnetic fields (EMF), specifically related to the use of mobile telephones, on the nervous system in humans have been the subject of a large number of experimental studies in recent years. There is some evidence of an effect of exposure to a Global System for Mobile Telecommunication (GSM)-type signal on the spontaneous electroencephalogram (EEG). This is not corroborated, however, by the results from studies on evoked potentials. Although there is some evidence emerging that there may be an effect of exposure to a GSM-type signal on sleep EEG, results are still variable. In summary, exposure to a GSM-type signal may result in minor effects on brain activity, but such changes have never been found to relate to any adverse health effects. No consistent significant effects on cognitive performance in adults have been observed. If anything, any effect is small and exposure seems to improve performance. Effects in children did not differ from those in healthy adults. Studies on auditory and vestibular function are more unequivocal: neither hearing nor the sense of balance is influenced by short-term exposure to mobile phone signals. Subjective symptoms over a wide range, including headaches and migraine, fatigue, and skin itch, have been attributed to various radiofrequency sources both at home and at work. However, in provocation studies a causal relation between EMF exposure and symptoms has never been demonstrated. There are clear indications, however, that psychological factors such as the conscious expectation of effect may play an important role in this condition.

Neuropathic pain appears to be much more common in leprosy than has been generally appreciated. Emphasis in leprosy control programs has been on the distribution of multi-drug therapy, on early and better detection, and on the prevention of disability related to anesthetic limbs. Most have thus been inattentive to the problem of neuropathic pain in leprosy patients. Neuropathic pain does not respond to the usual analgesics employed for reactions, for example, and so it is important that those treating leprosy patients give this problem the special attention it requires, both in diagnosis and in treatment.

Many coaches use field tests to estimate athlete's aerobic capacity. Recently it has been has suggested that the 5 minute run an accurate estimator of aerobic capacity as is the 15 minute aerobic run. The aim of this experiment was to determine whether the 5 minute run was as accurate an indicator of aerobic capacity as the 15 minute run. Also we wished to determine some correlational values between measured VO2max and both the 15 minute and 5 minute runs as well as determining some regression equations to calculate VO2max (mls.kg-1.min-1) given the distance run in the 5 or 15 minute runs. We found that the 15 minute run was still the best indicator of aerobic capacity for all age groups (r = 0.881, 851, 671 and 881 for 12, 13, 14, and 15 years respectively). The 5 minute run correlated significantly with the 15 minute run and with VO2max, in all cases. Correlational values were all moderate to high in nature with no correlation being lower than r = 0.534. We would conclude that the best method to estimate aerobic capacity in a field situation is to use the 15 minute run.

We have cloned into Escherichia coli the genes for 38 type-II bacterial modification methyltransferases. The clones were isolated by selecting in vitro for protectively modified recombinants. Most of the clones modify their DNA fully but a substantial number modify only partially. In approximately one-half of the clones, the genes for the corresponding endonucleases are also present. Some of these clones restrict infecting phages and others do not. Clones carrying endonuclease genes but lacking methyltransferase genes have been found, in several instances, to be viable.

The HaeIII methyltransferase (MTase) gene from Haemophilus aegyptius (recognition sequence: 5'-GGCC-3') was cloned into Escherichia coli in the plasmid vector pBR322. The gene was isolated on a single EcoRI fragment and on a single HindIII fragment. Clones carrying additional adjacent fragments were found to code also for the HaeII restriction endonuclease and HaeII modification MTase (recognition sequence: 5'-PuGCGCPy-3'). The sequence of the HaeIII modification gene was determined. The inferred amino acid sequence of the protein was found to share extensive similarity with other sequenced m5C-MTases. The central 'non-conserved' region of the M.HaeIII MTase, thought to form the nucleotide sequence-specificity domain, is almost identical to that of the M.BsuRI, M.BspRI and M.NgoPII MTases, which also recognize the sequence 5'-GGCC-3'.