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- Eriksson, Peter S, 1959, et al.
(författare)
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Neurogenesis in the adult human hippocampus
- 1998
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Ingår i: Nat Med. - 1078-8956. ; 4:11, s. 1313-7
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Tidskriftsartikel (refereegranskat)abstract
- The genesis of new cells, including neurons, in the adult human brain has not yet been demonstrated. This study was undertaken to investigate whether neurogenesis occurs in the adult human brain, in regions previously identified as neurogenic in adult rodents and monkeys. Human brain tissue was obtained postmortem from patients who had been treated with the thymidine analog, bromodeoxyuridine (BrdU), that labels DNA during the S phase. Using immunofluorescent labeling for BrdU and for one of the neuronal markers, NeuN, calbindin or neuron specific enolase (NSE), we demonstrate that new neurons, as defined by these markers, are generated from dividing progenitor cells in the dentate gyrus of adult humans. Our results further indicate that the human hippocampus retains its ability to generate neurons throughout life.
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- Ahlström, Håkan, et al.
(författare)
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Preoperative localization of endocrine pancreatic tumours by intra-arterial dynamic computed tomography
- 1990
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Ingår i: Acta Radiologica. - 0284-1851 .- 1600-0455. ; 31:2, s. 171-175
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Tidskriftsartikel (refereegranskat)abstract
- Eleven patients with biochemically confirmed endocrine pancreatic tumours were examined with intra-arterial (i.a.) dynamic computed tomography (CT) and angiography preoperatively. Seven of the patients suffered from the multiple endocrine neoplasia type 1 (MEN-1) syndrome. All patients were operated upon and surgical palpation and ultrasound were the peroperative localization methods. Of the 33 tumours which were found at histopathologic analysis of the resected specimens in the 11 patients, 7 tumours in 7 patients were correctly localized by both i.a. dynamic CT and angiography. Six patients with MEN-1 syndrome had multiple tumours and this group of patients together had 28 tumours, of which 5 (18%) were localized preoperatively by both CT and angiography. I.a. dynamic CT, with the technique used by us, does not seem to improve the localization of endocrine pancreatic tumours, especially in the rare group of MEN-1 patients, as compared with angiography.
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- Asplund, Martin, et al.
(författare)
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Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars
- 1997
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 318:2, s. 521-534
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum o
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- Björk-Eriksson, Thomas, 1960, et al.
(författare)
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The in vitro radiosensitivity of human head and neck cancers
- 1998
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Ingår i: Br J Cancer. - 0007-0920. ; 77:12, s. 2371-5
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of the intrinsic radiosensitivity of 140 biopsy and surgical specimens of malignant head and neck tumours of different histologies. Using a soft-agar clonogenic assay, the material was assessed for the ability to grow in culture (colony-forming efficiency; CFE) and inherent tumour radiosensitivity (surviving fraction at 2 Gy, SF2). The success rate for obtaining growth was 74% (104/140) with a mean CFE of 0.093% (median 0.031) and a range of 0.002-1.3%. SF2 was obtained for 88 of 140 specimens, representing a success rate of 63% with a mean SF2 of 0.48 (median 0.43) and a range of 0.10-1.00. There were no significant differences in radiosensitivity between different sites of the head and neck region. There were no significant relationships between SF2 and disease stage, nodal status, tumour grade, patient age, primary tumour growth pattern and CFE. The results were compared with those for other tumour types previously analysed with the same assay. The distribution of the SF2 values for the head and neck tumours was similar to that for 145 cervix carcinomas and there was no significant difference in mean radiosensitivity between the two tumour types. Also, there was no significant difference in radiosensitivity between head and neck tumours and either breast or colorectal cancers. However, a group of eight lymphomas was significantly more radiosensitive. These results confirm the feasibility of carrying out radiosensitivity measurements using a soft-agar clonogenic assay on head and neck tumours. In addition, the work has shown that radiosensitivity is independent of many clinical parameters and that the mean value is similar to that reported for cervix carcinomas.
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- Campbell, D, et al.
(författare)
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The cyanobacterium Synechococcus resists UV-B by exchanging photosystem II reaction-center D1 proteins
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424 .- 1091-6490. ; 95:1, s. 364-369
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Tidskriftsartikel (refereegranskat)abstract
- Current ambient UV-B levels can significantly depress productivity in aquatic habitats, largely because UV-B inhibits several steps of photosynthesis, including the photooxidation of water catalyzed by photosystem II, We show that upon UV-B exposure the cyanobacterium Synechococcus sp, PCC 7942 rapidly changes the expression of a family of three psbA genes encoding photosystem II D1 proteins, In wild-type cells the psbAI gene is expressed constitutively, but strong accumulations of psbAII and psbAIII transcripts are induced within 15 min of moderate UV-B exposure (0.4 W/m(2)), This transcriptional response causes an exchange of two distinct photosystem II D1 proteins, D1:1 is encoded by psbAI, but on UV-B exposure, it is largely replaced by the alternate D1:2 form, encoded by both psbAII and psbAIII, The total content of D1 and other photosystem II reaction center protein, D2, remained unchanged throughout the UV exposure, as did the content and composition of the phycobilisome, Wild-type cells suffered only slight transient inhibition of photosystem II function under UV-B exposure, In marked contrast, under the same UV-B treatment, a mutant strain expressing only psbAI suffered severe (40%) and sustained inhibition of photosystem II function, Another mutant strain with constitutive expression of psbAII and psbAIII was almost completely resistant to the UV-B treatment, showing no inhibition of photosystem II function and only a slight drop in electron transport, In Synechococcus the rapid exchange of alternate D1 forms, therefore, accounts for much of the cellular resistance to UV-B inhibition of photosystem II activity and photosynthetic electron transport, This molecular plasticity may be an important element in community-level responses to UV-B, where susceptibility to UV-B inhibition of photosynthesis changes diurnally.
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- Eriksson, Kent, 1964-, et al.
(författare)
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EXPERIENTIAL KNOWLEDGE AND COST IN THE INTERNATIONALIZATION PROCESS
- 1997
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Ingår i: Journal of International Business Studies. - : Palgrave Macmillan. - 0047-2506 .- 1478-6990. ; 28:2, s. 337-360
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Tidskriftsartikel (refereegranskat)abstract
- Using a behavioral approach, this study identifies and delineates components of experiential knowledge in the internationalization process. Three hypotheses are developed and tested. They center around the lack of knowledge in the areas of foreign business, foreign institutions and firm internationalization, as well as the effect that this lack of knowledge has on the managers´ perceived cost in the internationalization process. With the help of a LISREL-based structural model, the three hypotheses are tested on a sample of 362 service firms. The analysis shows that lack of internationalization knowledge has a strong impact on the lack of both business and institutional knowledge which, in turn, influence the perceived cost in internationalization. But there is no direct effect of lack of internationalization knowledge on perceived cost in internationalization.
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