Tidsskrift For Den Norske Laegeforening, Apr 1, 2006
One of several probable causation theories of Parkinson disease postulates that brain tissue cann... more One of several probable causation theories of Parkinson disease postulates that brain tissue cannot generate sufficient levels of various growth factors required to sustain the viability of dopamine-producing nerve cells in the presence of as yet unknown toxic factors. The study reported here evaluates the ability of externally applied growth factors to protect the dopamine fibres in the basal ganglia in a toxin-induced animal model of the disease. All animals (rats) were subjected to selective destruction of the dopamine-producing cells in substantia nigra. The rats were divided into three groups. Two groups received intracerebral treatment with either glia-cell derived neurotrophic factor (GDNF) or a combination of brain-derived neurotrophic factor (BDNF) and GDNF. The third group acted as untreated controls and were given sterile saline. The growth factors were infused directly into the brain by an osmotic pump over a period of 28 days. Brain sections taken from all three groups were evaluated by immunocytochemistry. The two groups of rats that received growth factor infusion displayed a significant improvement in their motor behaviour compared to control animals. Immunocytochemistry studies demonstrated that the group receiving a combination of GDNF and BDNF had an increased number of surviving active fibres in the dopamine system striatum in comparison to the control and GDNF groups. In addition the infusion of growth factors resulted in a proliferation of subventricular cells in the basal ganglia. The improved motor function following growth factor treatment in this rat model might be due to a delayed retrograde degeneration of the nigrostriatal nerve fibers. Growth factor infusion also clearly stimulated endogenous stem cells and caused their migration towards the striatum. Our observations indicate that the infusion of growth factors into the brain have a symptomatic and neuroprotective effect in this model.
Tidsskrift for den Norske lægeforening : tidsskrift for praktisk medicin, ny række, Jan 23, 2006
One of several probable causation theories of Parkinson disease postulates that brain tissue cann... more One of several probable causation theories of Parkinson disease postulates that brain tissue cannot generate sufficient levels of various growth factors required to sustain the viability of dopamine-producing nerve cells in the presence of as yet unknown toxic factors. The study reported here evaluates the ability of externally applied growth factors to protect the dopamine fibres in the basal ganglia in a toxin-induced animal model of the disease. All animals (rats) were subjected to selective destruction of the dopamine-producing cells in substantia nigra. The rats were divided into three groups. Two groups received intracerebral treatment with either glia-cell derived neurotrophic factor (GDNF) or a combination of brain-derived neurotrophic factor (BDNF) and GDNF. The third group acted as untreated controls and were given sterile saline. The growth factors were infused directly into the brain by an osmotic pump over a period of 28 days. Brain sections taken from all three groups ...
Regimens with ranitidine bismuth citrate (RBC) or omeprazole (O) are effective in eradicating Hel... more Regimens with ranitidine bismuth citrate (RBC) or omeprazole (O) are effective in eradicating Helicobacter pylori. This randomized, open, multicentre trial compares three different regimens with these drugs. Consecutive H. pylori +ve outpatients were included. The alternative regimens were: 1) O 20 mg, clarithromycin (C) 250 mg and metronidazole (M) 500 mg (O.C.M), 2) RBC 400 mg, C 250 mg and M 500 mg (RBC.C.M), 3) RBC 400 mg, tetracycline (T) 1000 mg and M 500 mg [RBC.T.M]. All drugs were given twice daily for 7 days. H. pylori infection was assessed with H. pylori urea breath tests. 426 H. pylori +ve patients were included (mean age 58 years [range 18-88], male/female: 244/182). The eradication rates (intention to treat) in the O.C.M, RBC.C.M and RBC.T.M groups were 117/137 (85%), 141/146 (97%) and 117/143 (82%), respectively (P < 0.001, overall assessment). There were no significant differences in side effects between the alternatives. In this trial, RBC.C.M was the most effective one, it was well tolerated and compliance was satisfactory. RBC.T.M is an alternative to regimens with clarithromycin.
European Journal of Gastroenterology & Hepatology, 1998
In this study we compared the cure rates of two clarithromycin-based regimens in patients in whom... more In this study we compared the cure rates of two clarithromycin-based regimens in patients in whom anti-Helicobacter pylori therapy had previously failed. Thirty-three patients were randomized to receive either regimen OAC (20 mg omeprazole, 750 mg amoxicillin, and 250 mg clarithromycin) or BTC (240 mg bismuth subcitrate, 750 mg oxytetracycline, and 250 mg clarithromycin), all twice daily for 10 days. A further 28 patients were all treated with OAC. Previously failed therapy included combinations of bismuth (B), omeprazole (O), tetracycline (T), metronidazole (M), amoxicillin (A), or clarithromycin (C) in BTM (n = 48), OAM (n = 13), OA (n = 7), OCM (n = 2), or BCM (n = 1). H. pylori infection was confirmed by culture of biopsy specimens, and antimicrobial susceptibility testing was performed with the E test. H. pylori infection was cured in all patients (n = 18) with OAC and in 8 patients (53%) with BTC (P = 0.001) in the randomized group and in 27 patients (96%) receiving OAC in the open-label group. Ten-day OAC is highly effective and superior to BTC in patients in whom metronidazole-based treatment has previously failed.
Expression of the growth arrest DNA damage-inducible protein,GADD45, has recently been reported t... more Expression of the growth arrest DNA damage-inducible protein,GADD45, has recently been reported to be induced by a wide range of stimuli, especially those that produce a high level of base pair damage. We have investigated the expression ofGADD45in brain tissue obtained from patients suffering from Alzheimer's disease (AD). Our results demonstrate that many neurons express theGADD45protein, and that expression of this protein in neurons is associated with expression of the anti-apoptotic proteinBcl-2, and the presence of DNA damage, but not closely associated with tangle-bearing neurons. Additionally, cell lines overexpressing this protein confer resistance to apoptosis induced by DNA damage agent, suggesting that this protein may participate in cell survival mechanisms.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
The water permeability of cell membranes differs by orders of magnitude, and most of this variabi... more The water permeability of cell membranes differs by orders of magnitude, and most of this variability reflects the differential expression of aquaporin water channels. We have recently found that the CNS contains a member of the aquaporin family, aquaporin-4 (AQP4). As a prerequisite for understanding the cellular handling of water during neuronal activity, we have investigated the cellular and subcellular expression of AQP4 in the retina and optic nerve where activity-dependent ion fluxes have been studied in detail. In situ hybridization with digoxigenin-labeled riboprobes and immunogold labeling by a sensitive postembedding procedure demonstrated that AQP4 and AQP4 mRNA were restricted to glial cells, including MHller cells in the retina and fibrous astrocytes in the optic nerve. A quantitative immunogold analysis of the MHller cells showed that these cells exhibited three distinct membrane compartments with regard to AQP4 expression. End feet membranes (facing the vitreous body ...
One of the major problems in glutamate immunocytochemistry has been the difficulty involved in se... more One of the major problems in glutamate immunocytochemistry has been the difficulty involved in separating immunocytochemical labelling due to metabolic glutamate from the labelling caused by transmitter glutamate. Another problem appears to be the accessibility of antigenic sites in conventional light microscopic preparations. In the present report, we have applied the primary glutamate antiserum onto ultrathin tissue sections, followed by the use of a colloidal gold detection system. The use of this postembedding immunogold procedure allows equal access of antibodies to all cellular compartments exposed at the section surface, allows quantitative assessment of the immunoreactivity, and affords a high resolution compatible with studies at the organelle level. When applied to slice preparations the immunogold procedure can be used to identify releasable pools of glutamate. These methodological advances have greatly increased the usefulness of glutamate immunocytochemistry as a tool t...
Glutamate, a major excitatory transmitter substance, is neurotoxic at high concentrations. Brain ... more Glutamate, a major excitatory transmitter substance, is neurotoxic at high concentrations. Brain dialysis experiments have demonstrated an extracellular overflow of glutamate during ischemia, and there is good evidence from several animal models that glutamate antagonists offer partial protection against the development of ischemic cell degeneration. These and other experimental data indicate that glutamate may be involved in the pathogenesis of ischemic brain damage. Quantitative immunocytochemical investigations carried out in the authors' laboratory suggest that ischemia is associated with loss of glutamate from nerve cell bodies, and reduced ability of the glial cells to metabolize glutamate. We discuss possibilities of new therapeutic strategies.
Alzheimer's disease (AD) is associated with the accumulation of extracellular deposits of the... more Alzheimer's disease (AD) is associated with the accumulation of extracellular deposits of the beta-amyloid protein (Abeta). Abeta is a result of misprocessing of the beta-amyloid precursor protein (APP). Gamma-secretase is involved in APP misprocessing and one hypothesis holds that this secretase is identical to PS1. We tested this hypothesis by determining whether PS is co-localised with Abeta in situ. Using confocal analyses and a sensitive immunogold procedure we show that PS and Abeta are co-localised within discrete microdomains of neuronal plasma membranes in AD patients and in aged dogs, an established model of human brain aging. Our data indicate that APP misprocessing occurs in discrete plasma membrane domains of neurons and provide evidence that PS1 is critically involved in Abeta formation.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
The water permeability of cell membranes differs by orders of magnitude, and most of this variabi... more The water permeability of cell membranes differs by orders of magnitude, and most of this variability reflects the differential expression of aquaporin water channels. We have recently found that the CNS contains a member of the aquaporin family, aquaporin-4 (AQP4). As a prerequisite for understanding the cellular handling of water during neuronal activity, we have investigated the cellular and subcellular expression of AQP4 in the retina and optic nerve where activity-dependent ion fluxes have been studied in detail. In situ hybridization with digoxigenin-labeled riboprobes and immunogold labeling by a sensitive postembedding procedure demonstrated that AQP4 and AQP4 mRNA were restricted to glial cells, including MHller cells in the retina and fibrous astrocytes in the optic nerve. A quantitative immunogold analysis of the MHller cells showed that these cells exhibited three distinct membrane compartments with regard to AQP4 expression. End feet membranes (facing the vitreous body ...
In situ hybridization techniques and quantitative western blotting were used to study the express... more In situ hybridization techniques and quantitative western blotting were used to study the expression of the glial glutamate transporter GLT-1 and GLAST in the brains of normal (implanted, non-kindled) and fully kindled rats. Wistar rats were implanted with stimulating electrodes in the basolateral amygdala, and killed 28 days after the stimulated group had shown stage 5 seizures on five occasions. The brains were processed for in situ hybridization of messenger RNA for GLT-1 using 35S-labelled oligonucleotide probes or digoxigenin-labelled riboprobes. Paired (kindled and non-kindled) sections were used for qualitative and quantitative analyses. Image analysis of autoradiograms showed no change in expression of GLT-1 messenger RNA in any region of the hippocampus or in the cortex. An increase in expression of GLT-1 messenger RNA (expressed as percentage difference of control) was observed bilaterally in the striatum in kindled animals (16-21%, P<0.05). Nuclear emulsion-dipped sect...
Little is known about how amyloid-beta (Abeta) is deposited in relation to the complex ultrastruc... more Little is known about how amyloid-beta (Abeta) is deposited in relation to the complex ultrastructure of the brain. Here we combined serial section immunoelectron microscopy with 3D reconstruction to elucidate the spatial relationship between Abeta deposits and ultrastructurally identified cellular compartments. The analysis was performed in a transgenic mouse model with mutant presenilin-1, and mutant amyloid-beta protein precursor (AbetaPP) and tau transgenes (3xTg-AD mice) and in aged dogs that develop Abeta plaques spontaneously. Reconstructions based on serial ultrathin sections of hippocampus (mice) or neocortex (dogs) that had been immunolabeled with Abeta (Abeta(1-42)) antibodies showed that the organization of extracellular Abeta deposits is more complex than anticipated from light microscopic analyses. In both species, deposits were tightly associated with plasma membranes of pyramidal cell bodies and major dendrites. The deposits typically consisted of thin sheets as well...
The effect of 20 min of ischemia on the cellular and subcellular distribution of glutamate, gluta... more The effect of 20 min of ischemia on the cellular and subcellular distribution of glutamate, glutamine and taurine in the rat hippocampus was studied by means of an immunocytochemical procedure based on antisera raised against protein glutaraldehyde conjugates of the respective amino acids. Forebrain ischemia was induced by temporary occlusion of the common carotid arteries in rats with permanently occluded vertebral arteries. Within 90 s after removal of the carotid ligatures, the rats were perfused through the heart with a mixture of glutaraldehyde and paraformaldehyde. For semiquantitative electron microscopic analysis, ultrathin sections were incubated in a primary antiserum followed by a secondary antibody coupled to colloidal gold particles. The gold particle densities over different tissue compartments within the CA1 field and the mossy fiber zone of the hippocampus were determined by means of a specially designed computer program, and values from normal and ischemic animals were compared. It was found that in the astrocytes, the level of immunoreactivity for glutamine and taurine is unchanged or slightly decreased after ischemia, while that for glutamate is increased, particularly within the mitochondria (by about 100%). In contrast, pyramidal cell bodies display a reduced immunolabeling for all three amino acids following the ischemic episode. The results show that ischemia causes a redistribution of glutamate from neurons to glia. The observed increase in the glial immunolabeling for glutamate indicates that the capacity of the glial cells to metabolize glutamate is exceeded during ischemia. This glial response to ischemia has not previously been recognized and may play a role in the chain of events leading to &quot;excitotoxic&quot; cell death during or following an ischemic episode. The reduction of glutamate and taurine immunolabeling in neurons points to a possible amino acid efflux and is compatible with previous biochemical studies demonstrating an elevated extracellular level of these amino acids during ischemia.
Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astr... more Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astrocytes. Astrocytic endfoot membranes exhibit tenfold higher densities of AQP4 than non-endfoot membranes, making AQP4 an excellent marker of astrocyte polarization. Loss of astrocyte polarization is known to compromise astrocytic function and to be associated with impaired water and K+ homeostasis. Here we investigate by a combination of light and electron microscopic immunocytochemistry whether amyloid deposition is associated with a loss of astrocyte polarization, using AQP4 as a marker. We used the tg-ArcSwe mouse model of Alzheimer's disease, as this model displays perivascular plaques as well as plaques confined to the neuropil. 3D reconstructions were done to establish the spatial relation between plaques and astrocytic endfeet, the latter known to contain the perivascular pool of AQP4. Changes in AQP4 expression emerge just after the appearance of the first plaques. Typically,...
Multiphoton Microscopy in the Biomedical Sciences VIII, 2008
Cerebrovascular pathology is closely coupled to cognitive function decline, as indicated by numer... more Cerebrovascular pathology is closely coupled to cognitive function decline, as indicated by numerous studies at the system level. To better understand the mechanisms of this cognitive decline it is important to resolve how pathological changes in the vasculature - such as perivascular plaques - affect local cerebral blood flow dynamics. This issue is ideally studied in the intact brain at
Tidsskrift For Den Norske Laegeforening, Apr 1, 2006
One of several probable causation theories of Parkinson disease postulates that brain tissue cann... more One of several probable causation theories of Parkinson disease postulates that brain tissue cannot generate sufficient levels of various growth factors required to sustain the viability of dopamine-producing nerve cells in the presence of as yet unknown toxic factors. The study reported here evaluates the ability of externally applied growth factors to protect the dopamine fibres in the basal ganglia in a toxin-induced animal model of the disease. All animals (rats) were subjected to selective destruction of the dopamine-producing cells in substantia nigra. The rats were divided into three groups. Two groups received intracerebral treatment with either glia-cell derived neurotrophic factor (GDNF) or a combination of brain-derived neurotrophic factor (BDNF) and GDNF. The third group acted as untreated controls and were given sterile saline. The growth factors were infused directly into the brain by an osmotic pump over a period of 28 days. Brain sections taken from all three groups were evaluated by immunocytochemistry. The two groups of rats that received growth factor infusion displayed a significant improvement in their motor behaviour compared to control animals. Immunocytochemistry studies demonstrated that the group receiving a combination of GDNF and BDNF had an increased number of surviving active fibres in the dopamine system striatum in comparison to the control and GDNF groups. In addition the infusion of growth factors resulted in a proliferation of subventricular cells in the basal ganglia. The improved motor function following growth factor treatment in this rat model might be due to a delayed retrograde degeneration of the nigrostriatal nerve fibers. Growth factor infusion also clearly stimulated endogenous stem cells and caused their migration towards the striatum. Our observations indicate that the infusion of growth factors into the brain have a symptomatic and neuroprotective effect in this model.
Tidsskrift for den Norske lægeforening : tidsskrift for praktisk medicin, ny række, Jan 23, 2006
One of several probable causation theories of Parkinson disease postulates that brain tissue cann... more One of several probable causation theories of Parkinson disease postulates that brain tissue cannot generate sufficient levels of various growth factors required to sustain the viability of dopamine-producing nerve cells in the presence of as yet unknown toxic factors. The study reported here evaluates the ability of externally applied growth factors to protect the dopamine fibres in the basal ganglia in a toxin-induced animal model of the disease. All animals (rats) were subjected to selective destruction of the dopamine-producing cells in substantia nigra. The rats were divided into three groups. Two groups received intracerebral treatment with either glia-cell derived neurotrophic factor (GDNF) or a combination of brain-derived neurotrophic factor (BDNF) and GDNF. The third group acted as untreated controls and were given sterile saline. The growth factors were infused directly into the brain by an osmotic pump over a period of 28 days. Brain sections taken from all three groups ...
Regimens with ranitidine bismuth citrate (RBC) or omeprazole (O) are effective in eradicating Hel... more Regimens with ranitidine bismuth citrate (RBC) or omeprazole (O) are effective in eradicating Helicobacter pylori. This randomized, open, multicentre trial compares three different regimens with these drugs. Consecutive H. pylori +ve outpatients were included. The alternative regimens were: 1) O 20 mg, clarithromycin (C) 250 mg and metronidazole (M) 500 mg (O.C.M), 2) RBC 400 mg, C 250 mg and M 500 mg (RBC.C.M), 3) RBC 400 mg, tetracycline (T) 1000 mg and M 500 mg [RBC.T.M]. All drugs were given twice daily for 7 days. H. pylori infection was assessed with H. pylori urea breath tests. 426 H. pylori +ve patients were included (mean age 58 years [range 18-88], male/female: 244/182). The eradication rates (intention to treat) in the O.C.M, RBC.C.M and RBC.T.M groups were 117/137 (85%), 141/146 (97%) and 117/143 (82%), respectively (P &lt; 0.001, overall assessment). There were no significant differences in side effects between the alternatives. In this trial, RBC.C.M was the most effective one, it was well tolerated and compliance was satisfactory. RBC.T.M is an alternative to regimens with clarithromycin.
European Journal of Gastroenterology & Hepatology, 1998
In this study we compared the cure rates of two clarithromycin-based regimens in patients in whom... more In this study we compared the cure rates of two clarithromycin-based regimens in patients in whom anti-Helicobacter pylori therapy had previously failed. Thirty-three patients were randomized to receive either regimen OAC (20 mg omeprazole, 750 mg amoxicillin, and 250 mg clarithromycin) or BTC (240 mg bismuth subcitrate, 750 mg oxytetracycline, and 250 mg clarithromycin), all twice daily for 10 days. A further 28 patients were all treated with OAC. Previously failed therapy included combinations of bismuth (B), omeprazole (O), tetracycline (T), metronidazole (M), amoxicillin (A), or clarithromycin (C) in BTM (n = 48), OAM (n = 13), OA (n = 7), OCM (n = 2), or BCM (n = 1). H. pylori infection was confirmed by culture of biopsy specimens, and antimicrobial susceptibility testing was performed with the E test. H. pylori infection was cured in all patients (n = 18) with OAC and in 8 patients (53%) with BTC (P = 0.001) in the randomized group and in 27 patients (96%) receiving OAC in the open-label group. Ten-day OAC is highly effective and superior to BTC in patients in whom metronidazole-based treatment has previously failed.
Expression of the growth arrest DNA damage-inducible protein,GADD45, has recently been reported t... more Expression of the growth arrest DNA damage-inducible protein,GADD45, has recently been reported to be induced by a wide range of stimuli, especially those that produce a high level of base pair damage. We have investigated the expression ofGADD45in brain tissue obtained from patients suffering from Alzheimer's disease (AD). Our results demonstrate that many neurons express theGADD45protein, and that expression of this protein in neurons is associated with expression of the anti-apoptotic proteinBcl-2, and the presence of DNA damage, but not closely associated with tangle-bearing neurons. Additionally, cell lines overexpressing this protein confer resistance to apoptosis induced by DNA damage agent, suggesting that this protein may participate in cell survival mechanisms.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
The water permeability of cell membranes differs by orders of magnitude, and most of this variabi... more The water permeability of cell membranes differs by orders of magnitude, and most of this variability reflects the differential expression of aquaporin water channels. We have recently found that the CNS contains a member of the aquaporin family, aquaporin-4 (AQP4). As a prerequisite for understanding the cellular handling of water during neuronal activity, we have investigated the cellular and subcellular expression of AQP4 in the retina and optic nerve where activity-dependent ion fluxes have been studied in detail. In situ hybridization with digoxigenin-labeled riboprobes and immunogold labeling by a sensitive postembedding procedure demonstrated that AQP4 and AQP4 mRNA were restricted to glial cells, including MHller cells in the retina and fibrous astrocytes in the optic nerve. A quantitative immunogold analysis of the MHller cells showed that these cells exhibited three distinct membrane compartments with regard to AQP4 expression. End feet membranes (facing the vitreous body ...
One of the major problems in glutamate immunocytochemistry has been the difficulty involved in se... more One of the major problems in glutamate immunocytochemistry has been the difficulty involved in separating immunocytochemical labelling due to metabolic glutamate from the labelling caused by transmitter glutamate. Another problem appears to be the accessibility of antigenic sites in conventional light microscopic preparations. In the present report, we have applied the primary glutamate antiserum onto ultrathin tissue sections, followed by the use of a colloidal gold detection system. The use of this postembedding immunogold procedure allows equal access of antibodies to all cellular compartments exposed at the section surface, allows quantitative assessment of the immunoreactivity, and affords a high resolution compatible with studies at the organelle level. When applied to slice preparations the immunogold procedure can be used to identify releasable pools of glutamate. These methodological advances have greatly increased the usefulness of glutamate immunocytochemistry as a tool t...
Glutamate, a major excitatory transmitter substance, is neurotoxic at high concentrations. Brain ... more Glutamate, a major excitatory transmitter substance, is neurotoxic at high concentrations. Brain dialysis experiments have demonstrated an extracellular overflow of glutamate during ischemia, and there is good evidence from several animal models that glutamate antagonists offer partial protection against the development of ischemic cell degeneration. These and other experimental data indicate that glutamate may be involved in the pathogenesis of ischemic brain damage. Quantitative immunocytochemical investigations carried out in the authors' laboratory suggest that ischemia is associated with loss of glutamate from nerve cell bodies, and reduced ability of the glial cells to metabolize glutamate. We discuss possibilities of new therapeutic strategies.
Alzheimer's disease (AD) is associated with the accumulation of extracellular deposits of the... more Alzheimer's disease (AD) is associated with the accumulation of extracellular deposits of the beta-amyloid protein (Abeta). Abeta is a result of misprocessing of the beta-amyloid precursor protein (APP). Gamma-secretase is involved in APP misprocessing and one hypothesis holds that this secretase is identical to PS1. We tested this hypothesis by determining whether PS is co-localised with Abeta in situ. Using confocal analyses and a sensitive immunogold procedure we show that PS and Abeta are co-localised within discrete microdomains of neuronal plasma membranes in AD patients and in aged dogs, an established model of human brain aging. Our data indicate that APP misprocessing occurs in discrete plasma membrane domains of neurons and provide evidence that PS1 is critically involved in Abeta formation.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
The water permeability of cell membranes differs by orders of magnitude, and most of this variabi... more The water permeability of cell membranes differs by orders of magnitude, and most of this variability reflects the differential expression of aquaporin water channels. We have recently found that the CNS contains a member of the aquaporin family, aquaporin-4 (AQP4). As a prerequisite for understanding the cellular handling of water during neuronal activity, we have investigated the cellular and subcellular expression of AQP4 in the retina and optic nerve where activity-dependent ion fluxes have been studied in detail. In situ hybridization with digoxigenin-labeled riboprobes and immunogold labeling by a sensitive postembedding procedure demonstrated that AQP4 and AQP4 mRNA were restricted to glial cells, including MHller cells in the retina and fibrous astrocytes in the optic nerve. A quantitative immunogold analysis of the MHller cells showed that these cells exhibited three distinct membrane compartments with regard to AQP4 expression. End feet membranes (facing the vitreous body ...
In situ hybridization techniques and quantitative western blotting were used to study the express... more In situ hybridization techniques and quantitative western blotting were used to study the expression of the glial glutamate transporter GLT-1 and GLAST in the brains of normal (implanted, non-kindled) and fully kindled rats. Wistar rats were implanted with stimulating electrodes in the basolateral amygdala, and killed 28 days after the stimulated group had shown stage 5 seizures on five occasions. The brains were processed for in situ hybridization of messenger RNA for GLT-1 using 35S-labelled oligonucleotide probes or digoxigenin-labelled riboprobes. Paired (kindled and non-kindled) sections were used for qualitative and quantitative analyses. Image analysis of autoradiograms showed no change in expression of GLT-1 messenger RNA in any region of the hippocampus or in the cortex. An increase in expression of GLT-1 messenger RNA (expressed as percentage difference of control) was observed bilaterally in the striatum in kindled animals (16-21%, P<0.05). Nuclear emulsion-dipped sect...
Little is known about how amyloid-beta (Abeta) is deposited in relation to the complex ultrastruc... more Little is known about how amyloid-beta (Abeta) is deposited in relation to the complex ultrastructure of the brain. Here we combined serial section immunoelectron microscopy with 3D reconstruction to elucidate the spatial relationship between Abeta deposits and ultrastructurally identified cellular compartments. The analysis was performed in a transgenic mouse model with mutant presenilin-1, and mutant amyloid-beta protein precursor (AbetaPP) and tau transgenes (3xTg-AD mice) and in aged dogs that develop Abeta plaques spontaneously. Reconstructions based on serial ultrathin sections of hippocampus (mice) or neocortex (dogs) that had been immunolabeled with Abeta (Abeta(1-42)) antibodies showed that the organization of extracellular Abeta deposits is more complex than anticipated from light microscopic analyses. In both species, deposits were tightly associated with plasma membranes of pyramidal cell bodies and major dendrites. The deposits typically consisted of thin sheets as well...
The effect of 20 min of ischemia on the cellular and subcellular distribution of glutamate, gluta... more The effect of 20 min of ischemia on the cellular and subcellular distribution of glutamate, glutamine and taurine in the rat hippocampus was studied by means of an immunocytochemical procedure based on antisera raised against protein glutaraldehyde conjugates of the respective amino acids. Forebrain ischemia was induced by temporary occlusion of the common carotid arteries in rats with permanently occluded vertebral arteries. Within 90 s after removal of the carotid ligatures, the rats were perfused through the heart with a mixture of glutaraldehyde and paraformaldehyde. For semiquantitative electron microscopic analysis, ultrathin sections were incubated in a primary antiserum followed by a secondary antibody coupled to colloidal gold particles. The gold particle densities over different tissue compartments within the CA1 field and the mossy fiber zone of the hippocampus were determined by means of a specially designed computer program, and values from normal and ischemic animals were compared. It was found that in the astrocytes, the level of immunoreactivity for glutamine and taurine is unchanged or slightly decreased after ischemia, while that for glutamate is increased, particularly within the mitochondria (by about 100%). In contrast, pyramidal cell bodies display a reduced immunolabeling for all three amino acids following the ischemic episode. The results show that ischemia causes a redistribution of glutamate from neurons to glia. The observed increase in the glial immunolabeling for glutamate indicates that the capacity of the glial cells to metabolize glutamate is exceeded during ischemia. This glial response to ischemia has not previously been recognized and may play a role in the chain of events leading to &quot;excitotoxic&quot; cell death during or following an ischemic episode. The reduction of glutamate and taurine immunolabeling in neurons points to a possible amino acid efflux and is compatible with previous biochemical studies demonstrating an elevated extracellular level of these amino acids during ischemia.
Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astr... more Aquaporin-4 (AQP4) is the predominant water channel in brain and is selectively expressed in astrocytes. Astrocytic endfoot membranes exhibit tenfold higher densities of AQP4 than non-endfoot membranes, making AQP4 an excellent marker of astrocyte polarization. Loss of astrocyte polarization is known to compromise astrocytic function and to be associated with impaired water and K+ homeostasis. Here we investigate by a combination of light and electron microscopic immunocytochemistry whether amyloid deposition is associated with a loss of astrocyte polarization, using AQP4 as a marker. We used the tg-ArcSwe mouse model of Alzheimer's disease, as this model displays perivascular plaques as well as plaques confined to the neuropil. 3D reconstructions were done to establish the spatial relation between plaques and astrocytic endfeet, the latter known to contain the perivascular pool of AQP4. Changes in AQP4 expression emerge just after the appearance of the first plaques. Typically,...
Multiphoton Microscopy in the Biomedical Sciences VIII, 2008
Cerebrovascular pathology is closely coupled to cognitive function decline, as indicated by numer... more Cerebrovascular pathology is closely coupled to cognitive function decline, as indicated by numerous studies at the system level. To better understand the mechanisms of this cognitive decline it is important to resolve how pathological changes in the vasculature - such as perivascular plaques - affect local cerebral blood flow dynamics. This issue is ideally studied in the intact brain at
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