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- Ericsson, Peter, et al.
(författare)
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ECL Cell Histamine Mobilization Studied byGastric Submucosal Microdialysis in Awake Rats:Methodological Considerations.
- 2003
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Ingår i: Pharmacology and Toxicology. - : Wiley. - 1600-0773 .- 0901-9928. ; 93:2, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- The ECL cells are endocrine/paracrine cells in the acid-producing part of the stomach. They secrete histamine in response to circulating gastrin. Gastric submucosal microdialysis has been used to study ECL-cell histamine mobilization in awake rats. In the present study we assess the usefulness and limitations of the technique. Microdialysis probes were implanted in the gastric submucosa. Histological analysis of the stomach wall around the probe revealed a moderate, local inflammatory reaction 1-2 days after implantation; the inflammation persisted for at least 10 days. Experiments were conducted 3 days after the implantation. The "true" submucosal histamine concentration was determined by perfusing at different rates (the zero flow method) or with different concentrations of histamine at a constant rate (the no-net-flux method): in fasted rats it was calculated to be 87±5 (means±S.E.M.) nmol/l and 76±9 nmol/l, respectively. The corresponding histamine concentrations in fed rats were 93±5 and 102±8 nmol/l, respectively. With a perfusion rate of 74 mul/hr the recovery of submucosal histamine was 49%, at 34 mul/hr the recovery increased to 83%. At a perfusion rate below 20 mul/hr the microdialysate histamine concentration was close to the actual concentration in the submucosa. The ECL-cell histamine mobilization was independent of the concentrations of Ca2+ in the perfusion medium (0-3.4 mmol/l Ca2+). In one experiment, histamine mobilization in response to gastrin (10 nmol/kg/hr subcutaneously) was monitored in rats pretreated with prednisolone (60 mg/kg) or indomethacin (15 mg/kg). The two antiinflammatory agents failed to affect the concentration of histamine in the microdialysate either before or during the gastrin challenge, which was in accord with the observation that the inflammatory reaction was modest and that inflammatory cells were relatively few around the probe and in the wall of the probe. In another experiment, rats were given aminoguanidine (10 mg/kg) or metoprine (10 mg/kg) 4 hr before the start of gastrin infusion (5 nmol/kg/hr intravenously). Metoprine (inhibitor of histamine N-methyl transferase) did not affect the microdialysate histamine concentration, while aminoguanidine (inhibitor of diamine oxidase) raised both basal and gastrin-stimulated histamine concentrations. We conclude that microdialysis can be used to monitor changes in the concentration of histamine in the submucosa of the stomach, and that the inflammatory reaction to the probe is moderate and does not affect the submucosal histamine mobilization.
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- Lundgren, Björn, et al.
(författare)
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Assessments in Virtual Environments
- 2002
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The demands of good instructional design increase as the expansion of net-based education continue. In staff development at Malmö University we pay special attention to collaborative learning models. A key issue for successful accomplishment of a course is assessment and formal examination. This must reflect the instructional design of the course. Prof. Anders Nattestad, Copenhagen University and prof. Rolf Attström, Malmö University, have created a tool for examination in a virtual environment, Learning On-line , LEO, http://tmk.odont.ku.dk/leo/ . The tool is developed for educations in odontology. The tool presents a problem, which can be an authentic case. The students return their solutions into the system, which automatically presents solutions produced by ?experts?. By comparing their own solutions with the expert solutions, identify pros and cons, differences and similarities, the students analyse and evaluate their own learning. Assessment can then be based on the analysis alone or in combination with the original solutions. Studies are performed to evaluate the impact of using LEO on students´ learning, both in Odontology (Attström and Nattestad pers comm.), Teacher Education (Lundgren) and Environmental Ethics (Lundgren and Westerberg pers comm.) A further development of the tool to fascilitate collaborative work is suggested.
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| 5. |
- Lundgren, Magnus, et al.
(författare)
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Three replication origins in Sulfolobus species : synchronous initiation of chromosome replication and asynchronous termination
- 2004
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 101:18, s. 7046-7051
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Tidskriftsartikel (refereegranskat)abstract
- Chromosome replication origins were mapped in vivo in the two hyperthermophilic archaea, Sulfolobus acidocaidarius and Sulfolobus solfataricus, by using microarray-based marker frequency analysis. Bidirectional replication was found to be initiated in near synchrony from three separate sites in both organisms. Two of the three replication origins in each species were located in the vicinity of a cdc6/orc1 replication initiation gene, whereas no known replication-associated gene could be identified near the third origin in either organism. In contrast to initiation, replication termination occurred asynchronously, such that certain replication forks continued to progress for >40 min after the others had terminated. In each species, all replication forks advanced at similar DNA polymerization rates; this was found to be an order of magnitude below that displayed by Escherichia coli and thus closer to eukaryotic elongation rates. In S. acidocaidarius, a region containing short regularly spaced repeats was found to hybridize aberrantly, as compared to the rest of the chromosome, raising the possibility of a centromere-like function.
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| 7. |
- Robinson, Nicholas P., et al.
(författare)
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Identification of two origins of replication in the single chromosome of the archaeon Sulfolobus solfataricus
- 2004
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Ingår i: Cell. - 0092-8674 .- 1097-4172. ; 116:1, s. 25-38
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic chromosomes possess multiple origins of replication, whereas bacterial chromosomes are replicated from a single origin. The archaeon Pyrococcus abyssi also appears to have a single origin, suggesting a common rule for prokaryotes. However, in the current work, we describe the identification of two active origins of replication in the single chromosome of the hyperthermophilic archaeon Sulfolobus solfataricus. Further, we identify conserved sequence motifs within the origins that are recognized by a family of three Sulfolobus proteins that are homologous to the eukaryotic initiator proteins Orc1 and Cdc6. We demonstrate that the two origins are recognized by distinct subsets of these Orc1/Cdc6 homologs. These data, in conjunction with an analysis of the levels of the three Orc1/Cdc6 proteins in different growth phases and cell cycle stages, lead us to propose a model for the roles for these proteins in modulating origin activity.
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