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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 98 out of 330
| Title |
Effect of fetal exposure to ultrasound on the development of functional, antigen-specific B lymphocytes in fetal and neonatal BALB/c mice. |
| Author |
Desai BB, Sosolik RC, Ciaravino V, Teale JM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
In this study, the influence of fetal exposure to ultrasound on the development of immunocompetence is addressed. Pregnant BALB/c mice were exposed to various intensities of ultrasound ranging from 0.1-3.0 W/cm2. B cells from 19 day old fetal livers or 5 and 10 day old neonatal spleens were assessed for the following: (a) differentiation into plasma cells after mitogenic stimulation with lipopolysaccharide (LPS); (b) development and frequency of 2,4-dinitrophenyl (DNP)-specific B cells, and (c) the ability to produce antibody in response to DNP. Comparison between ultrasound-exposed and sham-treated groups did not reveal any evident differences in the above tests. The results suggest that ultrasound neither hinders nor augments the development of immunocompetent B cells. |
| Title |
Effect of free radical scavengers on changes in ion conductance during exposure to therapeutic ultrasound. |
| Author |
Dinno MA, Al-Karmi AM, Stoltz DA, Matthews JC, Crum LA. |
| Journal |
Membr Biochem |
| Volume |
|
| Year |
1993 |
| Abstract |
Ultrasound has been used in physical therapy for > 4 decades. Recent studies indicate that non-thermal mechanisms such as cavitation are involved in the observed effects. Free radicals and other highly reactive compounds are known to form during sonochemical reactions associated with acoustic cavitation. Using frog skin as a biological model, the possibility that the increase in ionic conductance (Gt) upon exposure to therapeutic ultrasound is due to the effect of free radicals generated by sonochemical reactions, was investigated. It was found that the presence of cystamine, cysteamine and sodium ascorbate significantly reduced the increase in conductance caused by the exposure to 300 mW/cm2 (1 MHz CW) therapeutic ultrasound. The attenuation in the effects was dependent on the concentration of the radical scavengers/antioxidants used, the incubation time, and the intensity of ultrasound. The effects were also dependent on the lipid solubility of free radical scavengers/antioxidants. The time constant for the recovery process of Gt in the presence of free radical scavengers and antioxidants after exposure to ultrasound was found to be not significantly different from control. These results suggest that the increase in Gt due to ultrasound is induced by free radicals and other reactive species generated from acoustic cavitation. This study provides an indirect evidence to the contingent that free radicals are generated and act inside the cells. Furthermore, the radical scavengers and antioxidants used provide protection from oxidative damage without being involved in the recovery of Gt towards steady state values after sonication. |
| Title |
Effect of free radicals induced by ultrasonic cavitation on cell killing. |
| Author |
Kondo T, Kano E. |
| Journal |
Int J Radiat Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
The present study was undertaken to elucidate the mechanism of in vitro cell killing induced by 1.0 MHz continuous wave ultrasound at an intensity of 5.8 W/cm2. The chemical effects and mechanical effects arising from acoustic cavitation were determined by the amount of liberated iodine and the number of DNA double-strand breaks, respectively. The survival of mouse L cells immediately after irradiation was estimated by counting the number of cells which are not stained by trypan blue and the clonogenicity of surviving cells remaining immediately after irradiation was monitored by colony-forming ability. The effectiveness of the dissolved gases in liberating iodine was in the order O2 greater than Ar greater than N2 greater than N2O approximately 0. However, the effect of dissolved gases on the yield of double-strand breaks of DNA and on the two kinds of end points of cell killing was in the order O2 = Ar = N2 greater than N2O approximately 0. These results suggest that the different amounts of free radicals induced by ultrasound are not directly related to the ultrasonically induced cell killing. The presence of cysteamine (2 mmol dm-3) during sonication completely inhibited a decrease in clonogenicity of.surviving cells, but did not inhibit that of cell survival immediately after sonication. These results suggest that the decrease of survival immediately after sonication is due to mechanical shear stress arising from cavitation, while the decrease of clonogenicity of the remaining surviving cells is due to free radicals induced by cavitation. The contribution of free radicals to total cell killing was estimated as about 1 per cent at the level of 95 per cent cell killing immediately after sonication. |
| Title |
Effect of gas-containing microspheres and echo contrast agents on free radical formation by ultrasound. |
| Author |
Kondo T, Misik V, Riesz P. |
| Journal |
Free Radic Biol Med |
| Volume |
|
| Year |
1998 |
| Abstract |
Stabilized microbubbles (microspheres) are widely used to enhance the contrast of ultrasound imaging. Our data provide direct evidence that the contrast agents, Levovist, PVC-AN (polyvinylidene chloride-acrylonitryl copolymer), and Albunex (compared to 5% human albumin), at concentrations comparable to those used for ultrasound imaging, enhance H(2)O(2) production (through the superoxide-dependent pathway) in air-saturated aqueous solutions exposed to 47 kHz ultrasound above the cavitation threshold. These agents also act as scavengers of *H atoms and *OH radicals, thus lowering H(2)O(2) formation (by recombination of *OH radicals) in argon-saturated solutions. EPR spin trapping also reveals that secondary radicals derived from the contrast agents are produced by reactions with *H and *OH which are formed by pyrolysis of water inside cavitation bubbles. In addition, the contrast agents themselves undergo pyrolysis reactions in the cavitation bubbles as demonstrated by formation of methyl radicals. Possible deleterious consequences of the formation of sonochemical intermediated may have to be assessed, particularly since some of the echo contrast agents have been shown to lower the cavitation threshold of diagnostic ultrasound. Unlike the microspheres formed from organic molecules, inorganic microspheres, Eccospheres, because of their stability and inert nature with respect to participation in free radical processes, appear to be suitable tools are enhancing the yields of aqueous sonochemical reactions. |
| Title |
Effect of gaseous inclusions on the frequency dependence of ultrasonic attenuation in liver. |
| Author |
Bamber JC, Nassiri DK. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
The greatest variation in published data of the attenuation of ultrasound in mammalian liver in vitro occurs at the lower end of the 0.5 to 7 MHz frequency range and gives rise to some departure from a linear or simple power law dependence of attenuation on frequency. These effects do not appear to be highly dependent on the method of measurement. It is suggested that they are due to a varying presence of small gas bubbles distributed throughout the tissue--a suggestion based on calculated estimates of the attenuation due to microscopic bubbles and on the measured frequency dependence of attenuation in water loaded sponges containing varying amounts and distribution of gas. We now believe that preferred methods of tissue specimen preparation, for in vitro measurement of ultrasonic attenuation or scattering, should involve either pressurization as described elsewhere (Frizzell et al., 1979) or storage under refrigeration. |
| Title |
Effect of intense ultrasound on the structure of concentrated polymer solutions. |
| Author |
Fedorova NM. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1965 |
| Abstract |
An explanation is offered to account for the effect of high intensity ultrasound on the structure of concentrated polymer solutions, postulating as the underlying mechanism a change in the probability of node disintegration in the polymer network configuration. It is shown that this explanation is well grounded in the experimental results of an investigation into the temperature dependence of the threshold potentials and the dependence of sound absorption in the solutions at structural dissociation on the potential applied to the emitting quartz. The experimental investigation of the first dependence enables one to determine the relative intermolecular coupling energies. |
| Title |
Effect of intensity of ultrasound on conduction of motor axons. |
| Author |
Farmer WC. |
| Journal |
Phys Ther |
| Volume |
|
| Year |
1968 |
| Abstract |
This investigation compares the effect of varying intensities of ultrasound on the conductivity of human motor axons. Results confirm that ultrasound can significantly alter peripheral nerve propagation. Intensities on the order of 0.5 watts/cm» tend to increase motor nerve conduction velocity, whereas intensities from 1 watt/cm² to 2 watts/cm² tend to decrease the conduction velocity, whereas intensities of 3 watts/cm² tend to increase it. A comparison of the amplitude of muscle action potentials preceding and following ulnar nerve sonation also was made. many of the actions of ultrasound on various tissues may be explained on the basis of primary action of the neutral element. |
| Title |
Effect of low intensity ultrasound on nucleic acid components. |
| Author |
Gupta AB, Wang SY. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1976 |
| Abstract |
To understand the effect of ultrasound in living cells at the molecular level, nucleic acid bases, nucleosides, nucleotides, and polynucleotides were sonicated at low intensities (* 5W/cm2) and sonolysis was followed by UV-spectral decrease. The order of reactivity for bases was: thymine > uracil > cytosine > guanine > adenine. A similar order of reactivity was observed for nucleosides and nucleotides, although with slower rates of changes. The order of reactivity for uracil derivatives was: uracil > uridine > UMP > poly U. The effect of several experimental variables such as sonication intensity, pH, and dissolved gases were studied. Identification of major sonoproducts is presented and a mechanism of sonolysis is proposed. |
| Title |
Effect of mode conversion on ultrasonic heating at tissue interfaces. |
| Author |
Haken BA, Frizzell LA, Carstensen EL. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1992 |
| Abstract |
A number of investigators have observed localized heating by ultrasound beams near impedance discontinuities within tissues. It has been suggested that mode conversion to shear waves at impedance discontinuities and subsequent absorption of these waves in a very small distance was the explanation for this heating. A mathematical model for mode conversion at a plane interface between two viscoelastic media is presented. Longitudinal and shear properties are used to calculate the amount of mode conversion that occurs at muscle-air and muscle-bone interfaces. Shear waves in bone are found to be an important source of heating, but shear waves in the muscle provide a negligible effect on heating at the interface. |
| Title |
Effect of mode conversion on ultrasonic heating at tissue interfaces. |
| Author |
Haken BA. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1992 |
| Abstract |
A number of investigators have observed localized heating by ultrasound near impedance discontinuities within tissues. It has been suggested that mode conversion to shear waves at impedance discontinuities and subsequent absorption of these waves in a very small distance were the explanations for this heating. A mathematical model for mode conversion at a plane interface between two viscoelastic media is presented. Longitudinal and shear properties are used to calculate the amount of mode conversion that occurs at muscle-bone and muscle air interfaces. Shear waves in bone are found to be an important source of heating, but shear waves in the muscle provide a negligible effect on heating at the interface.
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