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RF Dosimetry
Rodent Neurobiology
Rodent Neurobiology
Studies of rodents have the advantage of tight experimental control and the ability to obtain measures too invasive for human subjects. These factors are imperative in elucidating specific biological mechanisms within the brain which may explain reported RF bioeffects in humans.   

 

Two streams of research will thus utilise rodents for these purposes: In vitro and In vivo research.  In Vitro studies involve examination of the effect of RF on nervous (or other biological) tissue that has been extracted from rodents.  This enables identification of RF effects on individual components of the nervous system, such as an isolated neuron, which may not be observable within the overall nervous system.  Conversely, In Vivo studies, in which the effects of RF on live rodents is measured, enable identification of RF effects on the intact nervous system, sometimes observed indirectly through behavioural and other signs.  The distinction between these research approaches is important because there may be, for example, RF effects on individual components of the nervous system whose harm is eliminated through interactions within the intact nervous system (or vice-versa), and so both research streams are needed for adequate interpretation of any RF effects.

 

 

Current Projects

 

The effect of RF on Gap Junction permeability

 

Project leader: A/Prof Andrew W Wood

 

NHMRC funded research staff: Dr Yuen (Linda) Chen (ACRBR Postdoctoral Fellow), Dr Vladimir Dubaj (ACRBR Postdoctoral fellow)

 

Aims: to assess the effects of RF on gap junction permeability

 

Methods: A calibrated exposure chamber that was used in previous studies will be modified to enable this study.  Laser Scanning Confocal Microscope (LSCM) techniques will be used for studying junction communication, based on dual labeling of cell samples with dyes that can be seen under microscope. Effects of RF with and without melatonin on this transfer rate will be assessed.

Results:

Conclusion:

 

The Effect of RF on Blood-brain barrier permeability

 

Project leader: A/Prof Andrew W Wood

 

NHMRC funded research staff: Dr Yuen (Linda) Chen (ACRBR Postdoctoral Fellow), Dr Vladimir Dubaj (ACRBR Postdoctoral fellow)

 

Background: The blood brain barrier (BBB) is composed of brain endothelial cells and astrocytes. The tight junction of the BBB is a selectively permeable barrier to protect the central nervous system (CNS) from damage. It has been speculated that RF exposure may alter blood brain barrier permeability and therefore cause CNS damage.

 

Aims: To investigate the effects of 900 MHz modulated RF radiation on the permeability of a synthetic blood brain barrier (BBB), formed by co-culture method. 

 

Methods:

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A synthetic BBB was produced by co-culturing rat cerebral endothelial cells and astrocytes on a poly-(ethylene terephtalate) PET membrane.  The electrical resistance of the BBB was measured (pre-exposure) 

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RF exposure (900MHz) administered in a purpose-made RF exposure chamber (was developed and made in our laboratory) in which cellular Specific Absorption Rate (SAR) had been previously established in our laboratory through mathematical modelling. During the 30 minutes RF exposure, temperature were monitored by an optical temperature probe and stabilised by perfusion of pre-warmed DMEM at 37oC.

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Post-exposure electrical resistance and permeability assays were then performed in the RF chamber. Protein permeability assay was performed by perfusing 500l 1mg/ml albumin through the RF chamber. Due to the special design of our RF chamber, perfused DMEM could be collected on the other side of the BBB.

 

Results: Experimentation commenced in December 2005.  All main experiments are scheduled for completion by April 2006, with the final results to be completed by late 2006.

 

 

The effect of RF on cell surface glycoconjugates

 

Project leader: A/Prof Andrew W Wood

 

NHMRC funded research staff: Dr Yuen (Linda) Chen (ACRBR Postdoctoral Fellow), Dr Vladimir Dubaj (ACRBR Postdoctoral fellow)

 

Background: Glycoconjugates are suggested to be involved in cell adhesion and cell growth regulation.  Tumour-associated glycoconjugates may be involved in the uncontrolled growth and metastatic properties of cancer cells. Cell surface glycoconjugates have long been considered a candidate for RF-cell membrane interactions (Adey). 

 

Aims: to examine the effects of 915 MHz RF radiation on cell surface glycoconjugate expression in rat (hippocampal) neuronal cells. 

 

Methods:

1.  300um hippocampal slices were taken from 2-week old Sprague-Dawley (SD) rats

2.  Various lectins will be applied in this study to detect glycoconjugates expression: complex carbohydrate will be stained by Phaseolus vulgaris agglutinin (PHA); Sialic acid will be stained by Triticum vulgaris agglutinin (WGA); Purkinje cells will be stained by concanavalin A (ConA) and WGA; Glial cells and endothelial cells will be stained by Griffonia simplicifolia (GS-IB4).  Lectins were incubated with the hippocampus slices or tissue culture samples at 37oC for 30 min to 45 min.

3.  Followed by washing with PBS.

4.  RF exposure(Sham exposure group and RF exposure group). Slices were exposed within a calibrated purpose-made exposure chamber developed previously in this laboratory. Temperature was monitored by an optical temperature probe and stabilised at 37oC.  

5.   Imaging by Laser Scanning Confocal Microscope (LSCM) and DIC microscope.

6.   Image processing 

Results: The main experiments for this project are scheduled for May 06 – Sept 06. Final results are expected by the end of 2006

 

 

Mathematical modelling of absorbed energy from mobile phone handsets in nearfield regions (face and ear)

 

Project leader: A/Prof Andrew W Wood

 

NHMRC funded research staff: Teddy Kurniawan, Swinburne Full-time PhD student

 

Background: The electromagnetic field generated by an antenna can be classified as near-field (defined as the portion of the field that is within one-quarter of the electromagnetic wavelength from the antenna) or far-field (the portion of the field that exists at greater distances from the antenna).  Electric and magnetic field strength at points within the far-field can be reliably predicted according to established laws of physics.  However, the determinants of electrical and magnetic field values within the near-field are not well understood.  This makes it more difficult to calculate energy deposition in biological tissue due to mobile phone use, since mobile phone users are exposed to near-field electromagnetic fields. 

 

Aims: To calculate near-field electric (E) and magnetic (H) field values computed via Matlab and XFDTD.

 

Methods:

Mr. Kurniawan has made much progress on this project (which will form the basis of his PhD thesis) in 2005, including: 

 

  1. Completion of a literature review of RF dosimetry studies specific to mobile phone radiation, plus attendance at a course in cellular biophysics (Feb -  May 2005)
  2. Completion of experimental work of RF dosimetry (performed at then Telstra Research Laboratory) to strengthen the background knowledge as well as collaboration work in ACRBR platform (June – August 2005)
  3. Performance of initial near field analysis and electromagnetic phenomenon around a typical dipole antenna representing mobile phone antenna (April – May 2005, August – October 2005)
  4. Development of initial analysis tools and performing initial simulations in MATLAB® platform (April – May 2005, September – November 2005)
  5. Performance of comprehensive near field analysis and electromagnetic phenomenon around a typical dipole antenna representing mobile phone antenna (ongoing – expected to finish in the first semester of 2006)
  6. Modelling of a number of tissue, cells and/or particular sections of human head in close proximity with RF exposure from mobile phone antenna (ongoing – expected to finish within the third quarter of 2006)
  7. Development of comprehensive analysis tools in MATLAB® platform (ongoing – expected to finish the major part in late 2006)
  8. Deductions and thesis writing (third and fourth quarter 2007)

 

 

 

Effect of mobile telephony on blood-brain barrier permeability in the fetal mouse brain.

 

Project leader: Dr. John Finnie

 

NHMRC funded research staff: Dr Zhao Cai (ACRBR Postdoctoral Fellow)

 

Aims: To study the effect of mobile telephone exposure on blood-brain barrier (BBB) permeability in the immature brain.

 

Methods: Using a purpose-designed exposure system at 900 MHz, pregnant mice were given a single, far-field, whole body exposure at a specific absorption rate of 4 W/kg for 60 min/day from day 1 to day 19 of gestation. Pregnant control mice were sham-exposed or freely mobile in a cage without further restraint and a positive control group with cadmium-induced BBB damage was also included. Immediately prior to parturition on gestational day 19, fetal heads were collected, fixed in Bouin's fixative and paraffin embedded. Disruption of BBB integrity was detected immunohistochemically using endogenous albumin as a vascular tracer in cerebral cortex, thalamus, basal ganglia, hippocampus, cerebellum, midbrain and medulla.

 

Results: No albumin extravasation was found in exposed or control brains.

 

Conclusion: In this animal model, whole of gestation exposure to global system for mobile communication-like radiofrequency fields did not produce any increase in vascular permeability in the fetal brain regions studied using endogenous albumin as a light microscopic immunohistochemical marker.

 

Ref:Pathology. 2006 Feb; 38(1):63-5.

 

 

 

Expression of the immediate early gene, c-fos, in mouse brain after acute global system for mobile communication microwave exposure

 

Project leader: Dr. John Finnie

 

NHMRC funded research staff: Dr Zhao Cai (ACRBR Postdoctoral Fellow)

 

Aims: To study the effect of acute exposure to global system for mobile communication radiofrequency fields on immediate early gene, c-fos, expression in the brain.

 

Methods: Using a purpose-designed exposure system at 900 MHz, mice were given a single, far-field, whole body exposure for 60 minutes at a specific absorption rate of 4 W/kg. Control mice were sham-exposed or freely mobile in a cage without further restraint. c-fos protein expression was detected immunohistochemically in perfusion-fixed brains.

 

Results: Activation of c-fos in exposed and sham-exposed brains was comparable, but was greatly increased compared with freely moving controls.

 

Conclusion: These results suggest that the majority of the acute genomic response detected by c-fos expression was due to immobilisation rather than irradiation.

 

Ref: Pathology. 2005 Jun;37(3):231-3.

 

 

Expression of the immediate early gene, c-fos, in fetal brain after whole of gestation exposure of pregnant mice to global system for mobile communication microwaves

 

Project leader: Dr. John Finnie

 

NHMRC funded research staff: Dr Zhao Cai (ACRBR Postdoctoral Fellow)

 

Aims: To study immediate early gene, c-fos, expression as a marker of neural stress after whole of gestation exposure of the fetal mouse brain to mobile telephone-type radiofrequency fields. 

 

Methods: Using a purpose-designed exposure system at 900 MHz, pregnant mice were given a single, far-field, whole body exposure at a specific absorption rate of 4 W/kg for 60 min/day from day 1 to day 19 of gestation. Pregnant control mice were sham-exposed or freely mobile in a cage without further restraint. Immediately prior to parturition on gestational day 19, fetal heads were collected, fixed in 4% paraformaldehyde and paraffin embedded. Any stress response in the brain was detected by c-fos immunohistochemistry in the cerebral cortex, basal ganglia, thalamus, hippocampus, midbrain, cerebellum and medulla. 

 

Results: c-fos expression was of limited, but consistent, neuroanatomical distribution and there was no difference in immunoreactivity between exposed and control brains. 

 

Conclusion: In this animal model, no stress response was detected in the fetal brain using c-fos immunohistochemistry after whole of gestation exposure to mobile telephony.

 

Pathology 2006 (in press).

 

 

Neonatal mouse brain exposure to mobile telephony and effect on blood-brain barrier permeability.

 

Project leader: Dr. John Finnie

 

NHMRC funded research staff: Dr Zhao Cai (ACRBR Postdoctoral Fellow)

 

Aims: To study the effect of mobile telephone exposure on BBB permeability in the immature brain during the neonatal period.

 

Methods: Using a purpose-designed exposure system at 900 MHz, newborn mice were given a single, far-field, whole body exposure at a specific absorption rate of 4 W/kg for 60 min/day during the first 7 days postnatal. Control mice were sham-exposed or freely mobile in a cage without further restraint. On day 7, heads were collected, fixed in Bouin’s and paraffin embedded. Disruption of BBB integrity was detected immunohistochemically using endogenous albumin as a vascular tracer in cerebral cortex, thalamus, basal ganglia, hippocampus, cerebellum, midbrain and medulla.

 

Results: No albumin extravasation was found in exposed or control brains.

 

Conclusion: In this animal model, exposure to global system for mobile communication-like radiofrequency fields for the first postnatal week did not produce any increase in vascular permeability in the brain regions studied using endogenous albumin as a light microscopic immunohistochemical marker.

 

Pathology 2006 (in press).

 

 

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