T Mee

Publications of T Mee

• Exposure to radio frequency electromagnetic fields from wireless computer networks: duty factors of Wi-Fi devices operating in schools.

  Authors: M Khalid, T Mee, A Peyman, D Addison, C Calderon, M Maslanyj, S Mann

  Progress in biophysics and molecular biology. 08/2011; 107(3):412-20.

  The growing use of wireless local area networks (WLAN) in schools has prompted a study to investigate exposure to the radio frequency (RF) electromagnetic fields from Wi-Fi devices. InternationalThe growing use of wireless local area networks (WLAN) in schools has prompted a study to investigate exposure to the radio frequency (RF) electromagnetic fields from Wi-Fi devices. International guidelines on limiting the adverse health effects of RF, such as those of ICNIRP, allow for time-averaging of exposure. Thus, as Wi-Fi signals consist of intermittent bursts of RF energy, it is important to consider the duty factors of devices in assessing the extent of exposure and compliance with guidelines. Using radio packet capture methods, the duty factor of Wi-Fi devices has been assessed in a sample of 6 primary and secondary schools during classroom lessons. For the 146 individual laptops investigated, the range of duty factors was from 0.02 to 0.91%, with a mean of 0.08% (SD 0.10%). The duty factors of access points from 7 networks ranged from 1.0% to 11.7% with a mean of 4.79% (SD 3.76%). Data gathered with transmit time measuring devices attached to laptops also showed similar results. Within the present limited sample, the range of duty factors from laptops and access points were found to be broadly similar for primary and secondary schools. Applying these duty factors to previously published results from this project, the maximum time-averaged power density from a laptop would be 220 μW m(-2), at a distance of 0.5 m and the peak localised SAR predicted in the torso region of a 10 year old child model, at 34 cm from the antenna, would be 80 μW kg(-1).

• Assessment of exposure to electromagnetic fields from wireless computer networks (wi-fi) in schools; results of laboratory measurements.

  Authors: A Peyman, M Khalid, C Calderon, D Addison, T Mee, M Maslanyj, S Mann

  Health physics. 06/2011; 100(6):594-612.

  Laboratory measurements have been carried out with examples of Wi-Fi devices used in UK schools to evaluate the radiofrequency power densities around them and the total emitted powers. UnlikeLaboratory measurements have been carried out with examples of Wi-Fi devices used in UK schools to evaluate the radiofrequency power densities around them and the total emitted powers. Unlike previous studies, a 20 MHz bandwidth signal analyzer was used, enabling the whole Wi-Fi signal to be captured and monitored. The radiation patterns of the laptops had certain similarities, including a minimum toward the torso of the user and two maxima symmetrically opposed across a vertical plane bisecting the screen and keyboard. The maxima would have resulted from separate antennas mounted behind the top left and right corners of the laptop screens. The patterns for access points were more symmetrical with generally higher power densities at a given distance. The spherically-integrated radiated power (IRP) ranged from 5 to 17 mW for 15 laptops in the 2.45 GHz band and from 1 to 16 mW for eight laptops in the 5 GHz band. For practical reasons and because access points are generally wall-mounted with beams directed into the rooms, their powers were integrated over a hemisphere. These ranged from 3 to 28 mW for 12 access points at 2.4 GHz and from 3 to 29 mW for six access points at 5 GHz. In addition to the spherical measurements of IRP, power densities were measured at distances of 0.5 m and greater from the devices, and consistent with the low radiated powers, these were all much lower than the ICNIRP reference level.

• Occupational exposure of UK adults to ELF magnetic fields.

  Authors: T Mee, P Whatmough, L Broad, C Dunn, M Maslanyj, S Allen, K Muir, P A McKinney, M van Tongeren

  Occupational and environmental medicine. 05/2009;

  BACKGROUND: More recently, epidemiological studies have tended to categorise occupational exposure to extremely low frequency (ELF) magnetic fields (MF) on the basis of a job-exposure matrix (JEM),BACKGROUND: More recently, epidemiological studies have tended to categorise occupational exposure to extremely low frequency (ELF) magnetic fields (MF) on the basis of a job-exposure matrix (JEM), based solely on job title. However, occupational exposure in the UK general population is poorly documented. AIMS: To assess occupational exposure to ELF MF in the UK and evaluate the use of a rigid JEM to assign exposures to subjects in the UK Adult Brain Tumour Study (UKABTS). METHODS: Personal ELF MF measurements were preformed using Emdex II magnetic field meters. Exposure was classified by Standard Occupational Classification (2000), Standard Industrial Classification (1997), and a combined occupation-industry classification. LME models determined the contribution of occupational exposure to the 24 hr cumulative exposure and the contribution of occupation and industry to total variance. RESULTS: 236 individuals provided occupational data covering 117 different occupations. Average exposure was significantly higher at work than at home. Elevated average occupational exposure was found for welding trades, printers, telephonists and filing and other records assistants. The discrimination of a rigid JEM based on occupation is improved by linking the classification with industry and by use of contextual information. CONCLUSIONS: This report constitutes a substantial expansion of information on adult exposure to ELF MF in the UK. There is evidence that the accuracy of exposure assessments based solely on job codes is improved by linking with either industry code or contextual knowledge of equipment, such as electron beam welders, and of power lines or substations in the work environment.

• p53 binds the nuclear matrix in normal cells: binding involves the proline-rich domain of p53 and increases following genotoxic stress.

  Authors: M Jiang, T Axe, R Holgate, C P Rubbi, A L Okorokov, T Mee, J Milner

  Oncogene. 10/2001; 20(39):5449-58.

  The tumour suppressor p53 is a multifunctional protein important for the maintenance of genomic integrity. It is able to form molecular complexes with different DNA targets and also with cellularThe tumour suppressor p53 is a multifunctional protein important for the maintenance of genomic integrity. It is able to form molecular complexes with different DNA targets and also with cellular proteins involved in DNA transcription and DNA repair. In mammalian cells the biochemical processing of DNA occurs on a nuclear sub-structure termed the nuclear matrix. Previously Deppert and co-workers have identified p53 in association with the nuclear matrix in viral- and non-viral transformed cell lines. In the present study we demonstrate, for the first time, that p53 is bound to the nuclear matrix in primary cultures of normal mammalian cells and that this binding increases following DNA damage. Analysis of cell lines expressing structural mutants of p53 revealed that association with the nuclear matrix is independent of the tertiary and quaternary structure of p53. However, the proline-rich domain towards the N-terminus of p53 (residues 67 to 98) appeared important for binding to the nuclear matrix. This was demonstrated by TET-ON regulated expression of p53-derived constructs in p53(-/-) murine embryonic fibroblasts (MEF p53(-/-)). The proline-rich domain of p53 has potential for SH3 protein-protein interaction, and has a role in p53-mediated apoptosis and possibly base excision repair of DNA damage. We discuss our observations in relation to the ability of p53 to facilitate DNA repair and also review evidence indicating that matrix-bound p53 in SV40-transformed cells may facilitate the transforming potential of SV40 large T antigen.

• Proteolytic cleavage of p53 mutants in response to mismatched DNA.

  Authors: T Mee, A L Okorokov, S Metcalfe, J Milner

  British journal of cancer. 10/1999; 81(2):212-8.

  Interaction of p53 with mismatched DNA induces proteolytic cleavage with release of a 35-kDa protein fragment from the p53-DNA complexes. The 35-kDa cleavage product is activated for specificInteraction of p53 with mismatched DNA induces proteolytic cleavage with release of a 35-kDa protein fragment from the p53-DNA complexes. The 35-kDa cleavage product is activated for specific biochemical function(s) and may play a role in the cellular response to DNA damage (Molinari et al (1996) Oncogene 13: 2077-2086; Okorokov et al (1997) EMBO J 16: 6008-6017). In the present study we have asked if mutants of p53 retain the ability to undergo similar proteolytic cleavage, and compared sequence-specific 'DNA contact' with 'structural' mutants commonly found in human cancer. In addition, a series of phosphorylation site mutants were generated to investigate the possible effects of phosphorylation/dephosphorylation on the proteolytic cleavage of p53. All mutants tested bound to a mismatched DNA target in vitro. Moreover, studies in vitro and in vivo indicate that p53 mutants with intact conformational structure (as determined by immunoreactivity with PAb246 and PAb1620) retain the ability to undergo proteolytic cleavage similar, if not identical, to the wild-type p53 protein. Our results suggest that the capacity for p53 to bind mismatched DNA is independent of structural conformation of the central core domain. Proteolytic cleavage, however, is crucially dependent upon a wild-type conformation of the protein.