Effect of 2 MHz ultrasound on DNA, RNA and protein synthesis in Pisum sativum root meristem cells

Microstreaming inside Model Cells Induced by Ultrasound and Microbubbles

Studies on the bioeffects produced by ultrasound and microbubbles have focused primarily on transport in bulk tissue, drug uptake by individual cells, and disruption of biological membranes. Relatively little is known about the physical perturbations and fluid dynamics of the intracellular environment during ultrasound exposure. To investigate this, a custom acoustofluidic chamber was designed to expose model cells, in the form of giant unilamellar vesicles, to ultrasound and microbubbles. The motion of fluorescent tracer beads within the lumen of the vesicles was tracked during exposure to laminar flow (∼1 mm s^-1), ultrasound (1 MHz, ∼150 kPa, 60 s), and phospholipid-coated microbubbles, alone and in combination. To decouple the effects of fluid flow and ultrasound exposure, the system was also modeled numerically by using boundary-driven streaming field equations. Both the experimental and numerical results indicate that all conditions produced internal streaming within the vesicles. Ultrasound alone produced an average bead velocity of 6.5 ± 1.3 μm/s, which increased to 8.5 ± 3.8 μm/s in the presence of microbubbles compared to 12 ± 0.12 μm/s under laminar flow. Further research on intracellular forces in mammalian cells and the associated biological effects in vitro and in vivo are required to fully determine the implications for safety and/or therapy.

Effect of low frequency ultrasonic stimulation on the secretion of siboflavin produced by Ecemothecium Ashbyii

The structure of the cell membrane of Ecemothecium ashbyii is considered to be one of the main obstacles in the improvement of riboflavin productivity, which impedes the release of riboflavin from the cell into the fermentation broth. The results of the present study show that stimulation on growth and riboflavin biosynthesis phase, the content of riboflavin was most obviously enhanced, as compared with the control and the total riboflavin quantity released by ultrasonic treatment. The optimal stimulation time was from 104 to 112 h and ultrasonic should be loaded every 1.5 h.

Applications of lipid-coated microbubble ultrasonic contrast to tumor therapy

Lipid-coated microbubbles (LCM) make an excellent diagnostic ultrasonic contrast agent in experimental tumor systems. LCM have been shown to aggregate in brain tumors and subcutaneous tumors after intravenous administration, and to provide persistent image enhancement for many minutes. In this work, experimental subcutaneous Walker Carcinosarcoma is insonated after the bubbles are given intravenously. Selective necrosis, lymphocyte proliferation and hemorrhage within the tumor can be demonstrated. Preliminary data are given to demonstrate this phenomenon. The mechanism of the effect is discussed in the context of both heating and cavitation.

A review of the ultrasonic bioeffects of microsonation, gas-body activation, and related cavitation-like phenomena

Ultrasonic exposures localized to regions smaller than a wavelength minimize the thermal mechanism, but promote nonthermal mechanisms of ultrasonic bioeffects. Microsonation experiments with vibrating needles or wires exploit this situation for the study of nonthermal mechanisms such as acoustic microstreaming flow. Shear stress in microstreaming flow, which is in excess of critical values for biomembranes, leads to cell lysis. Plane wave exposure of small bodies of gas also yields localized exposure, with further amplification of nonthermal mechanisms by resonance activation of oscillation. Gas body activation in vitro causes gathering of suspended cells by radiation forces, aggregation, cellular effects and lysis by microstreaming. When suitable gas bodies are present, these effects may occur at levels below the threshold for ultrasonic cavitation. In vivo, gas body activation generates intracellular microstreaming in Elodea leaves and disrupts the cells for super-critical shear stress levels. Similar phenomena seem to account for cell death, growth and mitotic index reductions in other plant tissues, and developmental abnormalities and delayed death in fruit flies. Only fragmentary and equivocal evidence presently exists on the medically relevant question of whether such subthreshold cavitation-like activity and bioeffects occur in vertebrates.