Showing papers by "Anders Björklund published in 1991"
TL;DR: NGF-infused rats showed improved retention of previously acquired place navigation performance and improved spatial acuity over the former platform site when the invisible platform was removed and NGF infusion also had a significant effect in the much more severely impaired 30-month-old rats.
Abstract: Aged rats were tested for place navigation in a circular water maze for spatial memory ability at 18 and 30 months of age; 45% of the 18-month-old rats displayed impaired place navigation performance relative to young control rats, while essentially all of the 30-month-old rats were impaired The aged impaired rats were retested twice during NGF or vehicle infusion in the right lateral ventricle In the 18-month-old group, NGF-infused rats showed improved retention of previously acquired place navigation performance and improved spatial acuity over the former platform site when the invisible platform was removed NGF infusion also had a significant effect in the much more severely impaired 30-month-old rats: while the vehicle-infused aged rats showed a progressive decline in the performance between the first and second test weeks, the performance of the NGF-infused rats remained stable throughout the infusion period The interpretation of these effects in the oldest animals, however, was confounded by a progressive decline in swim speed seen in the vehicle-infused animals The 30-month-old vehicle-infused control rats showed a significant cell loss and cell shrinkage relative to the young control rats in the septal/diagonal band area, the striatum, and the nucleus basalis as assessed by NGF-receptor (NGFr) and ChAT double-label immunocytochemistry A significant increase in the size but not in the number of cells was observed on the side of the NGF infusion in the 30-month-old NGF-infused rats(ABSTRACT TRUNCATED AT 250 WORDS)
263 citations
160 citations
TL;DR: Grafts implanted into dopamine-denervated hosts showed a normal morphological maturation of both DARPP-32-positive and -negative areas, although no tyrosine hydroxylase-positive innervation appeared within the grafts.
101 citations
TL;DR: It is concluded that graft‐to‐host projections, running along and inside host myelinated bundles, are formed from intrastriatal striatal grafts within 1–2 weeks of implantation, consistent with previous work showing that outgrowing axons lose their M6 immunoreactivity as they mature and become myelination.
Abstract: The developmental time-course and growth characteristics of efferent graft-to-host projections were studied from mouse fetal striatal grafts (E13 - 14) implanted as a cell suspension into the ibotenate-lesioned striatum of immunosuppressed adult rats. A cell surface monoclonal antibody specific for mouse neurons (M6) was used to identify the donor cells and their projections into the host brain. At 3 - 5 days after implantation, sparse fascicles of M6-positive graft-derived fibres extended for approximately 0.3 - 0.4 mm across the graft - host border into the surrounding host striatum. From the beginning they were selectively orientated in one direction, i.e. caudally along the myelinated fibre bundles of the internal capsule. At 8 days, the graft-derived fibres were more numerous and more densely labelled. They ran in dense fascicles inside the myelinated bundles of the host internal capsule and reached the rostral host globus pallidus, a distance of approximately 1.2 mm from the caudal tip of the graft. Two weeks after grafting, the M6-positive fibre fascicles were clearly seen to branch within the globus pallidus to form terminal-like networks. From this time onwards, the immunoreactivity of the outgrowing fibre fascicles gradually diminished, although small but dense terminal-like networks could be found in the host globus pallidus in most, but not all, of the rats at longer survival times (3 - 15 weeks). This is consistent with previous work showing that outgrowing axons lose their M6 immunoreactivity as they mature and become myelinated. Control grafts of fetal neocortical and fetal cerebellar tissue were used to assess the tissue-type specificity of the efferent fibre growth. The neocortical implants projected densely up to about 3 mm into the host brain, along the internal capsule and the corpus callosum and into the overlying cortex. By contrast, although the cerebellar grafts survived well, they showed very little efferent fibre growth. Double immunostaining for DARPP-32 and M6 revealed that all M6-positive fibre fascicles extending from the striatal (but not neocortical) grafts also showed DARPP-32 positivity, and thus that it was the DARPP-32-positive regions of the striatal grafts that projected to the host brain. It is concluded that graft-to-host projections, running along and inside host myelinated bundles, are formed from intrastriatal striatal grafts within 1 - 2 weeks of implantation. Grafts of neocortical tissue grew well along the same trajectory, whereas neurons of a type not normally projecting along the internal capsule, i.e. cerebellum, failed to extend axons over any significant distance along this trajectory.
87 citations
TL;DR: The results indicate that hippocampal ACh release is maintained in aged rats that exhibit severe spatial learning and memory impairments and that the septo-hippocampal cholinergic system retains its capacity to increase its A Ch release in response to both K(+)-induced depolarization and behavioral activation in the aged rat.
72 citations
TL;DR: It is concluded that down-regulation of marker proteins, such as AChE and NGFr, and cellular atrophy precede cell death in the axotomized septohippocampal system and that about 1/3 of the axonia-fornix septal cholinergic neurons may survive for a long time in a down-regulated atrophic state.
71 citations
TL;DR: In this paper, the authors investigated the relationship between unemployment and the personal distribution of income using Swedish time-series data and found that higher unemployment risks are highest among people with low earnings capacity, even when they have a job.
Abstract: For a long time, Swedish politicians have been devoted to keeping unemployment at low levels. The main reason for this devotion is probably the belief that higher unemployment increases inequality of income and welfare. This is a reasonable belief since unemployment risks are highest among people with low earnings capacity, even when they have a job. By means of micro data it is easy to verify a marked low-income profile of unemployment. Further, the Swedish unemployment insurance system replaces only about 70 per cent of foregone income and quite many unemployed do not qualify for any benefits; see Bjorklund and Holmlund (1991). Increases in unemployment, however, are associated with many changes in the economy with complex consequences for the personal distribution of income. In addition to the income losses suffered by those who become unemployed, higher unemployment also affects the factor shares of income. The profit share typically declines during recessions and because upper-income groups receive a relatively high proportion of their income from capital income, a countervailing mechanism is involved. Changes in unemployment also affect inflation which, in turn, might influence the personal distribution of income. The distributional effects of inflation are an open question. This note makes an investigation into the relationship between unemployment and the personal distribution of income using Swedish time-series data. The method was first used on U.S. data by Blinder and
59 citations
Book•
25 Jul 1991
TL;DR: In this article, the authors evaluate the economic performance of direct job creation in the United States and Western Europe and present some theoretical and economic lessons for the US and Western European countries about what works and for whom.
Abstract: Part 1 Direct job creation - economic evaluation and lessons for the United States and Western Europe: employment and training policy - some theoretical considerations employment and training policy - macro-economic and exchange rate implications evaluation of job creation programmes what do we know about what works and for whom? conclusions and appendix cost-benefit rules for job-training programmes labour market training - the lesson from Swedish evaluations. Part 2 The economics of unemployment insurance - the case of Sweden: problems in insurance markets the Swedish system incentive effects unemployment insurance and income distribution aspects of optimal unemployment insurance.
29 citations
TL;DR: The results indicate that the locus coeruleus grafts, despite their ectopic location, can become functionally integrated with the hostbrain, and that the activity of the transplanted noradrenergic neurons can, under some circumstances, be modulated from the host brain in response to environmental challenges.
Abstract: Release properties of intrahippocampal transplants of noradrenergic neurons were monitored by microdialysis in awake and halothane-anaesthetized rats. Fetal locus coeruleus neurons were implanted as a cell suspension into hippocampi deprived of their innate noradrenalin (NA) innervation by intraventricular 6-hydroxydopamine treatment. Dialysis probes of the loop type were implanted into the dorsal hippocampus 1 - 2 days before each experiment, i.e. 7 - 11 months after grafting. Age-matched intact and lesion-only animals served as controls. Microscopic analysis showed a graft-derived tyrosine hydroxylase immunoreactive, presumably noradrenergic, fibre network throughout the dorsal hippocampal formation, surrounding the probe site. The innervation density varied from sub- to supranormal. The grafts restored baseline NA release in the graft-reinnervated hippocampus to near-normal levels both in awake and halothane-anaesthetized animals. Potassium chloride (100 mM) in the perfusion fluid induced a dramatic increase in NA release that was similar in magnitude in the grafted and intact hippocampi. A NA uptake blocker (desipramine) added to the perfusion fluid at 5 microM induced a similar increase in NA output in the grafted and intact hippocampi, and the output was substantially reduced by tetrodotoxin, added at 1 microM in the presence of uptake blockade. Electrical stimulation of the lateral habenular nucleus (15 Hz, 0.5 mA) in halothane-anaesthetized rats induced a significant increase in NA output both in the intact and grafted hippocampi. This effect was abolished by transection of the fasciculus retroflexus, which carries the efferent projections of the habenular complex. Behavioural activation through handling induced a consistent increase in NA release only in the intact animals, but in a few grafted rats (which also responded to habenular stimulation) the NA output was clearly elevated by handling. Forced immobilization induced a significant increase in NA output both in the intact and grafted hippocampi, but in the grafted ones the response was somewhat smaller and more transient. In the same set of animals, swimming in warm water (25 - 30 degrees C) induced a sharp increase in NA output in the intact animals, whereas only one of the grafted rats responded by increased NA output. The results indicate that the locus coeruleus grafts, despite their ectopic location, can become functionally integrated with the host brain, and that the activity of the transplanted noradrenergic neurons can, under some circumstances, be modulated from the host brain in response to environmental challenges.
17 citations
Journal Article•
TL;DR: Interestingly, in denervated striatum, grafts of modified fibroblast cells produce DOPA which was efficiently converted into dopamine by the host striatal tissue, and the implications of these results in the context of Parkinson disease are discussed.
Abstract: The relative importance of synaptic versus paracrine dopamine transmission for the occurrence of functional effects following intrastriatal grafting is not fully established. In the present study we grafted cell lines, expressing the form I of human tyrosine hydroxylase after infection with a recombinant retrovirus and selection in tyrosine-free-medium, to the denervated striatum in order to analyse the extent to which extracellular dopamine levels can be restored and the effect of a diffuse release of dopamine on motor impairement in a rat model of Parkinson's disease. In petri dish, the modified fibroblast cells (NIH.3T3) release DOPA constitutively whereas the modified endocrine cells (RIN) store and release dopamine in a regulated way. Interestingly, in denervated striatum, grafts of modified fibroblast cells produce DOPA which was efficiently converted into dopamine by the host striatal tissue. In the grafted striatum, both fibroblast and endocrine cells restore subnormal levels of diffuse release of dopamine which is notably unaffected and stimulated, respectively, by high concentration of potassium, in connection with the in vitro properties of the grafted cells. The intrastriatal grafts of modified cells partially reversed the apomorphine-induced but not the amphetamine-induced motor asymmetry. We discuss the implications of these results in the context of Parkinson disease.
15 citations