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PubMed2001

Technetium-99m HMPAO-labeled leukocyte imaging compared with endoscopy, ultrasonography, and contrast radiology in children with inflammatory bowel disease.

BACKGROUND: The purpose of this study was to evaluate retrospectively the value of leukocyte-labeled scintigraphy, ultrasonography, and contrast radiography compared with endoscopy in children suspected of having inflammatory bowel disease (IBD). METHODS: Twenty-eight children (17 boys; mean age, 10.2 years) with IBD based on standard colonoscopic, histologic, and radiologic criteria (16 with Crohn's disease, 5 with ulcerative colitis, 5 with nonspecific colitis, I with granulomatous disease, and I with Beh,cet's disease) were included. Endoscopic, ultrasonographic, and contrast radiologic examinations were realized for 28, 23, and 19 children respectively. RESULTS: Sensitivity and specificity were 75% and 92% for leukocyte-labeled scintigraphy, 39% and 90% for ultrasonography, and 58% and 83% for contrast radiography. The authors noted discontinuous uptake for 14 of 15 true-positive results for patients with Crohn's disease and continuous uptake for 4 of 4 true-positive results for patients with ulcerative colitis. A negative correlation between scan activity index and Lloyd-Still clinical score was found for 11 patients with Crohn's disease (r = -0.77). CONCLUSIONS: Leukocyte-labeled scintigraphy, a noninvasive and reproducible technique, is a useful tool in the diagnosis and therapeutic strategy of IBD, and provides information on the presence, the intensity, and the extent of the disease, particularly in the terminal ileum. Leukocyte-labeled scintigraphy may not replace colonoscopy with biopsies for diagnosis confirmation. Its reliability seems higher than that of ultrasonography.

Adolescent↗
PubMed1988

Effects of procainamide on automatic and triggered impulse initiation in isolated preparations of canine cardiac Purkinje fibers.

The effects of procainamide (40 mg/L) were studied on automatic and triggered impulse initiation in isolated preparations of canine cardiac Purkinje fibers using standard microelectrode techniques. Procainamide decreased normal automaticity by 48% in Purkinje fibers superfused with standard (KCl 4 mM) Tyrode's solution. In contrast, procainamide decreased the rate of normal Purkinje fibers that had been treated with isoproterenol (1 microM) by only 6% (NS). For comparison, the effects of lidocaine (4 mg/L) and quinidine (5 mg/L) were studied on isoproterenol-treated fibers. Lidocaine and quinidine both significantly decreased the isoproterenol-enhanced rate of normal automaticity (by 45 and 10%, respectively). In studies of the effects of procainamide on Purkinje fibers with abnormal automaticity (i.e., the pacemakers had maximal diastolic potentials less than -60 mV), it was found that drug treatment decreased the rate of 24 h infarct zone Purkinje fibers by 22% and barium chloride (250 microM) treated Purkinje fibers by 51%. In studies of another five infarct zone preparations, the Purkinje fibers had maximal diastolic potentials greater than -75 mV and showed triggered activity with delayed afterdepolarizations. Procainamide decreased the triggered activity in only one of these preparations. Ventricular tachycardias that respond to procainamide may be caused by abnormal automaticity, whereas procainamide refractory tachycardias may result from triggered activity or from catecholamine-enhanced normal automaticity.

Action Potentials↗
PubMed1996

Barium-induced diastolic depolarization and controlling mechanisms in guinea pig ventricular muscle.

Barium-induced diastolic depolarization (Ba(2+)-DD) and its modulation were studied in guinea pig papillary muscle and single ventricular myocytes. In papillary muscles, Cs+ (4 mM) abolished the DD induced by Ba2+ (0.05-0.2 mM) by abolishing the undershoot at the end of the action potential (AP; consistent with a block of an outward current). Acetylcholine (ACh 1 microM) had little effect on Ba(2+)-DD, whereas norepinephrine (NE 1 microM) enhanced it by increasing the undershoot and by inducing an oscillatory potential. Low [Ca2+]o (0.54 mM) decreased the resting potential and increased Ba(2+)-DD amplitude. High [Ca2+]o (8.1 mM) had opposite effects. Cs+ also reduced Ba(2+)-DD in low [Ca2+]o. In isolated myocytes, Ba(2+)-DD and the pacemaker current induced by Ba2+ (Ba(2+)-IKdd) increased on depolarization and reversed on hyperpolarization. Although not significantly, high [Ca2+]o slightly decreased and low [Ca2+]o slightly increased Ba(2+)-IKdd. Cd2+ markedly reduced the slow inward current ICa and the AP duration (APD), but did not affect Ba(2+)-IKdd. We conclude that Ba(2+)-DD (a) is entirely due to a voltage- and time-dependent decrease in gK1, since it is abolished by Cs+ (no contribution of a nonblocked decaying IK) by eliminating the undershoot (no If), (b) is potentiated by NE through an increased undershoot and an oscillatory potential, (c) is modified by high and low [Ca2+]o mostly through changes in the resting potential, and (d) is not affected by the block of the slow channel by Cd2+.

Acetylcholine↗
PubMed2002

Terikalant and barium decrease the area of vulnerability to ventricular fibrillation induction by T-wave shocks.

The area of vulnerability (AOV) to ventricular fibrillation (VF) induction by high-voltage shocks has been proposed as a measure of vulnerability to VF. Biphasic shocks spanning the T wave and ranging between 50 V and the upper limit of vulnerability (ULV) to VF were delivered before and after terikalant (1 mg/kg) and barium (1.1 mg/kg load followed by 0.05-0.10 mg/kg/min maintenance) or vehicle in dogs. The AOV decreased by 34% and 28% (p < 0.01) after terikalant and barium (n = 8 dogs each), respectively. Mean ULV, defibrillation threshold (DFT), and ventricular vulnerability period (VVP) decreased by 16%, 23%, and 31% (p < 0.01), respectively, after terikalant, and by 25%, 17% (p < 0.01), and 13% (p = 0.08), respectively, after barium. Vehicle (n = 14) did not significantly alter any of these variables. The ULV was correlated with the DFT before and after terikalant (r = 0.78, p < 0.01) and barium (r = 0.83, p < 0.01). Potassium channel blockers of the current reduce the ability to induce VF; this effect may be related to the anti-fibrillatory action of class III anti-arrhythmic drugs and their ability to decrease DFT.

Action Potentials↗
PubMed1997

Achalasia presenting as acute stridor.

We report a case of achalasia presenting as acute stridor and respiratory distress in an 87-year-old woman. A mega-oesophagus was decompressed by aspiration through a naso-oesophageal tube, stiffened with paediatric endoscopic biopsy forceps before placement. Subsequent barium swallow showed mega-oesophagus secondary to achalasia causing tracheal compression at the level of the thoracic inlet. There have been 28 previous case reports of mega-oesophagus due to achalasia causing tracheal obstruction and the literature is reviewed. Recognition and urgent treatment of this very rare complication of achalasia by naso-oesophageal decompression may avoid fatality.

Aged↗
PubMed2000

Dissecting intramural haematoma of the oesophagus.

Dissecting intramural haematoma of the oesophagus is an under-recognized cause of sudden onset chest pain. Diagnosis is aided by the common co-existence of haematemesis, odynophagia, and dysphagia. Oesophagoscopy, barium swallow and cross-sectional radiology are all appropriate modalities of investigation. The latter is useful in excluding aortic dissection from the differential diagnosis. The condition usually follows a benign course with spontaneous healing requiring supportive treatment only. A systematic analysis of all the cases of dissecting intramural haematoma of the oesophagus (DIHO) reported in the worldwide literature reveals that this is essentially a benign condition. Eighty per cent of patients have at least two of the three typical presenting features of chest pain, haematemesis and dysphagia or odynophagia. Forty-nine per cent of cases are associated with sudden pressure changes within the oesophagus (e.g. due to swallowing) or secondary to direct trauma to the oesophagus. A further group appears to arise spontaneously and may be associated with underlying abnormal pressure changes within the oesophagus or a bleeding tendency. Awareness of the condition prevents the pain being mistakenly attributed to a cardiac cause. With conservative management the symptoms usually resolve within 2 weeks of presentation. The only mortality associated with DIHO is due to operative intervention or where there is another underlying life-threatening condition.

Age Distribution↗
PubMed2005

Geometric factors affecting dentin bonding in root canals: a theoretical modeling approach.

Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded surface area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses to debond the material from dentin, thereby decreasing retention and increasing leakage. The important variables influencing bonding adhesive root-filling materials to canals was examined using a truncated inverted cone model. C-factors in bonded root canals exhibit a negative correlation with sealer thickness. For a 20 mm-long canal prepared with a size 25 file, calculated C-factors ranged from 46 to 23,461 with decreasing sealer thickness (500-1 microm), compared to a C-factor of 32 when the canal was filled only with sealer. As the thickness of the adhesive is reduced, the volummetric shrinkage is reduced, which results in a reduction in shrinkage stress (S-factor). C-factors above 954 calculated with sealer thickness smaller than 25 microm are partially compensated by increases in bonding area and decreases in shrinkage volume. However, the interaction of these two geometrically related factors (C- and S-factors) predicts that bonding of adhesive root-filling materials to root canals is highly unfavorable when compared with indirect intracoronal restorations with a similar resin film thickness.

Barium Compounds↗
PubMed2005

Cleavage of von Willebrand factor by ADAMTS-13 in vitro: effect of temperature and barium ions on the proteolysis kinetics.

The multimeric size of von Willebrand factor (VWF) is regulated by the specific cleaving metalloprotease, ADAMTS-13. Laboratory assays for ADAMTS-13 are useful for identifying severe protease-deficient activity. ADAMTS-13 activity is currently assayed by prolonged dialysis of plasma at 37 degrees C in low-ionic-strength denaturing buffer. We investigated the effect of temperature and divalent cation supplementation on the kinetics of VWF proteolysis by ADAMTS-13 in vitro. Proteolysis was monitored for 24 h at 37, 22, and 4 degrees C, in the presence or absence of barium ions, by measuring the binding of VWF to collagen. Complete VWF proteolysis was observed at 37 degrees C in the presence of BaCl2, while about 25% VWF still bound to collagen when BaCl2 supplementation was omitted. Proteolysis kinetics at 22 and 4 degrees C was slower but complete, even in the absence of added barium. A subphysiological temperature might influence the proteolysis kinetics by determining minor variations of the ADAMTS-13 structure, or further modification of the VWF substrate. We describe a simple procedure to analyse the kinetics of VWF proteolysis that is suitable for routine diagnostic use. Furthermore, we offer new insight into the biochemistry of ADAMTS-13.

ADAM Proteins↗
PubMed2005

Long-term normoglycemia in rats receiving transplants with encapsulated islets.

BACKGROUND: To follow up on previously successful transplantation of encapsulated islets in mice, the present study was performed in rats to determine the effects of several factors, including alginate composition and concentration of cross-linking agent and capsule size on the effectiveness of encapsulated islets. METHODS: Highly purified alginate of either high guluronic acid or high mannuronic acid (M) with low endotoxin content was used. Regular-size (0.8-1.1 mm) or small microcapsules (0.5-0.7 mm) were produced by cross-linking with BaCl2 without additional poly-L-lysine coating and were transplanted into abdominal cavity of normoglycemic (empty capsules) or streptozotocin induced diabetic Lewis rats (islet containing capsules). RESULTS: Empty regular-size capsules made of different alginate compositions had similar biocompatibility and stability results. Compared with empty capsules, regular-size capsules made of high-M alginate containing syngeneic islets had inferior stability indicated with lower fractional volume retrieved. Islet-containing smaller-size microcapsules made of high-M alginate were more stable and had less cellular attachment compared with the regular-size capsules, although the normoglycemic period was comparable between two groups of rats receiving transplants with smaller-size microcapsules (48+/-8 days, n=8) or regular-size capsules (59+/-11 days, n=4) in allogeneic experiments. In syngeneic experiments, all of the rats (n=4) maintained normoglycemia up to 210 days after transplantation. CONCLUSION: These results indicate that regular-size alginate capsules do less well in rats than in our previous experiments with mice. Smaller capsules made of alginate cross-linked with barium appear to provide better stability and may be a useful strategy for use in larger recipients.

Animals↗
PubMed1991

Calcium-permeable ion channels in cerebellar neurons from mdx mice.

Recordings of single-channel activity were made from cell-attached patches on cerebellar granule cells from normal and mdx mice. Recordings from mdx granule cells show the activity of ion channels that are open for seconds at negative holding potentials near rest. These channels are permeable to divalent cations and have a conductance of 8-10 pS with either Ca2+ or Ba2+ as the charge carrier in the patch electrode. Under similar recording conditions, channel activity is virtually absent from normal mouse granule cells. The absence of dystrophin in neurons, as well as in skeletal muscle, is associated with an increase in the activity of Ca(2+)- permeable ion channels. Increased channel activity may be an early event leading to pathophysiological accumulation of intracellular Ca2+ in Duchenne muscular dystrophy.

Animals↗
PubMed2002

Evidence of registry at the interface during inorganic nucleation at an organic template.

In situ synchrotron x-ray diffraction studies of the nucleation of barium fluoride from supersaturated solutions, at fatty-acid monolayer templates, reveal a commensurate relationship between the interfacial lattices of the organic molecules and the inorganic atoms. At the onset of growth, the barium fluoride layer is very thin and the lateral unit cell is contracted by as much as 4%; at the same time the organic molecules tilt, expanding the organic unit cell. This flexibility is what allows the lattice parameters to be commensurate. Such registry is expected to play an important precursor role in controlled biomineralization and organic-matrix-mediated materials synthesis.

Barium Compounds↗
PubMed2001

Tetragonal SmBa2Cu3O7-x [x = 0.74(4)].

Crystals of the title compound, samarium barium copper oxide, were prepared by a modified top-seeded solution-growth method. The crystals thus prepared showed no superconductivity down to 4.2 K. A careful examination showed that the structure closely resembles that of tetragonal YBCO, and there is no atom mixing at the Ba or other sites, within experimental accuracy. A bond-valence-sum calculation at the Ba site also indicated the absence of Sm. Each site is fully occupied by a single atom, except for the oxygen site in the basal plane of the CuO(6) octahedron. The occupancy of this oxygen site is significantly reduced [0.13 (2)], as is commonly observed in the 123 system. The atomic displacement parameters of the atoms in the CuO(2) plane, as well as of the Sm atom, are very small, indicating that two equivalent CuO(2) planes tightly sandwich the Sm atom.

Journal Article↗
PubMed1988

Structure of barium perchlorate trihydrate.

Ba(ClO4)2.3H2O, Mr = 390.28, hexagonal, P63/m, a = 7.277 (2), c = 9.656 (1) A, V = 442.9 (1) A3, Z = 2, F(000) = 368, D chi = 2.93 g cm3, lambda(Mo K alpha) = 0.71069 A, T = 295 K, mu = 52.60 cm1, 456 unique reflections, R = 0.023. The barium atoms in this structure are coordinated by six water oxygens, O(3), at 2.919 (1) A and by six perchlorate oxygens, O(2), at 3.026 (2) A in a slightly distorted icosahedral arrangement, the average Ba-O separation thus being approximately 2.97 A. The perchlorate ion just fails to have regular tetrahedral geometry within the experimental error, and has an average Cl-O bond length of 1.433 (6) A. Consistent with hydrogen bonding delineated on the basis of least-squares-refined hydrogen-atom positions, each axial [O(1)] perchlorate oxygen is hydrogen bonded to three water molecules and each trigonal [O(2)] perchlorate oxygen is hydrogen bonded to two water molecules; thus each perchlorate ion is hydrogen bonded to nine water molecules. Conversely, each water molecule [O(3)] oxygen is hydrogen bonded to six perchlorate ions to two through axial [O(1)] oxygens and to four through trigonal [O(2)] oxygens.

Barium↗
PubMed1992

Polarized dispersion, glide-rule-forbidden reflections and phase determination in barium bromate monohydrate.

Reflections forbidden by a glide-plane rule are observed in diffraction experiments with a crystal of barium bromate monohydrate using linearly polarized synchrotron radiation with wavelength near the bromine K-absorption edge. Their intensities change with azimuth in agreement with equations derived using a tensor model of the anomalous scattering of the bromate ion and are consistent in scale with earlier measurements of that tensor in sodium bromate. The intensity of each forbidden h0l reflection gives the magnitude and phase of the bromine part of the structure factor of the allowed 2h,0,2l reflection. The x and z coordinates of the Br atom determined from such data for 11 reflections are within 0.02 A of those from two crystal structure determinations.

Barium↗
PubMed2002

Second-order theories for extensional vibrations of piezoelectric crystal plates and strips.

An infinite system of two-dimensional (2-D) equations for piezoelectric plates with general symmetry and faces in contact with vacuum is derived from the 3-D equations of linear piezoelectricity in a manner similar to that of previous work, in which an infinite system of 2-D equations for plates with electroded faces was derived. By using a new truncation procedure, second-order equations for piezoelectric plates with faces in contact with either vacuums or electrodes are extracted from the aforementioned infinite systems of equations, respectively. The second-order equations for plates with or without electrodes are shown to predict accurate dispersion curves by comparing to the corresponding curves from the 3-D equations in a range up to the cut-off frequencies of the first symmetric thickness-stretch and the second symmetric thickness-shear modes without introducing any correction factors. Furthermore, a system of 1-D second-order equations for strips with rectangular cross section is deduced from the 2-D second-order equations by averaging variables across the narrow width of the plate. The present 1-D equations are used to study the extensional vibrations of barium titanate strips of finite length and narrow rectangular cross section. Predicted frequency spectra are compared with previously calculated results and experimental data.

Barium Compounds↗
PubMed2002

Extensional, thickness-stretch and symmetric thickness-shear vibrations of piezoceramic disks.

A set of two-dimensional (2-D), second-order approximate equations for extensional, thickness-stretch and symmetric thickness-shear vibrations of piezoelectric ceramic plates with electroded faces is extracted from the infinite system of 2-D equations deduced previously. The new truncation procedure developed recently is used for it improves the accuracy of calculated dispersion curves. Closed-form solutions are obtained for free vibrations of circular disks of barium titanate. Dispersion curves calculated from the present approximate 2-D equations are compared with those obtained from the 3-D equations, and the predicted resonance frequencies are compared with experimental data. Both comparisons show good agreement without any corrections. The frequencies of the edge modes calculated from the present 2-D equations are very close to the experimental data. Furthermore, mode shapes at various frequencies are calculated in order to identify the frequency segments of the spectrum at which one of the coupled modes--i.e., the radial extension (R), edge mode (Eg), thickness-stretch (TSt), and symmetric thickness-shear (s.TSh)--is predominant.

Barium Compounds↗
PubMed2006

Evolution of nanodomains in the uniaxial relaxor Sr0.61Ba0.39Nb2O6:Ce.

The evolution of the nanodomain pattern of the uniaxial relaxor ferroelectric strontium barium niobate doped with cerium was studied by piezoresponse force microscopy (PFM). The fractal-like nanodomains observed at room temperature decay on heating. At temperatures up to about 15 K above the Curie temperature, Tc = 320 K, areas of correlated polarization are still visible. On cooling from the paraelectric state to below Tc, a slow isothermal growth of nanodomain was found. The mean domain size increases according to a logarithmic law as predicted for the three-dimensional random field Ising model.

Barium Compounds↗
PubMed2006

Dielectric spectroscopy of nano BaTiO3 confined in MCM-41 mesoporous molecular sieve materials.

Dielectric properties of barium titanate (BaTiO3) particles, synthesized directly in the pores of MCM-41 materials, have been investigated in the frequency range from 20 Hz to 1 MHz for temperature intervals from 100 K to 500 K. The dielectric spectra of BaTiO3 confined in these molecular sieves were compared with the results obtained from the investigation of pure MCM-41 materials. Obtained results confirmed successful incorporation of BaTiO3 into porous matrix, but no phase transition from paraelectric to ferroelectric phase was observed due to the particle size being smaller than the critical size. Also, the overall dielectric response of investigated materials is strongly influenced by adsorbed water molecules.

Barium Compounds↗