Sensitivity of calcium binding in cerebral tissue to weak environmental electric fields oscillating at low frequency

Abstract

Weak sinusoidal electric fields modify the calcium efflux from freshly isolated chick and cat cerebral tissues bathed in Ringer's solution, at 36 degrees. Following incubation (30 min) with radioactive calcium (45Ca2+), each sample, immersed in fresh solution, was exposed for 20 min to fields at 1, 6, 16, 32, or 75 Hz, with electric gradients of 5, 10, 56, and 100 V/m in air. 45Ca2+ efflux in the solution was then measured in 0.2 ml aliquots and compared with efflux from unexposed control samples. Field exposures resulted in a general trend toward a reduction in the release of the preincubated 45Ca2+. Both frequency and amplitude sensitivities were observed. Maximum decreases occurred at 6 and 16 Hz (12-15%). Thresholds were around 10 and 56 V/m for chick and cat tissues, respectively. Similar but nonsignificant trends occurred during other field exposures. All results were statistically compared with matched samples of controls. Tissue gradients could not be measured, but estimates were of the order of 0.1 muV/cm. The susceptibility of the electrochemical equilibrium in the neuronal membrane to small extracellular perturbations is discussed and a possible role for weak intrinsic cerebral fields in neuronal excitability is suggested.

AI evidence extraction

Main findings

Exposure to weak sinusoidal electric fields (1, 6, 16, 32, or 75 Hz; 5, 10, 56, or 100 V/m in air) was associated with a general trend toward reduced 45Ca2+ efflux compared with unexposed matched controls. Maximum decreases were reported at 6 and 16 Hz (12–15%), with estimated thresholds around 10 V/m for chick tissue and 56 V/m for cat tissue; other exposures showed similar but nonsignificant trends.

Outcomes measured

• 45Ca2+ (radioactive calcium) efflux from cerebral tissue into solution

Limitations

• Sample size not reported in abstract
• Tissue electric field gradients could not be measured; only estimates provided
• Some reported trends at other frequencies/amplitudes were nonsignificant
• In vitro tissue preparation may not generalize to intact organisms

Suggested hubs

• mechanisms-calcium-signaling (0.9)
  Study measures changes in calcium efflux from cerebral tissue under weak ELF electric field exposure.
• elf-emf (0.75)
  Exposure frequencies are 1–75 Hz with specified electric field gradients (V/m).

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": "other",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "20 min exposure; 30 min incubation with 45Ca2+ prior to exposure"
    },
    "population": "Freshly isolated chick and cat cerebral tissues bathed in Ringer's solution (36°C)",
    "sample_size": null,
    "outcomes": [
        "45Ca2+ (radioactive calcium) efflux from cerebral tissue into solution"
    ],
    "main_findings": "Exposure to weak sinusoidal electric fields (1, 6, 16, 32, or 75 Hz; 5, 10, 56, or 100 V/m in air) was associated with a general trend toward reduced 45Ca2+ efflux compared with unexposed matched controls. Maximum decreases were reported at 6 and 16 Hz (12–15%), with estimated thresholds around 10 V/m for chick tissue and 56 V/m for cat tissue; other exposures showed similar but nonsignificant trends.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Tissue electric field gradients could not be measured; only estimates provided",
        "Some reported trends at other frequencies/amplitudes were nonsignificant",
        "In vitro tissue preparation may not generalize to intact organisms"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "ELF electric fields",
        "sinusoidal fields",
        "calcium efflux",
        "45Ca2+",
        "cerebral tissue",
        "chick",
        "cat",
        "frequency sensitivity",
        "amplitude sensitivity",
        "threshold"
    ],
    "suggested_hubs": [
        {
            "slug": "mechanisms-calcium-signaling",
            "weight": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "Study measures changes in calcium efflux from cerebral tissue under weak ELF electric field exposure."
        },
        {
            "slug": "elf-emf",
            "weight": 0.75,
            "reason": "Exposure frequencies are 1–75 Hz with specified electric field gradients (V/m)."
        }
    ]
}

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