| 1. |
- Gustavsson, Per-Erik, et al.
(författare)
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Direct measurements of convective fluid velocities in superporous agarose beads
- 1998
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 795:2, s. 199-210
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Tidskriftsartikel (refereegranskat)abstract
- Superporous agarose beads contain two sets of pores, diffusion pores and so-called superpores or flow pores, in which the chromatographic flow can transport substances to the interior of each individual bead [Gustavsson and Larsson, J. Chromatogr. A 734 (1996) 231]. The existence of pore flow may be proven indirectly by the chromatographic performance of beads but it has never been directly demonstrated in a chromatographic bed. In this report, pore flow was directly measured by following the movement of micro-particles (dyed yeast cells) in a packed bed. The passage of the micro-particles through the superpores and through the interstitial pores was followed by a microscope/video camera focused on beads which were situated four layers from the glass wall. The video recordings were subsequently used to determine the convective fluid velocities in both the superpores and the interstitial pores. Experiments were carried out with three different bead size ranges, all of which contained superporous beads having an average superpore diameter of 30 mu m. The superpore fluid velocity as % of interstitial fluid velocity was determined to be 2-5% for columns packed with 300-500-mu m beads (3% average value), 6-12% for columns packed with 180-300 mu m beads (7% average value) and 11-24% for columns packed with 106-180-mu m beads (17% average value). These data were compared to and found to agree with theoretically calculated values based on the Kozeny-Carman equation. In order to observe and accurately measure fluid velocities within a chromatographic bed, special techniques were adopted. Also, precautions were made to ensure that the experimental conditions used were representative of normal chromatography runs. (C) 1998 Elsevier Science B.V.
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| 2. |
- Gustavsson, Per-Erik, et al.
(författare)
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Superporous agarose beads as a hydrophobic interaction chromatography support
- 1999
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 830:2, s. 275-284
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Tidskriftsartikel (refereegranskat)abstract
- Superporous agarose beads were used as a support for hydrophobic interaction chromatography. These beads have large connecting flow pores in addition to their normal diffusion pores. The flow pores, which are approximately one fifth of the overall diameter of the superporous agarose beads, were earlier shown to give the beads improved mass transfer properties relative to homogeneous agarose beads (Gustavsson and Larsson, J. Chromatogr. A, 734 (1996) 231-240). Superporous agarose beads and homogeneous agarose beads of the same particle size range (106-180 mu m) were derivatized with phenyl groups. The properties of the superporous beads were then compared with the homogeneous beads in the separation of a mixture of three model proteins (ribonuclease A, lysozyme and bovine serum albumin) at various superficial flow velocities from 30 to 600 cm/h. The superporous beads gave satisfactory separation at flow velocities five times higher than was possible for homogeneous beads. The performance of the two types of beads was also compared in the purification of lactate dehydrogenase from a beef heart extract at a superficial flow velocity of 150 cm/h. The superporous beads performed considerably better, leading to twice the purification factor and twice the concentration of the desired product. The results were interpreted using the theoretical treatment given by Carta and Rodrigues (Carta and Rodrigues, Chem. Eng. Sci., 48 (1993) 3927). (C) 1999 Elsevier Science B.V. All rights reserved.
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| 3. |
- Larsson, Anders, et al.
(författare)
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Peroxidase labelling of chicken anti-bodies
- 1999
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Ingår i: Food and Agricultural Immunology. - : Informa UK Limited. - 0954-0105 .- 1465-3443. ; 11:1, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- Chicken antibodies have several advantages over mammalian antibodies due to the phylogenetical differences between birds and mammals, resulting in an increased sensitivity and a decreased background in many immunological assays. So far, there has been a very limited use of avian antibodies. This is probably partly due to tradition but also because there are very few optimized methods for the labelling of chicken antibodies. We report upon the suitable conditions for peroxidase-labelling of chicken antibodies with a modified periodate method.
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| 4. |
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| 5. |
- Larsson, Per-Olof, et al.
(författare)
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Direct measurement of intraparticle fluid velocity in superporous agarose beads
- 1998
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Ingår i: Journal of Molecular Recognition. - 1099-1352. ; 11:1-6, s. 270-272
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Tidskriftsartikel (refereegranskat)abstract
- Superporous agarose beads contain both normal diffusion pores and special, very wide superpores through which part of the chromatographic flow is transported, a situation that may greatly improve the chromatographic performance. For the first time such pore flow was measured directly by following the movement of microparticles (dyed yeast cells) through superporous beads packed in a chromatographic bed. The passage of the microparticles through the superpores and through the interstitial pores was recorded by a microscope/video camera, The video recordings were subsequently used to determine flow paths as well as the convective fluid velocities in both the superpores and the interstitial pores. The superpore fluid velocity was found to be proportional to the ratio between the squares of the respective pore diameters, which is in agreement with the Kozeny-Carman equation, Values for two-dimensional and three-dimensional tortuosity of the flow paths were measured and calculated respectively. (C) 1998 John Wiley & Sons, Ltd.
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| 6. |
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| 7. |
- Odin, Elisabeth, 1955, et al.
(författare)
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Rapid method for relative gene expression determination in human tissues using automated capillary gel electrophoresis and multicolor detection
- 1999
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Ingår i: J Chromatogr B Biomed Sci Appl. - 1387-2273. ; 734:1, s. 47-53
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate a direct and automated post-polymerase chain reaction (PCR) detection system to simultaneously determine the relative gene expression levels of nine cancer-related human genes. Total RNA was prepared from flash-frozen biopsies derived from human colorectal tumors or normal mucosa and reverse-transcribed to cDNA which was PCR-amplified using primer pairs corresponding to the studied genes. In each reaction, the forward primer was labeled with a fluorescent dye. The PCR products were pooled and an internal size standard with a uniquely colored fluorescent dye was added. The samples were then subjected to automated capillary gel electrophoresis. Fragment analysis software was used to calculate the relative gene expression using beta-actin as the reference gene. We found that automated capillary gel electrophoresis with multicolor detection is a rapid, accurate and highly reproducible method for separation and quantification of PCR-amplified cDNA.
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| 8. |
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| 9. |
- Berglund, Olof, et al.
(författare)
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Factors influencing organochlorine uptake in age-0 brown trout (Salmo trutta) in lotic environments
- 1997
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 54:12, s. 2767-2774
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Tidskriftsartikel (refereegranskat)abstract
- In 1994 and 1995, we investigated the relationship between stream morphology and water chemistry and levels of organochlorines (HCB, PCB, and DDT) in young-of-the-year brown trout (Salmo trutta) from 25 streams in southern Sweden. Contrary to earlier findings for lakes, we found a positive relationship between trophic status (total phosphorus) and uptake of persistent pollutants in stream biota (trout). This difference between benthic, stream environments and pelagic, lake environments may be related to processes affecting pollutant uptake, i.e., pollutant "spiralling" or the shift from heterotrophy to autotrophy in streams. Land use in the catchment area of the streams also affected pollutant levels in trout, with higher levels in agricultural landscapes and lower levels in forested areas. Size of catchment area, however, did not influence uptake of pollutants in trout. The results indicate that eutrophication of streams by agricultural activities and excessive nutrient loading may increase uptake of persistent pollutants in stream biota.
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| 10. |
- Carling, Tobias, et al.
(författare)
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Hyperparathyroidism of multiple endocrine neoplasia type 1 : candidate gene and parathyroid calcium sensing protein expression
- 1995
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Ingår i: Surgery. - 0039-6060 .- 1532-7361. ; 118:6, s. 924-931
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:Hyperparathyroidism affects most patients with multiple endocrine neoplasia type 1 (MEN 1). This study investigates expression of the candidate MEN1 gene phospholipase C beta 3 (PLC beta 3) and expression and function of a putative calcium sensing protein (CAS) in hyperparathyroidism of MEN 1.METHODS:In 31 parathyroid glands from 17 patients with MEN 1, CAS distribution was studied immunohistochemically and parallel sections were explored for PLC beta 3 mRNA expression by in situ hybridization. Enzymatically dispersed parathyroid cells were analyzed for cytoplasmic calcium concentrations [Ca2+]i and parathyroid hormone (PTH) release.RESULTS:All glands exhibited a heterogeneously reduced CAS immunoreactivity, especially meager in nodularly assembled parathyroid cells. Calcium regulated [Ca2+]i and PTH release tended to be more deranged in the glands possessing the lowest immunostaining. Parathyroid PLC beta 3 invariably was homogeneously expressed, and this included even MEN 1 patients with reduced PLC beta 3 expression in endocrine pancreatic tumors.CONCLUSIONS:The findings support variable calcium insensitivity of [Ca2+]i and PTH release in hyperparathyroidism of MEN 1, apparently coupled to heterogeneously reduced CAS expression. For clarification of the role of PLC beta 3 in MEN 1 parathyroid tumorigenesis further study of this protein is required.
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| 11. |
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| 12. |
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| 13. |
- Larsson, Gunilla, et al.
(författare)
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Crystal structure of the Escherichia coli dUTPase in complex with a substrate analogue (dUDP)
- 1996
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 3:6, s. 532-538
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Tidskriftsartikel (refereegranskat)abstract
- We have determined the structure of the homotrimeric dUTPase from Escherichia coli, complexed with an inhibitor and substrate analogue, dUDP. Three molecules of dUDP are found symmetrically bound per trimer, each in a shallow cleft between adjacent subunits, interacting with evolutionary conserved residues. The interactions of the uracil ring and the deoxypentose with the protein are consistent with the high specificity of the enzyme with respect to these groups. The positions of the two phosphate groups and adjacent water molecules are discussed in relation to the mechanism and kinetics of catalysis. The role that dUTPase plays in DNA metabolism makes the enzyme a potential target for chemotherapeutic drugs: the results presented here will aid in the design and development of inhibitory compounds.
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| 14. |
- Larsson, Kjell, et al.
(författare)
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Hyaluronic acid (hyaluronan) in BAL fluid distinguishes farmers with allergic alveolitis from farmers with asymptomatic alveolitis
- 1992
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Ingår i: Chest. - : Elsevier BV. - 1931-3543 .- 0012-3692. ; 101:1, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- Pulmonary function measurements, bronchoalveolar lavage (BAL), and analyses of precipitating antibodies in blood were performed in 12 farmers wtih no symptoms from the airways and 12 farmers who were admitted to the hospital due to acute symptoms of alveolitis (all nonsmokers). In addition, a bronchial methacholine provocation test was performed in the asymptomatic farmers. In 11 of the 12 symptomatic farmers but in none of the asymptomatic farmers, precipitating antibodies against one or more of the microorganisms which usually occur in a farmer's environment were found. In the farmers with symptomatic alveolitis, a restrictive impairment of pulmonary function was found, while pulmonary function was normal in all asymptomatic farmers. Findings in the BAL fluid showed increased concentrations of total cells, lymphocytes, and neutrophils and elevated levels of albumin, fibronectin, and angiotensin-converting enzyme in asymptomatic farmers compared with our own reference group. The same analyses in BAL fluid from the symptomatic farmers revealed a further increase in all parameters compared with the asymptomatic farmers. The BAL fluid from asymptomatic farmers had normal levels of hyaluronic acid (hyaluronan) and procollagen 3 N-terminal peptide, while these levels were significantly increased in the symptomatic group. We conclude that inflammation in the alveolar space and signs of activation of alveolar macrophages are present in farmers regardless of respiratory symptoms, although these findings are more pronounced in the presence of symptoms of acute alveolitis; however, the findings of impaired pulmonary function and the occurrence of precipitins and elevated levels of hyaluronic acid and procollagen 3 N-terminal peptide in BAL fluid were exclusively found in the farmers with airways symptoms. We postulate the hyaluronic acid, due to its pronounced ability to immobilize water, may be of importance in the development of the pulmonary function impairment observed in farmer's lung disease.
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| 15. |
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| 16. |
- Larsson, Per, et al.
(författare)
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Persistent pollutants in a salmon population (Salmo salar) of the southern Baltic Sea
- 1996
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 53:1, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- Persistent pollutants in an Atlantic salmon (Salmo salar) population spawning in a river of southern Sweden were investigated. The population was characterized by a high growth rate. Some males reached 20-30 kg after 3 to 4 years in the sea. The fat content of migrating salmon varied by one order of magnitude and was the most significant correlate of pollutant concentrations. No relationships were recorded between fat content and gender, age (weight, length), year at sea, or different measures of condition. The reasons for this may be the varied evolutionary strategies for maximizing reproductive output; male salmon may enter the spawning river as small grilse and spawn opportunely, or migrate at a larger size, when they can hold spawning territories in the river. Females have a greater and more uniform size, and spend more energy on gonadal products. The varying fat content of individual fish may also be attributed to foraging in different areas of the Baltic and thereby to migration distances as well as foraging strategies. When pollutant levels were normalized for fat content, other factors such as age (weight, length) were shown to be important for uptake; older fish had higher levels of pollutants than younger ones
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| 17. |
- Nygren, Jonas, et al.
(författare)
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Preoperative gastric emptying : the effects of anxiety and carbohydrate administration
- 1995
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Ingår i: Annals of Surgery. - : Lippincott Williams & Wilkins. - 0003-4932 .- 1528-1140. ; 222:6, s. 728-734
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Tidskriftsartikel (refereegranskat)abstract
- Background: Overnight fasting is routine before elective surgery. This may not be the optimal way to prepare for surgical stress, however, because intravenous carbohydrate supplementation instead of fasting has recently been shown to reduce postoperative insulin resistance. In the current study, gastric emptying of a carbohydrate-rich drink was investigated before elective surgery and in a control situation. Methods: Twelve patients scheduled for elective surgery were randomly given 400 mL of either a carbohydrate-rich drink (285 mOsm/kg, 12.0% carbohydrates, n = 6) or water 4 hours before being anesthetized. Gastric emptying was measured (gamma camera, 99Tcm). Each patient repeated the protocol postoperatively as a control. All values were presented as the mean ± SEM by means of a nonparametric statistical evaluation. Results: Despite the increased anxiety experienced by patients before surgery (p < 0.005), gastric emptying did not differ between the experimental and control situations. Initially, water emptied more rapidly than carbohydrate. However, after 90 minutes, the stomach was emptied regardless of the solution administered (3.2 ± 1.1% [mean ± SEM] remaining in the stomach in the carbohydrate group versus 2.3 ± 1.2% remaining in the stomach in the water group). Conclusions: Preoperative anxiety does not prolong gastric emptying. The stomach had been emptied 90 minutes after ingestion of both the carbohydrate-rich drink and water, thereby indicating the possibility of allowing an intake of iso-osmolar carbohydrate-rich fluids before surgery.
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| 18. |
- Pihlsgård, Per, et al.
(författare)
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Aroma analysis of liquid sugars
- 1998
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Ingår i: International Sugar Journal. - 0020-8841. ; 100:1197, s. 431-436
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Tidskriftsartikel (refereegranskat)abstract
- Use of liquid sugars can be very attractive in various applications, especially sugar from process streams, since there are less losses than for crystallised products. However, odour and flavour intensities are higher in sugar from process syrups - which may be critical in some potential applications. Detection, analysis and control of odour components are therefore important, albeit complex, activities.
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| 19. |
- Pihlsgård, Per, et al.
(författare)
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Chemical and sensory properties of liquid beet sugar
- 1999
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:10, s. 4346-4352
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Tidskriftsartikel (refereegranskat)abstract
- Sensory analysis and headspace gas chromatography-flame ionization detection (GC-FID) analysis of liquid sugars (sucrose) designated for food- industrial use were performed in order to elucidate which compounds are responsible for perceived off-odors and off-flavors in liquid sugar. The liquid sugar samples investigated had various kinds of off-odors and off- flavors that might influence the quality of any food product in which they might be used, such as a jam or a soft drink. The sensory scores for the different attributes and the levels of different volatile compounds as measured by GC were analyzed for correlation using partial least-squares (PLS) analysis. A link between sensory analysis and GC analysis was thereby established, and compounds critical for the odor and flavor were identified using MS (mass spectrometry). Approximately 10 compounds were found to be correlated with the defined sensory attributes. Among these compounds associated with the sensory attributes were dimethyl disulfide, 2,6- dimethylpyrazine, 4-methoxyphenol, and 2,5-dimethylfuran.
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