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Duan, Wei-Ming
(författare)
Immunological and Inflammtory Responses against Intrastriatal Neural Grafts in the Rat
1997
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Intracerebral neural transplantation offers a new strategy to combat Parkinson’s and Huntington’s diseases. However, a host immune response against a histoincompatible neural graft in the brain may jeopardize transplant survival. We transplanted dissociated mesencephalic tissue prepared from Sprague-Dawley (SD) (syngeneic), Lewis (allogeneic) rats or mice (xenogeneic), into 6-hydroxydopamine (6-OHDA) lesioned or normal striatum of SD rats. We addressed the following issues: (i) the survival of syngeneic, allogeneic and xenogeneic neural grafts at different time-points after transplantation and the time-pattern of inflammatory and immunological reactions against them. (ii) if a first intrastriatal neural allograft leads to rejection of a second genetically identical allograft. (iii) if neural allografts can survive in the hosts which are immunized using orthotopic skin allografts before and after intracerebral surgery. (iv) the importance of graft immunogenicity for graft survival by supplementing allogeneic neuronal cell suspension with allogeneic spleen cells from the same Lewis donor rats. (v) the impact of severe local inflammation induced by an intrastriatal injection of quinolinic acid on the survival of neural allografts. (vi) the effects of methylprednisolone on the survival of intrastriatal concordant neural xenografts from mice. The results show: (1) Syngeneic and allogeneic neural grafts can survive transplantation to the striatum for prolonged periods. The inflammatory or immunological responses against such grafts are only weak and transient. In contrast, concordant xenogeneic neural grafts are in most cases rejected rapidly. (2) Neural allografts are not rejected by a host which has already received genetically identical allografts before. (3) Neural allografts are rejected if the host is immunized by an orthotopic skin allograft 6 weeks prior to, at the same time as, or 2 weeks after, neural transplantation surgery. However, neural allografts are not always promptly rejected if the orthotopic skin grafting is performed 6 weeks after the neural transplantation, although there is a massive inflammatory and immunological response against them. By 12 weeks after skin grafting, most of these allografts are rejected. (4) Addition of allogeneic spleen cells increases the immunogenicity of neural allografts and leads to rejection of mixed allografts following transplantation. (5) Severe inflammation in the striatum induced by quinolinic acid injection does not result in the rejection of neural allografts. (6) Rejection of concordant neural xenografts can be prevented by systemic administration of a daily high dose of methylprednisolone. In conclusion, the brain is an immunologically privileged site, but this privilege is not absolute. In our animal model, intrastriatal neural allografts can achieve long-term survival probably due to a very low immunogenicity and lack of antigen presenting cells in the grafted neural tissue. Even if neural allografts are implanted in a brain region that is affected by severe inflammation, they survive without clear signs of rejection. Nevertheless, rejection of neural allografts can be induced if the hosts are efficiently immunized with the same alloantigens before or soon after transplantation, rather than at later time-points. Methylprednisolone can be used as an alternative immunosuppressive drug to prevent rejection of concordant intracerebral neural xenografts.
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Ekerot, Carl-Fredrik, et al.
(författare)
Chapter 24 The control of forelimb movements by intermediate cerebellum
1997
Ingår i: Progress in brain research. - 0079-6123. - 0444801049 ; 114, s. 423-429
Bokkapitel (övrigt vetenskapligt/konstnärligt) abstract
In a series of studies, the functional organization of cerebellar regions contributing to the control of forelimb movements via the rubro- and corticospinal tracts has been characterized in the cat. The system consists of the cerebellar cortical C1, C3 and Y zones and their efferent intracerebellar nucleus, the interpositus anterior. Based on analyses of cutaneous and muscle afferent climbing fibre input, of corticonuclear connections and of limb movements controlled, a modular organization of this cerebellar control system is proposed. Each module consists of a number of cortical microzones, defined by their homogeneous climbing fibre input, and a group of neurones in nucleus interpositus anterior on which these microzones converge. The input to climbing fibres is multi-modal and originates from cutaneous A beta (tactile), A delta and C (nociceptive) fibres and from muscle afferents. The cutaneous receptive fields have spatial characteristics suggestive of a relation to elemental movements. For most climbing fibres, the spatial relationship between cutaneous and muscle afferent input is such that the muscle afferent input originates from muscles that, if activated, would tend to move the cutaneous receptive field of the climbing fibre towards a stimulus applied to the skin. By contrast, the limb movement controlled by the module often has the opposite direction, and would thus tend to move the cutaneous receptive field away from a stimulus applied to the skin. Functional implications of this organization for the involvement of these regions in acute and adaptive motor control of limb movements are discussed.
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Friberg, Hans
(författare)
Ischemic and Hypoglycemic Brain Damage, Involvement of the Mitochondrial Permeability Transition Pore
1999
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Brain damage from ischemia-reperfusion and hypoglycemia are major causes of morbidity and mortality. Therapeutic strategies include hypothermia, glutamate-receptor blockade, immunosuppression and lately treatment aiming at preserving mitochondrial integrity and function. Mitochondria are the main producers of cellular energy but mitochondria also participate in cell signaling and take an active part in the life/death decision of a cell. Oxidative stress and high mitochondrial calcium loads can trigger the formation of a large pore in the mitochondrial inner membrane, the mitochondrial permeability transition pore. The consequent disruption of the mitochondrial membrane potential, osmotic swelling and loss of metabolites and mitochondrial proteins through a ruptured outer membrane may lead to immediate or delayed cell death. In this study we demonstrate that isolated mitochondria from different brain regions have different sensitivity to calcium-induced permeability transition and furthermore that this correlates with the selective vulnerability of these regions to ischemia-reperfusion injury. Also, important modulators of the pore such as Bcl-2 and free radical production are altered after ischemia. Thus, Bcl-2 levels decrease at 4h and at 24h after forebrain ischemia in parallel with a 50% increase of free radical production in mitochondria isolated from the vulnerable hippocampus. These alterations are not seen in isolated mitochondria from the more resistant cortex region. We also show that cyclosporin A and MeValCsA, potent blockers of the mitochondrial permeability transition pore, protect neurons from oxygen/glucose deprivation in vitro and from ischemia-reperfusion injury in vivo. Moreover, cyclosporin A protects mitochondria and neurons from hypoglycemic brain damage. We conclude that calcium-induced mitochondrial permeability transition differs between brain regions and that mitochondria from different regions respond differentially to ischemic stress. The results of the present thesis support the view that the mitochondrial permeability transition pore is of importance in the development of brain injury after ischemia-reperfusion and hypoglycemia.
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Gestblom, Carolina
(författare)
Characterization of the perturbed differentiation in neuroblastoma, aided by the analysis of normal sympathetic nervous system development
1997
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Neuroblastoma is a pediatric tumor derived from cells in the sympathetic nervous system. In an attempt to explain the heterogeneous clinical behavior of neuroblastoma tumors, neuroblastomas have been characterized with regard to their degree of sympathetic differentiation. Their expression of genes and proteins that regulate normal sympathetic development and cell cycle/cell death regulators was assessed by in situ hybridization and immunohistochemistry. The cell types of the developing prenatal sympathetic nervous system were also characterized in order to identify marker genes that distinguish between neuronal and neuroendocrine sympathetic cell types. Principally two groups of neuroblastomas have been identified. Unfavorable prognosis, nondifferentiating neuroblastomas expressed marker genes of immature sympathetic neuroblasts. Differentiating neuroblastoma tumors, often with favorable prognosis, also expressed neuronal marker genes, but only in the immature, proliferating cells adjacent to the fibrovascular stroma. With increasing distance from the stroma, these tumor cells cease to proliferate, downregulate their expression of neuronal marker genes, differentiate, and upregulate their expression of neuroendocrine marker genes. Thus, it appears that in these tumors initially neuroblastic cells mature towards a neuroendocrine lineage. Also cell cycle and cell death regulators were expressed in a physiological context resembling normal cellular behavior in these tumors. Proliferating cells expressed Bcl-2. With differentiation, cells downregulate Bcl-2 and upregulate p53. Cells adjacent to the p53 expressing cells die by apoptosis. Karyorrhectic cells, as defined by the mitosis-karyorrhexis index, were identified to be either proliferating or apoptotic. Neuroblastoma cell lines, established from high stage tumors, were analyzed with regard to their inability to respond to nerve growth factor (NGF). These cell lines expressed the high-affinity NGF receptor TrkA and the low-affinity receptor, and yet they did not respond to NGF. By the introduction of exogenous TrkA, NGF-responsiveness was partly restored in these cell lines.
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Gidö, Gunilla
(författare)
Mechanisms of Brain Damage Following Focal Cerebral Ischemia: Changes in Ion Homeostasis and the Importance of Free Radical Formation
1998
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In this thesis mechanisms of neuronal damage were investigated in an experimental stroke model i.e focal ischemia. The influence of SD-induced calcium transients on neuronal damage were studied in animals with reduced energy supply. The influence of bioenergetic failure on K+e concentration and Ca2+e homeostasis were also investigated in transient focal ischemia. Moreover, the free radical formation was assessed in focal ischemia/reperfusion, as was the scavenging effect of PBN. Animals with a reduction in energy supply showed prolonged SD-induced calcium transients. These prolonged calcium lead occasionally to mild neuronal damage. Similar SDs are recorded in the ischemic penumbra in focal ischemia, and are probably caused by decreased energy supply. The second bioenrgetic failure in the ischemic focus as recorded in K+e concentration increase occurs at 4-6 h of reperfusion after 2 h MCAO. Treatment with PBN delays or prevent the late increase in K+e level. Recordings of Ca2+e and total calcium content in focal ischemia /reperfusion showed disturbed calcium homeostasis in the cortical core and penumbral zone. Free radical formation were enhanced in the recirculation phase after 2 h MCAO, and treatment with PBN did not reduce these free radical formation. It is concluded that the cellular calcium load in energy compromised brain tissue is tolerated without extensive neuronal damage. This indicates that other mechanisms than only exaggerated calcium transients lead to development of the infarct in focal ischemia. Recordings of Ca2+e and total calcium content in focal ischemia /reperfusion suggest that the tissue is irreversibly damaged after 6 h of recirculation. The lack of an effect of BPN treatment despite its neuroprotective effect may suggest that PBN is effective in small compartments e.g the endothelium.
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Hansson, Stefan R
(författare)
The Serotonin Transporter and the Vesicular Monoamine Transporters During Development
1998
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In the present study, the mRNA encoding the serotonin transporter (5-HTT) and two isoforms of the vesicular monoamine transporters (VMAT1 and VMAT2) have been mapped in the rat throughout gestation and early postnatal development using in situ hybridization, RT PCR and immunohistochemistry. 5-HTT mRNA was found in serotonergic neurons and VMAT2 mRNA in all monoaminergic neurons from early gestation. A transient 5-HTT and VMAT2 mRNAs expression was also detected in thalamic neurons lacking tryptophan hydroxylase (TPH), the enzyme of 5-HT synthesis. VMAT1 mRNA was expressed in several limbic structures, cerebellum and the subventricular zone. In peripheral structures 5-HTT and both VMAT mRNAs were expressed in neural crest derived tissues such as autonomic and sensory ganglia. In addition, VMAT1 mRNA was expressed by organs of the endocrine system. Neuroepithelial cells were isolated from the snout and identified as Merkel cells. These cells exclusively expressed 5-HTT mRNA and were in vitro shown to have a transient, fluoxetine sensitive 3H-5-HT uptake. Unilateral denervation of the snout was shown to decrease specific 5-HTT binding in thalamus suggesting that particular pathways may be vulnerable during critical periods. The wide expression of 5-HTT and VMAT mRNAs in the developing embryo suggests potential new roles for monoamines transporters in establishing the wiring of the different sensory pathways as well as maintaining an appropriate microenvironment for migrating and differentiating neural crest cells. Our findings provide a guide for future studies on the role of monoamines during development.
