| 1. |
- Gromada, J, et al.
(författare)
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Glucagon-like peptide I increases cytoplasmic calcium in insulin-secreting beta TC3-cells by enhancement of intracellular calcium mobilization
- 1995
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 44:7, s. 767-774
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Tidskriftsartikel (refereegranskat)abstract
- In the insulin-secreting beta-cell line beta TC3, stimulation with 11.2 mmol/l glucose caused a rise in the intracellular free Ca2+ concentration ([Ca2+]i) in only 18% of the tested cells. The number of glucose-responsive cells increased after pretreatment of the cells with glucagon-like peptide I (GLP-I)(7-36)amide and at 10(-11) mol/l; 84% of the cells responded to glucose with a rise in [Ca2+]i. GLP-I(7-36)amide induces a rapid increase in [Ca2+]i only in cells exposed to elevated glucose concentrations (> or = 5.6 mmol/l). The action of GLP-I(7-36)amide and forskolin involved a 10-fold increase in cytoplasmic cAMP concentration and was mediated by activation of protein kinase A. It was not associated with an effect on the membrane potential but required some (small) initial entry of Ca2+ through voltage-dependent L-type Ca2+ channels, which then produced a further increase in [Ca2+]i by mobilization from intracellular stores. The latter effect reflected Ca(2+)-induced Ca2+ release and was blocked by ryanodine. Similar increases in [Ca2+]i were also observed in voltage-clamped cells, although there was neither activation of a background (Ca(2+)-permeable) inward current nor enhancement of the voltage-dependent L-type Ca2+ current. These observations are consistent with GLP-I(7-36) amide inducing glucose sensitivity by promoting mobilization of Ca2+ from intracellular stores. We propose that this novel action of GLP-I(7-36)amide represents an important factor contributing to its insulinotropic action.
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| 2. |
- ALDEN, M, et al.
(författare)
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INFLUENCE OF SELECTED VARIABLES ON HEAT OF FUSION DETERMINATIONS BY OSCILLATING DSC
- 1995
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Ingår i: THERMOCHIMICA ACTA. - : ELSEVIER SCIENCE BV. - 0040-6031. ; 265, s. 89-102
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The influence of variables on the determination of the heat of fusion for phases with different crystallinity was investigated using oscillating differential scanning calorimetry (ODSC). The hydrophobic drug griseofulvin (GRIS) represented a crystalline s
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| 3. |
- Bjarnadottir, M, et al.
(författare)
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Intracellular accumulation of the amyloidogenic L68Q variant of human cystatin C in NIH/3T3 cells
- 1998
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Ingår i: Molecular Pathology. - : BMJ. - 1366-8714. ; 51, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To study the cellular transport of L68Q cystatin C, the cystatin variant causing amyloidosis and brain haemorrhage in patients suffering from hereditary cystatin C amyloid angiopathy (HCCAA).METHODS: Expression vectors for wild-type and L68Q cystatin C were constructed and used to transfect mouse NIH/3T3 cells. Stable cell clones were isolated after cotransfection with pSV2neo. Clones expressing human wild-type and L68Q cystatin C were compared with respect to secreted cystatin C by enzyme linked immunosorbent assay (ELISA), and for intracellular cystatin C by western blotting and immunofluorescence cytochemistry. Colocalisation studies in cells were performed by double staining with antibodies against human cystatin C and marker proteins for lysosomes, the Golgi apparatus, or the endoplasmic reticulum, and evaluated by confocal microscopy.RESULTS: Concentrations of human cystatin C secreted from transfected NIH/3T3 cells were similar to those secreted from human cells in culture. In general, clones expressing the gene encoding L68Q cystatin C secreted slightly lower amounts of the protein than clones expressing wild-type human cystatin C. Both immunofluorescence cytochemistry and western blotting experiments showed an increased accumulation of cystatin C in cells expressing the gene encoding L68Q cystatin C compared with cells expressing the gene for the wild-type protein. The intracellularly accumulating L68Q cystatin C was insoluble and located mainly in the endoplasmic reticulum.CONCLUSIONS: The cellular transport of human cystatin C is impeded by the pathogenic amino acid substitution Leu68-->Gln. The resulting intracellular accumulation and increased localised concentration of L68Q cystatin C might be an important event in the molecular pathophysiology of amyloid formation and brain haemorrhage in patients with HCCAA.
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| 4. |
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| 5. |
- Odmark, S, et al.
(författare)
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Effects of UVB radiation in a microbenthic community of a marine shallow-water sandy sediment
- 1998
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Ingår i: Marine Biology. - 0025-3162. ; 132:2, s. 335-345
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Tidskriftsartikel (refereegranskat)abstract
- The role of ambient and enhanced ultraviolet-B radiation (UVB; 280 to 315 nm) in a natural sand-associated microbenthic community was studied in a 3-week experiment by incubating intact sediment cores from a shallow bay in an outdoor flow-through system with 27 aquaria. After sampling of initial cores, the remaining cores tone per aquarium) were given one of three treatments: no, ambient, and moderately enhanced UVB, and sampled, nine at a time, after 5, 12, and 19 d. The response of the community was studied by analysing algal and meiofaunal composition and biomass, chlorophyll a content, composition of pigments and fatty acids, and content of UV-absorbing compounds (state variables), as well as carbon fixation and allocation, and bacterial productivity (rate variables). Among rate variables, significant effects of UVB-treatments were found for carbon fixation and allocation, while bacterial productivity was not affected. For state variables, a significant response was observed for the composition of microalgae and fatty acids, and for chlorophyll a content. The effect of treatments was mainly observed as differences in development with time (two-way analysis of variance, treatment x time interaction). Towards the end of the experiment, the no-UVB treatment most often differed from one or both of the two treatments with UVB exposure, the latter showing lower values. There were marked successional changes in the community, irrespective of treatment. The microalgal community changed from being dominated by coccoid cyanobacteria and epipsammic diatoms to a dominance of epipelic diatoms and filamentous cyanobacteria. The pattern of carbon allocation, as well as an increased C/N ratio of the sediment, suggested limitation of growth, perhaps by nutrients, at the end of the experiment. This may possibly have acted synergistically with UVB exposure to create the treatment effects. The new knowledge gained from our experiment is that ambient UVB can exert a stress on the function of sand-associated microbenthic communities in shallow waters and that this effect coincides with structural differences in the community.,More experiments in natural or semi-natural systems are needed to allow better prediction of microbenthic community-level responses to UVB.
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| 6. |
- Sundbäck, Kristina, 1949, et al.
(författare)
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Effects of enhanced UVB radiation on a marine benthic diatom mat
- 1997
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Ingår i: Marine Biology. - 0025-3162. ; 128:1, s. 171-179
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Tidskriftsartikel (refereegranskat)abstract
- In order to study the ecophysiological response of a natural diatom-dominated microbial mat to an enhanced level of ultraviolet-B radiation (UVBR), intact sediment cores from a shallow microtidal bay on the Swedish west coast were incubated in an outdoor flow-through system and exposed to either no UVBR or to an artificially enhanced level of UVBR. The microbial mat was cohesive and dominated by the large (approximate to 400 mu m) motile diatom Gyrosigma balticum. Functional response to UVBR was assessed by measuring carbon fixation (C-14) and allocation of photosynthetic products. Sediment oxygen microprofiles were measured as indicators of the balance between the photosynthetic and respiratory activity of the community. Structural variables included biomass and composition of microalgae, pigment composition (HPLC), content of UV-absorbing compounds, and composition of fatty acids. An enhanced level of UVBR resulted in significant functional changes in the microalgal community. Significantly decreased carbon fixation and lower net oxygen production (as calculated from oxygen microprofiles) suggest that primary productivity in the type of microbial mat studied is potentially sensitive to an enhanced level of UVBR. The pattern of carbon allocation hinted a change as to the photosynthetically active part of the community when exposed to UVBR, indicating a differential sensitivity among algal cells. Despite significant functional effects, pigment or algal composition were not significantly affected by enhanced UVBR. The concentration of UV-absorbing compounds was low and did not increase at UVBR exposure. Due to the short duration of the experiment (4 d), a change in algal biomass or composition was not to be expected. Moreover, the thickness of the sampled sediment layer, may have contributed to the lack of observed structural effects of enhanced UVBR. Visual observations suggested that UVBR affected the motility of G. balticum. This study, as well as other experiments with a similar diatom mat, suggest that vertical migration is a key mechanism to be further studied in relation to UVBR exposure of diatom-dominated microbial mats.
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| 7. |
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| 8. |
- Wulff, Angela, 1963, et al.
(författare)
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UV radiation effects on microbenthos - a four month field experiment
- 1999
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Ingår i: Aquatic Microbial Ecology. - 0948-3055. ; 19:3, s. 269-278
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Tidskriftsartikel (refereegranskat)abstract
- A 4 mo field experiment, covering the period May to September, was carried out in a shallow microtidal sandy bay on the Swedish west coast. To test whether the ambient UV radiation (UVR) had any effect on a marine microbenthic community, screens of Plexiglas, Plexiglas + Mylar-D film and polycarbonate were used. This gave 3 different treatments: Ambient (PAR+UVAR+UVBR), NoUVB (PAR+UVAR) and NoUV (PAR) plus Control (areas without screens to test the 'frame effect'). The response of the community was studied on 2 occasions (June, September) by measuring primary productivity (C-14), carbon allocation (C-14) and bacterial productivity (H-3-thymidine) (rate variables), as well as biomass and composition of microalgae and meiofauna, pigment composition (HPLC), content of mycosporine-like amino acids (MAA, HPLC) and composition of fatty acids (GC). The UVR maximum penetration depth (1%) in the sediment, measured by microsensors, was 800 mu m for UVAR and 600 mu m for UVB. No UVR effects were found for any structural variables but ostracodalbiomass, which doubled when exposed to WR compared with the UVR excluding treatments. Significant treatment effects were found for the rate variables primary productivity and carbon allocation. The effects on primary productivity and ostracods were observed in September only. All the treatment effects were found between exclusion of and exposure to UVR. Primary productivity increased in treatments shielded from UVR. For carbon allocation, significant effects on all fractions were found, however, with a partly different outcome in June and September. We conclude that the UVBR part of the spectrum exerted some stress on the microbenthic community, but this was almost exclusively found for rate variables in September, and that the ambient UVAR did not have any harmful effects. It is also concluded that the choice of time scales and experimental approach (laboratory vs field experiments) is crucial for the out come and interpretation of UVBR experiments.
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