Objectives: This in vitro study assesses the effect of different external ultrasound frequencies on the disruption of human thrombi. Background: Ultrasound energy has been shown to disrupt human thrombi in vitro. However, there have been no previous studies to assess the effect of a range of different ultrasound frequencies on the rate and extent of thrombus disruption. Methods: In vitro, we exposed 56, 1- to 3-hour-old human blood thrombi to continuous wave ultrasound (2.9 W/cm2) for 3 minutes. Seven different frequencies, ranging from 243 kHz to 25 kHz, were used. Results: There was a gradual increase in the total reduction of thrombus weight as well as the percent thrombus disruption with the use of lower ultrasound frequencies, reaching 99% at 25 kHz (p < 0.001) and 86% (p < 0.001) at 39 kHz, compared with 25% at 243 kHz. The average particle size of the disrupted thrombi was 3.26 µm (range 2.8-3.8). Conclusions: Our in vitro data with external ultrasound show that for a given power intensity of ultrasound, the extent and magnitude of thrombus disruption is progressively increased as frequencies decrease from 243 to 25 kHz. This might be related to the fact that larger acoustic bubbles are induced by lower frequency ultrasound, which gives rise to greater mechanical energy for thrombus disruption during bubble vibration and their collapse.
The D21S13 locus has shown linkage to a gene for familial Alzheimer disease (FAD) on chromosome 21 (St. George-Hyslop et al. 1987). The limited informativeness of probes for this locus have hindered precise mapping of the FAD locus and analysis of nonallelic heterogeneity in FAD (Schellenberg et al. 1988; St. George-Hyslop et al. 1987). We describe a new EcoRI polymorphism at the D21S13 locus that may be useful for the further study of FAD families.
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