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Biomedical subjects

M Sandberg

Publications and source records attributed to M Sandberg.

At least 163 records · Page 9Linked to original sources
PubMed1986

Ouabain-induced changes in extracellular aspartate, glutamate and GABA levels in the rabbit olfactory bulb in vivo.

The effect of ouabain on extracellular amino acid levels was investigated in the rabbit olfactory bulb using brain dialysis. Extracellular field potentials, elicited by stimulation of the lateral olfactory tract (LOT), were recorded simultaneously. Ouabain (100 microM) induced a rapid increase in extracellular aspartate, glutamate and gamma-aminobutyric acid. LOT-evoked potentials changed concomitantly, suggesting a neuronal depolarization.

Amino Acids↗
PubMed1986

Extracellular overflow of neuroactive amino acids during severe insulin-induced hypoglycemia: in vivo dialysis of the rat hippocampus.

Hypoglycemia-evoked changes in levels of extracellular excitatory and inhibitory amino acids were studied using the microdialysis technique. A newly designed dialysis probe was inserted stereotaxically into the rat hippocampus. Animals were then subjected to insulin-induced hypoglycemia; then blood glucose levels were restored by glucose injections after a 30-min period of isoelectric electroencephalography. Dialysates were collected before, during, and after the isoelectric period. Amino acids in the dialysates were analyzed by liquid chromatography and fluorescence detection following automatic precolumn derivatization with o-phthaldialdehyde. During the isoelectric phase, the concentration of aspartate increased 15-fold, whereas glutamate, gamma-amino-butyric acid, taurine, and phosphoethanolamine levels were elevated three- to sixfold. Smaller increases were observed for nonneuroactive amino acids such as asparagine, alanine, and phenylalanine. In contrast to all other amino acids, the glutamine content was reduced to less than 30% of preisoelectric values. The concentrations of the neuroactive amino acids were restored to normal in the post-isoelectric phase. These data demonstrate that there is an extracellular overflow of neuroactive amino acids, especially aspartate, during severe hypoglycemia.

Amino Acids↗
PubMed1986

B cell activation in multiple sclerosis.

A microtechnique was established for the study of the limited numbers of cells available in CSF. The method allowed for the determination of the number of immunoglobulin-secreting cells (IgSC) as well as the quantitation of immunoglobulin or specific antibody secreted into the culture medium. Dose-response curves and kinetic profiles for the IgSC responses induced by pokeweed mitogen (PWM), a polyclonal B cell activator, were similar for CSF cells (CSFC) and peripheral blood mononuclear cells (PBMC). When equal numbers of unstimulated CSFC and PBMC from patients with multiple sclerosis (MS) were cultured, both the number of IgSC and the amount of secreted IgG were significantly greater in CSFC cultures. The addition of PWM resulted in the differentiation of B cells among both CSFC and PBMC, as shown by an increase of both the number of IgSC and the amount of secreted IgG. Results with cultures of unstimulated cell suspensions from MS patients suggested that CSF cells from these patients may be activated in vivo. The addition of mitomycin-C treated autologous peripheral blood mononuclear cells (PBMCM) to cultures of small numbers of CSFC or PBMC resulted in an augmentation of the number of IgSC in both, whether or not they were stimulated with PWM, and also in an increased secretion of IgG into the culture supernatants. This culture system should prove useful in functional studies when limited numbers of cells are available.

B-Lymphocytes↗
PubMed1985

Metabolically derived aspartate--elevated extracellular levels in vivo in lodoacetate poisoning.

Glycolysis was blocked in the hippocampus of the otherwise unaffected rabbit by perfusion of a previously implanted thin dialysis tube with a medium containing 0.1 mM iodoacetate. The perfusate from the dialysis tube was analyzed for free amino acids with liquid chromatographic separation of ortophthaldialdehyde derivatives. The data were used to calculate approximate levels of extracellular amino acids. Within 15 min after the beginning of iodoacetate perfusion, extracellular aspartate increased measurably, and the increase was tenfold within less than 2 hr. Although most other amino acids were unaffected, an elevation of taurine, phosphoethanolamine, and ethanolamine was observed with a delay of 30-40 min after the effect on aspartate.

Amino Acids↗
PubMed1985

Ischemia-induced shift of inhibitory and excitatory amino acids from intra- to extracellular compartments.

Brain ischemia was induced for 10 or 30 min by clamping the common carotid arteries in rabbits whose vertebral arteries had previously been electrocauterized. EEG and tissue content of high energy phosphates were used to verify the ischemic state and to evaluate the degree of postischemic recovery. Extracellular levels and total contents of amino acids were followed in the hippocampus during ischemia and 4 h of recirculation. At the end of a 30-min ischemic period, GABA had increased 250 times, glutamate 160 times, and aspartate and taurine 30 times in the extracellular phase. The levels returned to normal within 30 min of reflow. A delayed increase of extracellular phosphoethanolamine and ethanolamine peaked after 1-2 h of reflow. Ten minutes of ischemia elicited considerably smaller but similar effects. With respect to total amino acids in the hippocampus, glutamate and aspartate decreased to 30-50% of control while GABA appeared unaffected after 4 h of reflow. Alanine, valine, phenylalanine, leucine, and isoleucine increased severalfold. The importance of toxic extracellular levels of excitatory amino acids, as well as of high extracellular levels of inhibitory amino acids, are considered in relation to the pathophysiology of neuronal cell loss during cerebral ischemia.

Amino Acids↗
PubMed1985

Effect of cortico-striate pathway lesion on the activities of enzymes involved in synthesis and metabolism of amino acid neurotransmitters in the striatum.

The activities of several enzymes involved in the metabolism of aspartate and glutamate were measured in striatal (nucleus caudatus and putamen) homogenates 2-3, 6-7, and 35-40 days following frontoparietal and frontal cortical ablation. The activity of glutamine synthetase (GS) was substantially increased (46-48%) on the operated side 6-7 days following the lesion whereas smaller changes were observed at 2-3 and 35-40 days after lesion. In contrast, decreased levels of glutaminase and malate dehydrogenase (MDH) were observed by 6-7 days while no significant change was found at either 2-3 or 35-40 after the lesion. The activities of glutamate dehydrogenase (GDH) and glutamate decarboxylase (GAD) were elevated after 35-40 days whereas no changes in the levels of either GDH or aspartate aminotransferase (ASAT) were found at 2-3 or 6-7 days after the fronto-parietal decortication. When only the frontal cortex was removed quantitatively similar changes were observed in striatal GS and glutaminase activity. The content of glutamate and glutamine in the denervated striatum followed qualitatively the changes in glutaminase and GS. The results indicate that the degeneration of cortico-striatal terminals causes a profound glial reaction in the striatum, and both glutaminase and MDH are present in relatively high concentrations in the corticostriatal terminals.

Amino Acids↗
PubMed1984

Kinetic properties of glutaminase from cerebral cortex.

The rates of phosphate activated glutaminase activity in finely homogenised cerebral cortex and synaptosomes were measured. Activity was 25-50% higher at pH 7.0 than at pH 8.0. Glutamate inhibited activity with a Ki of 2-3 mM while aspartate had little effect. Calcium (1 mM) activated the enzyme but magnesium was without action. The pH profiles of the effects of these modulators of glutaminase activity in these finely ground preparations showed that all agents were more effective at pH 7.0 than at pH 8.0.

Animals↗
PubMed1984

Effect of lesions of the olfactory bulb on the levels of amino acids and related enzymes in the olfactory cortex of the guinea pig.

Olfactory bulb removal and consequential degeneration of the lateral olfactory tract led to a decrease in the levels of glutaminase and malate dehydrogenase in the ipsilateral olfactory cortex. These changes in enzyme activity may account for the well established decrease in the levels of aspartate and glutamate in the olfactory cortex following ipsilateral bulbectomy. The level of glutamine synthetase, a glial marker enzyme, was slightly increased while the activities of glutamate decarboxylase, glutamate dehydrogenase, and glutamate oxaloacetic transaminase were unchanged.

Amino Acids↗
PubMed1984

The sensitizing capacity of atranorin.

The allergenic potential of the aromatic lichen substance atranorin has been investigated by means of the guinea pig maximization test of Magnusson & Kligman. Sensitivity was induced in 30% of the animals, which corresponds to a moderate allergenic capacity (grade III). This is in agreement with the clinically-observed frequency of 1.5% among our patients. A modified photoallergy test on the same animals was performed, but irradiation did not increase the number of positive reactions. 4 patients with proven contact sensitivity to atranorin, evernic, usnic or physodic acid, were examined with different dilutions from 0.001 to 0.1%. Irradiation of the test series did not provoke any clear-cut photoallergic reaction.

Adult↗
PubMed1983

Amino acids in the dorsal lateral geniculate nucleus of the cat--collection in vivo.

A dialysis sampling probe was used to collect amino acids from the dorsal lateral geniculate nucleus (LGN) in vivo. The sampling probe was equipped with an electrode to allow local stimulation and recording of nerve activity. The amino acids in the dialysates were determined fluorimetrically by precolumn derivation and hplc-separation. Local electrical stimulation of the LGN caused a multifold increase in glutamate, aspartate and GABA levels. Smaller changes were observed for taurine, alanine and glycine. The results indicate that the dialysis sampling probe is rather atraumatic and can be used to detect stimulation-induced changes in extracellular amino acid concentrations.

Alanine↗
PubMed1983

Release of endogenous amino acids from superior colliculus of the rabbit: in vitro studies after retinal ablation.

Tissue slices from the superior colliculi (SC) of the rabbit were superfused and investigated 1 week after unilateral eye removal. Amino acid levels were determined both in the tissue slices and in the medium after chemical depolarisation (56 mM K). The amino acid determinations were done fluorimetrically by precolumn derivation and HPLC separation. Colliculi contralateral to the enucleation exhibited a 16% reduction in glutamate compared with the ipsilateral colliculi. The Ca-dependent release of glutamate or other amino acids tested was not appreciably affected by enucleation. However, both the total and the Ca-independent release of glutamate was lower from contralateral SC slices compared with the ipsilateral slices. The results do not favour glutamate as the major optic nerve transmitter in the rabbit, but do not rule out glutamate as a transmitter in a minor population of retinal fibres.

Amino Acids↗
PubMed1982

Perfume allergy due to oak moss and other lichens.

During a period of 2 1/2 years, 7 of 2000 patients routinely tested at our laboratory revealed contact allergy to oak moss in perfumes. All reacted to a mixture of different lichens and to some specific lichen compounds. The sensitivity was probably induced by cosmetics containing lichen substances. The following 3 compounds caused reactions in all patients tested: atranorin, evernic and usnic acids. 3 patients were photosensitive, but stronger reactions were elicited by prolonged contact during occlusion of the patches and complete protection against light, rather than by irradiation alone. The data suggest that the sensitizing capacity of the lichen compounds is primarily of a contact rather than of a photocontact nature.

Adult↗
PubMed1981

beta-Alanine, a possible neurotransmitter in the visual system?

The chemically evoked efflux of endogenous amino acids from perfused rabbit superior colliculus (SC) slices was studied. Amino acids in the perfusates were determined fluorimetrically with a precolumn derivatisation method and subsequent separation on an HPLC column. Potassium-induced depolarisation caused a calcium-dependent release of beta-alanine, GABA, glutamate, and aspartate. Veratridine-evoked efflux was essentially similar in selectivity and could be blocked by tetrodotoxin (TTX). The results are indicative of a neurotransmitter role of beta-alanine, GABA, glutamate, and aspartate in the SC of the rabbit.

Alanine↗
PubMed1980

Potassium stimulated release of axonally transported radioactivity from slices of rabbit superior colliculus.

The radioactivity in the trichloroacetic acid (TCA) soluble pool in the terminals of the retinal ganglion cells in the superior colliculus (SC) was studied one month after labelling of the nerve cell bodies in the retina with different radioactive amino acids. The TCA soluble fraction in the SC represented a few per cent of the total radioactivity of the isolated tissue and was mainly derived from protein degradation. The perfused slice of the SC responded to high K+ depolarization with an increased release of TCA-soluble radioactivity, while small changes occurred for TCA-precipitable fractions. The evoked release of TCA-soluble radioactivity was particularly prominent after labelling with [3H]glycine. The release was Ca2+-dependent and the response to repetitive depolarization indicated a continuous replenishment of the releasable pool.

Amino Acids↗