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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 248 out of 330
| Title |
The absorption of ultrasound in aqueous solutions of biological polymers. |
| Author |
O'Brien WD Jr. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1970 |
| Abstract |
The ultrasonic absorption and velocity were measured in aqueous solutions of four biologically important molecules, viz., hemoglobin, ovalbumin, serum albumin and deoxyribose nucleic acid, so that the principle mechanisms responsible for the ultrasonic absorption in biological media could be further investigated. The majority of the data were taken at 10.0 degrees C over the frequency range 1.6-50 MHz. A distribution of relaxation processes was necessary to characterize the absorption spectra for all the biological solutions investigated. No correlation can be suggested relative to the absorption magnitude and speciman purity, i.e., uncrystallized, twice crystallized, etc. Also, molecular weight differences appear to be unimportant (ovalbumin ? M = 46,000 and bovine serum albumin ? M = 68,000). Ultrasonic absorption mechanisms of dynamic shear viscosity, mode conversion, electroviscous effects and particulate relaxation have been shown to be unimportant as the primary processes repsonsible for the absorption of acoustic energy in aqueous protein solutions at their isoelectric point. Since all of the aqueous solutions at their isoelectric point in this study possess approximately the same frequency dependence and magnitude within the frequency range investigated, the absorption mechanism is considered the same. It is felt that the mechanism is the interaction of the acoustic wave with the hydration layer of the macromolecule and is not directly associated with the macromolecular configuration since the DNA structure is worm-like while the globular protein structure is a rigid, compact ellipsoid...Hemoglobin and ovalbumin solutions were examined as a function of pH over the range 1.5-13.5 at 10 degrees C, the former over the frequency range 2,390-50.5 MHz while the latter only at 14.80 MHz. These ultrasonic absorption titration curves exhibited maxima around pH 2-4 and 11-13 in addition to the hemoglobin curves possessing a bow shape within the pH range 4-9. The shape of these curves closely resemble those for bovine serum albumin (J. Phys. Chem., 73, 4256, 1969). The peaks in the absorption titration curves for these three globular proteins are attributed to the proton transfer reaction occuring between particular amino acid side chain groups and the solvent. The bow shape resulting in the hemoglobin titration curves is attributed to the proton transfer reaction resulting from the imidazolium fuction of the histidine amino acid...The ultrasonic absorption of aqueous deoxyribose nucleic acid (salmon sperm, M = approximately 10 to the sixth) solutions were measured in the acid pH range over the frequency range 5.690-19.30 MHz at 10.0 degrees C and 25.0 degrees C. The alkaline pH range was investigated by Lang and Cerf (J. Chim. Phys., 66, 81, 1969). The ultrasonic absorption titration curves for deoxyribose nucleic acid shows peaks around pH 2.6 and 12 which are attributed to the transfer of hydrogen bonds from base-base to base-solvent. Proton transfer is considered unimportant as the pk values of the nucleotide bases do not occur within the appropriate pH range. Aqueous hemoglobin solutions were investigated as a function of guanidine hydrochloride (GuHCl) concentration up to almost 7 molar, at 10.0 degrees C, over the frequency range 8.870-50.50 MHz. The absorption, at constant frequency, increased with increasing GuHCl concentrations to around 2 molar and then decreased, leveling off for GuHCl concentration grater than 4-5 molar. No correlation between the acoustic absorption and known conformational changes (Biochemistry, 4, 1203, 1965) results. The maximum around 2 molar GuHCl is attributed to the proton transfer reaction which can result when the guanidinium ion (GuH +) partakes in a proton exchange reaction with water when a second solution (hemoglobin) forms strong hydrogen bonds with either water or GuH + (J. Phys. Chem., 73, 2853. 1969)...This investigation was supported by the Institute of General Medical Sciences, National Institute of Health (Contract No. GM 12281). |
| Title |
The absorption of ultrasound in aqueous solutions of bovine serum albumin and polyethylene glycol. |
| Author |
Kessler LW. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1968 |
| Abstract |
No abstract available. |
| Title |
The absorption of ultrasound in aqueous solutions of dextran. |
| Author |
Kessler LW. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1966 |
| Abstract |
No abstract available. |
| Title |
The absorption of ultrasound in aqueous solutions of polyethylene glycol. |
| Author |
O'Brien WD Jr. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1968 |
| Abstract |
No abstract available. |
| Title |
The accumulative effect of phloridizin, ultrasound, and ultraviolet light on Krebs-2 mouse tumor cell oxygen consumption. |
| Author |
Chuml HR. |
| Journal |
Thesis(MS): Catholic Univ of America |
| Volume |
|
| Year |
1963 |
| Abstract |
No abstract available. |
| Title |
The accuracy and precision of estimating tissue displacements from ultrasonic images. |
| Author |
Chen EJ, Jenkins WK, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1992 |
| Abstract |
In many medical ultrasound imaging systems, clinical data are often presented in the form of tissue displacement and tissue velocity maps. The accuracy of tissue displacement estimates obtained using a well-established cross-correlation, speckle tracking technique is determined. The accuracy of the cross-correlation technique is evaluated as function of three parameters: (1) the magnitude of the tissue displacement; (2) the size of the region being tracked; and (3) of host tissue type. Three different sample types (porcine liver, porcine muscle and woolen sea sponge) are used to study the effect of different scattering media on displacement estimates. For identically sized target regions and displacements, liver samples produce estimates with the largest uncertainties. For all three sample types, the accuracy and precision of displacement estimates deteriorates with increasing sample displacements and decreasing target dimensions. |
| Title |
The accurate measurement of blood flow using ultrasound and time domain correlation. |
| Author |
Embree PM. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1982 |
| Abstract |
No Abstract Available. |
| Title |
The action of low-intensity pulsed ultrasound on amphibian embryonic tissues. |
| Author |
Sarvazyan AP, Beloussov LV, Petropavlovskaya MN, Ostroumova TV. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
Amphibian embryos at different stages of development, and ectomesodermal explants (small pieces of embryonic tissue extirpated from lateral parts of the embryos just after neurulation), have been irradiated with continuous and pulsed ultrasound at a frequency of 0.88 MHz, spatial and temporal average intensities being within the range 0.025-0.1 W cm2. Ultrasound pulse repetition frequencies were varied within 10-1000 Hz, duty factor being constant and equal to 0.5. Destruction of embryonic tissue as an immediate effect, and interruption or distortion of development as delayed (24 hr) effects, were registered. Significant damaging effects of non-cavitational and non-thermal origin and dependent on pulse repetition frequencies, were observed. Highly frequency-dependent resonance-type effects were obtained for irradiated explants. The maximum effect on Rana temporaria explants was obtained at pulse repetition frequencies of 10-20 Hz and on Xenopus laevis explants at 110-130 Hz. |
| Title |
The action of ultrasound on human erythrocytes in suspension. |
| Author |
Connolly CC. |
| Journal |
Thesis(PhD): Univ of London |
| Volume |
|
| Year |
1960's |
| Abstract |
The mechanisms of interaction of ultrasonic energy with biological material is still in doubt. Mechanical and thermal interactions have been postulated as being the prime cause of destruction of biological cells. This thesis shows that mechanically induced surface stressed are of prime importance on cells in suspension. Heating is implicated as a factor of major importance in decreasing the mechanical resistance of the membrane to stress...Experiments have been carried out at frequencies from 1-10 MHz and at intensities of up to 330 watts cms to the ?2 in the plane wave. Pulsing conditions in the ultrasonic beam have been found to be of major importance in affecting blood cells, due to the viscoelasticity of the cell surface. A new method of assessing viscoelasticity of cell surfaces has been found.. |
| Title |
The angiogenic response is dependent on ultrasound contrast agent concentration. |
| Author |
Johnson CA, O'Brien WD Jr. |
| Journal |
Vascular Cell |
| Volume |
|
| Year |
2012 |
| Abstract |
ABSTRACT:
OBJECTIVE:
Ultrasound (US) and ultrasound contrast agents (UCAs) provide a way to noninvasively and spatially induce angiogenesis. However there exists a lack of understanding regarding the mechanisms of this process that has suppressed progress. This study sought to characterize the angiogenic response, by exploring the role of UCA concentration ([UCA]) in bioeffect induction at 0 days post exposure (DPE) and as a possible potentiator of angiogenesis at 5 DPE.
METHOD:
S: A 1-MHz transducer was used to expose the gracilis muscles of Sprague Dawley rats for a 5 min exposure duration with a 10-us pulse duration, 10-Hz pulse repetition frequency, and 0.7-MPa peak rarefactional acoustic pressure (pr). Four [UCA]s were tested: 0x (saline), 1x, 5x, and 10x, where 1x is 5% Definity by volume of solution. Evans blue dye (EBD) was used to quantify acute vascular permeability (0 DPE), and VEGF expression was quantified at 5 DPE to support that angiogenesis had occurred. CD31 staining was used to assess capillary density at both time points.
RESULTS:
: This study showed that [UCA] was a significant parameter for determining EBD leakage (permeability) and VEGF expression (p < 0.001 for both). However, [UCA] was not a significant parameter for capillary density at 0 or 5 DPE. Multiple comparisons between 0 and 5 DPE showed that only 10x [UCA] at 5 DPE was significantly different than 0 DPE suggesting a [UCA] dependence of the angiogenic response.
CONCLUSION:
This study suggests that [UCA] is a significant parameter in the induction of an angiogenic response with US and UCAs. It also suggests that mechanically induced bioeffects could potentiate the angiogenic response. |
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