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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 108 out of 330
Title |
Effects of ultrasound on Drosophila: III. Exposure of larvae to low-temporal-average-intensity, pulsed irradiation. |
Author |
Child SZ, Carstensen EL, Lam SK. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1981 |
Abstract |
The larvae of Drosophila melanogaster were exposed to repetitive, microsecond length pulses of 2 MHz ultrasound. The observed effects included killing of larvae and delayed lethality in the pupal stage. The effects depended strongly upon the temporal peak intensity with killing observed at spatial, temporal peak intensities above 10 W/cm(^2). In fact, the observations suggest that there may be a threshold for these effects at approximately this intensity. Temporal average intensity appears to be a poor predictor for these biological effects. Marked decreases in survival rates were observed at spatial, temporal average intensities as low as 3mW/cm(^2). |
Title |
Effects of ultrasound on nucleic acid bases. |
Author |
McKee JR, Christman CL, O'Brien WD Jr, Wang SY. |
Journal |
Biochemistry |
Volume |
|
Year |
1977 |
Abstract |
To understand the effects of ultrasound in biological systems at the molecular level, sonolysis of nucleic acid bases at sonic intensities less than or equal to 5 W/cm2 was studied. These sonoreactions were followed by UV-spectral decrease and by.sonoproduct analysis. The order of reactivity was found to be thymine greater than uracil greater than cytosine greater than guanine greater than adenine. The extent of sonoreactions depends on the exposure time and the rate of the intensity..Aeration was necessary for maintenance of a reasonable reaction rate. "Threshold" intensities for uracil and thymine were observed at approximately 0.5 W/cm2. The effectiveness of the dissolved gases in producing sonoreactions was Ar greater.than 02 greater than air greater than N2 greater than He greater than N2O, suggestive of free radicals mediating these reactions since N2O is an effective radical scavenger. Studies of the effects of substituents have shown that electronic rather than steric effects may have a greater influence. Preliminary identification indicates that cis- and trans-uracil glycols are the major products of uracil. Thus, a stepwise mechanism of pyrimidine sonolysis is proposed. Sonolysis of a dilute aqueous solution of uracil yielded pseudo-first-order kinetics in terms of [Ura] with a rate constant of 3.9 X 10(-2) min-1, implying that the rate-limiting step is the reaction of HO- with the base. |
Title |
Effects of ultrasound on placental transfer during the last third of gestation in the rat. |
Author |
Atkinson DE, Sibley CP, Williams AR. |
Journal |
Ultrasonics |
Volume |
|
Year |
1990 |
Abstract |
The effect of ultrasound on placental transfer in the rat has been measured in vivo. At 15, 18, 21 and 22 days of gestation one uterine horn of each anaesthetized rat was exposed, after laparatomy, to ultrasound. The control horn was effectively shielded. Radio-labelled tracers were then injected into the maternal circulation via a jugular vein cannula and fetuses removed simultaneously from both experimental and control horns at times predetermined to ensure minimal backflux from fetus to mother. Samples of maternal plasma were also taken at suitable intervals. The radioactive content of fetuses and plasma were measured and a unidirectional materno-fetal clearance value (Kmf) for each fetus calculated. It was shown that in rats whose body temperature was accurately maintained at 37 degrees C, ultrasound at the level used in the present study had no effect on placental clearance. However, in rats whose body temperature was allowed to fall to 32 degrees C, a 3 min exposure to 1.1 MHz continuous wave ultrasound at 1 W cm-2 caused a significant (p less than 0.001) decrease in the placental clearance of 22Na (by 55%) and 51Cr-EDTA (by 45%) in rats at 15 days of gestation. These effects showed no dose response and were not observed in rats at any of the other stages of gestation which we investigated. However, in rats at 21 days of gestation the clearance of 45Ca2+ was significantly (p less than 0.01) reduced (by 30%) by a similar exposure to ultrasound. It is concluded that although an interesting biological effect of ultrasound at low body temperatures has been observed, it has little relevance for the normal use of ultrasound in obstetrics. |
Title |
Effects of ultrasound on solid mammalian tissues and tumors in vivo. |
Author |
Lele PP. |
Journal |
Ultrasound |
Volume |
|
Year |
1987 |
Abstract |
No abstract available. |
Title |
Effects of ultrasound on the brain of rabbits. A histological study. |
Author |
Jankowiak J, Majewski C, Kubiak E. |
Journal |
Am J Phys Med |
Volume |
|
Year |
1963 |
Abstract |
No abstract available. |
Title |
Effects of ultrasound on the dog ureter and a clinical trial. |
Author |
Goodfriend R. |
Journal |
Proc West Pharmacol Soc |
Volume |
|
Year |
1973 |
Abstract |
No abstract available. |
Title |
Effects of ultrasound on the mouse exposed at different stages of gestation: Acute studies. |
Author |
Stolzenberg SJ, Torbit CA, Edmonds PD, Taenzer JC. |
Journal |
Radiat Environ Biophys |
Volume |
|
Year |
1980 |
Abstract |
At five stages of gestation, mice were exposed dorsally to ultrasonic irradiation at 1 W/cm2 (spatial and temporal average), 2 MHz, and 34 and 37 degrees C (temperature at beginning of exposure). The results indicated that ultrasonic exposure up to at least 100 s is not hazardous to a pregnant mouse or its offspring in utero under the conditions of our experiment. Thresholds for both undesirable and lethal effects on the dam and its embryos or fetuses appeared between 100 and 200 s. Temperature rises in the uterus to more than 40 degrees C and similarity of results obtained with continuous-wave and burst modes of irradiation suggest a thermal mechanism as one cause of these effects. Preliminary conclusions are that thresholds for both tissue damage to the dam and deleterious effects on pregnancy were similar; however, they occurred at spatial average intensity and exposure levels far in excess of those used in clinical diagnostic medicine. |
Title |
Effects of ultrasound on the prenatal development of the rat. Part 1. 3.2 MHz continuous wave at nine days of gestation. |
Author |
Sikov MR, Hildebrand BP. |
Journal |
J Clin Ultrasound |
Volume |
|
Year |
1976 |
Abstract |
Individual nine-day rat embryos were exposed for 5 or 15 minutes to graded intensities of well-characterized focused beams of 3.2 MHz continuous wave ultrasound. Fetuses were examined for effects at 20 days of gestation. Analysis of the exposure-response relationships indicates an "apparent threshold" for prenatal mortality at 3 W/cm2 (95 per cent fiducial limits 0.5-6 W/cm2). Fetal size was unaffected at any exposure level and there were only a few malformations, which occured at 10.5 W/cm2 and above. |
Title |
Effects of ultrasound on the prenatal development of the rat. Part 1. 3.2 MHz continuous wave at nine days of gestation. |
Author |
Sikov MR, Hildebrand BP. |
Journal |
J Clin Ultrasound |
Volume |
|
Year |
|
Abstract |
Individual nine-day rat embryos were exposed for 5 or 15 minutes to graded intensities of well-characterized focused beams of 3.2 MHz continuous wave ultrasound. Fetuses were examined for effects at 20 days of gestation. Analysis of the exposure-response relationships indicates an "apparent threshold" for prenatal mortality at 3 W/cm2 (95 per cent fiducial limits 0.5-6 W/cm2). Fetal size was unaffected at any exposure level and there were only a few malformations, which occured at 10.5 W/cm2 and above. |
Title |
Effects of ultrasound on the prenatal development of the rat. Part 1. 3.2 MHz continuous wave at nine days of gestation. |
Author |
Sikov MR, Hildebrand BP. |
Journal |
J Clin Ultrasound |
Volume |
|
Year |
1976 |
Abstract |
Individual nine-day rat embryos were exposed for 5 or 15 minutes to graded intensities of well-characterized focused beams of 3.2 MHz continuous wave ultrasound. Fetuses were examined for effects at 20 days of gestation. Analysis of the exposure-response relationships indicates an "apparent threshold" for prenatal mortality at 3 W/cm2 (95 per cent fiducial limits 0.5-6 W/cm2). Fetal size was unaffected at any exposure level and there were only a few malformations, which occured at 10.5 W/cm2 and above. |
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