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| 2. |
- Björklund, Anders, et al.
(författare)
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Intracerebral grafting of neuronal cell suspensions. I. Introduction and general methods of preparation.
- 1983
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Ingår i: Acta Physiologica Scandinavica. ; Suppl. 522, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The steps involved in the grafting of mesencephalic and septal embryonic tissue in the form of dissociated cell suspensions are described in detail. This includes dissection of the donor embryos, incubation in trypsin, mechanical dissociation, and stereotaxic injection into the brains of adult recipient rats. Some of the technical problems and limitations are discussed.
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| 3. |
- Björklund, Anders, et al.
(författare)
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Intracerebral grafting of neuronal cell suspensions. II. Survival and growth of nigral cells implanted in different brain sites
- 1983
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Ingår i: Acta Physiologica Scandinavica. ; Suppl. 522, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Dissociated dopamine-rich cell suspensions were prepared from the ventral mesencephalon of rat embryos and injected in one or several sites in striatal and non-striatal regions in the dopaminergically denervated brain of adult rats. While the grafts survived well in all sites, the dopamine fibre outgrowth was markedly different depending on whether the grafts occurred in an area normally innervated by the mesencephalic dopamine neurones (i.e. neostriatum or nc. accumbens) or in areas not normally innervated by these neurones (i.e. parietal cortex, lateral hypothalamus or substantia nigra). Moreover, in grafts placed at different sites along the trajectory of the nigrostriatal pathway the outgrowing fibres remained confined to the graft, and there was little evidence that the implanted neurones could elongate their axons along the pathway of the nigrostriatal tract to reach the striatum from a distance. Thus, the intracerebral suspension grafts provided efficient reinnervation of a denervated target only when placed in the immediate vicinity of the target area. The results of multiple graft placements indicate that a relatively complete restoration of a lost innervation should be possible to achieve in large areas of the brain, such as the striatal complex, with the suspension grafting technique.
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| 4. |
- Björklund, Anders, et al.
(författare)
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Intracerebral grafting of neuronal cell suspensions. VI. Survival and growth of intrahippocampal implants of septal cell suspensions
- 1983
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Ingår i: Acta Physiologica Scandinavica. ; Suppl. 522, s. 49-58
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Tidskriftsartikel (refereegranskat)abstract
- The survival and growth of intrahippocampal septal suspension grafts were investigated by acetylcholine esterase (AChE) histochemistry in animals with lesions of the intrinsic septohippocampal cholinergic pathways. AChE was demonstrable in the grafts after the first postoperative week, and AChE-positive fibres were seen to extend into the host hippocampus by 3 weeks. Rapid fibre outgrowth occurred between 3 weeks and 3 months after grafting, and continued at a slower rate thereafter. By 6 months a fairly complete reinnervation of the initially denervated hippocampus was achieved in most specimens, and this persisted at 14 months, the longest postoperative time analysed. A comparison between the development of the AChE-positive neurones in the suspension grafts with that seen during ontogeny in situ suggested that the grafted neurones lagged behind normal development by at least 1 week. Similar to our previous observations on septal grafts implanted as solid tissue pieces, the pattern of the newly-formed AChE-positive innervation in the host hippocampal formation, established from the septal suspension grafts, was remarkably similar to that of the normal AChE-positive septal innervation. This pattern became established as soon as the graft-derived fibres first grew in, suggesting that the ingrowing axons extended and ramified preferentially into those hippocampal subfields which normally receive an AChE-positive innervation from the septal-diagonal band area.
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| 5. |
- Björklund, Anders, et al.
(författare)
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Intracerebral grafting of neuronal cell suspensions. VII. Recovery of choline acetyltransferase activity and acetylcholine synthesis in the denervated hippccampus reinnervated by septal suspension implants
- 1983
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Ingår i: Acta Physiologica Scandinavica. ; Suppl. 522, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The time-course and magnitude of fibre outgrowth from septal suspension grafts injected into the previously denervated hippocampal formation was monitored by measurements of choline acetyltransferase (ChAT), and the activity of the grafted neurons was assessed by measurements of [14C]acetylcholine (ACh) synthesis from [14C]glucose in vitro. Graft-derived ChAT activity was barely detectable 10 days after grafting, but increased sharply between 10 days and 1 month in the areas of the hippocampus located close to the septal implants. By 6 months ChAT activity was restored to near normal levels in all segments of the previously denervated hippocampus. The overall hippocampal [14C]ACh synthesis was also restored to normal levels in the grafted animals, and estimates of the ACh turnover rate suggested that the transmitter machinery of the newly established "septo-hippocampal" connections operated at a rate similar to that of the intrinsic septohippocampal pathway. The intrahippocampal septal suspension grafts, similar to the intrastriatal nigral grafts, thus seem to be capable of maintaining function at a relatively "physiological" level despite their abnormal positions.
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| 6. |
- Björklund, Anders
(författare)
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Studies in the dynamics of unemployment
- 1981
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- From chapter 1: The point of departure for the collection of studies presented in the following is the message delivered by American economists during the beginning of the 70’s that a proper understanding of the unemployment problem requires a dynamic view of the labor market in general and unemployment in particular. The "dynamic view" should emphasize the flows into and out of unemployment. By analyzing these flows a better understanding should be obtained of (i) the causes of unemployment and (ii) the welfare consequences of unemployment. The first study, presented in Chapter 2, aims at giving an empirical picture of "the dynamics of unemployment" in Sweden. Several decompositions of unemployment, which highlight the causes and welfare implications of unemployment, are made. In Chapter 3 one possible explanation to the longer unemployment spells during the seventies is examined, namely the unemployment benefits which were extended in different ways for different groups both in 1968 and in 1974. The analytical approach in the chapter is to analyze the "surviving rates" of the unemployed, i.e. the probability of remaining unemployed from one period (quarter) to the next. In Chapter 4 the same analytical approach is applied to the analysis of the cyclical fluctuations of unemployment spells. The search theoretic literature has suggested two different explanations of these cyclical fluctuations; one has emphasized the importance of inflationary surprises and the other the quantity-rationing constraints facing the unemployed. The empirical importance of these comparative explanations are analyzed using Swedish and U.S. data. A model of the "transition rate" for the unemployed, which captures both mechanisms, is specified. The study in Chapter 5 aims at giving an improved empirical picture of unemployment as a welfare and distributional problem. The first issue analyzed is whether unemployment has deleterious effects on individuals’ subsequent labor market prospects, in particular the subsequent wage level. The second issue analyzed is whether unemployment tends to hit the relatively low-paid in the labor force. The issue whether unemployment duration rather than the stock of unemployed should be the guideline for labor market policy is also discussed in the chapter. In Chapter 6, finally, some important topics for future research in this field are dicussed.
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| 7. |
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| 8. |
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| 9. |
- Björklund, Anders, et al.
(författare)
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Youth Employment in Sweden
- 1983
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Ingår i: Youth at Work. An International Survey. ; , s. 232-268
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Dunnett, S B, et al.
(författare)
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Intracerebral grafting of neuronal cell suspensions. IV. Behavioural recovery in rats with unilateral implants of nigral cell suspensions in different forebrain sites
- 1983
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Ingår i: Acta Physiologica Scandinavica. ; Suppl. 522, s. 29-38
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Tidskriftsartikel (refereegranskat)abstract
- Single and multiple implants of nigral cell suspensions were grafted to the forebrains of rats with unilateral 6-hydroxydopamine-induced dopamine denervations. Control lesions alone induced a marked behavioural asymmetry, as assessed by amphetamine- and apomorphine-induced rotation, sensorimotor tests and side bias in an unbaited T-maze, and the animals were hyperactive to a low dose of apomorphine. Single suspension placements into different denervated striatal regions were capable of reversing the behavioural asymmetries dependent upon the specific placement for each test. Multiple suspension grafts were capable of reversing all behavioural asymmetries, and additionally abolished the supersensitive hyperactivity to apomorphine. By contrast, single suspension grafts placed into the substantia nigra or lateral hypothalamus had no detectable effect on any functional measure. The results indicate that nigral suspension grafts can be at least as effective as solid grafts in reversing the functional deficits induced by dopamine denervation, provided that placements are selected within appropriate dopamine terminal regions of the forebrain (e.g. caudate-putamen or nucleus accumbens).
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