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- El-Salhy, M, et al.
(författare)
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Neuroendocrine peptide levels in the gastrointestinal tract of mice after unilateral cervical vagotomy
- 2000
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Ingår i: Regulatory Peptides. - 0167-0115 .- 1873-1686. ; 88:1-3, s. 15-20
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Tidskriftsartikel (refereegranskat)abstract
- The effects of left and right unilateral cervical vagotomy on the content of several neuroendocrine peptides were studied in different parts of the murine gastrointestinal tract, known to receive vagal innervation. The neuroendocrine peptides investigated were secretin, gastric inhibitory peptide (GIP), gastrin, motilin, peptide YY (PYY), somatostatin, substance P, VIP, neurotensin, neuropeptide Y (NPY), and galanin. The neuroendocrine peptide concentration was affected after both left and right vagotomy, and that the changes in the concentrations of the neuroendocrine peptide levels occurred in all the gastrointestinal segments investigated, namely antrum, small and large intestine. However, these changes varied, depending on which side was vagotomized and the interval after vagotomy. It is concluded that the vagus nerve had an important impact on the neuroendocrine system in the murine gut. It is suggested, furthermore that the contradictory results obtained earlier on the effect of vagotomy on the gastrointestinal peptides may depend on differences in the vagotomy methods used and on differences in observation time after vagotomy.
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- Käämbre, T, et al.
(författare)
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Study of oxygen-C compound formation by NEXAFS and RIXS
- 2001
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Ingår i: The European Physical Journal D. ; 16:1-3, s. 357-360
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of oxygen with C60 molecules was studied on a C60 film which had been exposed simultaneously to oxygen and UV-light for 190 hours, producing an approximately C60O1 stoichiometry in the bulk of the sample. C K-edge and O K-edge NEXAFS (using total fluorescence yield detection) and resonant X-ray inelastic scattering (RIXS) spectra from the sample film were measured and the C K-edge data were compared to the spectra from pristine C60 as reference. The C K-edge absorption and emission spectral profiles of the oxygen-doped sample are similar to those of the C60 reference, suggesting that cage breaking of C60 under these conditions, if any, is negligible. However, the redistribution of intensities in the spectra indicates changes in the occupancies of different molecular orbitals, possibly due to changes in electron density upon reaction. Similarities of the O K-edge soft X-ray emission (SXES) spectra to several small oxygen-containing molecules is being discussed in terms of bonding models.
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- Nyberg, M., et al.
(författare)
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Bond formation in titanium fulleride compounds studied through x-ray emission spectroscopy
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:11, s. art. no.-115117
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Tidskriftsartikel (refereegranskat)abstract
- The geometric and electronic structures of titanium fulleride complexes have been studied at the gradient corrected density-functional theory level by using various C60Tix (x=1,2) clusters. The cluster with the Ti atom binding on the six-ring site (eta (6)) Of the fullerene is shown to be lower in energy than those with Ti atom adsorbed on either five-ring (eta (5)) Or bridge(eta (2)) sites. The bond formation for titanium fulleride has further been examined by calculated nonresonant, resonant, and off-resonant . x-ray emission spectra of the clusters, and a comparison to the experimental counterpart. The examination shows that only the theoretical spectra of clusters with a six-ring adsorption site are in close agreement with the experimental x-ray emission spectra of titanium fulleride films. Our results indicate that off-resonant x-ray emission spectra provide an excellent basis for the probing of the bonding between metals and organic molecules.
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- Telang, S, et al.
(författare)
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Strain-specific iron-dependent virulence in Escherichia coli
- 2001
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Ingår i: Journal of Infectious Diseases. - 0022-1899 .- 1537-6613. ; 184:2, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- For reasons unknown, certain Escherichia coli strains become highly virulent when injected with hemoglobin or other soluble iron sources. Two clinical isolates (virulent and nonvirulent) showed equivalent hemoglobin-mediated growth acceleration in vitro. However, when injected intraperitoneally into mice without hemoglobin, the virulent strain was cleared more slowly (t(1/2), >4 h vs. <30 min). The virulent E. coli strain had a polysialic acid-containing capsule, whereas the nonvirulent strain did not. Virulent E. coli grown at 20C (which blocks polysialylation) were cleared as rapidly as nonvirulent organisms. In another virulent E. coli strain having abundant outer membrane polysialic acid, targeted deletion of the polysialyltransferase accelerated host clearance and blocked iron-dependent virulence. The iron-dependent virulence of certain E. coli strains may represent the combined effect of slow in vivo clearance-associated, in this case, with outer membrane polysialylation coupled with accelerated growth permitted by iron compounds.
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