| 1. |
- Hällgren, R, et al.
(författare)
-
Hyaluronic acid accumulation and redistribution in rejecting rat kidney graft. Relationship to the transplantation edema.
- 1990
-
Ingår i: Journal of Experimental Medicine. - 0022-1007 .- 1540-9538. ; 171:6, s. 2063-76
-
Tidskriftsartikel (refereegranskat)abstract
- By using biotin-labeled proteoglycan core protein and an avidin-enzyme system, hyaluronic acid (HA) was visualized in rat kidney. In the normal kidney, HA was localized in the extracellular space of the inner medulla and increased markedly towards the papillary tip. No staining for HA was seen in the interstitial tissue of the cortex or the outer medulla. During the development of rejection of allogeneic renal grafts, a progressive increase in accumulated HA was seen in the interstitial tissue of the cortex and outer medulla. The extractable amounts of HA increased, on average, 40 times in the cortex and outer medulla; no increase was measured in the inner medulla and papilla. The relative water content of the cortex and outer medulla also increased progressively and correlated with the HA accumulation. The extractable amounts of HA in syngeneic grafts increased by day 2 and then leveled off, indicating that surgical trauma may induce some transient HA accumulation after transplantation. Interstitial accumulation of HA, a glycosaminoglycan with unique water-binding qualities, would presumably influence water transport and osmotic activity and should thereby be implicated in the normal papillary function, but also in the development of the interstitial edema of the cortex and outer medulla during rejection of renal grafts.
|
|
| 2. |
- Stålhammar-Carlemalm, Margaretha, et al.
(författare)
-
Protein rib: a novel group B streptococcal cell surface protein that confers protective immunity and is expressed by most strains causing invasive infections
- 1993
-
Ingår i: Journal of Experimental Medicine. - 1540-9538. ; 177:6, s. 1593-1603
-
Tidskriftsartikel (refereegranskat)abstract
- The group B Streptococcus, an important cause of invasive infections in the neonate, is classified into four major serotypes (Ia, Ib, II, and III) based on the structure of the polysaccharide capsule. Since the capsule is a known virulence factor, it has been extensively studied, in particular in type III strains, which cause the majority of invasive infections. Two cell surface proteins, alpha and beta, have also been studied in detail since they confer protective immunity, but these proteins are usually not expressed by type III strains. We describe here a cell surface protein, designated protein Rib (resistance to proteases, immunity, group B), that confers protective immunity and is expressed by most strains of type III. Protein Rib was first identified as a distinct 95-kD protein in extracts of a type III strain, and was purified to homogeneity from that strain. Rabbit antiserum to protein Rib was used to demonstrate that it is expressed on the cell surface of 31 out of 33 type III strains, but only on 1 out of 25 strains representing the other three serotypes. Mouse protection tests showed that antiserum to protein Rib protects against lethal infection with three different strains expressing this antigen, including a strain representing a recently identified high virulence type III clone. Protein Rib is immunologically unrelated to the alpha and beta proteins, but shares several features with the alpha protein. Most importantly, the NH2-terminal amino acid sequences of the Rib and alpha proteins are identical at 6 out of 12 positions. In addition, both protein Rib and the alpha protein are relatively resistant to trypsin (and Rib is also resistant to pepsin) and both proteins vary greatly in size between different clinical isolates. Finally, both protein Rib and the alpha protein exhibit a regular ladderlike pattern in immunoblotting experiments, which may reflect a repetitive structure. Taken together, these data suggest that the Rib and alpha proteins are members of a family of proteins with related structure and function. Since protein Rib confers protective immunity, it may be valuable for the development of a protein vaccine against the group B Streptococcus, an encapsulated bacterium.
|
|
| 3. |
- Cohn, Marita, et al.
(författare)
-
Evolutionary relations between subtypes of telomere-associated repeats in Chironomus
- 1991
-
Ingår i: Journal of Molecular Evolution. - 0022-2844. ; 32:6, s. 463-468
-
Tidskriftsartikel (refereegranskat)abstract
- Telomere-associated DNA in Chironomus pallidivittatus contains tandemly repeated 340-bp units. We show that they are distributed among several subtypes of which we have characterized two, M1 and D1, with regard to base sequence, homogeneity, and intertelomeric distribution. Each subpopulation is highly homogeneous and the two subtypes have identical consensus sequences throughout 90% of their lengths. In the remaining part the homology is only about 60%. Each subpopulation has its specific intertelomeric distribution and there is no difference in the degree of homogenization within and between telomeres. The repeat unit contains two pairs of subrepeats embedded in linker DNA. This provides a model that makes it possible to relate the two subtypes to each other with regard to evolutionary history. The difference between the two subtypes is due to mutations that have occurred in only one of them, D1, resulting in a decreased similarity between one of its pairs of subrepeats. This type of repeat unit is therefore believed to be derived from the other, M1. The local decrease in similarity between M1 and D1 suggests that homogenization between them occurs by gene conversion.
|
|
| 4. |
- Cohn, Marita, et al.
(författare)
-
Telomere-associated repeats in Chironomus form discrete subfamilies generated by gene conversion
- 1992
-
Ingår i: Journal of Molecular Evolution. - 0022-2844. ; 35:2, s. 114-122
-
Tidskriftsartikel (refereegranskat)abstract
- In dipteran insects the most distal telomere-associated DNA known to exist consists of long, complex tandem repeats. We have classified the 340-bp tandemly arranged repeats in Chironomus pallidivittatus. The repeats are distributed in a small number of subfamilies. One type of the repeat has the character of a master unit from which other main units can be derived usually by simple changes. The derived subfamilies contain segments that are degenerate versions of the corresponding segment in the master sequence. Such segments can also occur together in one and the same repeat unit in different combinations. There is a complete absence of subfamily-specific base variants in regions lying outside of the degenerate segments. Homogenization takes place between DNA sequences that are often smaller than a whole repeat unit. The mosaic structure of the repeat arrays suggests that gene conversion is an important force in the generation and maintenance of this family of repeats.
|
|
| 5. |
- Wadsö, Lars
(författare)
-
Describing non-Fickian water-vapour sorption in wood
- 1994
-
Ingår i: Journal of Materials Science. - 0022-2461. ; 29:9, s. 2367-2372
-
Tidskriftsartikel (refereegranskat)abstract
- Moisture transport and sorption in wood may not be accurately described by Fick's law of diffusion. The problem of making a model of non-Fickian behaviour (NFB) for wood is discussed. Some measurements in which NFB in wood is clearly seen are also reviewed. Four criteria, which must be satisfied by a model describing sorption in wood cell walls, are presented: (1) the model should not only describe the response to step changes in vapour pressure; (2) it should be able to predict sorption with more than one time scale; (3) the sorption rate should not depend on the thickness of the cell wall; (4) small rapid changes in vapour pressure should give slower fractional weight change than large rapid changes. A review of models of NFB in synthetic polymers indicates that there is presently no model of NFB which fulfills the above criteria. More measurements of the sorption behaviour of the cell wall are needed to construct such a model for wood. This model can then probably be used, together with a Fickian diffusion model, to model the sorption behaviour of whole wood.
|
|
| 6. |
- Guo, S.J., et al.
(författare)
-
Magnetic field dependence of the critical current density for the bismuth-based bulk high-Tc superconductors
- 1992
-
Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 27:11, s. 3043-3049
-
Tidskriftsartikel (refereegranskat)abstract
- Three types of bismuth-based bulk samples were prepared through uniaxial pressing at room temperature, hot isostatic pressing (HIP) and drawing and rolling. Transport current properties were characterized in a steady field up to 1.12 T at 77 K (T/T c=0.75). The Josephson weak-link decoupling fields have been found to be 5 mT for the cold-pressed pellet and 30 mT for the HIPed pellet and the rolled tape. At the decoupling field the transport critical current density,J c, drops 80% from 124 (OT) to 29 A cm-2 (5 mT) for the cold-pressed pellet, 80% from 582 (OT) to 126 A cm-2 (30 mT) for the HIPed sample and 50% from6500 (0 T) to 2850 A cm-2 (30 mT) for the rolled tape. In the flux flow regime, whereB is perpendicular to thec-axis a modified Kim's modelJ c=(α/B 0)/[(1+B/B 0)] n can be used to describe the field dependence of the critical current density, Jc, in the field range 0.2-1.12 T. The effective upper critical fields were estimated to be 0.98, 1.54 and 1.94 T for the three types of samples, respectively. An adjustable range ofB c2 for bismuth-based bulk highT c superconductors is given. Flux shear may operate in these materials. The prediction of this pinning mechanism is yielded from fitting the equation qualitatively. WhenB is parallel to thec-axis, the absence of strongly intragranular flux-pinning is emphasized by the poor flux flow regime for the rolled tape sample.
|
|
| 7. |
- Ion, John, et al.
(författare)
-
Laser surface modification of a 13.5% Cr, 0.6% C steel
- 1991
-
Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 26:1, s. 43-48
-
Tidskriftsartikel (refereegranskat)abstract
- A 13.5% Cr, 0.6% C steel, with an initial microstructure of chromium carbides in a ferrite matrix, was heat-treated by scanning a high-power laser beam over the surface. The aim was to compare the physical and chemical properties produced by this type of selective surface treatment with those resulting from a conventional furnace desensitization and quench-hardening heat treatment. Surface heating homogenized the carbon originally bound in the carbides sufficiently to produce martensite, giving hardening to levels comparable with a conventional heat treatment. Chromium-rich zones, carbides and retained austenite were also detected in the heated microstructure. Surface melting produced complete homogenization of both carbon and chromium, which resulted in the retention of large amounts of austenite in the microstructure on cooling to room temperature. Subsequent refrigeration at - 196 °C transformed some of the austenite to martensite. Pitting corrosion and local reductions in hardness were observed adjacent to treated areas under certain conditions, due to precipitation of secondary carbides and elevated tempering, respectively.
|
|
| 8. |
- Larker, Rickard, et al.
(författare)
-
AEM investigation of ceramic/incology 909 diffusional reactions after joining by HIP
- 1994
-
Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 29:16, s. 4404-4414
-
Tidskriftsartikel (refereegranskat)abstract
- Diffusion bonding by hot isostatic pressing (HIP) was performed between Incoloy 909 and five different ceramics. Two of the ceramics were composites made from powder mixtures of Si3N4 and either 60 vol% TiN or 50 vol% TiB2, while three were monolithic materials, namely Si3N4 with 2.5 wt% Y2O3 as a sintering additive, Si3N4 without additives, and Si2 N2O without additives. A diffusion couple geometry was developed to facilitate the preparation of thin-foil specimens for examination by analytical electron microscopy (AEM). Diffusion bonding was performed by HIP at 927°C (1200K) and 200 MPa for 4 h. The formation of reaction layers was very limited, being less than 1 μm in total layer thickness. Two reaction products were found by AEM; a continuous, very thin, (≤100 nm) layer of fine TiN crystals at the initial ceramic/metal interface, and larger grains extending about 100–500 nm into the superalloy and forming a semi-continuous layer of a G-phase suicide containing mainly nickel, silicon and niobium.
|
|
| 9. |
- Lindberg, K. A. H., et al.
(författare)
-
Morphology of polyamide 6-polybutadiene multiblock copolymers
- 1991
-
Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 26:16, s. 4383-4388
-
Tidskriftsartikel (refereegranskat)abstract
- The morphology of polyamide 6-polybutadiene multiblock copolymers, commonly used for reaction injection moulding, have been investigated using transmission electron microscopy, dynamic mechanical techniques, calorimetry and wide angle X-ray diffraction. Phase separation is found to be almost complete and the crystallization of the PA6 blocks is slightly higher than in pure PA6. The morphology shows similarities to what has been reported for segmented polyether-esters. The PA6 lamellar dimensions found in the micrographs agree with dimensions calculated from melting point depression and X-ray data.
|
|
