Effects of millimeter-wave radiation on monolayer cell cultures. III. A search for frequency-specific athermal biological effects on protein synthesis.

Abstract

A method recently developed in this laboratory has been used to directly expose BHK-21/C13 cells to high levels of microwave radiation without significant microwave-induced heating (less than or equal to 0.1 degrees C). Monolayer cultures were grown on microwave-transparent polystyrene coverslips, placed on the open end of a wave guide, and maintained at 37.2 degrees C during irradiation at frequencies in both the E- and U-bands (average power densities 292 and 177 mW/cm2, respectively). Effects of microwave radiation were assessed at 0.1 GHz increments in the ranges of 38-48 GHz and 65-75 GHz. Protein synthesis was measured in quadruplicate cultures that were allowed to incorporate labeled methionine during the 15-minute period of microwave irradiation. Autoradiographs of each monolayer culture were scanned along the region corresponding to the longer axis of the wave guide aperture using a microdensitometer to quantify incorporation. Since microwave power incident on the cells was previously shown to vary along this axis according to a cosine2 relationship from zero at each edge of the wave guide to twice the average power density at the center of the wave guide, this technique should reveal biological effects that might only be manifested in narrow amplitude domains or "power windows." Observations of protein synthesis in monolayer cultures irradiated at 202 closely spaced frequencies in the E- and U-bands failed to reveal changes associated with microwave exposure. Thus no evidence was obtained in support of the existence of frequency-specific athermal biological effects of microwaves. In addition, no support was found for the existence of amplitude-specific "power windows."

AI evidence extraction

Main findings

BHK-21/C13 monolayer cultures were exposed with minimal heating (≤0.1°C) across 202 closely spaced frequencies in the 38–48 GHz and 65–75 GHz ranges at average power densities of 292 and 177 mW/cm2. No changes in protein synthesis were observed, and the study reports no evidence for frequency-specific athermal effects or amplitude-specific “power windows.”

Outcomes measured

• protein synthesis (labeled methionine incorporation)

Limitations

• Sample size not reported in abstract (only notes quadruplicate cultures).
• Only one cell line and one endpoint (protein synthesis) assessed.
• Exposure duration limited to 15 minutes.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "mmWave",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "15-minute period of microwave irradiation"
    },
    "population": "BHK-21/C13 monolayer cell cultures",
    "sample_size": null,
    "outcomes": [
        "protein synthesis (labeled methionine incorporation)"
    ],
    "main_findings": "BHK-21/C13 monolayer cultures were exposed with minimal heating (≤0.1°C) across 202 closely spaced frequencies in the 38–48 GHz and 65–75 GHz ranges at average power densities of 292 and 177 mW/cm2. No changes in protein synthesis were observed, and the study reports no evidence for frequency-specific athermal effects or amplitude-specific “power windows.”",
    "effect_direction": "no_effect",
    "limitations": [
        "Sample size not reported in abstract (only notes quadruplicate cultures).",
        "Only one cell line and one endpoint (protein synthesis) assessed.",
        "Exposure duration limited to 15 minutes."
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "millimeter-wave",
        "microwave",
        "E-band",
        "U-band",
        "athermal effects",
        "protein synthesis",
        "power windows",
        "BHK-21/C13",
        "cell culture"
    ],
    "suggested_hubs": []
}

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