Hemorrhage near fetal rat bone exposed to pulsed ultrasound

Effects of long-term Doppler ultrasound exposure on cochlea and cochlear nucleus in prenatal period in an experimental model

BACKGROUND

New generation Doppler ultrasonography (DUSG) application effects on cochlea and cochlear nucleus (CN) are unclear. We aimed to investigate the effects of new generation DUSG application at different frequencies in prenatal period on cochlea and CN in rats.

OBJECTIVE

Twenty-four pregnant female rats were divided into three groups (n = 8). Group 1 was the control group and was not subjected to any treatment. Group 2 was determined as the USG every day (USGED) treatment group. Group 2 has received DUSG application every day from the 4th to 18th day (20 min/15 per day). Group 3 has received DUSG application as "2 days/one dose as every other day application" (USG2D1) from the 4th to 18th day (20 min/8 every other day). Twenty-four female rats were sacrificed in 21 days. Also, 24 pups were sacrificed after two days. First day after born, the cochlear activities of the right ears of all pups were examined using DPOAEs. Second day, neural tissues from CN were evaluated histopathologically and immunohistochemically.

RESULTS

There was no any statistical difference between the groups in respect of histopathologically. USGED group showed mild caspase-3 positive neurons and glial cells. However, there was no significant difference between the USGED and other groups (p>.05). Similarly, the rats applied with USG2D1 had mild caspase-3 expression, but no significant difference between the USG2D1 and other groups (p>.05). Differences in DPOAE amplitudes, and therefore in cochlear activity, between the groups were revealed. The decrease in cochlear activity between the groups involved frequencies at 2, 8, 16, and 32 kHz (p<.05).

CONCLUSIONS

Multiple administration of new generation DUSG to pregnant rats has not shown harmful effects on the cochlear neural tissue. High frequencies are more sensitive in cochlea to apply DUSG.

Ultrasound contrast agents affect the angiogenic response

OBJECTIVES

The interaction of ultrasound contrast agents (UCAs) and ultrasound (US) provides a way to spatially and temporally target tissues. Recently, UCAs have been used therapeutically to induce localized angiogenesis. Ultrasound contrast agents, however, have been documented to induce negative bioeffects. To further understand the balance of risks and benefits of UCAs and to examine the mechanism of US-UCA-induced angiogenesis, this study explored the role of UCAs, in particular Definity (Lantheus Medical Imaging, Inc, North Billerica, MA), in producing an angiogenic response.

METHODS

The gracilis muscles of Sprague Dawley rats were exposed to 1-MHz US. The rats were euthanized the same day or allowed to recover for 3 or 6 days post exposure (DPE). Ultrasound peak rarefactional pressures (P(r)s) of 0.25, 0.83, 1.4, and 2.0 MPa were used while rats were infused with either saline or Definity. Assessments for angiogenesis included capillary density, inflammation, and vascular endothelial growth factor (VEGF), both acutely (0 DPE) and at 3 and 6 DPE.

RESULTS

The results of this study suggest that the angiogenic response is dependent on infusion media, P(r), and DPE. While capillary density did not reach significance, VEGF expression was significant for infusion media, P(r), and DPE with inflammation co-occurrence (P < .05).

CONCLUSIONS

These results suggest that the angiogenic response is elicited by a mechanical effect of US-UCA stimulation of VEGF that is potentially optimized when collapse occurs.

Ultrasound-Induced Cell Death of Nasopharyngeal Carcinoma Cells in the Presence of Curcumin

Objectives. Curcumin, a natural pigment from a traditional Chinese herb, has been attracting extensive attention. The present study aims to investigate cell death of nasopharyngeal carcinoma (NPC) cells induced by ultrasound sonication in the presence of curcumin in vitro. Methods. The NPC cell line CNE2 was chosen as a tumor model, and curcumin concentration was kept constant at 10 µM while the cells were subjected to ultrasound exposure for 8 s at an intensity of 0.46 W/cm2. Cell death was evaluated using flow cytometry with annexinV-FITC and propidium iodine staining, and nuclear staining with Hoechst 33258. Mitochondrial membrane potential and intracellular reactive oxygen species (ROS) were analyzed using flow cytometry with rhodamine 123 and dichlorodihydrofluorecein diacetate staining. Results. Flow cytometry showed that the combination of ultrasound and curcumin significantly increased the necrotic or late apoptotic rate by up to 31.37% compared with the controls. Nuclear condensation was observed in the nuclear staining, and collapse of ΔΨm and ROS increase were found in the CNE2 cells after the treatment with curcumin and ultrasound. Conclusions. The findings demonstrate that the presence of curcumin significantly enhances the ultrasound-induced cell death and ROS level, and induces the collapse of ΔΨm, suggesting that ultrasound sonication can increase the cell death of NPC cells in the presence of curcumin and that the treatment using curcumin and ultrasound together is a potential therapeutic modality in the management of malignant tumors.

Ultrasound bioeffects and safety

The main mechanisms by which ultrasound can induce biological effects as it passes through the body are thermal and mechanical in nature. The mechanical effects are primarily related to the presence of gas, whether drawn out of solution by the negative going ultrasound pressure wave (acoustic cavitation), a naturally occurring gas body (such as lung alveoli), or deliberately introduced into the blood stream to increase imaging contrast (microbubble contrast agents). Observed biological effects are discussed in the context of these mechanisms and their relevance to ultrasound safety is discussed.

Fetal ultrasound: mechanical effects

In this discussion, any biological effect of ultrasound that is accompanied by temperature increments less than 1 degrees C above normal physiologic levels is called a mechanical effect. However, one should keep in mind that the term mechanical effect also includes processes that are not of a mechanical nature but arise secondary to mechanical interaction between ultrasound and tissues, such as chemical reactions initiated by free oxygen species generated during cavitation and sonoluminescence. Investigations with laboratory animals have documented that pulsed ultrasound can produce damage to biological tissues in vivo through nonthermal mechanisms. The acoustic output used to induce these adverse bio-effects is considerably greater than the output of diagnostic devices when gas bodies are not present. However, low-intensity pulsed ultrasound is used clinically to accelerate the bone fracture repair process and induce healing of nonunions in humans. Low-intensity pulsed ultrasound also has been shown to enhance repair of soft tissue damage and accelerate nerve regeneration in animal models. Although such exposures to low intensity do not appear to cause damage to exposed tissues, they do raise questions about the acoustic threshold that might induce potentially adverse developmental effects in the fetus. To date, bioeffects studies in humans do not substantiate a causal relationship between diagnostic ultrasound exposure during pregnancy and adverse biological effects to the fetus. However, the epidemiologic studies were conducted with commercially available devices predating 1992, having outputs not exceeding a derated spatial-peak temporal-average intensity (ISPTA.3) of 94 mW/cm2. Current limits in the United States allow an ISPTA.3 of 720 mW/cm2 for obstetric modes. At the time of this report, available evidence, experimental or epidemiologic, is insufficient to conclude that there is a causal relationship between obstetric diagnostic ultrasound exposure and adverse nonthermal effects to the fetus. However, low-intensity pulsed ultrasound effects reported in humans and animal models indicate a need for further investigation of potentially adverse developmental effects.