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Objective: The purpose of the study is to examine the anatomical relationship between the vertebral artery (VA), the cervical pedicle, and their surrounding structures including the incidence of irregularities. The second objective is to provide data delineating a “safety zone” and its[for full text, please go to the a.m. URL], 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien

Parathyroidhormone (PTH) measurement is important in the evaluation of bone disease in patients with chronic renal failure. Large carboxyl-terminal PTH fragments (C-PTH) cross-react with second-generation PTH assays, lead to an overestimation of biologically active PTH, and are evaluated by a combination of second- and third-generation PTH assays. The aim of our study was to examine whether the use of 4 different PTH assays of putatively same specificity leads to comparable results detecting C-PTH fragments.In 70 chronic dialysis patients, total PTH and PTH(1-84) were measured in parallel by 4 novel PTH assays (Nichols Advantage Intact PTH and Bio-Intact PTH Chemiluminescence Assay, Nichols Institute Diagnostics, USA, DUO Total and CAP PTH IRMA, Scantibodies Laboratory, USA). The C-PTH concentration was quantitated by subtracting PTH(1-84) from total PTH. Consecutively, the PTH(1-84)/C-PTH ratio was calculated.Nichols Intact PTH and DUO Total PTH assays were highly correlated (r = 0.985), as well as Nichols Bio-Intact and DUO CAP assays (r = 0.984). However, total PTH values measured by the Nichols assay were 30% higher (median (range): 185 (9.9 - 2,332) versus 130 (2.3 - 1,271.1) pg/ml, p0.01). PTH(1-84) values, measured by the Nichols Bio-Intact PTH assay were 8% higher compared to the Scantibodies CAP assay (median (range): 79.6 (7.5 - 1,060.9) versus 73.7 (4.4 - 918.9) pg/ml, p = NS). Thirty-six patients had a ratio1 measured by the Nichols assays, whereas only 8 patients showed the same ratio when measured by the Scantibodies assays. In 28 patients (40%), contradictory PTH(1-84)/C-PTH ratios were found, showing a ratio1 when measured by the Nichols assays, but1 when the Scantibodies assays were used.In conclusion, our results suggest that the PTH(1-84)/C-PTH ratio cannot be equally used as a predictor of bone turnover when different PTH assays are used. Depending on those assays, differences in total PTH values mathematically lead to varying amounts of C-PTH fragments resulting in variable, even contradictory PTH(1-84)/C-PTH ratios.

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The potential of C-13-NMR spectroscopy of stationary samples for the study of mechanisms of anisotropic molecular motion of Mo(CO)(6) adsorbed in zeolites has been examined. Free diffusional rotation or jump processes about the various symmetry axes of the octahedral complex cause motional averaging of C-13 chemical shift anisotropy, allowing for the characterization of the different motional mechanisms. At 110 K a large portion of the Mo(CO)(6) molecules is firmly fixed in zeolites NaY and HY as indicated by a broad (ca. 410 ppm) chemical shift powder pattern. A narrow C-13-NMR component is observed in both zeolites for molecules undergoing isotropic motion or rotation about a three-fold axis. An additional line, which is inverted in shape and reduced in width by a factor of -1/2 compared to the rigid case, is only observed for NaY. This line is assigned to molecules undergoing free rotation about the four-fold axis, but it may also be due to Mo(CO)(6) jumping about a two-fold axis. The changes in the distribution of molecules in different motional states was explored between 1 10 K and ambient temperature. Molecules undergoing rotations or jumps about the four-or two-fold axes only exist in NaY at lower temperatures when stationary Mo(CO)(6) molecules are also present. At 180 K and higher temperatures, rotation about the three-fold axis or isotropic motion are the sole types of molecular motion. (C) 1997 Elsevier Science B.V

The electric field gradient (EFG) has been calculated in zeolite clusters at the aluminium site surrounded by four SiO4 tetrahedra. Density functional theory (DFT) with the 6-31G * * basis set has been employed. Formation of a Bronsted acid site by protonation of one oxygen atom of the AlO4 tetrahedron perturbs the coordination of aluminium, i.e., the corresponding Al-O bond is considerably weaker than in the unprotonated case. This leads to a large EFG, and the calculated quadrupole coupling constant (QCC) for Al-27 is 18.2 MHz. Different probe molecules were adsorbed on the Bronsted site. The hydrogen bond formed between the acid proton and the probe molecule weakens the zeolitic O-H bond. For conservation of the overall bond order of the oxygen atom, its bonds to the neighboring tetrahedral atoms (Si, Al) become stronger. As a consequence, the perturbation of the AlO4 tetrahedron and the EFG at the aluminium position decrease depending on the strength of the hydrogen bond. Perturbation of an oxygen atom of the AlO4 tetrahedron by accepting a hydrogen bond from the base molecule also affects the corresponding Al-O bond order. A linear correlation is found between the calculated QCC constants for Al-27 and the Al-O bond orders of the oxygen atoms which are perturbed by protonation or by hydrogen bonds. A geometrical shear strain parameter and a simple electrostatic point charge model are less successful at predicting the trends in EFG which clearly shows the importance of the chemical bonds. Published by Elsevier Science B.V