Physical Factors Involved in Ultrasonically Induced Changes in Living Systems: I. Identification of Non-Temperature Effects
W. J. Fry, V. J. Wulff, D. Tucker, F. J. Fry
The Journal of the Acoustical Society of America 1950, 22, 867-876 · 10.1121/1.1906707
Abstract
The results of the first step in a systematic investigation of the mechanism of the action of ultrasound on tissue are reported. The temperature changes resulting from absorption of acoustic energy were determined while irradiation was in progress. Experimental evidence is presented which demonstrates the existence of non-temperature effects in various nerve tissue preparations.
Abstract via crossref.
Exposures
Exposure 1: Crayfish ventral abdominal nerve cord (ganglia) and walking leg nerves
Target: crayfish neurons — “ventral abdominal nerve cord (ganglia 1 and 2) and walking leg nerves of crayfish”
Device: custom-built
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 975, 980swept | ✓✓✓ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | not applicable | |
| Sonication duration (s) | 43.5 | ✓✓✓ |
| Free-field pressure (kPa) | 1,013 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 35 | ✓✓✓⚑ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not applicable | |
| In-situ pressure (kPa) | not applicable | |
| In-situ Isppa (W/cm²) | not applicable | |
| In-situ Ispta (W/cm²) | not applicable |
Continuous-wave ultrasound (~35 W/cm2) was applied to two adjacent ganglia and the connecting commissure of the excised ventral nerve cord; spontaneous spike frequency first increased, then decreased, then disappeared entirely after 43.5 s of exposure, recovering over about 25-30 s once the sound was switched off. Similar observations were made on six other preparations, and similar exposures of the excised walking-leg nerve gave negative results.
Exposure 2: Excised frog sciatic nerve
Target: sciatic nerve — “excised frog sciatic nerve suspended in Ringer's solution”
Device: custom-built
| Waveform | not reported | |
|---|---|---|
| Fundamental frequency (kHz) | 975, 980swept | ✓✓✓ |
| Pulse duration (ms) | not reported | |
| Pulse repetition frequency (Hz) | not reported | |
| Duty cycle (%) | not reported | |
| Sonication duration (s) | not reported |
| Free-field pressure (kPa) | 1,013 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 35 | ✓✓✓ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not applicable | |
| In-situ pressure (kPa) | not applicable | |
| In-situ Isppa (W/cm²) | not applicable | |
| In-situ Ispta (W/cm²) | not applicable |
Prolonged application of ultrasound to excised frog sciatic nerves suspended in Ringer's solution and in contact with salt bridges produced no detectable change in wave form, spike magnitude or excitability, whether the sound was incident on the stimulating electrodes, the recording electrodes, or the intermediate region; no intensity or duration is given for this specific test.
Exposure 3: Intact frog, lumbar enlargement of the spinal cord sonicated through the back
Target: lumbar spinal cord — “lumbar enlargement of the spinal cord, intact frog, sound beam incident on the dorsal surface”
Device: custom-built
| Waveform | continuous, pulsed | |
|---|---|---|
| Fundamental frequency (kHz) | 975, 980swept | ✓✓✓ |
| Pulse duration (ms) | 10, 80swept | ✓✓✓ |
| Pulse repetition frequency (Hz) | 2, 20swept | ✓✓✓ |
| Duty cycle (%) | not reported | |
| Sonication duration (s) | 2.8, 3.3, 4.3, 7.3swept | ✓✓✓ |
| Free-field pressure (kPa) | 1,013 | ✓✓✓ |
|---|---|---|
| Free-field Isppa (W/cm²) | 35 | ✓✓✓ |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported |
Frogs suspended under water were exposed to a single continuous sonication of the lumbar spinal cord region: complete, permanent paralysis of the hind legs followed exposures of 4.3 s at room temperature (21-25C) or 7.3 s at 1-2C, while shorter exposures gave no or only temporary paralysis. In a separate comparison at room temperature, repetitive short pulses (0.08 s at 2/s, or 0.01 s at 20/s) were used to vary the temperature-rise time course; the slower/longer pulse train (0.08 s, 2/s) paralysed frogs despite reaching a lower peak cord temperature than the faster/shorter train (0.01 s, 20/s), which did not paralyse.
Flags from extraction
exposures[0].free_field.isppa_w_cm2— Paper calls this the approximate intensity used ('~35 w/cm2'); domain is inferred as free-field from the paper's separate statement that 'the measured free field sound intensity at the positions used in the experiments ... is between 30 and 40 w/cm2', not stated explicitly for this experiment.exposures[2].timing.waveform— The lumbar spinal cord exposure combines a continuous single-burst paralysis-threshold protocol (4.3 s / 7.3 s) with a separate pulsed temperature-matching sub-experiment (0.08 s at 2/s vs 0.01 s at 20/s); only the pulsed condition that produced paralysis (0.08 s, 2 Hz) is captured in the numeric pulse fields. Duty cycle is not stated and not computed here.n_subjects— The paper reports many different sub-group sizes across sub-experiments (e.g. 12 frogs at room temperature, 50 frogs cooled, 6 frogs for histology, 5+5 frogs for the two pulsed-duration comparisons, 7 crayfish nerve-cord preparations) without ever stating an aggregate total across the whole study.subject_unit— Study mixes intact frogs (animal), excised crayfish nerve-cord/leg-nerve preparations, and excised frog sciatic nerve (preparation); 'animal' is used as the majority category.