Sister-chromatid exchanges in human lymphocytes exposed in vitro to therapeutic ultrasound

Investigation of genotoxic effect of ultrasound in cases receiving therapeutic ultrasound by using micronucleus method

In 1991, reported that therapeutic ultrasound (US) did not induce sister chromatid exchanges (SCEs) in patients whereas, in 1984, reported that each of 10 patients exposed to therapeutic US had a statistically significant increase in SCEs. The present study was planned to investigate if there was chromosomal damage resulting from therapeutic US by using a micronucleus (MN) method, and to counter the lack of reports in this area over the past 10 years. A total of 20 female volunteers were included in the study; 10 of them with low back pain (mechanical low back pain and facet syndrome) were treated with US and 10 healthy cases constituted the control group. Patients with low back pain received 10 sessions of US therapy at an intensity of 2 W/cm(2) and a frequency of 1 MHz for 10 min and patients in the control group received sham US therapy for 10 min. Peripheral blood taken before and after the fifth and tenth applications of US therapy was cultured for MN frequencies both for the treatment and the control groups. The scores of MN assessed before the therapy were compared with those at the end of the fifth session and the end of the tenth session in the treatment and the control groups. Pretreatment, end of the fifth session and end of the tenth session MN frequencies were compared between the treatment and the control groups. There was no statistically significant difference in MN frequencies between pretreatment and fifth session or pretreatment and tenth session in both groups. Nor was there any significant difference in the MN frequencies of the treatment and control groups between pretreatment, fifth session and tenth session evaluations. In conclusion, we observed that therapeutic US did not induce increases in MN frequency, which are a sign of cytogenetic damage.

Effects of ultrasound on the growth and function of bone and periodontal ligament cells in vitro

The effects of therapeutic ultrasound (US) on tissue healing processes in vivo are likely to involve US-induced changes in key cellular functions. However, these have not yet been clearly delineated and the present study has, therefore, examined the effects of a single 5-min CW exposure of 3.00-MHz US on the growth and functional activity of a human osteoblast-like cell line (MG63 cells) and human periodontal ligament (PDL) cells in vitro. Although cell proliferation was found to be largely unaffected by spatial average intensity (I(SA)) values of between 140-990 mW/cm(2), flow cytometry (FCM) analysis showed that there were pronounced and differential effects on cell function. Thus, bone-associated proteins were down-regulated, whereas collagen type I (COL I) was unaffected and fibronectin (FN) was up-regulated at low intensities in MG63 cells. In contrast, bone protein expression was found to be dose-dependent, and FN and COL I were down-regulated in PDL cells. These results show that US has potentially important effects on the functional activities of connective tissue cells in vitro, which could markedly influence tissue repair and regeneration processes in vivo.

Correlation of ultrasound-induced hemolysis with cavitation detector output in vitro

A 20-MHz passive acoustic detector was used to quantify the amount of transient acoustic cavitation occurring in a sample exposed to intense pulsed ultrasound. A dilute suspension of human erythrocytes with and without a microbubble echo-contrast agent was exposed in vitro to 500 W/cm2 (SPPA) ultrasound of center frequency 1 MHz and tone burst duration 20, 100, 200, 500 and 1000 microseconds at a pulse repetition frequency of 20 Hz. Inertial cavitation occurring within the sample, as measured by the temporal average of the detector output, correlated well with hemolysis, suggesting that violent bubble collapse is responsible for cell damage. The result also raises the prospect of cavitation monitoring as a possible predictor of adverse bioeffects when echo-contrast agents are used clinically.

A review of in vitro bioeffects of inertial ultrasonic cavitation from a mechanistic perspective

This selective review of the biological effects of ultrasound presents a synopsis of our current understanding of how cells insonated in vitro are affected by inertial cavitation from the standpoint of physical and chemical mechanisms. The focus of this review is on the physical and chemical mechanisms of action of inertial cavitation which appear to be effective in causing biological effects. There are several fundamental conditions which must be satisfied before cavitation-related bioeffects may arise. First, bubbles must be created and then brought into proximity to cells. Exposure methods are critical in this regard, and simple procedures such as rotation of a vessel containing the cells during exposure can drastically alter the results. Second, once association is achieved between bubbles and cells, the former must interact with the latter to produce a bioeffect. It is not certain that the inertial event is the prime mechanism by which cells are lysed; there is evidence that the turbulence associated with bubble translation may cause lysis. Additionally, there appear to be chemical and other physical mechanisms by which inertial cavitation may affect cells; these include the generation of biologically effective sonochemicals and the apparent emission of ultraviolet (UV) and soft X-rays. The evidence for inertial cavitation occurring within cells is critically reviewed.

Sister-chromatid exchanges in 52 Korean women living in the vicinity of an industrial complex

Sister-chromatid exchanges (SCE) were examined in the peripheral lymphocytes of 52 Korean women living in the vicinity of an industrial complex. They were generally non-smokers ranging from 22 to 56 years of age. The mean SCE score of the volunteers was 6.01 +/- 0.15 (SE). Only coffee intake produced a significant increase of SCE by comparison with the mean SCE for those that did not take coffee. Other parameters, including alcohol intake, working in industry and the presence of hepatitis B surface antigen (HBsAg), did not produce an increase in SCE. There was no effect on SCE due to age.

Factors that influence formation of sister chromatid exchanges in human blood lymphocytes

Sister chromatid exchange (SCE) reflects an interchange of DNA sequences between helices in a replicating chromosome. This was initially accomplished by Taylor and colleagues (1957) using tritiated thymidine incorporation followed by autoradiography. The development of an elegant technique for differential staining of sister chromatids by incorporating a thymidine analog, 5-bromodeoxyuridine (BrdU) has greatly simplified the detection of SCEs in metaphase chromosomes. In recent years, the analysis of SCE has been considered to be a highly sensitive and additional (i.e., with chromosome aberrations) end point for measuring mutagenic/carcinogenic potential of various environmental agents and is increasingly being used to detect and differentiate among chromosome fragility human diseases that predispose to neoplasia. Attention has been focused to see if the induction of SCEs in lymphocyte cultures can be used as a reliable "biological dosimeter" for genetic risk assessment and to monitor the exposed populations. Several physical or preparatory as well as biological factors that modify the response and formation of SCEs make the monitoring difficult. The purpose of this article is to review and analyze these factors to facilitate an effective development of a standard protocol for SCE testing and for appropriate evaluation of test results. This may also provide clues to understand the yet unknown molecular mechanism(s) and biological significance of SCE formation.