Technique for simultaneous x-ray visualization of the entire lower extremity arterial tree (distal aorta to foot) without a film changer.
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Angiography↗
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[Pathomorphologic changes in the arterial wall following x-ray endovascular dilatation in chronic ischemia of the lower extremities].
Intravital and postmortem (7 and 14 cases, respectively) x-ray endovascular dilatation of the limb arteries studied morphologically is shown to induce traumatic lesion of the vascular wall presenting with plaque cracking and detachment, disintegration of the cover, necrosis of smooth muscle cells. A clear-cut change of the plaque size was not recorded. Vascular dilatation at the site of stenosis treated by the balloon may be caused mainly by the plaque cracks and detachment from the vessel wall entailing partial recovery of its elasticity. Mechanical aftereffects of the balloon introduction noted morphologically involve also smoothing of convolution of the internal elastic membrane and the absence of the typical vascular superficial microrelief.
Arteriosclerosis↗
Determination of lower extremity anthropometric parameters using dual energy X-ray absorptiometry: the influence on net joint moments during gait.
OBJECTIVE: The purpose of this study was threefold: (1) to report on a method of determining lower extremity anthropometric data using dual energy X-ray absorptiometry, (2) to compare values obtained with this method to predictions from cadaver-based estimates, and (3) to quantify the extent to which these data affect the calculation of net joint moments during walking. BACKGROUND: Anthropometric data used in inverse dynamics equations are often estimated from older cadaveric specimens. A practical method for determining population-specific data is needed. METHODS: Using DXA scans obtained from 20 healthy adults, the mass, center of mass, and moment of inertia of each lower extremity segment were determined and compared to cadaver-based estimates. In addition, gait analysis was performed on 10 of these subjects, and net joint moments (sagittal plane) were calculated at the ankle, knee, and hip using anthropometric data obtained from (a) DXA, and (b) cadaver-based estimates. RESULTS: Statistically significant differences were identified for DXA-derived and cadaver-based anthropometric values. Overall, moment curves computed using the two data sets differed more during the swing phase than during the stance of gait. CONCLUSIONS: DXA appears to be an appropriate method for obtaining population-specific anthropometric data. Moment calculations for activities involving high accelerations and no ground reaction forces (i.e. swing phase of gait, kicking, etc.) would be most influenced by the differences between the anthropometric data sets.
Absorptiometry, Photon↗
Exposure to extremely low frequency magnetic fields suppresses x-ray-induced transformation in mouse C3H10T1/2 cells.
We designed and manufactured equipment for exposure of cultured cells to extremely low frequency magnetic fields (ELFMF) at 5, 50, and 400 mT and examined the effect of ELFMF on cellular transformation in mouse C3H10T1/2 cells (clone 8). Transformed foci, Type II and Type III, were independently counted as transformants. The cells were exposed to ELFMF alone at 5, 50, and 400 mT for 24 h or X-irradiated with 3 Gy followed by the ELFMF exposure. No significant difference in the transformation was observed between sham-exposed control and the ELFMF exposure from 5 to 400 mT. The transformation frequency for X-rays plus ELFMF was decreasing compared with X-rays alone. When 12-O-tetra-decanoylphorbol-13-acetate (TPA) was contained in the medium throughout the experiment, the transformation frequency by X-rays alone was elevated more. In the combined treatment with X-rays followed by ELFMF, the transformation frequency was slightly decreased at 50 and 400 mT even in the medium containing TPA. The long-term exposure at 5 mT suppressed both spontaneous and X-ray-induced transformations significantly. It is well known that overexpressing protein kinase C (PKC) failed to yield identifiable transformation of foci induced by ionizing radiation. We demonstrated previously that exposure to high-density ELFMF induced expression of several genes through an increase in PKC activity. From these results, it is suggested that ELFMF might suppress X-ray-induced transformation through activation of PKC by ELFMF.
Animals↗
Reduced X-ray resistance and homologous recombination frequencies in a RAD54-/- mutant of the chicken DT40 cell line.
rad54 mutants of the yeast Saccharomyces cerevisiae are extremely X-ray sensitive and have decreased mitotic recombination frequencies because of a defect in double-strand break repair. A RAD54 homolog was disrupted in the chicken B cell line DT40, which undergoes immunoglobulin gene conversion and exhibits unusually high ratios of targeted to random integration after DNA transfection. Homozygous RAD54-/- mutant clones were highly X-ray sensitive compared to wildtype cells. The rate of immunoglobulin gene conversion was 6- to 8-fold reduced, and the frequency of targeted integration was at least two orders of magnitude decreased in the mutant clones. Reexpression of the RAD54 cDNA restored radiation resistance and targeted integration activity. The reported phenotype provides the first genetic evidence of a link between double-strand break repair and homologous recombination in vertebrate cells.
Alkylating Agents↗
Diagnosis of acute fractures of the extremities: comparison of low-field MRI and conventional radiography.
The aim of this study was to compare low-field MRI (0.2 T) and conventional radiography for the detection of acute fractures of the distal part of the extremities. X-ray and MRI examinations of 78 (41 fractures, 37 without fracture) patients with the clinical suspicion of an acute fracture in the distal part of the extremities were compared. Four experienced radiologists, two for each of the two modalities, independently analyzed the images. Interobserver variability and receiver operating characteristic (ROC) analysis for both methods were established. The MRI and conventional radiography revealed an accuracy of 81.4 and of 79.5%, respectively, in the detection of acute fractures. The diagnostic accuracy of MRI to detect fractures in the hand and forefoot proved to be significantly inferior to conventional X-ray examinations. On the other hand, MRI achieved a better accuracy for the examination of bones near a large joint. The interobserver variability for both methods was rated as moderate. In ROC analysis both methods were rated as good. There was no statistical difference of the accuracy between low-field MRI and conventional radiography in the detection of acute fractures of the distal part of the extremities. Consequently, a routine use of low-field MRI as an alternative to conventional radiography to diagnose acute fractures of the extremities seems not to be justified.
Adult↗
Quality assurance in diagnostic radiology--for its own sake or that of the patient.
X-Ray departments are expensive to equip and run. This paper illustrates how a quality assurance programme may help to limit the wastage of resources. The production of good quality medical X-ray images is extremely complex and can only be guaranteed by implementing some form of quality assurance programme. The exposure of patients to X-rays also entails a risk of radiation injury and a quality assurance programme is necessary in order to limit this risk to a level as low as reasonably practicable. Because of this, in countries within the CEC, legislation now requires such a programme to be implemented. The aims of a QA programme are defined, and the implications arising from these aims are discussed. The role of international organisations in helping to achieve these aims is also discussed. The pitfalls of a QA programme in radiology are also identified particularly: (1) the tendency to carry out a large programme and acquire a considerable amount of data so that the original aims are obscured; (2) the possibility of carrying out tests which are expensive to perform and are not cost effective and (3) the failure to adapt constantly the content of the QA programme to the ever changing needs of the local department and the radiological community generally. The various components of a QA programme are presented together with illustrations of their possible impact on the standard of work of the X-ray department. These include: (1) resource management through film reject analysis; (2) patient dose measurements; (3) equipment inspection programme; (4) equipment maintenance programme; (5) training and education of staff.(ABSTRACT TRUNCATED AT 250 WORDS)
Cost-Benefit Analysis↗
Nuclear magnetic resonance solution and X-ray structures of squash trypsin inhibitor exhibit the same conformation of the proteinase binding loop.
A comparison of the solution nuclear magnetic resonance (n.m.r.) structures of squash trypsin inhibitor from seeds of the squash Cucurbita maxima with the X-ray structure of a trypsin complex of the inhibitor shows that the n.m.r. and X-ray structures are similar in terms of the global folding and secondary structure. The average atomic root-mean-square difference between the 36 n.m.r. structures on the one hand and the X-ray structure is 0.96 A for the backbone atoms and 1.95 A for all heavy atoms. The n.m.r. and X-ray structures exhibit extremely similar conformations of the primary proteinase binding loop. Despite the overall similarity, there are small differences between the mean computed structure and the X-ray structure. The n.m.r. structures have slightly different positions of the segments from residues 16 to 18, and 24 and 25. The n.m.r. results show that the inclusion of stereospecific assignments and precise distance constraints results in a significant improvement in the definition of the n.m.r. structure, making possible a detailed analysis of the local conformations in the protein.
Binding Sites↗
Agreement in the interpretation of extremity radiographs of injured children and adolescents.
OBJECTIVES: To measure agreement beyond chance (kappa) for comparison interpretations of extremity radiographs by pediatric radiologists and emergency physicians (EPs) and to identify factors associated with disagreement. METHODS: A random sample of 205 radiographs was selected from 1,016 patients having x-rays of their extremities in the emergency and radiology departments of a tertiary care pediatric hospital. Interpretations by the "official" reporting pediatric radiologist (ORPR), the treating EP, and a pediatric radiologist blinded to all clinical information (BPR) were compared for three categories: "abnormal" (one or more of fracture, dislocation, or effusion); "possibly abnormal"; and "normal." RESULTS: The overall weighted kappa (Kw) for the ORPRs and the EPs was 0.55. For fractures alone, the Kw for the ORPRs vs the EPs was 0.77; and for effusions alone, the value was 0.34. The Kw for the ORPRs vs the BPR was 0.63 (range 0.43-0.83 for individual ORPRs). The main areas of disagreement were in the identification of joint effusions and of nondisplaced fractures of the phalanges, elbow joint, tarsals, or metatarsals. CONCLUSIONS: There is good agreement between EPs and pediatric radiologists in interpreting extremity radiographs of injured children and adolescents. Disagreement occurs mainly for effusions or minor fractures and for the elbow region. Because of the importance of recognizing abnormalities in this region, an educational intervention to improve this area of deficiency is recommended.
Adolescent↗
Crystallization and preliminary X-ray characterization of aspartate aminotransferase from an extreme thermophile, Thermus thermophilus HB8.
Recombinant aspartate aminotransferase from an extremely thermophilic bacterium, Thermus thermophilus HB8, has been crystallized in two different crystal forms. The crystals of both forms are orthorhombic and belong to space group P212121 with cell dimensions a = 124.3, b = 113.6 and c = 61.6 A for form I and a = 197.3, b = 109.7 and c = 80.3 A for form II. The crystals of form I and II diffract to 2.1 and 2.5 A resolution, respectively, on a conventional laboratory rotating-anode source. Two heavy-atom derivatives have been identified for form I.
Aspartate Aminotransferases↗
[Radiation exposure during x-ray angiography].
During 73 cardiac angiographies and 10 angiograms of the abdomen and extremities, the x-ray doses were determined at the arm and forehead (eyes) of the radiologists and assistant staff. The results are discussed and compared with the recommendations of the ICRP and valid legislation. It is recommended to use an additional dosimeter at the forehead if higher frequencies are employed.
Angiography↗
[Bimomentous ascending oblique functional-dynamic phlebography of the lower extremities with caudal deflection of the central ray].
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Aged↗
Multiple wavelength anomalous diffraction (MAD) crystal structure of rusticyanin: a highly oxidizing cupredoxin with extreme acid stability.
The X-ray crystal structure of the oxidized form of the extremely stable and highly oxidizing cupredoxin rusticyanin from Thiobacillus ferrooxidans has been determined by the method of multiwavelength anomalous diffraction (MAD) and refined to 1.9 A resolution. Like other cupredoxins, rusticyanin is a copper-containing metalloprotein, which is composed of a core beta-sandwich fold. In rusticyanin the beta-sandwich is composed of a six- and a seven-stranded beta-sheet. Also like other cupredoxins, the copper ion is coordinated by a cluster of four conserved residues (His85, Cys138, His143, Met148) arranged in a distorted tetrahedron. Rusticyanin has a redox potential of 680 mV, roughly twice that of any other cupredoxin, and it is optimally active at pH values < or = 2. By comparison with other cupredoxins, the three-dimensional structure of rusticyanin reveals several possible sources of the chemical differences, including more ordered secondary structure and more intersheet connectivity than other cupredoxins. The acid stability and redox potential of rusticyanin may also be enhanced over other cupredoxins by a more extensive internal hydrogen bonding network and by more extensive hydrophobic interactions surrounding the copper binding site. Finally, reduction in the number of charged residues surrounding the active site may also make a major contribution to acid stability. We propose that the resulting rigid copper binding site, which is constrained by the surrounding hydrophobic environment, structurally and electronically favours Cu(I). We propose that the two extreme chemical properties of rusticyanin are interrelated; the same unique structural features that enhance acid stability also lead to elevated redox potential.
Azurin↗
Time-delay compensated monochromator in the off-plane mount for extreme-ultraviolet ultrashort pulses.
The design of ultrafast monochromators using grazing-incidence gratings in the off-plane mount for the spectral selection of extreme-ultraviolet femtosecond pulses in a broad spectral region is presented. Their application in the selection of high-order laser harmonics is analyzed in detail. The main advantage of the off-plane mount is a much higher efficiency than that of the classical mount. It is shown that two-grating configurations preserve the length of the optical paths of different diffracted rays, maintaining the extremely short time duration of the pulse. Configurations with plane or toroidal gratings are discussed. As a test case, the design of a monochromator for the 17-61 nm region with a time compensation better than 1 fs is presented.
Journal Article↗
Kinetics of the main phase transition of hydrated lecithin monitored by real-time X-ray diffraction.
A method is described for observing and recording in real-time x-ray diffraction from an unoriented hydrated membrane lipid, dipalmitoylphosphatidylcholine (DPPC), through its thermotropic gel/liquid crystal phase transition. Synchrotron radiation from the Cornell High Energy Synchrotron Source (Ithaca, New York) was used as an x-ray source of extremely high brilliance and the dynamic display of the diffraction image was effected using a three-stage image intensifier tube coupled to an external fluorescent screen. The image on the output phosphor was sufficiently intense to be recorded cinematographically and to be displayed on a television monitor using a vidicon camera at 30 frames X s1. These measurements set an upper limit of 2 s on the DPPC gel----liquid crystal phase transition and indicate that the transition is a two-state process. The real-time method couples the power of x-ray diffraction as a structural probe with the ability to follow kinetics of structural changes. The method does not require an exogenous probe, is relatively nonperturbing, and can be used with membranes in a variety of physical states and with unstable samples. The method has the additional advantage over its static measurement counterpart in that it is more likely to detect transiently stable intermediates if present.
Chemical Phenomena↗
[Inspection of inner structure of sealed 60Co sources by the autoradiography with radcolor film].
In studies using 60Co gamma-ray irradiation, an extremely high dose rate is often required and samples must be placed very near a 60Co source. The dose rate in the vicinity of the source depends on the inner structure of the source. Therefore, it is necessary to examine the distribution of source activity. As a method of the examination an autoradiographic technique using several coloring materials for irradiation was tried. The materials used were "Radcolor film" developed by our center, besides a glass, polymethylmethacrylate (PMMA) and a blue cellophane. Results showed that the autoradiography with Radcolor film is very useful to examine the position, the size and the activity difference of 60Co pieces by the change of color.
Autoradiography↗
Three-dimensional molecular modeling of bovine caseins: alpha s1-casein.
Structures derived from X-ray crystallography are extremely important in elucidating functional relationships for many proteins. However, the caseins of bovine milk are one class of noncrystallizable proteins. The complete primary and partial secondary structures of these proteins are known, but homologous proteins of known crystallographic structure cannot be found. Therefore, sequence-based predictions of secondary structure were made and adjusted to conform with global secondary structures determined by Raman spectroscopy. With this information, a three-dimensional structure for alpha s1-casein was constructed using molecular modeling programs. The predicted structure of alpha s1-casein contains a hydrophobic and a hydrophilic domain, which are connected by a segment of alpha-helix. This unrefined structure shows good agreement with global biochemical and chemical information concerning alpha s1-caseins A, B, and C.
Amino Acid Sequence↗
Three-dimensional molecular modeling of bovine caseins: kappa-casein.
Three-dimensional structures derived from X-ray crystallography are extremely important in elucidating relationships between structure and function for many proteins. However, not all proteins can be crystallized. The caseins of bovine milk are one class of noncrystallizable proteins. The complete primary and partial secondary structures of these proteins are known, but homologous proteins with known crystallographic structure are not available. In this report, sequence-based predictions of secondary structure were made and adjusted to conform with global secondary structures derived from Fourier transform infrared spectroscopy. With this information, a three-dimensional structure for kappa-casein was constructed using molecular modeling computer programs. The constructed model contains two unstranded beta-sheets; both are predominantly hydrophobic and capable of forming quaternary structural interaction sites with alpha s1-casein. This unrefined structure is in good agreement with much of the biochemical information available for kappa-casein.
Amino Acid Sequence↗