Effects of millimeter-wave radiation on monolayer cell cultures. II. Scanning and transmission electron microscopy.

Abstract

Both thermal and athermal effects of millimeter-wave radiation of BHK-21/C13 cells were sought using scanning and transmission electron microscopy in conjunction with an in vitro technique that allows direct exposure of monolayer cultures to high average power densities. Culture dishes were irradiated by placing them on the open end of an E- or U-band wave guide. This technique exposes different regions of the cell monolayer lying along the longer axis of the wave guide aperture to varying power densities ranging from zero at each edge to twice the average power density at the center. Cell ultrastructure was unaffected by microwave radiation for 1 hour (41.8 or 74.0 GHz, average power densities = 320 or 450 mW/cm2, respectively) with or without cooling by rapid recirculation of the culture medium. Temperature in recirculated cultures was held at 37.2 degrees C, and that in noncooled cultures never exceeded 42 degrees C during irradiation at either power density. In contrast, cell morphology was affected by microwave exposure whenever irradiation conditions were altered so that the temperature of the monolayer reached or exceeded 44.5 degrees C. Ultrastructural alterations included breakage of cell processes, progressive detachment of cells from the substrate, increased clumping of heterochromatin in the nuclei, and the appearance of large empty vesicles in the cytoplasm. Such morphological changes resulted from either application of higher average power densities or irradiation at the power densities described above at a higher ambient temperature (greater than or equal to 38.5 degrees C).

AI evidence extraction

Main findings

Cell ultrastructure was unaffected after 1 hour of exposure at 41.8 or 74.0 GHz (average power densities 320 or 450 mW/cm^2) when monolayer temperature was maintained at ~37.2°C with recirculation cooling or did not exceed 42°C without cooling. Morphological/ultrastructural alterations were observed when irradiation conditions led the monolayer temperature to reach or exceed 44.5°C, either via higher power densities or higher ambient temperature (≥38.5°C).

Outcomes measured

• Cell ultrastructure (scanning and transmission electron microscopy)
• Cell morphology changes (e.g., detachment, nuclear heterochromatin clumping, cytoplasmic vesicles)
• Temperature during irradiation

Limitations

• Sample size not reported in abstract
• Only one cell line (BHK-21/C13) studied
• Exposure conditions involve high average power densities and waveguide setup; generalizability to other exposure scenarios not stated

Suggested hubs

• 5g-policy (0.2)
  Study involves millimeter-wave frequencies (41.8 and 74.0 GHz), which overlap with mmWave discussions relevant to 5G, though this is an in vitro high-power exposure study.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "mmWave",
        "source": "waveguide irradiation (E- or U-band)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "1 hour"
    },
    "population": "BHK-21/C13 cells (monolayer cell cultures)",
    "sample_size": null,
    "outcomes": [
        "Cell ultrastructure (scanning and transmission electron microscopy)",
        "Cell morphology changes (e.g., detachment, nuclear heterochromatin clumping, cytoplasmic vesicles)",
        "Temperature during irradiation"
    ],
    "main_findings": "Cell ultrastructure was unaffected after 1 hour of exposure at 41.8 or 74.0 GHz (average power densities 320 or 450 mW/cm^2) when monolayer temperature was maintained at ~37.2°C with recirculation cooling or did not exceed 42°C without cooling. Morphological/ultrastructural alterations were observed when irradiation conditions led the monolayer temperature to reach or exceed 44.5°C, either via higher power densities or higher ambient temperature (≥38.5°C).",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Only one cell line (BHK-21/C13) studied",
        "Exposure conditions involve high average power densities and waveguide setup; generalizability to other exposure scenarios not stated"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "millimeter-wave radiation",
        "microwave",
        "BHK-21/C13",
        "in vitro",
        "monolayer cultures",
        "electron microscopy",
        "thermal effects",
        "athermal effects",
        "41.8 GHz",
        "74.0 GHz",
        "power density",
        "temperature"
    ],
    "suggested_hubs": [
        {
            "slug": "5g-policy",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Study involves millimeter-wave frequencies (41.8 and 74.0 GHz), which overlap with mmWave discussions relevant to 5G, though this is an in vitro high-power exposure study."
        }
    ]
}

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