Killing of drosophila larvae by the fields of an electrohydraulic lithotripter

Effects and Mechanisms

“…The same conclusion was reached by Carstensen et al [635], who, following the suggestion of Child et al [630] that larval gas pockets might be used to model the response of bubbles within mammalian cells, killed roughly one-half of a population of fruit fly larvae (Drosophilia melanogaster) subjected to 3-10 double shocks at 2-3 MPa from a Wolf electrohydraulic lithotripter (Model 2137.50). Addition of negative pressure to the exposure, which would increase cavitation from free-floating bubble nuclei, had little effect.…”

“…The effect was related to temporal peak, rather than the temporal average, intensity. These results are further interpreted in the light of subsequent lithotripsy results [635], outlined below. It should be pointed out that though these larval nuclei may model the mechanics of gas pockets in mammalian tissue, they do not reflect the distribution, which in test animals is generally unknown.…”

“…This indicates that the mechanism of damage was not tensile-excited expansion of the small gas bodies stabilised within the respiratory system of the larvae. Carstensen et al [635] suggest that this is because the containment inhibits the expansion of the bodies, that this system might provide a good model for the behaviour of gas bubbles within mammalian cells and that the bioeffects from lithotripsy may be related to the positive pressures. Earlier workers had suggested that the negative pressure, relating as it does to the energy of the cavitation response of a free-floating bubble nucleus in an infinite liquid, is the better predictor of bioeffects associated with the activation of gas bodies within tissues [116,117,635,[648][649][650].…”

“…Carstensen et al [635] suggest that this is because the containment inhibits the expansion of the bodies, that this system might provide a good model for the behaviour of gas bubbles within mammalian cells and that the bioeffects from lithotripsy may be related to the positive pressures. Earlier workers had suggested that the negative pressure, relating as it does to the energy of the cavitation response of a free-floating bubble nucleus in an infinite liquid, is the better predictor of bioeffects associated with the activation of gas bodies within tissues [116,117,635,[648][649][650]. Hypothesised killing mechanisms for the lithotripter through simple crushing (tested by application of a pseudostatic pressure) and indirectly through drowning (by external water entering the trachea, tested by the use of dye) have proven unlikely [635].…”

The Risk of Exposure to Diagnostic Ultrasound in Postnatal Subjects

“…Their design of a lithotripter pulse intended to minimize bubble expansion resulted in fewer ruptured vessels in animal studies. Carstensen et al 80,81 had earlier proposed that a similar mechanism, the ultrasonically induced expansion of a preexisting gas body, could produce the tissue injury observed in Drosophila larvae. While it may be difficult to conceive that a nearly empty bubble can push on tissue strongly enough to damage it, the concentration of applied stress near a void and the resulting strain in the surrounding material are generally accepted to be how fractures grow in brittle materials 82,83 ; a similar mechanism has been proposed for tissue.…”