| 1. |
- Anderson, Leif G., et al.
(författare)
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The effect of the Siberian tundra on the environment of the shelf seas and the Arctic Ocean
- 1999
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Ingår i: Ambio. - 0044-7447. ; 28:3, s. 270-280
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Tidskriftsartikel (refereegranskat)abstract
- The Tundra Ecology -94 expedition investigated inflow of inorganic and organic carbon to the shelf seas by river runoff, and its transformation by biochemical processes in seawater and sediment. In addition, anthropogenic radionuclides, 137Cs, 90Sr, and 239,240Pu, were studied in water and sediments. The distribution of dissolved inorganic carbon indicates that the majority of the Ob and Yenisey discharges flow into the Laptev Sea before entering the central Arctic Ocean. The sediment study shows that there is a marked difference in benthic oxygen uptake, efflux of dissolved inorganic carbon and nutrients between localities. 137Cs activity from the Chernobyl accident is 30% in the Barents, Kara, and Laptev Seas. 137Cs increased from 5-8 Bq m-3 in Barents Sea, 5-13 Bq m-3 in the Kara Sea to 8-15 Bq m-3 in the Laptev Sea, but with locally low concentrations at the river mouths. Corresponding values for 90Sr were 2.5, 3, and 4 Bq m-3, respectively.
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| 2. |
- Arvidsson, Per-Ola, et al.
(författare)
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Violaxanthin accessibility and temperature dependency for de-epoxidation in spinach thylakoid membranes
- 1997
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Ingår i: Photosynthesis Research. - 0166-8595. ; 52:1, s. 39-48
-
Tidskriftsartikel (refereegranskat)abstract
- Using DTT and iodoacetamide as a novel irreversible method to inhibit endogenous violaxanthin de-epoxidase, we found that violaxanthin could be converted into zeaxanthin from both sides of the thylakoid membrane provided that purified violaxanthin de-epoxidase was added. The maximum conversion was the same from both sides of the membrane. Temperature was found to have a strong influence both on the rate and degree of maximal violaxanthin to zeaxanthin conversion. Thus only 50% conversion of violaxanthin was detected at 4 degreesC, whereas at 25 degreesC and 37 degreesC the degree of conversion was 70% and 80%, respectively. These results were obtained with isolated thylakoids from non-cold acclimated leafs. Pigment analysis of sub-thylakoid membrane domains showed that violaxanthin was evenly distributed between stroma lamellae and grana partitions. This was in contrast to chlorophyll a and beta-carotene which were enriched in stroma lamellae fractions while chlorophyll b, lutein and neoxanthin were enriched in the grana membranes. In combination with added violaxanthin de-epoxidase we found almost the same degree of conversion of violaxanthin to zeaxanthin (73-78%) for different domains of the thylakoid membrane. We conclude that violaxanthin de-epoxidase converts violaxanthin in the lipid matrix and not at the proteins, that violaxanthin does not prefer one particular membrane region or one particular chlorophyll protein complex, and that the xanthophyll cycle pigments are oriented in a vertical manner in order to be accessible from both sides of the membrane when located in the lipid matrix.
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| 3. |
- Boguszewski, C L, et al.
(författare)
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Cloning of two novel growth hormone transcripts expressed in human placenta.
- 1998
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 83:8, s. 2878-85
-
Tidskriftsartikel (refereegranskat)abstract
- Several isoforms of human GH (hGH) are produced by two related genes expressed in the pituitary (hGH-N) and in the placenta (hGH-V). These genes consist of five exons (denoted 1-5) separated by four introns (denoted A-D). In the present report, two new transcripts of the hGH-V gene are described. The coding region of the hGH-V gene was amplified by RT-PCR using placental complementary DNA as template. DNA sequencing of several clones revealed two novel transcripts. One had a 45-bp deletion caused by the use of an alternative splice acceptor site within exon 3, similar to that in the hGH-N gene, predicting a 20-kDa isoform of hGH-V. The other transcript was generated by the use of an alternative splice donor site causing a 4-bp deletion in the end of exon 4, predicting a 24-kDa protein with 219 amino acids, which we refer to as hGH-V3. The carboxy-terminal sequence of hGH-V3 differs from 22-kDa hGH-V and hGH-V2, the two previously reported transcripts of the hGH-V gene, and does not contain a predicted transmembrane domain as described for hGH-V2. Ligase chain reaction was then used to analyze the possible use of the same splicing pattern in transcripts derived from the other genes of the hGH-gene cluster. Alternatively spliced transcripts encoding the 20-kDa hGH isoform were detected from the hGH-N and hGH-V genes, but not from the human chorionic somatomammotropin-A/B genes. The alternative splicing generating hGH-V3 was only demonstrated in transcripts derived from the hGH-V gene. Using competitive RT-PCR, the expression of hGH-V3 was estimated to be 10% of the hGH-V messenger RNA in full-term normal placentas and in placentas from pathological pregnancies. The 20-kDa hGH-V was detected in two of four full-term normal placentas, whereas a weak signal was observed in one of the pathological placentas. We conclude that the hGH-V primary transcript undergoes alternative splicing pathways generating at least four different messenger RNAs, predicting the expression of different hGH isoforms, including two with a complete sequence divergence in the carboxy-terminus.
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| 4. |
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| 5. |
- Johnson, M S, et al.
(författare)
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Characterization and chromosomal localization of rat scavenger receptor class B type I, a high density lipoprotein receptor with a putative leucine zipper domain and peroxisomal targeting sequence.
- 1998
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 139:1, s. 72-80
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Tidskriftsartikel (refereegranskat)abstract
- High density lipoprotein (HDL) participates in reverse cholesterol transport and in the delivery of cholesterol to steroid-producing tissues. Scavenger receptor class B type I (SR-BI) was recently shown to bind HDL and mediate internalization of its cholesterol content. We have cloned the rat homolog of this receptor, determined its chromosomal location, and examined its expression in rat tissues and in a model of follicular development, ovulation, and luteinization. The predicted protein contained two transmembrane domains, a leucine zipper motif, and a peroxisomal targeting sequence. The rat and human SR-BI genes were mapped to a region previously linked between rat and human chromosomes 12. SR-BI gene expression was detected in several rat tissues, with high levels in ovarian tissue, liver, and adrenal cortex, as determined by ribonuclease protection assay and in situ hybridization. A significant increase in SR-BI gene expression was detected in the late phase of corpus luteum formation, and transcripts were abundant in corpus luteum and in thecal cells at all stages of follicular development. In conclusion, the rat SR-BI complementary DNA predicted a protein with several conserved motifs, including a putative leucine zipper and a peroxisomal targeting sequence. The chromosomal locations of the rat and human SR-BI homologs suggest that this gene is a new member of a previously reported, conserved synteny group. SR-BI gene expression was high in steroid-producing tissues and in the liver, consistent with a role of this receptor in the uptake of HDL cholesterol.
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| 6. |
- Karlsson, C, et al.
(författare)
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Effects of growth hormone treatment on the leptin system and on energy expenditure in abdominally obese men.
- 1998
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Ingår i: European journal of endocrinology / European Federation of Endocrine Societies. - 0804-4643. ; 138:4, s. 408-14
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Tidskriftsartikel (refereegranskat)abstract
- The present study has examined the short- and long-term effects of growth hormone (GH) treatment on the leptin system and energy expenditure. Thirty male individuals with abdominal obesity were randomised to GH or placebo treatment in a 9-month, double-blind study. The dose of GH was 9.5 microg/kg, administered subcutaneously every evening. Serum leptin concentrations were measured by a human leptin RIA. Total RNA was isolated from adipose tissue biopsies and leptin mRNA levels were determined by a semi-quantitative reverse transcriptase-PCR assay. Body composition was determined by potassium-40 and the basal metabolic rate (BMR) was measured by a computerised, ventilated, open-hood system. As compared with placebo, an overall decrease in serum leptin concentrations as assessed by the area under the curve (AUC) (P < 0.05) and an increase in BMR (AUC, P < 0.05) were observed during GH treatment. The overall GH-induced changes were due to marked changes in serum leptin concentrations and BMR after 6 weeks of treatment. After 9 months of GH treatment there was a significant reduction in body fat (BF) while serum leptin concentrations and BMR did not differ from baseline values. Leptin mRNA levels did not change over the study period. We speculate that long-term GH treatment induces a new energy balance steady state with decreased BF stores. The effects of GH on the leptin system is suggested to be of importance for the maintenance of a lower BF mass.
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| 7. |
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| 8. |
- Svensson, Per-Arne, 1969, et al.
(författare)
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Scavenger receptor class B type I in the rat ovary: possible role in high density lipoprotein cholesterol uptake and in the recognition of apoptotic granulosa cells.
- 1999
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 140:6, s. 2494-500
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Tidskriftsartikel (refereegranskat)abstract
- Scavenger receptor class B type I (SR-BI) mediates the selective uptake of high density lipoprotein cholesterol. SR-BI is expressed at high levels in the ovary, indicating that it plays a role in the delivery of cholesterol as substrate for steroid hormone production. However, SR-BI also binds anionic phospholipids with high affinity and could therefore be involved in the recognition of apoptotic cells. In this study we have characterized the expression of SR-BI in rat ovarian follicles undergoing atresia. Atretic follicles with cells undergoing apoptosis were identified by in situ DNA end labeling, and SR-BI expression was determined by in situ hybridization and immunohistochemistry. SR-BI was expressed in thecal cells at all stages of follicular development, including atretic follicles, and in corpus luteum. Isolated apoptotic granulosa cells (but not viable granulosa cells) bound annexin V, indicating that they display anionic phospholipids on the cell surface. Transfection of COS-7 cells with an expression vector carrying the rat SR-BI complementary DNA resulted in increased binding to apoptotic granulosa cells (46 +/- 2% of the SR-BI-expressing cells bound at least one granulosa cell compared with 24 +/- 3% for the mock-transfected cells; P < 0.0001), whereas the binding to viable granulosa cells was unchanged. Apoptotic granulosa cells also bound to isolated thecal shells. We conclude that thecal cells of both nonatretic and atretic follicles express SR-BI. The location of SR-BI expression in the ovary supports a role of this receptor in the uptake of high density lipoprotein cholesterol. In addition, our data suggest that SR-BI mediates the recognition of apoptotic granulosa cells by the surrounding thecal cells and that it therefore may play a role in the remodeling of atretic follicles to secondary interstitial cells.
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| 9. |
- Ahlberg, Per, et al.
(författare)
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Geological fieldwork in the Kirwanveggen area
- 1992
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Ingår i: Swedish Antarctic research programme : a cruise report. 1991/92, Dronning Maud Land, Livingston Island, South Georgia. - 9197076988 ; , s. 13-21
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Bokkapitel (refereegranskat)
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| 10. |
- Allard, Per, et al.
(författare)
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Loss of dopamine uptake sites labeled with [3H]GBR-12935 in Alzheimer's disease.
- 1990
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Ingår i: European Neurology. - 0014-3022 .- 1421-9913. ; 30:4, s. 181-5
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Tidskriftsartikel (refereegranskat)abstract
- The binding of the dopamine uptake inhibitor [3H]GBR-12935 to postmortem putamen from a control group and patients with Alzheimer's disease/senile dementia of Alzheimer type (AD/SDAT) or vascular dementia (VD) was studied. The binding density (Bmax) in AD/SDAT was significantly reduced to 50% of control. A reduction of Bmax in VD was also noted, but it did not reach statistical significance. No differences in apparent binding affinity (Kd) between controls and dementia groups were obtained. The concentrations of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT) and homovanillic acid were also determined. The concentrations of DA and DOPAC were reduced by 30-40% in AD/SDAT and VD, but the reductions did not reach statistical significance. The concentration of 3-MT was reduced by 40% in AD/SDAT and by 30% in VD. The [3H]GBR-12935-binding densities correlated significantly with corresponding concentrations of DA in control brains. It is suggested that the loss of [3H]GBR-12935-binding sites in human putamen in AD/SDAT reflects a degeneration of dopamine neurites.
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| 11. |
- Arvidsson, Per-Ola, et al.
(författare)
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Purification and identification of the violaxanthin de-epoxidase as a 43 kDa protein
- 1996
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Ingår i: Photosynthesis Research. - 0166-8595. ; 49:2, s. 119-129
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Tidskriftsartikel (refereegranskat)abstract
- Violaxanthin deepoxidase (VDE) has been purified from spinach (Spinacia oleracea) leaves. The purification included differential sonication of thylakoid membranes, differential (NH4)2SO4 fractionation, gel filtration chromatography and finally either hydrophobic interaction chromatography or anion exchange chromatography. A total purification of more than 5000-fold compared to the original thylakoids enabled the identification of a 43 kDa protein as the VDE, in contrast to earlier reported molecular weight of 54–60 kDa. A detailed comparison was made for the VDE activity and polypeptide pattern for the different fractions throughout the purification and the best correlation was always found for the 43 kDa protein. The highest specific activity obtained was 256 mol g–1 s–1 protein, which is at least 10-fold higher than reported earlier. We estimate that there is 1 VDE molecule per 20–100 electron transport chains. The 43 kDa protein was N-terminally sequenced, after protection of cysteine residues with -mercaptoethanol and iodoacetamid, and a unique sequence of 20 amino acids was obtained. The amino acid composition of the protein revealed a high abundance of charged and polar amino acids and remarkably, 11 cysteine residues. Two other proteins (39.5 kDa and 40 kDa) copurifying with VDE were also N-terminally sequenced. The N-terminal part of the 39.5 kDa protein showed complete sequence identity both with the N-terminal part of cyt b 6 and an internal sequence of polyphenol oxidase.
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| 12. |
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| 13. |
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| 14. |
- Austrell, Per Erik, et al.
(författare)
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Survey of Design Methods and Material Characteristics in Rubber Engineering
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The unique properties of elastomeric materials are taken advantage of in many engineering applications. Elastomeric units are used as couplings or mountings between stiff structures. Examples of these are shock absorbers, vibration insulators, flexible joints, seals and suspensions.The development of computers and of analysis programs in this area has given engineers a new tool for the design of elastomeric components. Computer simulation by finite element analysis has become increasingly important, allowing the mechanical behavior of products with for complex geometries, as well as loading cases of different kinds to be evaluated. Computer simulations enable both static and dynamic aspects to be analyzed. These matters have been recognized by the manufacturers of rubber products and by their customers. The benefits are shorter time for product development and also quality improvements.However, the possibilities available for finding less complicated technical solutions at lower cost with the use of elastomers, has not been fully utilized. Rubber components could be employed more frequently in design if engineers were more familiar with materials of this sort.Part of the problem lies in education and in the dissemination of information. Engineers working in the design area tend to not be very familiar with elastomeric materials and their properties. The offerings of courses on the mechanics of polymers at schools and universities are very limited. Skillful engineers in this field have usually acquired their knowledge through many years of experience and not formal education.Moreover, the complicated nature of the material behavior involved makes it difficult to devise general design rules and design tools. Only recently have computers and analysis programs become powerful enough for the analysis of nonlinear elastic problems involving large strains.It is essential, if one is to become competitive in high-tech applications, to possess a thorough knowledge of computer methods, material models and test methods available.There has likewise been a lack of relevant data for the computer analysis of elastomeric materials. The design tools employed rely on the material models available and on the test data required for the calibration of these models. In many cases, the only information available for analysis is a value for the hardness of the rubber in question. The wide variety of rubber compounds is also a problem. The characterization of different materials is costly and time-consuming. There is thus a need for simple and reliable methods to characterize the different vulcanizates.
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| 15. |
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| 16. |
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| 17. |
- Bratt, Charlotte Eva, et al.
(författare)
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Regulation of violaxanthin de-epoxidase activity by pH and ascorbate concentration
- 1995
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Ingår i: Photosynthesis Research. - 0166-8595. ; 45:2, s. 169-175
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Tidskriftsartikel (refereegranskat)abstract
- The activity of violaxanthin de-epoxidase has been studied both in isolated thylakoids and after partial purification, as a function of pH and ascorbate concentration. We demonstrate that violaxanthin de-epoxidase has a Km for ascorbate that is strongly dependent on pH, with values of 10, 2.5, 1.0 and 0.3 mM at pH 6.0, 5.5, 5.0 and 4.5, respectively. These values can be expressed as a single Km±0.1±0.02 mM for the acid form of ascorbate. Release of the protein from the thylakoids by sonication was also found to be strongly pH dependent with a cooperativity of 4 with respect to protons and with an inflexion point at pH 6.7. These results can explain some of the discrepancies reported in the literature and provide a more consistent view of zeaxanthin formation in vivo.
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| 18. |
- Brånemark, Rickard, 1960, et al.
(författare)
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Biomechanical characterization of osseointegration: an experimental in vivo investigation in the beagle dog.
- 1998
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Ingår i: Journal of orthopaedic research : official publication of the Orthopaedic Research Society. - : Wiley. - 0736-0266. ; 16:1, s. 61-9
-
Tidskriftsartikel (refereegranskat)abstract
- This study reports the results of torsion tests, pull-out tests, and lateral loading tests on osseointegrated commercially pure titanium fixtures. The tests were performed in vivo on six beagle dogs. Three fixtures, each with a diameter of 3.7 mm, were installed bilaterally in the tibia of each animal. The mean maximal pull-out load was 1.55 kN (n = 4), the mean maximal lateral transverse load was 0.21 kN (n = 2), the mean maximal lateral axial load was 0.18 kN (n = 2), the mean breakpoint torque was 0.31 Nm (n = 3), and the mean maximal torque was 0.43 Nm (n = 3). The torsion test revealed an almost immediate plastic deformation of the interface between the implant and bone; this indicates that although the contact between the bone and the implant is close, there is no strong bond, at least not in shear. The major transfer of load from the implant to the surrounding bone tissue must therefore depend on the design of the implant. A histological evaluation with measurements of the amount of bone in contact with the fixtures was performed. By the use of the histological and mechanical data, it is possible to estimate shear stresses in bone tissue (pull-out test) and in the interface (torque test). The mean maximal shear stress in bone tissue in the pull-out tests was 100 MPa (n = 4); the mean shear stress in the interface was 4.3 MPa (n = 3) in the torsion tests at the breakpoint torque and was 6.0 MPa (n = 3) at the maximal torque. It was also possible to estimate the shear modulus of elasticity in the pull-out and torque tests. The mean shear modulus in pull-out was 119 MPa (n = 4), and the mean apparent shear modulus in torsion was 9 kPa (n = 3) for an assumed interface thickness of 100 nm and was 86 kPa (n = 3) for an assumed interface thickness of 1,000 nm.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
- Carlsson, Annika, 1965, et al.
(författare)
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Retrofit of heat exchanger networks
- 1991
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Ingår i: Föredrag vid 1992 IChem Research Event, University of Manchester, England, 9-10 januari, 1992.
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Konferensbidrag (refereegranskat)
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| 25. |
- Carlsson, Arne, 1943-, et al.
(författare)
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Studded tyres : socio-economic calculations
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The goal with this investigation is a revision of earlier investigations of studded tyres, i.e. the socio-economic consequences that may be expected from a ban on such tyres.The calculations were made for winter 1993/1994 and for winter 1999/2000. The conditions in winter 1993/1994 form the basis for the calculations, a quite normal winter. The conditions in 1999/20 00 are the same, except for the assumptions that all those using studded tyres will then be using lightweight studs and that wear resistant pavements will be more common. Everything else, for example winter maintenance will be the same as in 1993/1994.The following effects are included:Accidents (direct: at slipperiness. indirect: because of pavement wear)Road wear (pavement and road markings, cleaning signs)Car costs (tyres/rims, fuel consumption, washing)Environment (car washing)
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Carlsson, Jörgen, et al.
(författare)
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Conjugate chemistry and cellular processing of EGF-dextran
- 1999
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 38:3, s. 313-321
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Tidskriftsartikel (refereegranskat)abstract
- Conjugates with specific binding to the epidermal growth factor receptor, EGFR, of interest for radionuclide based imaging and therapy were prepared using mouse epidermal growth factor, mEGF, and dextran. In one type of conjugate, mEGF was coupled to dextran by reductive amination in which the free amino group on the mEGF N-terminal reacted with the aldehyde group on the reductive end of dextran. The end-end coupled conjugate could be further activated by the cyanopyridinium agent CDAP, thereby introducing tyrosines to the dextran part. In the other type of conjugate, the cyanylating procedure using CDAP was applied, first to activate dextran and then allowing for the amino terminus of mEGF to randomly attach to the dextran. In the latter case, radionuclide-labelled tyrosines or glycines could be added in the same conjugation step. All types of mEGF-dextran conjugates had EGFR-specific binding since the binding could be displaced by an excess of non-radioactive mEGF. The conjugates were to a large extent internalized in the test cells and the associated radioactivity was retained intracellularly for different times depending on both the type of cells and conjugate applied. Different intracellular 'traffic routes' for the radionuclides are discussed as well as applications for both imaging and therapy.
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| 34. |
- Carlsson, J, et al.
(författare)
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Lifetimes and Transition-probabilities of the Boron Atom Calculated With the Active-space Multiconfiguration Hartree-fock Method
- 1994
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 49:5, s. 3426-3431
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Tidskriftsartikel (refereegranskat)abstract
- Systematic multiconfiguration Hartree-Fock results are presented for the transition probabilities and excited-state lifetimes in the term system of the boron atom. Particularly, the interaction between the 1s(2)2s2p2 configuration and the 1s(2)2s2ns2S and 1s(2)2s2nd2D Rydberg series is considered. Term energies and transition-matrix elements are calculated to convergence using increasing active sets of s, p, d, f, and g orbitals.
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| 35. |
- Carlsson, J, et al.
(författare)
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Multiconfiguration Hartree-fock Calculations and Time-resolved Laser Spectroscopy Studies of Hyperfine-structure Constants In Sodium
- 1992
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Ingår i: Physica Scripta. Topical Issues. - : IOP Publishing. - 0281-1847. ; 46:5, s. 394-398
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Tidskriftsartikel (refereegranskat)abstract
- Hyperfine structure constants for the ground and first excited states of sodium are calculated using a newly written hyperfine structure program, which is part of the MCHF Atomic Structure Package. The calculated hyperfine structure constants are compared with the most reliable values obtained in other theoretical studies and in experiments. Also, a new accurate experimental determination of the 3p P-2(1/2) state hyperfine structure is presented.
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| 36. |
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| 37. |
- Carlsson, Jan, 1962, et al.
(författare)
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Transmission through corrugated slots
- 1995
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Ingår i: IEEE Transactions on Electromagnetic Compatibility. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9375 .- 1558-187X. ; 37:1, s. 114-121
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Tidskriftsartikel (refereegranskat)
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| 38. |
- Carlsson, Mats, et al.
(författare)
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Constraint-based resource allocation and scheduling in steel manufacturing
- 1999. - 1
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Konferensbidrag (refereegranskat)abstract
- This paper describes a flow maximization problem in steel manufacturing, decomposes it into three sub-problems, and models them in terms of finite domain constraints. Greedy algorithms are used for solving the sub-problems. The constraints are used for maintaining consistency rules, not for optimization. A tool implementing these algorithms and equipped with a GUI has been implemented.
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| 39. |
- Carlsson, Mats, et al.
(författare)
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Effects of fused tryptophan rich peptides to a recombinant protein A domain on the partitioning in polyethylene glycol-dextran and Ucon-dextran aqueous two-phase systems
- 1996
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 756:1-2, s. 107-117
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Tidskriftsartikel (refereegranskat)abstract
- Genetic engineering has been used to construct fusion proteins with tryptophan containing peptides. The peptides and the fusion proteins have been partitioned in aqueous two-phase systems of poly(ethylene glycol) (PEG)-dextran and Ucon-dextran. The studied model protein was ZZT0, where Z is an engineered domain of domain B of staphylococcal protein A. The specially designed hydrophobic peptides, Ala-Trp-Trp-Pro (T1) and (Ala-Trp-Trp-Pro)2 (T2), have been inserted into ZZT0, to give the peptide-protein fusions ZZT1 and ZZT2. In the experimental studies it was found that T1 and T2 preferred the PEG phase and even more the Ucon phase over the dextran phase. For T2 the partitioning was more one sided than for T1. For the fusion proteins, ZZT1 and ZZT2, the partitioning was enhanced into the PEG or Ucon rich phase as compared to ZZT0. The effects were lower than expected from independent contributions to the partition coefficient from the protein and the peptides. A heterogeneous lattice model was used to calculate theoretical peptide and protein partition coefficients. The calculations could reproduce the qualitative features of the experimental data. The model results suggest that a part of these experimentally observed effects is due to a depletion zone, i.e. a zone of reduced polymer concentration around the protein. The experimental results indicate a further reduction of the partition coefficient, beyond that predicted by the lattice calculations. A possible folding of the inserted peptide is discussed as a plausible mechanism for this further reduction in the partition coefficient.
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| 40. |
- Carlsson, M, et al.
(författare)
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Partitioning in Aqueous Polymer 2-phase Systems .1. Modeling of Affinity Partition
- 1995
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Ingår i: Bioseparation. - 1573-8272. ; 5:3, s. 155-166
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Tidskriftsartikel (refereegranskat)abstract
- Various factors influencing affinity partitioning in aqueous polymer two-phase systems are studied by model calculations using a self-consistent mean-field lattice theory. The latter is an extension of the theory of Scheutjens and Fleer, adapted to take affinity ligand binding into account. The dependence of partition coefficients on ligand concentration is studied for different binding strengths, polymer lengths, and polymer-protein interactions, and the effects of the ligand being attached at different positions of the polymer chain are investigated. The mechanism of the affinity partitioning is discussed. In particular, at saturation the enhanced partitioning by the presence of the ligand substituted polymers should be regarded as an expulsion from the minority phase rather than an attraction to the majority phase. Moreover, the results are put into relation with the multiple-equilibriascheme that has frequently been used to analyse affinity partition data, and comparisons with experimental findings are made. Some important principles for application of affinity partitioning concluded from the modelling results are: i) A higher selectivity can be expected if a polymer which has in general repulsive interactions with proteins is chosen as ligand-carrying polymer, ii) a higher Delta(lnK)(max) is expected for a longer ligand-carrying polymer as compared to a shorter one. With increased polymer length higher ligand concentration is however needed to reach the plateau value. iii) the ligand bound to the end of the polymer gives a higher Delta(lnK)(max) than when bound to the middle of the chain. iv) having both polymer ends carrying ligand should actually lead to a decrease in the Delta(lnK)(max). However, at quite low ligand concentrations the doubly substituted ligand-carrier should be more effective.
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| 41. |
- Carlsson, Margaretha S.
(författare)
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Pharmacokinetics of 2-mercaptopropionylglycine (Tiopronin) in man
- 1993
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 2-Mercaptopropionylglycine (2-MPG, tiopronin) has been used successfully in the treatment of cystinuria despite the lack of knowledge of its pharmacokinetics. Therefore methods based on high-performance liquid chromatography and fluorometric detection were developed for quantitative analysis. The total, non-protein-bound, and free (thiolic) tiopronin were measured in plasma using this method.The phannacokinetic disposition of tiopronin in plasma after intravenous administration was best described by a three exponential function. Plasma concentration time-curves of total tiopronin exhibited a rapid distribution phase, a B-phase corresponding to renal excretion, and a long terminal elimination phase. The latter was the result of strong disulphide binding of tiopronin to proteins. The non-protein-bound tiopronin was eliminated faster judging by its early appearance in urine. Mean bioavailability was 63 % in healthy volunteers with great interindividual variability (range 33-91%).Multiple dosing studies gave similar pharrnacokinetic parameters as for single dose studies and studies on patients with renal impaitment elucidated the renal clearance of the drug. In vitro studies showed a slow dissolution of the drug dosage form employed. A metabolite, 2-mercaptopropionic acid, was identified and its pharmacokinetics was investigated. The mechanism of action of the drug is discussed based on the results of measuring free tiopronin in plasma.
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- Carlsson, Per, et al.
(författare)
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A study of the initial stages of atmospheric corrosion of formed hot dip zinc coated steel
- 1997
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Ingår i: EUROCORR-97. - Trondheim, Norway.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Hot-dip zinc coated steel sheet is extensively used to improve the corrosion protection of steel constructions. When the sheet is formed cracks in the zinc coating develop in strained areas. The zinc coating gives a galvanic protection of the steel in damaged areas of the coating and at cut edges of the sheet. The degree of protection is, however, dependent on factors such as the geometry and the area of the defects, the coating thickness, the presence of corrosive ions in the electrolyte and the wet time. In this work we have studied the initial atmospheric corrosion of zinc coated steel in defects on bended and scribed material. The samples were exposed to a cyclic indoor corrosion test developed by Volvo (Volvo standard 1027). Scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) were used to monitor the initial stages of corrosion and the growth of corrosion products. The corrosion products were identified as predominantly zinc hydroxycarbonate, zinc hydroxychloride and zinc hydroxide. The amount of corrosion products increases with the size of the damaged area, which suggests that the cathodic reduction of oxygen at the steel substrate controls the corrosion rate.
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| 44. |
- Carlsson, Per, 1951-, et al.
(författare)
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An evaluation of prostate cancer screening using a decision analytic model
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- As early prostate cancer is often asymptomatic, the disease is often not diagnosed until it has reached an advanced, incurable stage. However, if diagnosed when it is still confined to the prostate, prostate caner is potentially curable. At present, there are no completed prospective evaluations or other scientific evidence to suggest that prostate cancer mortality is reduced or that quality of life is increased either by curative treatment or by screening programmes. However, the potential effects of a screening programme can be modelled using decision analytic computer software.The aim of this project was to develop a model for comparing the expected quality-adjusted life expectancy for a group of men subjected to a programme of screening for prostate cancer to that of a control group with conventional case-finding, given limited empirical data on the effectiveness of both strategies.Due to limitations of existing data, the analysis was developed during the early stages of evaluating a prostate cancer screening programme. We wish to illustrate how an analytic tool such as this model can be used in the future.The model was functionally separated into two parts. The first part, the observation submodel, covers the first 6 years of the programme and classifies the screened population into different quality of life states, based on observed outcomes. The second part, the simulation submodel, predicts quality adjusted life-years for healthy participants and for prostate cancer patients who receiving curative treatment or expectant management. Data for the model were obtained from a pilot programme on screening for prostate cancer in which a randomly selected population sample has been screened by digital rectal examination in Norrköping Sweden in 1987 and 1990. The outcome evaluated in the model was quality-adjusted life expectancy for individuals in the cohort invited to the screening programme, compared to results for population controls.While the preliminary results identify some health benefits associated with screening, more accurate empirical data for a number of key variables could improve the evaluation. One feature of this model is that it combines solid, empirical data from the observation submodel with simulated results. When better empirical data on the actual consequences of different strategies are available, they can easily be analysed by using this model.
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