Precise re-positioning of the head for serial CT examinations.
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[Computation of the arterial carbon dioxide pressure by means of CO2 re-breathing and infrared analysis].
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Adolescent↗
Filtered X ray beam dosimetry from 10(-3) to 10(2) Gy dose range by using phototransistors.
Low-cost, commercially available phototransistor-type semiconductor devices have been tested for monitoring filtered X ray beam dose. A Pantak X-ray unit was used to generate aluminium filtered X ray beams from 60 to 120 kV potentials. The analysis of the radiation detection behaviour as a function of the X ray tube parameters (peak kilovoltage and electrical current) are presented. The changes of the phototransistor electronic parameters have been evaluated and the results indicate that phototransistors can be used as X ray detectors for dose estimation in two different ways: electrical current read-out from 1 to 100 mGy dose range, and the changing of the radiation detection sensitivity in the dose range from 0.1 to 100 Gy. In addition, the devices show high reliability with no sign of substantial performance degradation with use and, in certain dose ranges, the cumulative dose evaluations could be performed up to 10,000 times with no need for re-calibration.
Dose-Response Relationship, Radiation↗
Lipopolysaccharide bilayer structure: effect of chemotype, core mutations, divalent cations, and temperature.
Lipopolysaccharide (LPS), the primary lipid on the surface of Gram-negative bacteria, is thought to act as a protective and permeability barrier. X-ray diffraction analysis of osmotically stressed LPS multilayers was used to determine the structure and interactive properties of LPSs from strains containing the minimum number of sugars necessary for bacterial survival (Re chemotype) to the maximum number of sugars found in rough bacteria (Ra chemotype). At 20 degrees C in the absence of divalent cations, LPS suspensions gave a sharp wide-angle reflection at 4.23 A and a broad low-angle band centered at 50-68 A depending on the chemotype, indicating the presence of gel phase bilayers separated by large fluid spaces. As osmotic pressure was applied, the apposing bilayers were squeezed together and lamellar diffraction at 6 A resolution was obtained. At low applied pressures (<10(6) dyn/cm2), the total repulsive pressure between bilayers could be explained by electrostatic double layer theory. At higher applied pressures, there was a sharp upward break in each pressure-distance relation, indicating the presence of a hydrophilic steric barrier whose range depended strongly on the LPS chemotype. The positions of these upward breaks, along with electron density profiles, showed that the sugar core width systematically increased from 10 A for the Re chemotype to 27 A for the Ra chemotype. In excess buffer, the addition of divalent cations brought the bilayers into steric contact. Electron density profiles were used to determine the locations of cation binding sites and polar substituents on the LPS oligosaccharide core. The area per hydrocarbon chain was approximately 26 A2 in liquid-crystalline LPS bilayers, an indication of an acyl chain packing that is much tighter than that found in bilayers composed of typical membrane lipids. This unusually tight packing could be a critical factor in the permeability barrier provided by LPS.
Barium↗
Binding of formamides to liver alcohol dehydrogenase.
Amides are analogs of aldehydes and potent inhibitors of liver alcohol dehydrogenases. They can be used for structural studies and for inhibiting the metabolism of alcohols that form toxic products. We studied N-alkyl amides that bind to the enzyme-NADH complex and act as uncompetitive inhibitors against varied concentrations of ethanol (millimolar Kii values, at pH 8 and 25 degrees C): N-propylacetamide (16), delta-valerolactam (1.6), N-formylpiperidine (0.14), N-isobutylformamide (0.028), N-(cyclohexylmethyl)-formamide (0.011), and N-cyclohexylformamide (0.0087). The lower affinity of delta-valerolactam and N-propylacetamide can be explained by steric hindrance with Phe93 of the enzyme. Replacing Phe93 with Ala in the S48T/F93A mutated enzyme, which resembles the natural alpha-isoenzyme of primates, improved binding of delta-valerolactam by 210-fold. The structures of horse liver enzyme complexed with NADH and N-cyclohexylformamide or N-formylpiperidine were determined by X-ray crystallography at 2.5 A resolution. In both complexes, the carbonyl oxygens of the inhibitors bind to the catalytic zinc and form a hydrogen bond to the hydroxyl group of Ser48 of the enzyme. The six-membered rings bind in overlapping, but rotated, positions that optimize hydrophobic interactions. The binding modes of the unreactive formamides appear to resemble the Michaelis complexes of the analogous substrates, with the re face of the carbonyl carbon suitably positioned to accept a hydrogen from NADH.
Alcohol Dehydrogenase↗
[Treatment of benign esophageal stenosis: re-evaluation after 20 years].
In 1972 we described a method for dilatation of esophageal stenosis. The purpose of this paper is to report the results obtained between 1970 and 1989, the patients were studied by X-Rays, "calibration" of the stenosis, endoscopy, biopsy, cytology, gastric analysis and esophageal motility. One hundred and seven patients were treated (mean 60.5 years, M/F 3.9/1). The most frequent etiology was reflux esophagitis (80.3%). Hiatus hernia was present in 84.9%. The stenosis was in the lower third of the esophagus in 92.5%. The BAO was mean: 3.6 mEq/h, and the MAO mean 16.4 mEq/h with a hypersecretion pattern in 33.1% of the cases. Cytology was negative for malignancy in 100%. Biopsy showed esophagitis in 86.9%, Barrett's epithelium in 12.1%, normal tissue in 6.5% and insufficient material in 1.8%. Endoscopy showed 98.1% of grade IV esophagitis. Esophageal motility showed a HPZ of mean 6.5 mmHg. and varying degrees of aperistalsis in 24.3% of the patients. The total number of dilatations was 555 (mean 5.1/pt). The "calibration" of the stenosis previous to the dilatation was mean 8.6 mm, and post dilatation mean 15.6 mm. The result of the procedure was good in 92.5%, regular in 2.8% and bad in 4.6%. The morbidity was 0.9% and the mortality 0.1%. There was relapse of the stenosis in 42% of the cases, the follow-up was mean 3.2 years. Twenty nine patients were submitted to surgery due to failure of the procedure with 68.1% of good results, morbidity of 9% and mortality of 9%. We conclude that this dilatation procedure offers excellent results with a very low morbi-mortality.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Synthesis, X-ray crystal structure and biological properties of acetylenic flavone derivatives.
The reactions of iodoflavone with 3-methyl-3-hydroxybut-1-yne and 3-methylbut-3-en-2-yne are described and the antimicrobial and cytotoxic activities of the obtained compounds have been tested. The molecular structures of 6-(3-hydroxy-3-methylbut-1-ynyl)-flavone (1a) and 6-(3-methylbut-3-en-1-ynyl) flavone (1b) have been determined by X-ray crystallography. The planar configuration of the two compounds has been attributed to intramolecular hydrogen bond interactions. In 1a, the presence of the hydroxyl group determines a dimeric arrangement of the molecules. In both compounds in the crystal state, molecular stacking has been observed.
Acetylene↗
Quality assurance of I-125 seed permanent implant therapy using a self-color developing reflection-type dosimetry sheet film.
PURPOSE: We evaluated a self-color developing sheet-type film for the detection of dead seeds in I-125 permanent implant therapy for prostate cancer. MATERIALS AND METHODS: As a preliminary study, we irradiated X-rays to a self-developing reflection-type sheet film and created a relational curve between absorbed dose and film density. I-125 seeds were placed on a film and the approximate absorbed dose of I-125 was calculated from the relational curve of X-rays. A cartridge in which a dead seed was loaded among 10 I-125 seeds was placed on the film and the detectability of the dead seed was evaluated. RESULTS: Using the relational curve of X-rays, it was possible to measure the approximate absorbed dose of I-125 seeds and to easily detect a dead seed at a glance. Using sterilized film, it was possible to detect a dead seed. CONCLUSION: The self-developing film method is feasible for the detection of a dead seed in a cartridge without re-sterilization of seeds.
Brachytherapy↗
Embryonic wound healing by apical contraction and ingression in Xenopus laevis.
We have characterized excisional wounds in the animal cap of early embryos of the frog Xenopus laevis and found that these wounds close accompanied by three distinct processes: (1) the assembly of an actin purse-string in the epithelial cells at the wound margin, (2) contraction and ingression of exposed deep cells, and (3) protrusive activity of epithelial cells at the margin. Microsurgical manipulation allowing fine control over the area and depth of the wound combined with videomicroscopy and confocal analysis enabled us to describe the kinematics and challenge the mechanics of the closing wound. Full closure typically occurs only when the deep, mesenchymal cell-layer of the ectoderm is left intact; in contrast, when deep cells are removed along with the superficial, epithelial cell-layer of the ectoderm, wounds do not close. Actin localizes to the superficial epithelial cell-layer at the wound margin immediately after wounding and forms a contiguous "purse-string" in those cells within 15 min. However, manipulation and closure kinematics of shaped wounds and microsurgical cuts made through the purse-string rule out a major force-generating role for the purse-string. Further analysis of the cell behaviors within the wound show that deep, mesenchymal cells contract their apical surfaces and ingress from the exposed surface. High resolution time-lapse sequences of cells at the leading edge of the wound show that these cells undergo protrusive activity only during the final phases of wound closure as the ectoderm reseals. We propose that assembly of the actin purse-string works to organize and maintain the epithelial sheet at the wound margin, that contraction and ingression of deep cells pulls the wound margins together, and that protrusive activity of epithelial cells at the wound margin reseals the ectoderm and re-establishes tissue integrity during wound healing in the Xenopus embryonic ectoderm.
Actins↗
Bone loss in long-term survivors after transplantation of hematopoietic stem cells: a prospective study.
Organ transplantation is associated with relevant bone loss. Bone loss of up to 20% of pretransplant bone mineral density (BMD) values within the first year after kidney, liver, heart and lung transplantation has been reported. Patients undergoing transplantation of hematopoietic stem cells provide an interesting model to study transplantation-induced bone loss, especially because most patients do not have preexisting bone disease. A longitudinal study was performed in 81 patients undergoing bone marrow or peripheral blood stem cell transplantation. BMD was determined by dual-energy X-ray absorptiometry before transplantation, at discharge from the hospital, and at 6 and 12 months after transplantation in all 81 patients. In 35 patients BMD was re-evaluated 24 months after transplantation. Vitamin D and parathyroid hormone, bone alkaline phosphatase as a marker of bone formation, and N-terminal telopeptide of type I collagen as a marker of bone resorption were assessed before transplantation and in the short-term follow-up 14 and 28 days after transplantation. The majority of patients (72%) showed normal BMD before transplantation. However, lower BMD was observed in patients who had received high-dose cytoreductive chemotherapy before transplantation compared with those who had received no chemotherapy or only hydroxyurea. Despite supplementation with elemental calcium (1000 mg/day) and vitamin D (1000 IU/day), the mean rate of bone loss during the first year was 7.2 +/- 6.3% at the lumbar spine, 11.9 +/- 8.1% at the femoral neck and 3.8 +/- 2.5% at the total body compartment. Evaluation of the pattern of bone loss during the first year demonstrated that the amount of bone loss was largest within the first 40 days after transplantation and small during the second half of the first year after transplantation. The majority of patients showed vitamin D deficiency and secondary hyperparathyroidism. Bone formation was normal before and after transplantation, whereas bone resorption was dramatically increased before and after transplantation. Exposure to glucocorticoids was associated with higher bone loss at spine and femoral neck but not at the total body compartment. Our data demonstrate rapid bone loss in patients undergoing transplantation of hematopoietic stem cells. Bone turnover is characterized by biochemical uncoupling of bone resorption and bone formation, changes interestingly pre-existing before transplantation. The observed alterations in bone mass and metabolism emphasize the importance of clinical trials with antiresorptive agents to prevent and treat post-transplantation osteoporosis in this group of patients.
Adolescent↗
The clinical indications for plain radiography in acute knee trauma.
OBJECTIVES: to assess the key symptoms and physical signs in the acutely injured knee that are significantly associated with fracture and utilise these to develop an algorithm for the use of radiography in acute knee trauma. DESIGN: retrospective review of all acute knee injuries presenting to the accident and emergency unit at a District General Hospital over a 6-month period in 1998 (over 500 cases). After exclusions, a study group of 370 eligible adults was obtained. These patients were reviewed for the key symptoms and physical signs, and radiological evidence of fracture. OUTCOME MEASURES: the X-ray films were interpreted by a consultant radiologist. Of those patients on whom radiographs were not performed, follow up was assessed by a review of any re-attendance to the A&E department. RESULTS: there was a statistically significant correlation, using chi-square (Mantel-Haentzel) and linear regression analysis, between the presence of a fracture and each of the following variables: age, non-weightbearing in the department (p<0.05), haemarthrosis, point bony tenderness, effusion (p<0.001). CONCLUSION: these key symptoms and physical signs may form the basis of an algorithm for examining knees radiologically, with acceptable positive and negative predictive values. (This is currently being tested prospectively).
Adult↗
Decreasing the dosimetric effects of misalignment when using a mono-isocentric technique for irradiation of head and neck cancer.
PURPOSE: The purpose of this study was to quantify and develop methods to decrease inhomogeneities created with field edge mismatch when using a mono-isocentric beam-split technique. METHODS AND MATERIALS: We validated techniques to determine dose across a half-blocked field edge and quantified potential sources of systematic matchline error. Then, two methods were used to evaluate matchline doses. The first used film dosimetry data from a half-beam field and a spreadsheet. Duplication and reversal provided two columns, each representing a beam-split field edge. Summation simulated perfect abutment and shifting created various gaps and overlaps. The second method involved obtaining dose profiles at midfield along the ray perpendicular to abutted, overlapped, and gapped beam-split fields on six linear accelerators. To enlarge the penumbra, we designed several field edge modifiers, then re-evaluated matchline doses. The field edge modifiers applicability to a 3-field head and neck treatment technique was also examined. RESULTS: Film-determined dose profiles provide similar information across a beam-split field edge as an ionization chamber. With the mono-isocentric beam-split technique, a 4-mm overlap or gap produces inhomogeneities nearly 60% above or below the intended dose. A 2-mm overlap or gap produces inhomogeneities nearly 30% above or below the intended dose. A customized penumbra generator decreased the magnitude of these inhomogeneities to 20% and 10%, respectively. CONCLUSION: The two methods of evaluating matchline dose described above gave similar results. When using the mono-isocentric half-field technique, small misalignments produce worrisome regions of inhomogeneity. Our penumbra generator substantially decreases the magnitude of the dose inhomogeneities, although the volume receiving an inhomogeneous dose increases.
Film Dosimetry↗
Oxorhenium(V) complexes with the non-sulfur-containing amino acid histidine.
Equivalent amounts of ReOX(3)(OPPh(3))(Me(2)S) (where X = Cl, Br) and L-histidine (L-hisH) in acetonitrile yield ReOX(2)(L-his), in which the amino acid monoanion is N,N,O-tridentate. X-ray diffraction work on both compounds shows that the three donors occupy a face in a distorted octahedron and the carboxylate oxygen is coordinated trans to the Re=O bond. The 2:1 complex [ReO(L-his)(2)]I is obtained by reacting 2 equiv of L-histidine with ReO(2)I(PPh(3))(2) in methanol in the presence of NaOCH(3). (1)H NMR spectroscopy indicates that these complexes contain one N,N,O-tridentate histidine anion coordinated as above and one N,N-bidentate histidine anion, whose carboxylate group is free. By refluxing ReOX(2)(L-his) in methanol, the carboxylic groups esterify and two octahedral units condense into an oxo-bridged dinuclear complex [ReOX(2)(L-hisMe)](2)O containing N,N-bidentate histidine methyl ester. The O=Re-O-Re=O backbone is approximately linear, and the two ReOX(2)(L-hisMe) units are related by a 2-fold axis through the central oxygen. Crystals of [ReOBr(2)(L-hisMe)](2)O consist of an ordered phase containing two of the possible diastereoisomers in a 1:1 ratio. (1)H NMR spectra of these crystals include two sets of signals, consistent with the presence of two isomers with C(2) symmetry, and the spectra of the nonrecrystallized material confirm that these are the only two isomers formed.
Journal Article↗
Synthesis and characterization of rhenium-copper sulfide cluster complexes [(Ph3P)2N][Re3(CuX)(mu3-S)4Cl6(PMe2Ph)3] (X = Cl, Br, I).
The reaction of a trinuclear rhenium sulfide cluster compound Re3S7Cl7 with dimethylphenylphosphine and CuX2 (X = Cl or Br) or CuX (X = Cl, Br, or I) formed tetranuclear cluster complexes [(Ph3P)2N][Re3(CuX)(mu3-S)4Cl6(PMe2Ph)3] (X = Cl, Br, or I). Their solutions have the characteristic intense blue color with visible spectral bands near 600 nm. Single-crystal X-ray structures show that three mu-S atoms in the intermediate trinuclear rhenium complex coordinate to a copper atom, forming elongated tetrahedral structures in which Re-Cu bonding interaction is negligible (Re-Cu distances are 3.50 to approximately 3.54 A as compared with Re-Re distances ranging from 2.69 to 2.81 A).
Journal Article↗
Superstructure in RE2-xFe4Si14-y (RE = Y, Gd-Lu) characterized by diffraction, electron microscopy, and Mössbauer spectroscopy.
Ternary rare-earth iron silicides RE(2-x)Fe4Si(14-y) (RE = Y, Gd-Lu; x approximately equal to 0.8; y approximately equal to 4.1) crystallize in the hexagonal system with a approximately equal to 3.9 A, c approximately equal to 15.3 A, Pearson symbol hP20-4.9. Their structures involve rare-earth silicide planes with approximate compositions of "RE1.2Si1.9" alternating with beta-FeSi2-derived slabs and are part of a growing class of rare-earth/transition-metal/main-group compounds based on rare-earth/main-group element planes interspersed with (distorted) fluorite-type transition-metal/main-group element layers. The rare-earth silicide planes in the crystallographic unit cells show partial occupancies of both the RE and Si sites because of interatomic distance constraints. Transmission electron microscopy reveals a 4a x 4b x c superstructure for these compounds, whereas further X-ray diffraction experiments suggest ordering within the ab planes but disordered stacking along the c direction. A 4a x 4b structural model for the rare-earth silicide plane is proposed, which provides good agreement with the electron microscopy results and creates two distinct Fe environments in a 15:1 ratio. Fe-57 Mössbauer spectra confirm these two different iron environments in the powder samples. Magnetic susceptibilities suggest weak (essentially no) magnetic coupling between rare-earth elements, and resistivity measurements indicate poor metallic behavior with a large residual resistivity at low temperatures, which is consistent with disorder. First-principles electronic-structure calculations on model structures identify a pseudogap in the densities of states for specific valence-electron counts that provides a basis for a useful electron-counting scheme for this class of rare-earth/transition-metal/main-group compounds.
Journal Article↗
Rhenium-based molecular rectangles as frameworks for ligand-centered mixed valency and optical electron transfer.
A series of six neutral, tetrametallic, molecular rectangles has been synthesized that have the form ([Re(CO)(3)](2)BiBzIm)(2)-mu,mu'-(LL)(2), where BiBzIm is 2,2'-bisbenzimidazolate and LL is a reducible, dipyridyl or diazine ligand. X-ray crystallographic studies of the six show that the rectangle frameworks, as defined by the metal atoms, range in size from 5.7 A x 7.2 A to 5.7 A x 19.8 A. The singly reduced rectangles are members of an unusual category of mixed-valence compounds in which the ligands themselves are the redox centers and interligand electronic communication is controlled by direct ligand orbital overlap rather than by superexchange through the metal ions. Despite nominally identical coordination-defined ligand positioning, the spectrally determined electronic strengths, H(ab)2, vary by roughly 100-fold. As shown by X-ray crystallography and computational modeling, the observed differences largely reflect detailed geometric configurational differences that can either facilitate or frustrate productive direct orbital overlap.
Journal Article↗
How useful is the skull x-ray examination in trauma?
Abnormalities were detected only in 24 (2.3%) of 1053 skull X-ray examinations performed in cases of suspected head trauma, at a cost of $1461 per positive finding. Only in six cases (0.6%) was treatment influenced by the radiological findings. Skull X-ray examination is indicated if a depressed fracture, compound fracture, or radio-opaque foreign body is suspected, and these patients are reliably selected by certain clinical criteria. The skull X-ray film is not a reliable guide to the presence or extent of intracranial injury, nor is it a substitute for careful clinical evaluation, observation and re-evaluation. The medicolegal implications of this restrictive policy are discussed.
Aged↗
[Differential after care for early detection of recurrence: from the surgical viewpoint].
Tumor recurrence following "curative" resection (= R0) of gastrointestinal cancer occurs in 30% (colorectal carcinoma) to 70% (ductal pancreatic cancer) of patients. Only colorectal cancer recurrence involves a substantial chance of a reintervention which again may result in complete cancer clearance (local recurrence 17%, metachronous liver metastases 20%, other abdominal intracavitary relapse 12%, pulmonary secondaries 17%). Five-year survival after complete re-resection approaches 40% irrespectively of the site of recurrent disease. Recognition of resectable recurrence in asymptomatic patients is based on ultrasound, endoscopy, and chest X-ray. Laboratory investigations alone, and even CEA-screening, do not suffice.
Adult↗