Permeability of the blood-brain barrier induced by 915 MHz electromagnetic radiation, continuous wave and modulated at 8, 16, 50, and 200 Hz.

Abstract

Biological effects of electromagnetic fields (EMF) on the blood-brain barrier (BBB) can be studied in sensitive and specific models. In a previous investigation of the permeability of the blood-brain barrier after exposure to the various EMF-components of proton magnetic resonance imaging (MRI), we found that the exposure to MRI induced leakage of Evans Blue labeled proteins normally not passing the BBB of rats [Salford et al. (1992), in: Resonance Phenomena in Biology, Oxford University Press, pp. 87-91]. In the present investigation we exposed male and female Fischer 344 rats in a transverse electromagnetic transmission line chamber to microwaves of 915 MHz as continuous wave (CW) and pulse-modulated with repetition rates of 8, 16, 50, and 200 s-1. The specific energy absorption rate (SAR) varied between 0.016 and 5 W/kg. The rats were not anesthetized during the 2-hour exposure. All animals were sacrificed by perfusion-fixation of the brains under chloral hydrate anesthesia about 1 hour after the exposure. The brains were perfused with saline for 3-4 minutes, and thereafter fixed in 4% formaldehyde for 5-6 minutes. Central coronal sections of the brains were dehydrated and embedded in paraffin and sectioned at 5 microns. Albumin and fibrinogen were demonstrated immunohistochemically. The results show albumin leakage in 5 of 62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves. Continuous wave resulted in 14 positive findings of 35, which differ significantly from the controls (P = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

AI evidence extraction

Main findings

Albumin leakage was observed in 5/62 controls and 56/184 rats exposed to 915 MHz microwaves. Continuous-wave exposure had 14/35 positive findings and differed significantly from controls (P = 0.002).

Outcomes measured

• Blood-brain barrier (BBB) permeability
• Albumin leakage (immunohistochemistry)
• Fibrinogen (immunohistochemistry)

Limitations

• Abstract is truncated; results for pulse-modulated conditions (8, 16, 50, 200 s-1) are not fully reported in the provided text.
• SAR is reported as a range (0.016 to 5 W/kg) without condition-specific values in the provided text.
• Fibrinogen results are not described in the provided text.

Suggested hubs

• rf-blood-brain-barrier (0.9)
  Animal study assessing BBB permeability/leakage after 915 MHz RF exposure.

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    "study_type": "animal",
    "exposure": {
        "band": "RF",
        "source": null,
        "frequency_mhz": 915,
        "sar_wkg": null,
        "duration": "2-hour exposure"
    },
    "population": "Male and female Fischer 344 rats",
    "sample_size": 246,
    "outcomes": [
        "Blood-brain barrier (BBB) permeability",
        "Albumin leakage (immunohistochemistry)",
        "Fibrinogen (immunohistochemistry)"
    ],
    "main_findings": "Albumin leakage was observed in 5/62 controls and 56/184 rats exposed to 915 MHz microwaves. Continuous-wave exposure had 14/35 positive findings and differed significantly from controls (P = 0.002).",
    "effect_direction": "harm",
    "limitations": [
        "Abstract is truncated; results for pulse-modulated conditions (8, 16, 50, 200 s-1) are not fully reported in the provided text.",
        "SAR is reported as a range (0.016 to 5 W/kg) without condition-specific values in the provided text.",
        "Fibrinogen results are not described in the provided text."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "blood-brain barrier",
        "BBB permeability",
        "albumin leakage",
        "fibrinogen",
        "Evans Blue",
        "915 MHz",
        "microwaves",
        "continuous wave",
        "pulse-modulated",
        "SAR",
        "rat"
    ],
    "suggested_hubs": [
        {
            "slug": "rf-blood-brain-barrier",
            "weight": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "Animal study assessing BBB permeability/leakage after 915 MHz RF exposure."
        }
    ]
}

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