| 1. |
- Abrahamson, Magnus
(författare)
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Molecular basis for amyloidosis related to hereditary brain hemorrhage
- 1996
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Ingår i: Scandinavian journal of clinical and laboratory investigation. Supplementum. - 0085-591X. ; 56:226, s. 47-56
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the project has been to elucidate molecular events leading to amyloidosis in Hereditary Cystatin C Amyloid Angiopathy (HCCAA) patients, to enable simple diagnosis of the disease and with the ultimate goal to understand the amyloid formation process in detail, in order to develop inhibitors to the process. At the DNA level, a point mutation segregating with HCCAA was identified in the cystatin C gene on chromosome 20, after basic characterization of cDNA and gene for the wildtype protein. The mutation results in the amino acid substitution Leu-68-Gin (L68Q) and abolishes a recognition site for Alu I. This information was used to design a PCR based assay for simple and rapid mutation detection in DNA from blood samples to allow routine diagnosis of HCCAA. Studies at the protein level, allowed through E. coli expression of wildtype and L68Q mutated cystatin C genes, revealed that both protein variants effectively inhibit the cysteine proteinase cathepsin B (equilibrium constants for dissociation: 0.4 and 0.3 nM, respectively), but differ considerably in their tendency to dimerize and form aggregates. The initial dimerization of L68Q-cystatin C results in complete loss of biological activity and is highly temperature-dependent, with a rise in incubation temperature from 37 to 40 degrees C resulting in a 150% increase in dimerization rate. This result might be of clinical relevance, since medical intervention to abort febrile periods of carriers of the disease trait may reduce the in vivo formation of L68Q-cystatin C aggregates. The three-dimensional structure of normal cystatin C, crystallized in a complex with cathepsin B, was elucidated by X-ray analysis and subsequent refinement of the structure to 3.0 A resolution. Besides pinpointing the cystatin C structures resulting in efficient target enzyme inhibition, the results demonstrated that the Leu-68 residue is buried in the hydrophobic core of the protein. Studies of the three-dimensional solution structure of wildtype cystatin C by NMR spectroscopy revealed that cystatin C dimers can be formed as a result of slight, localized structural changes under conditions preceding complete defolding and denaturation of the protein. Dimers of L68Q-cystatin C are likely similar but are formed at temperatures nearly 30 degrees C lower than needed for the wildtype protein, indicating that the Leu-68-Gln substitution lowers the transition temperature for unfolding. Thus, the results presented suggest that cystatin C provides a system where decreased stability of a mutant protein correlates with its amyloidogenic nature. The NMR results furthermore imply that the hydrophobic proteinase-binding region of cystatin C is directly involved in dimer formation and that compounds designed to interact with this region could serve as inhibitors to the dimerization, and likely also the subsequent amyloid formation process, of cystatin C in HCCAA patients.
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| 2. |
- Ackelid, U, et al.
(författare)
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Kinetics of ethylene oxidation on plane Pt/SiO2 catalysts in the viscous pressure regime: Evidence of support activity
- 1996
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Ingår i: Catalysis Letters. - 1011-372X. ; 39:1-2, s. 129-139
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Tidskriftsartikel (refereegranskat)abstract
- C2H4 oxidation on plane Pt/SiO2 model catalysts with various Pt loadings was studied at T = 373-473 K and in the pressure ranges 10-6-102 Torr C2H4 and 0.3-1500 Torr O2 (1 Torr = 133.3 Pa). Mass spectrometry combined with spatially resolved gas sampling enabled kinetic data to be collected far into the viscous pressure regime. Reaction orders and activation energies were similar to those of a macroscopic Pt surface. However, under fuel-lean conditions the global reaction rate decreases faster than the decrease in metal area. On the other hand, the global rate was independent of Pt loading and metal surface area in fuel-rich gas mixtures. This is interpreted in terms of a spillover effect.
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| 3. |
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| 4. |
- Adlercreutz, Patrick
(författare)
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Cofactor regeneration in biocatalysis in organic media
- 1996
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 14:1, s. 1-30
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Forskningsöversikt (refereegranskat)abstract
- Methods used for the regeneration of cofactors in organic media are reviewed. Substrate-driven regeneration methods include the use of a second substrate of the same enzyme and the use of a second enzyme and its substrate. The use of mediators in oxidoreductions is described and examples of photochemical and electrochemical regeneration methods are presented. General problems and possibilities of cofactor regeneration in organic media are discussed.
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| 5. |
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| 6. |
- Adner, Mikael, et al.
(författare)
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Contractile endothelin-B (ETB) receptors in human small bronchi
- 1996
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Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 1399-3003 .- 0903-1936. ; 9:2, s. 351-355
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Tidskriftsartikel (refereegranskat)abstract
- Endothelins (ETs) are a family of novel regulatory peptides and various lines of evidence suggest an important role for ETs in regulating pulmonary function. Two receptors for endothelin, ETA and ETB, have been found in the human lung, and according to recent studies a non-ETA receptor seems to mediate the contraction of large sized human bronchi. Several studies have emphasized the importance of small bronchi in the pathogenesis of airway disease. In the present paper, improved methodology was used which enables in vitro studies of small human bronchi down to a diameter of 0.5-1.0 mm. Using the new methodology we have tried to further characterize this receptor. Small bronchi from the distal parts of the bronchial tree were obtained from pulmonary tissue removed from 15 patients with lung cancer. They were dissected and cut into ring segments, in which isometric tension was recorded. ET-1, ET-2 and ET-3 elicited strong concentration-dependent contractions of the human small bronchus. Basically, the three peptides were equipotent with about the same maximal response. Upon reapplication, they all showed the same tachyphylaxis pattern, reaching half the initial contraction. Comparative analysis of IRL 1620, a selective ETB receptor agonist, revealed that the effect of the ETB agonist was, in all respects, similar to the responses induced by the ETs. PD 145065, a combined ETA/ETB receptor antagonist competitively inhibited the contractions induced by IRL 1620, whereas FR139317, a selective ETA receptor antagonist, was without effect. In conclusion, the present study shows that accurate measurements can be made in vitro on small human bronchi and all present data are in favour of an ETB receptor mediating endothelin-induced contraction of human bronchi smaller than 1.0 mm.
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| 7. |
- af Klinteberg, C, et al.
(författare)
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Laser-induced fluorescence diagnostics of basal cell carcinomas of the skin following topical ALA application
- 1996
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Ingår i: Optical Biopsies and Microscopic Techniques, Proceedings of. - : SPIE. - 0819423289 ; 2926, s. 32-40
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Konferensbidrag (refereegranskat)abstract
- Fourteen patients with superficial basal cell carcinomas (BCCs) and fifteen patients with nodular BCCs were investigated by means of laser-induced fluorescence (LIF) in connection with photodynamic therapy (PDT). Topical application of delta-amino levulinic acid (ALA) was performed six hours prior to the treatment session. Fluorescence spectra were recorded, using a point-monitoring system with an excitation wavelength of 405 nm. The measurements were performed in scans over the lesion and the surrounding normal skin before application of ALA, and immediately before and after the laser treatment. The selective uptake of the photosensitiser resulted in a fluorescence intensity ratio of 2.4:1 for superficial BCCs and 2.5:1 for nodular BCCs. If the fluorescence intensity was divided by the autofluorescence, this resulted in a contrast enhancement of about a factor 6 for tumour tissue. In seven patients (five with nodular BCC and two with superficial BCC), additional fluorescence measurements were performed two and four hours following the ALA application, and two hours after the PDT procedure. Thus, the kinetics of the transformation of ACA to protoporphyrin IX (PpIX) could be followed, which indicated that the synthesis of PpIX was more rapid in the tumour than in the normal tissue. After four hours, the PpIX level inside the tumour was saturated, while there still was an accumulation in the surrounding skin. The highest contrast between tumour and normal skin was reached within two hours after the ALA application.
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| 8. |
- Afanasjev, A. V., et al.
(författare)
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The coexistence of the intruder vi13/2, superdeformed and terminating bands in the A ∼ 135 mass region
- 1996
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 608:2, s. 176-201
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Tidskriftsartikel (refereegranskat)abstract
- The configuration-dependent shell-correction approach with the cranked Nilsson potential is employed for a systematic investigation of the high-spin spectra of the nuclei in the A ∼ 135 (Z = 57-61, N = 72-78) mass region, where superdeformed bands have been observed. Main attention is paid to the coexistence of intruder νi13/2, superdeformed and terminating bands in the yrast region. Recent developments of the formalism allow the identification of the high-j orbitals in each N-shell, for example, the g9/2 orbitals in the N = 4 shell, after the diagonalization of the cranked Nilsson potential. This turns out to be quite important for the understanding of the high collectivity of the observed bands. It is shown that the equilibrium deformation of the superdeformed bands is strongly dependent on the number of the proton holes in the g9/2 orbitals. With increasing neutron number above N = 75, the intruder νi13/2 bands are calculated triaxial. Especially for Z = 57, but also for higher proton numbers, we calculate some coexistent oblate non-collective states which are yrast for specific spin values at I ≥ 40h.
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| 9. |
- Agace, William
(författare)
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The role of the epithelial cell in Escherichia coli induced neutrophil migration into the urinary tract.
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study examined the molecular mechanisms of neutrophil migration to sites of mucosal bacterial infection. (1) Bacterial induction of neutrophil chemotactic cytokines and their role in neutrophil migration. Uropathogenic E.coli were shown to stimulate urinary tract epithelial cells to produce a specific array of cytokines including the neutrophil chemoattractant IL-8. IL-8 production was dependent on the adherence properties of the infecting strain. Deliberate colonisation of the human urinary tract with E.coli induced the local production of IL-8 and levels correlated with urinary neutrophil numbers. The E.coli induced IL-8 supported neutrophil migration across urinary tract epithelial layers in vitro and anti-IL-8 antibody blocked this response. The chemotactically active IL-8 was localised to the epithelial surface and these cells contained IL-8 receptor A and B mRNA. (2) The role of epithelial adhesion molecules in E.coli induced transuroepithelial migration. Uroepithelial cells constitutively expressed ICAM-1 and E.coli augmented ICAM-1 expression. Transuroepithelial neutrophil migration was dependent on epithelial ICAM-1 and neutrophil Mac-1 (CD11b/CD18) expression. Thus urinary tract epithelial cells provide two prerequisites for neutrophil migration to the mucosal lumen; neutrophil chemoattractants and cell adhesion molecules. (3) The role of bacterial fimbriae for the induction of inflammation in the urinary tract. Patients and mice infected with a type 1 positive P fimbriated uropathogenic E.coli clone O1:K1:H7 showed significantly higher inflammatory responses than type 1 negative O1:K1:H7 isolates. Insertion of an npt gene into fimH (encoding the type 1 fimbrial adhesin) of a type 1 positive O1:K1:H7 isolate resulted in the loss of the type 1 fimbrial phenotype and a reduction in virulence.
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| 10. |
- Agace, W. W.
(författare)
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The role of the epithelial cell in Escherichia coil induced neutrophil migration into the urinary tract
- 1996
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Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 9:8, s. 1713-1728
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophil influx to mucosal surfaces represents one of the earliest inflammatory responses to mucosal infection. We have been studying external interactions with urinary tract epithelial cells in an attempt to understand the molecular mechanisms behind this process. Uropathogenic Escherichia coli induced urinary tract epithelial cells to secrete the neutrophil chemoattractant interleukin-8 (IL-8). IL-8 secretion was higher in response to isogenic strains expressing type 1 or P fimbriae that adhered to the epithelial surface. Deliberate colonization of the human urinary tract with E. coli induced the local production of IL-8 and levels correlated with urinary neutrophil numbers suggesting a role for IL-8 in neutrophil migration. E. coli induced neutrophil migration across urinary tract epithelial layers in vitro, and this process was blocked with anti-IL-8 antibody. IL-8's activity was localized to the epithelial surface. Furthermore, these cells were shown to constitutively express IL-8 receptor A and B messenger ribonucleic acid (mRNA), suggesting a possible role for IL-8 on epithelial cell function. E. coli enhanced the expression of intercellular adhesion molecule-1 (ICAM-1) on urinary tract epithelial cells, and neutrophil migration across urinary tract epithelial layers in vitro was dependent on epithelial ICAM-1 and neutrophil Mac-1 (CD11b/CD18) expression. These results suggest that bacterial/epithelial cell interactions play a key role in the induction of neutrophil migration during mucosal infection, and show the necessity for host-derived chemotactic factors and cell adhesion events in E. coli induced transuroepithelial migration in vitro.
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