| 1. |
- Benveniste, Helene, et al.
(author)
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Determination of Brain Interstitial Concentrations by Microdialysis
- 1989
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In: Journal of Neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 52:6, s. 1741-1750
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Journal article (peer-reviewed)abstract
- Microdialysis is an extensively used technique for the study of solutes in brain interstitial space. The method is based on collection of substances by diffusion across a dialysis membrane positioned in the brain. The outflow concentration reflects the interstitial concentration of the substance of interest, but the relationship between these two entities is at present unclear. So far, most evaluations have been based solely on calibrations in saline. This procedure is misleading, because the ease by which molecules in saline diffuse into the probe is different from that of tissue. We describe here a mathematical analysis of mass transport into the dialysis probe in tissue based on diffusion equations in complex media. The main finding is that diffusion characteristics of a given substance have to be included in the formula. These include the tortuosity factor (λ) and the extracellular volume fraction (α). We have substantiated this by studies in a welldefined complex medium (red blood cell suspensions) as well as in brain. We conclude that the traditional calculation procedure results in interstitial concentrations that are too low by a factor of λ2/α for a given compound.
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| 2. |
- Blomqvist, Photjanee, et al.
(author)
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Cyclic AMP Concentrations in Rat Neocortex and Hippocampus During and Following Incomplete Ischemia : Effects of Central Noradrenergic Neurons, Prostaglandins, and Adenosine
- 1985
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 44:5, s. 1345-1353
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Journal article (peer-reviewed)abstract
- Abstract: The concentrations of cyclic AMP, noradrenaline, glycogen, glucose, lactate, pyruvate, labile phosphate compounds, and free fatty acids were investigated in the rat neocortex and hippocampus during and following cerebral ischemia. An incomplete ischemia of 5 and 15 min duration was induced by bilateral carotid clamping combined with hypotension. The postischemic events were studied after 5, 15, and 60 min of recirculation. Five minutes of ischemia did not significantly alter the neocortical or hippocampal concentrations of cyclic AMP. After 15 min of ischemia the neocortical levels decreased significantly below control values. In the recirculation period following ischemia a significant elevation of the cyclic AMP concentrations was observed. Following 5 min of recirculation after 5 min of ischemia the levels increased from 2.53 ± 0.21 nmol ± g−1 to 5.18 ± 0.09 nmol ± g−1 in the neocortex and from 2.14 ± 0.16 nmol ± g−1 to 3.52 ± 0.35 nmol ± g−1 in the hippocampus. Five minutes of recirculation following 15 min of ischemia led to a significant increase in the levels of cyclic AMP, to 12.86 ± 1.43 nmol ± g−1 in the neocortex to 5.58 ± 0.57 nmol ± g−1 in the hippocampus. With longer recirculation periods the cyclic AMP levels progressively decreased and were similar to control values after 60 min. Depletion of cortical noradrenaline by at least 95% was performed by injections of 6‐hydroxydopamine into the ascending axon bundles from the locus ceruleus. The lesion did not significantly change the ischemic or postischemic neocortical and hippocampal levels of cyclic AMP, glycogen, or free fatty acids including arachidonic acid. Treatment of the animals with theophyllamine (23, 46, and 92 mg ± kg−1) or indomethacin (10 mg ± kg−1) did not affect the postischemic levels of cyclic AMP. It is concluded that central noradrenergic neurons, prostaglandins, and adenosine are not of major importance for the observed postischemic elevations of cyclic AMP and that the changes in the concentrations of free fatty acids measured during and following ischemia are not mediated by noradrenergic neurons.
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| 3. |
- Ekström, Per, et al.
(author)
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Calmodulin‐Binding Proteins Within the Slow Phase of Axonal Transport in the Rabbit Vagus Nerve Per Ekstrom and Martin Kanje
- 1987
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 49:1, s. 146-151
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Journal article (peer-reviewed)abstract
- Abstract: : Calmodulin‐binding proteins (CBPs) in the rabbit vagus nerve were studied by means of calmodulin‐Sepha‐rose affinity chromatography and polyacrylamide gel electrophoresis. The soluble fraction (105g supernatant) of a nerve homogenate contained four CBPs with molecular weights of 44, 55, 91, and 93 kD, respectively. Slowly transported proteins were recovered in the vagus 3 days after injection of [35S]methionine into the nodose ganglion. Four labelled CBPs with molecular weights of 44, 55, 69, and 83 kD, respectively were found. The nodose ganglion con tained two labelled CBPs, 44 and 55 kD. The 55‐kD CBP was identified as tubulin after immunoblotting. In separate experiments it was also shown that bovine brain tubulin bound to the calmodulin column.
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| 4. |
- Engelsen, Bernt, et al.
(author)
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Effect of Insulin‐Induced Hypoglycemia on the Concentrations of Glutamate and Related Amino Acids and Energy Metabolites in the Intact and Decorticated Rat Neostriatum
- 1986
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 47:5, s. 1634-1641
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Journal article (peer-reviewed)abstract
- Abstract The glutamate (Glu) terminals in rat neostriatum were removed by a unilateral frontal decortication. One to two weeks later the effects of insulin‐induced hypoglycemia on the steady‐state levels of amino acids [Glu, glutamine (Gin), aspartate (Asp), γ‐aminobutyric acid (GABA), tau‐rine] and energy metabolites (glucose, glycogen, α‐ketoglu‐tarate, pyruvate, lactate, ATP, ADP, AMP, phosphocre‐atine) were examined in the intact and decorticated neostriatum from brains frozen in situ. The changes in the metabolite levels were examined during normoglycemia, hypoglycemia with burst‐suppression (BS) EEG, after 5 and 30 min of hypoglycemic coma with isoelectric EEG, and 1 h of recovery following 30 min of isoelectric EEG. In normoglycemia Glu decreased and Gin and glycogen increased significantly on the decorticated side. During the BS period no significant differences in the measured compounds were noted between the two sides. After 5 min of isoelectric EEG Glu, Gin, GABA, and ATP levels were significantly lower and Asp higher on the intact than on the decorticated side. No differences between the two sides were found after 30 min of isoelectric EEG. After 1 h of recovery from 30 min of isoelectric EEG Glu, Gin, and glycogen had not reached their control levels. Glu was significantly lower, and Gin and glycogen higher on the decorticated side. The Asp and GABA levels were not significantly different from control levels. The results indicate that the turnover of Glu is higher in the intact than in decorticated neostriatum during profound hypoglycemia.
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| 5. |
- Miyauchi, Yoshitoyo, et al.
(author)
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Noradrenaline Metabolism in Neocortex and Hippocampus Following Transient Forebrain Ischemia in Rats : Relation to Development of Selective Neuronal Necrosis
- 1989
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 53:2, s. 408-415
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Journal article (peer-reviewed)abstract
- Abstract: Noradrenaline (NA) metabolism tn the neocortex and hippocampus was examined in rats atl 1, 24, and 48 h following 15 min of reversible forebrain ischemia. As assessed by the ratio of accumulated 3,4‐dihydroxyphenylalanine (DOPA) to the tissue NA level after inhibition of DOPA decarboxylase, the NA turnover rates were markedly increased (120‐148% above the control) at 1 h postischemia in both the neocortex and hippocampal formation (CA1 and CA3 plus dentate gyrus). The DOPA:NA ratio went back to control levels after longer postischemic survival times. The ratio between levels of the deaminated NA metabolite, 3,4‐dihy‐droxyphenylethyleneglycol (DOPEG), and NA, which gives another measure of NA turnover rate, Showed similar changes. In the neocortex and the CA3 plus dentate gyrus, the DOPEG:NA ratio was markedly increased (89‐118%) 1 h after the ischemia, but this change had disappeared at 24 and 48 h. Thus, both the DOPA accumulation experiments and the NA and DOPEG measurements indicate that following transient forebrain ischemia, there is an increased NA turnover in the hippocampus and cortex only in the early recirculation period and not after longer postischemic survival times. The degree of neuronal necrosis in ihe CA1 region was examined light microscopically on celestine blue‐acid fuchsin‐stained sections at 24, 48, and 96 h following the ischemic insult. The neuronal damage in CA1 was sparse after 24 h of recovery, had increased markedly after 48 h. and was very pronounced at 96 h. Our data show that the changes in NA turnover in the neocortex and hippocampus follow a different time course than the development of neuronal damage in the hippocampal CA 1 region. The activation of the NA system occurs during and immediately after the period of high extracellular levels of glutamate. Excitatory amino acids have been proposed to be of major importance for the development of ischemic brain damage, whereas the NA afferents to the hippocampus and cortex (originating in the locus coeruleus) seem to have a protective role. We hypothesize that the increased activity of the locus coeruleus system, observed early postischemically in the present study, mitigates the detrimental effects evoked by excessive glutamate receptor stimulation, thereby reducing the degree of neuronal necrosis.
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| 6. |
- Westerberg, Eva, et al.
(author)
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Changes in Excitatory Amino Acid Receptor Binding in the Intact and Decorticated Rat Neostriatum Following Insulin‐Induced Hypoglycemia
- 1989
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 52:5, s. 1340-1347
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Journal article (peer-reviewed)abstract
- Abstract: An involvement of excitatory amino acid (EAA) transmitter–receptor interactions in the development of hypoglycemia‐induced neuronal damage has been suggested. We report here on the binding to EAA receptors in the rat caudate nucleus and cerebral cortex, during and following severe insulin‐induced hypoglycemia with an isoelectric EEG of 10 or 30 min duration. The binding of α[3H]amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid ([3H]AMPA) to quisqualate receptors, [3H]kainic acid (KA) to kainate receptors, and [3H]glutamate to N‐methyl‐D‐aspartate (NMDA)‐sensitive sites was determined by quantitative autoradiography. During EEG isoelectricity, AMPA binding was reduced by approximately 40%, which could represent quisqualate receptor desensitization. One hour following glucose‐induced recovery, AMPA binding was no longer different from control level. As the recovery period was prolonged to 1 or 4 weeks, AMPA binding decreased. The decrease was more pronounced in the dorsolateral than in the ventromedial part of the striatum. This correlates with the distribution of neuronal damage, and probably reflects loss of receptor binding sites due to cell death. During the period of EEG silence there was a tendency toward an increase in NMDA displaceable glutamate binding. Following 4 weeks of recovery, binding to NMDA receptors was significantly decreased. Glutamate binding to NMDA‐sensitive sites was remarkably resistant to neuronal necrosis and was not significantly different from control values in the dorsolateral caudate 1 week following the hypoglycemic coma. No changes in KA binding were found until 1 week posthypoglycemia, when a significant reduction in binding was noted in the lateral striatum. Two weeks following partial unilateral cortical ablation, binding to NMDA receptors in the striatum decreased in the lesioned hemisphere in control animals and remained significantly lower than in the contralateral hemisphere during EEG isoelectricity. In contrast, no hemispheric differences in AMPA binding were observed. The lack of desensitization of NMDA receptors during EEG isoelectricity and their relative resistance to neuronal necrosis could be of significance for the development of hypoglycemic neuronal damage.
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| 7. |
- Westerberg, Eva, et al.
(author)
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Lesions to the Corticostriatal Pathways Ameliorate Hypoglycemia‐Induced Arachidonic Acid Release
- 1986
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In: Journal of Neurochemistry. - : Wiley. - 0022-3042 .- 1471-4159. ; 47:5, s. 1507-1511
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Journal article (peer-reviewed)abstract
- Abstract The concentrations of free fatty acids (FFAs) in the neostriatum of control rats and rats subjected to unilateral cortical ablation were measured during and following severe insulin‐induced hypoglycemia. The total FFA concentration in the caudate nucleus contralateral to the lesion increased to approximately 1.5 and 3 times the control level after 5 and 30 min of isoelectricity, respectively, and was similar to the control value following 1 h of recovery. After 5 min of isoelectricity, the total FFA pool was significantly smaller in the decorticated striatum. No difference between hemispheres was noted after 30 min of isoelectricity. After 5 min of isoelectricity the levels of stearic and arachidonic acid were selectively increased whereas palmitic acid and oleic acid remained at control levels. In the decorticated striatum of lesioned animals the arachidonic acid concentration was significantly lower, whereas the level of stearic acid was not significantly different from the control value. After 30 min of isoelectricity the levels of all four FFA species were increased. Apart from a significantly lower level of oleic acid on the decorticated side, there were no interhemi‐spheric differences in the FFA levels. Since the early inter‐hemispheric differences in the levels of arachidonic and stearic acids coincide with a selective decrease in the levels of glutamate and a decreased energy utilization on the decorticated side, the results suggest that glutamate release during hypoglycemia induces an early receptor‐mediated degradation of phospholipids, presumably via the phospha‐tidylinositol cycle.
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| 8. |
- Spillmann, Dorothe, et al.
(author)
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Poly-N-acetyllactosamine glycans of cellular glycoproteins : predominance of linear chains in mouse neuroblastoma and rat pheochromocytoma cell lines.
- 1987
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In: Journal of Neurochemistry. - 0022-3042 .- 1471-4159. ; 49:3, s. 874-883
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Journal article (peer-reviewed)abstract
- To study the properties of protein-bound oligosaccharides in neuronally differentiating cells, two model systems were used: murine N1E-115 and N-18 neuroblastoma cells inducible by serum starvation and rat PC12 pheochromocytoma cells inducible by nerve growth factor. Glycopeptides were prepared from cells metabolically labeled with [3H]glucosamine and analyzed by gel filtration. The properties of the high-molecular-weight glycopeptides were studied using enzymatic digestion with neuraminidase and endo-beta-galactosidase. In contrast to other cell lines analyzed, the neuroblastoma and pheochromocytoma lines contained predominantly glycopeptides completely cleavable with endo-beta-galactosidase, which indicated that they were linear-type poly-N-acetyllactosamine glycans. The proportion of these linear chains in the high-molecular-weight fraction increased during neuronal differentiation in both cell systems. The linear nature of the glycans was also correlated with positive anti-i and negative anti-I reactivity of the cells in immunofluorescence microscopy. Specific cell surface labeling for poly-N-acetyllactosamine glycans and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed several glycoprotein components, some of which showed changes during neuronal differentiation. The high proportion of linear poly-N-acetyllactosamine chains in these neuronal cell lines and its increase during neuronal differentiation suggests that these glycans may be a characteristic feature of neuronal or neuronally differentiating cells.
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