Medical use of nonionizing electromagnetic waves in the radio and superhigh frequency range: hazards and standards.
Explore the source record for details and available documents.
Animals↗
SEARCH · PubMed Health
Results for “Radiation, Nonionizing”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Topological transition in aqueous nonionic micellar solutions.
We have studied the topological transition of the nonionic micelles of a penta-ethyleneglycol mono n-dodecyl ether (C12E5)/DL-alpha-phosphatidylcholine Dimyristoyl (DMPC) mixture in water by light scattering and viscosity measurements. The topological transition concentration decreases with an increase of the mixing ratio of DMPC to C12E5. The topological transition point is strongly affected by defect energies of the end cap (epsilon(1)) and a threefold junction (epsilon(3)) and is compared with a recent theoretical study. This experimental study shows the first clear evidence for the topological transition in a nonionic micellar system resulting from balancing the defect energies.
Dimyristoylphosphatidylcholine↗
Viscous fluid expulsion in the evaluation of the constipated patient.
PURPOSE: The aim of this study was to evaluate a viscous fluid expulsion test as a method for quantifying rectal outlet obstruction. METHODS: We examined the ability of 30 severely constipated patients and 40 healthy control subjects to expel a viscous fluid simulating feces. RESULTS: Constipated patients with defecographic rectal retention expelled a significant lower viscous fluid volume compared with controls (P < 0.0001). Considering the viscous fluid expulsion test to be positive if the patient expelled less than 160 ml of fluid (lower 95 percent confidence value in healthy controls) and using the presence of defecographic rectal outlet obstruction as a reference, the predictive value of a negative viscous fluid expulsion test was 100 percent, the predictive value of a positive test was 67 percent, and sensitivity and specificity was 100 percent and 82 percent, respectively. The viscous fluid test identified symptomatic outlet obstruction in almost twice as many patients as did defecography. Some patients, however are-despite their obstructive symptoms-able to evacuate their rectum when examined in the laboratory. CONCLUSION: The viscous fluid expulsion test is a simple, reproducible, nonionizing, and low-cost method of quantifying rectal outlet obstruction. A positive test result should lead to a defecography, whereas a negative test result renders defecography dispensable and spares the patient from pelvic radiation.
Adolescent↗
In vivo real-time microangiography of the liver in mice using synchrotron radiation.
BACKGROUND/AIMS: The aim of this study was to visualize hepatic microvessels (less than 100 microm in diameter) in vivo, which could not be visualized by conventional X-ray angiography, by using synchrotron radiation (ultra-bright and monochromatic X-ray). METHODS: Five female Balb/c nu/nu mice were used. To investigate the hepatic microvessels under nearly physiologic conditions, we performed in vivo aortography under anesthesia with 370 mgI/ml nonionic iodine contrast medium using monochromatic 17-keV X-rays generated by a synchrotron. Images were captured with a pixel matrix size of 1024 x 1024 at a rate of 30 pictures/s. The field of view was 7 mm x 7 mm and thus the pixel size was approximately 7 microm. Captured images were evaluated both qualitatively and quantitatively. RESULTS: Small hepatic arterial and portal venous branches of the liver were visualized separately during one sequential aortogram. The minimum diameter of the vessels observed was approximately 20 microm, and the vessels which ran parallel to the hepatic artery were observed and it seemed to be intrahepatic peribiliary arterial plexus. CONCLUSIONS: Our new experimental model would be useful for visualization of changes in the hepatic microcirculation under nearly physiologic conditions.
Angiography↗
The application of track calculations to radiobiology. II. Calculations of microdosimetric quantities.
In this second paper of a series, Monte Carlo-simulated proton tracks in water vapor are analyzed to yield a range of quantities that are of radiobiological interest. These include proximity functions of energy deposition, lineal energy distributions in micrometer and nanometer site sizes, and radial energy distributions. Many of these quantities cannot be measured with current experimental techniques. Some results are compared with those from analytic calculations. Also the effect on such quantities of the uncertainties in cross-sectional data used in the original Monte Carlo calculations is assessed, as is the effect of including nonionizing energy-loss events for analysis in the calculation.
Energy Transfer↗
Photodegradation of sulfamethoxazole: a chemical system capable of monitoring seasonal changes in UVB intensity.
Sulfamethoxazole (SMX) in its nonionized form in aqueous solution has ultraviolet (UV) absorption that is maximal at 268 nm but extends through the ultraviolet-B (UVB) region. It was found to be extremely susceptible to photodegradation when exposed to artificial UV radiation through a Pyrex filter or to unfiltered natural sunlight. The SMX anion was more stable. The quantum yields of the photodegradation of both forms were determined by use of monochromatic light and ferrioxalate chemical actinometry, the values of 0.47 (pH 3.0) and 0.084 (pH 9.0) at the maximum absorption wavelengths (268 and 257 nm, respectively) being obtained. Using literature data on sunlight intensity, the photochemical shelf-life of SMX solutions exposed to direct sunlight was calculated for Sydney (latitude 33.5 degrees S) as a function of season of the year and verified experimentally. A fixed correlation was established between the rate constant for SMX degradation and UVB intensity measured by a radiometer, suggesting the capacity of this chemical system to monitor changes in the UVB region of sunlight.
Humans↗
Detergent-induced solubilization of cytochrome c oxidase as detected in a novel reconstituted system.
A preparation of reconstituted cytochrome oxidase vesicles in which the enzyme is oriented facing inwards (such that it cannot interact with external cytochrome c) is described. No oxidase activity is expressed by these vesicles unless they are disrupted, allowing influx of cytochrome c or exposure of the oxidase-binding site to the external medium. We have exploited this property to follow detergent-induced solubilization of the membrane, a technique which allows membrane disruption and enzyme activity to be monitored simultaneously. This protocol can be employed to investigate the properties and mechanism of action of detergents as is illustrated for several ionic and nonionic detergents.
Animals↗
Differentiation of central lung tumor from postobstructive lobar collapse by rapid sequence computed tomography.
When central lung tumor is associated with lobar collapse, discrimination of tumor from atelectasis is important for determining operability or for field planning should radiation therapy be utilized. Because tumor and collapsed lung have similar attenuation values, they cannot always be distinguished with usual contrast-enhanced CT. The article describes separation of tumor from collapsed lung by means of RSCT with bolus injection of nonionic contrast medium. With this technique collapsed lung is appreciably enhanced, but tumor enhancement is slow and minimal. The difference is most marked from 40 seconds to 2 minutes after scanning begins. This phenomenon is probably related to the marked increase in blood flow per unit area of collapsed lung due to crowding of relatively large pulmonary arteries compared to tumor blood supply through small bronchial arteries. Tumor can also be delineated from atelectasis by differences in internal structure with this technique.
Aged↗
Performance of vibro-acoustography in detecting microcalcifications in excised human breast tissue: a study of 74 tissue samples.
X-ray mammography is the principal modality used today for detection of breast microcalcifications and breast lesions associated with breast cancer. X-ray mammography, however, is ionizing and its sensitivity is greatly reduced in dense breasts. Hence, alternative noninvasive and nonionizing breast imaging tools that can aid physicians to better diagnose early-stage breast lesions are of great interest. Vibro-acoustography is a novel noninvasive imaging technique that uses ultrasound in a fundamentally new way. This method uses the radiation force of ultrasound to vibrate the tissue at low (kilohertz) frequency and records the resulting response to produce images that are related to the mechanical properties of the tissue. The goal of this study is to evaluate the performance of vibro-acoustography in detecting breast microcalcifications by conducting vibro-acoustography on 74 fixed breast tissue samples with known microcalcifications based on their radiographs. The results indicate that in most cases micro-calcifications can be detected by vibro-acoustography. Further development of vibro-acoustography may lead to a novel-imaging tool for in vivo detection of microcalcifications.
Acoustics↗
Effect of 2'-deoxy-2'-(fluoromethylene) cytidine on the ultraviolet and X-ray sensitivity of HeLa cells.
The effects of treatment of HeLa cells with the antitumor nucleoside analog 2'-deoxy-2'-(fluoromethylene) cytidine (FMdC) on ultraviolet and X-ray sensitivity were examined. A 1-h pretreatment with FMdC increased cellular sensitivity to both X-rays and ultraviolet irradiation as determined by survival curve analysis. Increased sensitivity to killing was accompanied by a clear reduction in the rate and extent of X-ray-induced DNA strand break repair and in the closure of excision repair-dependent DNA breaks following ultraviolet irradiation. These studies demonstrate that FMdC treatment compromises the repair of both ionizing ("short-patch") and nonionizing ("long-patch") DNA damage. The mechanism by which this is likely to occur is discussed. Based on these findings, it is likely that FMdC, in addition to possessing inherent antitumor activity, might provide additional antineoplastic benefit when administered in combination therapies with radiation.
DNA Damage↗
Nonionizing radiant energy as an agent in altering the incidence of x-ray-induced chromatid aberrations. III. Action spectrum of far-red potentiation.
Explore the source record for details and available documents.
Bone Marrow↗
Isothermal titration calorimetry and dynamic light scattering studies of interactions between gemini surfactants of different structure and Pluronic block copolymers.
The interactions between triblock copolymers of poly(ethylene oxide) and poly(propylene oxide), P103 and F108, EO(n)PO(m)EO(n), m=56 and n=17 and 132, respectively, and m-s-m type gemini surfactants, m=8, 10, 12, and 18, and s = 3, 6, 12, and 16, have been studied in aqueous solution using isothermal titration calorimetry and dynamic light scattering techniques. The enthalpograms of F108 as a function of surfactant concentration show one broad peak at polymer concentrations C(p) < or = 0.50 wt%, below the cmc of the copolymer at 25 degrees C. It is attributed to interactions between the surfactant and the triblock copolymer monomer. DLS results show hydrodynamic radii (R(h)) initially consistent with copolymer monomers that change to values consistent with gemini surfactant micelles as the surfactant concentration is increased. In P103 solutions at C(p) > or = 0.05 wt%, two peaks appear in the enthalpograms, and they are attributed to the interactions between the gemini surfactant and the micelle or monomer forms of the copolymer. An origin-based nonlinear fitting program was employed to deconvolute the two peaks and to obtain estimates of peak properties. An estimate of the fraction of copolymer in aggregated form was also obtained. The enthalpy change due to interactions between the surfactants and P103 aggregates is very large compared to values obtained for traditional surfactants. This suggests that extensive reorganization of copolymer aggregates and surrounding solvent occurs during the interaction. DLS results for the P103 systems containing C(p) > or = 0.05% show evidence of very large aggregates in solution, likely P103 micelle clusters. The transitions observed in the hydrodynamic radii are consistent with a breakdown of micelle clusters with addition of gemini surfactant, followed by mixed micelle formation and/or deaggregation into monomer P103. This is followed by interactions similar to those typically observed in surfactant-nonionic polymer systems. Mechanisms for the interaction and the observed structural changes are discussed.
Biophysics↗
Oxidation of thallium by freshwater plankton communities.
Thallium is a toxic metal that is of emerlI(I) or Tl(III), and its oxidation state affects its complexation and subsequent bioavailability and toxicity. We conducted lab and field incubations with 204Tl(I) and natural plankton assemblages to study the occurrence and mechanism of Tl oxidation. We observed that Tl(III) comprised 74% of total dissolved Tl after a 60 h incubation in surface waters from Lake Ontario, revealing a maximum specific oxidation rate of 0.014 h(-1). No Tl(I) oxidation was observed in sterile-filtered control treatments, indicating that solar radiation alone does not oxidize Tl(I) to Tl(III). Additional incubations with pond water revealed that Tl(I) oxidation is mediated by microbial activity and is not related to the presence of abiotic particles or phytoplankton or protozoa. We also identified a minor fraction (5-13%) of nonion-exchangeable (Chelex-100 resin; pH 1.5) Tl that may represent dimethylthallium or complexed thallium. This study demonstrates that planktonic bacteria are responsible for oxidizing the thermodynamically stable Tl(I) to the more abundant Tl(III).
Animals↗
Nonionizing radiant energy as an agent in altering the incidence of x-ray-induced chromatid aberrations. I. Effects of far-red and infrared radiant energy on Tradescantia and Vicia.
Explore the source record for details and available documents.
Chromatids↗
Association of terminal complement proteins in solution and modulation by suramin.
The association of terminal complement proteins was investigated by analytical ultracentrifugation and multi-angle laser light scattering. Native C8 and C9 formed a heterodimer in solution of physiological ionic strength with a free-energy change DeltaG degrees of -8.3 kcal/mol and a dissociation constant Kd of 0.6 microM (at 20 degrees C) that was ionic strength- and temperature-dependent. A van't Hoff plot of the change in Kd was linear between 10 and 37 degrees C and yielded values of DeltaH degrees = -12.9 kcal/mol and DeltaS degrees = -15.9 cal mol-1 deg-1, suggesting that electrostatic forces play a prominent role in the interaction of C8 with C9. Native C8 also formed a heterodimer with C5, and low concentrations of polyionic ligands such as protamine and suramin inhibited the interaction. Suramin induced high-affinity trimerization of C8 (Kd = 0.10 microM at 20 degrees C) and dimerization of C9 (Kd = 0.86 microM at 20 degrees C). Suramin-induced C8 oligomerization may be the primary reason for the drug's ability to prevent complement-mediated hemolysis. Analysis of sedimentation equilibria and also of the fluorescence enhancement of suramin when bound to protein provided evidence for two suramin-binding sites on each C9 and three on each C8 in the oligomers. Oligomerization could be reversed by high suramin concentrations, but 8-aminonaphthalene-1,3,6- trisulfonate (ANTS2- ), which mimics half a suramin molecule, could not compete with suramin binding and oligomerization suggesting that the drug also binds nonionically to the proteins.
Calorimetry, Differential Scanning↗
Structure at 2.7 A resolution of the Paracoccus denitrificans two-subunit cytochrome c oxidase complexed with an antibody FV fragment.
The aa3 type cytochrome c oxidase consisting of the core subunits I and II only was isolated from the soil bacterium Paracoccus denitrificans and crystallized as complex with a monoclonal antibody Fv fragment. Crystals could be grown in the presence of a number of different nonionic detergents. However, only undecyl-beta-D-maltoside and cyclohexyl-hexyl-beta-D-maltoside yielded well-ordered crystals suitable for high resolution x-ray crystallographic studies. The crystals belong to space group P212121 and diffract x-rays to at least 2.5 A (1 A = 0.1 nm) resolution using synchrotron radiation. The structure was determined to a resolution of 2.7 A using molecular replacement and refined to a crystallographic R-factor of 20.5% (Rfree = 25.9%). The refined model includes subunits I and II and the 2 chains of the Fv fragment, 2 heme A molecules, 3 copper atoms, and 1 Mg/Mn atom, a new metal (Ca) binding site, 52 tentatively identified water molecules, and 9 detergent molecules. Only four of the water molecules are located in the cytoplasmic half of cytochrome c oxidase. Most of them are near the interface of subunits I and II. Several waters form a hydrogen-bonded cluster, including the heme propionates and the Mg/Mn binding site. The Fv fragment binds to the periplasmic polar domain of subunit II and is critically involved in the formation of the crystal lattice. The crystallization procedure is well reproducible and will allow for the analysis of the structures of mechanistically interesting mutant cytochrome c oxidases.
Binding Sites↗
Self-assembly of a nonionic photoresponsive surfactant under varying irradiation conditions: a small-angle neutron scattering and cryo-TEM study.
We have used small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM) to determine the structure of aggregates formed by the photoresponsive surfactants diethylene glycol mono(4',4-butyloxy, butyl-azobenzene) (C4AzoOC4E2) and diethylene glycol mono(4',4-hexyloxy, butyl-azobenzene) (C4AzoOC6E2) under different illumination conditions. At high concentrations, the self-assembly behavior of these surfactants changes remarkably in response to different radiation conditions. The trans isomers assemble into bilamellar (C4AzoOC4E2) and unilamellar (C4AzoOC6E2) vesicles, while the cis isomers (under UV light) form bicontinuous phases. These light-induced structural changes are attributed to a change in the sign of the Gaussian rigidity, which is the direct result of azobenzene photoisomerization.
Journal Article↗
Crystallization of halorhodopsin from Halobacterium sp. shark.
The chloride-ion-pumping channel, halorhodopsin from Halobacterium sp. shark was detergent-solubilized and 3-D crystallized. Proteins were solubilized using the nonionic detergent n-octyl-beta-D-glucoside and were crystallized as thin-plate crystals with polyethylene glycol 4000 as a precipitant. The crystals belong to the space group P4(1)2(1)2 with unit-cell dimensions a=b=74.5 A and c=138.6 A. The diffraction pattern was slightly anisotropic. The best ordered crystal diffracted up to 3.3 A resolution along c axis with synchrotron radiation.
Crystallization↗