Biomedical subjects

E Hansson

Publications and source records attributed to E Hansson.

At least 19 recordsLinked to original sources

PubMed1992

[Astrocytes are of vital significance for the central nervous system].

The tissue of the CNS (central nervous system) is composed of neurons and neuroglia. Whereas neurons develop an ability for the rapid transduction of specific signals, astrocytes develop an ability to modulate the extracellular neuronal environment, and in mature CNS tissue manifest a capacity for active uptake of amino acids and ions. Astrocytes can control extracellular volume by regulation of their own volume, and are intimately involved in the neuronal exchange of trophic substances and metabolites. Astrocytic processes extend to blood vessel walls, the brain surface, the ventricular wall, neuronal cell bodies and synapses. Astrocytes are abundantly supplied with membrane receptors for various neurotransmitters, coupled to such second messenger systems as cyclic AMP (adenosine monophosphate) or the phosphatidylinositol cycle. Activation of the receptors results in changes in oxidative metabolism, cell morphology, cell volume, and immunocompetence: and recent findings have shown the occurrence of receptor-mediated changes in amino acid uptake. Thus, by modulating the extracellular environment, astrocytes can simultaneously modulate the sensitivity and/or excitability of large numbers of neurons. In the article are presented recent research findings suggesting astroglial cells to be targets for neurotransmitters, and probably to be actively involved in higher cognitive functions. Advances in our knowledge of astroglial cell characteristics might improve our understanding of behavioural disturbances and diseases of the CNS.

Astrocytes↗

PubMed1992

Volume regulation of single astroglial cells in primary culture.

Relative volume variations in cultured astrocytes were examined by microspectrofluorimetry after loading the cells with the highly fluorescent intracellular probes 2,7-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF/AM) or fura-2/AM. At their isosbestic points, 450 nm and 358 nm, respectively, the probes were ion-insensitive and the fluorescent signals emitted related only to the intracellular dye concentration. By varying the excitation wavelengths, changes in intracellular pH or Ca2+ transients could be recorded simultaneously with the relative volume variations of the individual cells. After exposure to a hypotonic buffer, type 1 astrocytes swelled within 30 s and subsequently underwent regulatory volume decrease (RVD). When exposed to a hypertonic buffer, the astrocytes shrunk and exhibited regulatory volume increase (RVI). One mM glutamate induced an increase in astrocyte volume in 60 sec and evoked cytosolic Ca2+ transients but did not change intracellular pH.

Animals↗

PubMed1992

Receptor-coupled uptake of valproate in rat astroglial primary cultures.

Various receptor ligands were investigated for their effects on the uptake of the antiepileptic drug valproic acid (VPA) in primary astroglial cultures from cerebral cortex of neonatal rats. After stimulation with the alpha 1-adrenoceptor agonist phenylephrine, 5-hydroxytryptamine (5-HT) or the glutamate receptor agonists glutamate, quisqualate and kainate, the Vmax and Km values for the drug transport increased. On the contrary, after exposure to the alpha 2-adrenoceptor agonist clonidine, Vmax and Km decreased. The effects were reversed in comparison to the control level in the presence of selective receptor antagonists. The data indicate a specific coupling between receptors and the uptake system for VPA. Furthermore, the results may have significant implications, as they suggest that receptors on astrocytes can be involved in the local regulation of drug transport in brain.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1992

Chronic elevation of cAMP levels induces changes in the adenylate cyclase system, opiate receptor sensitivity and levels of Gs-mRNA in cultured neurons.

Neurons in primary culture were treated (5 days) with the adenylate cyclase stimulator 10(-5) M forskolin. The basal adenylate cyclase was decreased by 57%. The acute stimulatory effect of forskolin was down-regulated by 48%. The inhibitory effects of the 3 opiate receptor agonists (mu, delta and kappa) were partly abolished. The abundance of mRNA encoding the stimulatory G-protein (Gs) was decreased prominently. The data indicate that the cAMP system in neuronal cells in primary culture is under dynamic regulation, possibly including altered Gs-protein gene expression. Furthermore, long-term forskolin treatment might induce increased proliferation in susceptible neural blast cells.

Adenylyl Cyclases↗

PubMed1992

Agonist-evoked Ca2+ transients in primary astroglial cultures--modulatory effects of valproic acid.

Cytosolic Ca2+ ([Ca2+]i) activity was measured in individual type 1 astroglial cells in primary culture after exposure to glutamate (Glu), quisqualate (QA), gamma-aminobutyric acid (GABA), 5-hydroxytryptamine (5HT), and noradrenaline (NA) by using the Ca2+ indicator dye fura-2/AM in a computerized microspectrofluorimetric system. Various patterns of Ca2+ transients were observed, but the most common was biphasic, having an initial sharp peak, rising immediately after stimulation, and then declining to a lower but sustained Ca2+ level. The only substance that diverged from this pattern was GABA, which induced a Ca2+ response with longer latency and a single-phase curve. The effects of the anticonvulsive drug Na(+)-valproate (VPA) were also investigated. After both acute and chronic (5-7 days) exposure to 10(-4) M VPA, the GABA-evoked rises in [Ca2+]i were completely inhibited. VPA also had acute effects on the 5HT- and Glu-evoked Ca2+ spikes. The Ca2+ responses after 5HT stimulation were greatly reduced after exposure to 10(-4) M VPA. The responses after glutamate stimulation were, on the contrary, increased after a similar exposure. No VPA effects were seen on the curve patterns of QA and NA stimulations. The most frequent agonist-evoked responses were seen after stimulation with 5HT and NA, where over 80% of the tested cells responded. For QA and Glu, the response frequencies were about 40% each, while for GABA it was 20%. The responses after 5HT and NA stimulation were blocked to baseline levels after exposure to ketanserin (5HT2 receptor antagonist) and a combination of prazosin, yohimbine, and propranolol (alpha 1, alpha 2, and beta adrenoceptor antagonists, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Delta and kappa opiate receptors in primary astroglial cultures. Part II: Receptor sets in cultures from various brain regions and interactions with beta-receptor activated cyclic AMP.

In a previous paper, delta and kappa opiate receptors were shown to be co-localized on the same cell in enriched primary cultures of astroglia from neonatal rat cerebral cortex. Activation of the receptors inhibited adenylate cyclase. In this work, the presence of opiate receptors was investigated in astroglial primary cultures from neonatal rat striatum and brain stem. Cyclic adenosine 3',5'-monophosphate accumulation was quantified in the presence of different opioid receptor ligands after stimulation of the cyclic adenosine 3',5'-monophosphate system with forskolin. Morphine was used as a mu receptor agonist. [D-Ala2, D-Leu5]-enkephalin or [D-Pen2, D-Pen5]-enkephalin were used as delta receptor agonists and dynorphin 1-13 or U-50,488H were used as kappa receptor agonists. Specific antagonists for the respective receptors were used. After striatum or brain stem cultures had been incubated in 10(-9)-10(-5) M of each [D-Ala2, D-Leu5]-enkephalin, [D-Pen2, D-Pen5]-enkephalin and Dynorphin 1-13 or U-50,488H, dose related inhibitions of the 10(-5) M forskolin stimulated cyclic adenosine 3',5'-monophosphate accumulation were observed. The changes were reversed to the forskolin-induced control level in the presence of the respective antagonists. 10(-9)-10(-5) M morphine did not significantly change the forskolin-induced accumulation of cyclic adenosine 3',5'-monophosphate in the cultures studied. Furthermore, cultures from cerebral cortex, striatum or brain stem were incubated with isoproterenol alone or together with morphine or [D-Ala2, D-Leu5]-enkephalin.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1992

Interactions between valproate, glutamate, aspartate, and GABA with respect to uptake in astroglial primary cultures.

Astrocytes have been proposed to regulate the extracellular space in the brain, even if rather little is known about their specific functions. One possibility for obtaining more knowledge on the functions of astroglial cells is to examine how they respond on exposure to pharmacological agents. Na(+)-valproate is an anticonvulsive drug which is used in the treatment of several types of epilepsy. The mechanisms of action of the drug are not fully understood, but the GABA-ergic system, both in neurons and astrocytes, has been shown to be affected. In the present study, the effects of valproate were investigated on astroglial cells in primary cultures from newborn rat cerebral cortex. The transport of the drug itself and its effects on the transport of the amino acid transmitters glutamate, aspartate and gamma-aminobutyric acid (GABA) into astrocytes were examined. The [3H]valproate transport into the astrocytes was increased after exposure to L-glutamate but not L-aspartate. On the other hand, after acute exposure for the drug, the transport of [3H]L-glutamate and [3H]L-aspartate decreased, as also did the affinity but not the transport capacity for the [3H]GABA uptake. However, after 5 days chronic valproate exposure, no effects could be seen on the uptake kinetics of L-glutamate or L-aspartate. For GABA, the affinity decreased, while the transport capacity remained unchanged compared with controls. The results showed that valproate, glutamate, aspartate and GABA were capable of interacting significantly with each others transport into the astrocytes.

Animals↗

PubMed1992

Receptor-mediated volume regulation in astrocytes in primary culture.

Changes in astroglial volume were studied after incubating primary cultures from the cerebral cortex of newborn rats for 5 hr in taurine, glutamate or gamma-aminobutyric acid (GABA), alone or together with monoamine receptor agonists. Control cell volume was 2.2 microliters/mg protein. In the presence of taurine or glutamate there was a small increase in cell volume, further augmented when the cells were incubated in isoproterenol plus taurine or phenylephrine, or isoproterenol plus glutamate. After incubation in 5-hydroxytryptamine (5-HT) plus taurine, on the other hand, the cell volume was not different from the control value. In the presence of GABA, alone or together with adrenoceptor agonists (alpha 1, alpha 2 or beta) or 5-HT, there were no significant changes in cell volume. The regulation of astroglial volume is complicated and affected by ion fluxes, free amino acids and metabolic events including changes in pH. The results are discussed in relation to late data on receptor regulation of active uptake of amino acids. Astroglial volume might be influenced by amino acid transport, partly under control of monoamine receptors.

Amino Acids↗

PubMed1992

Antipeptide antibodies for analysis of pathotype-specific variations in cleavage activation of the membrane glycoprotein precursors of Newcastle disease virus isolates in cultured cells.

Antipeptide antibodies have been produced which target regions either side of the cleavage activation sites of Newcastle disease virus (NDV) membrane glycoprotein precursors. Use of complementary pairs of antibodies in Western blot analysis of mercaptoethanol-reduced extracts of NDV-infected BHK-21 cells enabled analysis of the susceptibilities of NDV fusion protein precursors (Fo-proteins) to cleavage activation in these cells. In addition, it was possible to determine whether or not isolates produce haemagglutinin-neuraminidase (HN)-proteins in precursor forms (HNo-proteins). This assay system has been evaluated with a series of Australian isolates of NDV with well defined virulence properties in order to validate its use in pathotyping NDV isolates. Less well defined isolates also produced data consistent with their biological properties and an isolate was characterised which, hitherto, was not known to be present in Australian poultry. The applicability of this assay system in fundamental studies of the processes of cleavage activation of NDV Fo- and HNo-proteins and formatting of the antisera into ELISA systems are discussed.

Amino Acid Sequence↗

PubMed1992

Altered amounts of G-protein mRNA and cAMP accumulation after long-term opioid receptor stimulation of neurons in primary culture from the rat cerebral cortex.

Primary neuronal enriched cultures were incubated with mu (morphine, 10(-5) M), delta (DPDPE, 10(-6) M) and kappa (U-50,488H, 10(-5) M) receptor agonists for 5 days, respectively. Thereafter the acute inhibitory actions of mu, delta or kappa receptor agonists on forskolin stimulated cAMP accumulation was assayed. The effect of long term opioid treatment on the steady-state level of G-protein mRNA (G alpha s, G alpha i-1 and G alpha i-2) was analyzed using an RNAase protection hybridization assay. Incubation for 5 days with kappa receptor agonist resulted in an attenuated ability to decrease the accumulation of cAMP by kappa receptors, as well as mu and delta receptors, which was also observed after 5 days of incubation with the delta receptor agonist. Furthermore, the adenylate cyclase responsiveness to forskolin stimulation was markedly reduced in cultures treated with either delta or kappa receptor agonists. Five days of incubation with kappa receptor agonist resulted in an increase in the levels of G alpha s and G alpha i-2 mRNAs. No effects on the amounts of G alpha s mRNA, G alpha i-1 mRNA or G alpha i-2 mRNA were detected after 5 days of delta receptor stimulation. On the other hand, 5 days of mu receptor stimulation decreased the amounts of G alpha s, G alpha i-1 and G alpha i-2 mRNA. Incubation with kappa receptor agonist for 24 h resulted in a significant decrease in the forskolin-stimulated accumulation of cAMP. The stimulatory effect of forskolin was further decreased after 3 days incubation with kappa receptor agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Regulation of G-PROTEIN mRNA abundancy and cAMP accumulation after long-term opioid incubation in primary cultures of astroglia from the rat cerebral cortex.

Primary astroglial cultures were incubated with delta (10(-6) M DPDPE) or kappa (10(-5) M U-50,488H) receptor agonists for 5 days. Thereafter, the acute inhibitory actions of delta or kappa receptor agonists on forskolin stimulated cAMP accumulation were assayed. The G alpha s, G alpha i-1 and G alpha i-2 mRNA levels were quantified after 5 days of either delta or kappa receptor agonist treatment using a solution hybridization, RNase protection assay. Pronounced effects were observed after 5 days of kappa receptor agonist [10(-5) M U-50,488H] incubation. This treatment resulted in an attenuation in the acute inhibitory action of delta and kappa receptor agonists. Furthermore, a decreased stimulatory action of forskolin was seen. Similar effects were also seen after delta receptor stimulation. We also investigated the effects after 24 h and 3 days of incubation with the kappa receptor agonist (10(-5) M) U-50,488H. The 24 h incubation resulted in a decreased sensitivity to the acute inhibitory action of delta and kappa receptor agonists in the astroglial cultures. This effect was further accentuated after the 3 days of incubation with 10(-5) M U-50,488H. No significant change was seen in the basal accumulation of cAMP after incubation with the kappa agonist U-50,488H. However, after 5 days of incubation with the delta agonist DPDPE, a significantly increased basal accumulation of cAMP was seen in the astroglial cultures. After 5 days of delta or kappa agonist incubation, an increase in G alpha s mRNA level and a decrease in G alpha i-2 mRNA level was seen compared with controls. No statistically significant alterations in the amount of G alpha i-1 mRNA were seen. The data obtained in the present study indicate that the effects of long-term opioid treatment alters the sensitivity of glial cell opioid receptors. Furthermore, long term opioid treatment induces alterations in glial G-protein mRNA levels.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1992

Chronic encephalopathies induced by mercury or lead: aspects of underlying cellular and molecular mechanisms.

Long term exposure to low doses of mercury or lead can induce neurasthenic symptoms with slight cognitive deficits, lability, fatigue, decreased stress tolerance, and decreased simultaneous capacity. After exposure to higher concentrations permanent neuropsychological deficits can be seen. The present paper gives a new idea of possible molecular mechanisms underlying the symptoms. Impairments of astrocyte function are probably important, especially due to their capacity to regulate the ionic and amino acid concentration in the extracellular micromilieu, brain energy metabolism, and cell volume. Recent results have shown that these functions are under monoaminergic control. Aspects of therapy are outlined.

Astrocytes↗

PubMed1992

Effect of delmopinol on the cohesion of glucan-containing plaque formed by Streptococcus mutans in a flow cell system.

Glucan-containing plaque was formed by Streptococcus mutans adhering to saliva-coated glass slides in flow cells thermostated at 37 degrees C. The substrate was Brain Heart Infusion broth containing 1% sucrose and 10% sterile saliva. During the build-up of the plaque, which lasted for 29 h, the plaque was subjected to three two-minute exposures to either 0.1 mol/L sodium acetate buffer, pH 6.0, or the same buffer containing 6.4 mmol/L (0.2%) of the surface-active anti-plaque substance delmopinol hydro-chloride. The glass slides carrying the plaque were weighed, and plaques subjected to delmopinol treatment weighed only seven percent of the control plaques. The glass slides were then mounted in a beaker containing buffer, subjected to ultrasonication, and re-weighed. The delmopinol-treated plaques lost 59% of their wet weight upon sonication, while the controls lost only 19%. Control plaques having the same weight as delmopinol-treated plaques were not different from the control plaques grown for 29 h with regard to reduction of plaque weight after sonication. Transmission electron micrographs (TEM) showed a plaque dominated by globular or fibrillar matrix components in controls, while the delmopinol-treated plaque showed empty or unordered matrix areas between more densely packed cells. The TEM results were confirmed by scanning electron micrographs, which showed amorphous material associated with the bacterial cells in the control but not in the delmopinol-treated plaque. In conclusion, delmopinol reduced surface-associated glucan synthesis and lowered the cohesion of the plaque, indicating that glucan-containing plaque formed during repeated rinsings with delmopinol may be easier to remove by mechanical means than a non-treated plaque of this type.

Bacterial Adhesion↗

PubMed1991

Adrenergic and 5-HT2 receptors on the same astroglial cell. A microspectrofluorimetric study on cytosolic Ca2+ responses in single cells in primary culture.

Noradrenaline (NA) or 5-hydroxytryptamine (5-HT) evoked cytosolic Ca2+ mobilization in single type 1 astrocytes in primary culture from the cerebral cortex of newborn rat. The Ca2+ indicator dye fura-2/AM was used in a microspectrofluorimetric system to visualize fluctuations in the intracellular Ca2+ concentration. Activation of the adrenergic receptors alpha 1, alpha 2 and beta, or activation of the 5-HT2 receptors elicited different responses of Ca2+ mobilization with different types of Ca2+ spikes or oscillations. Principally, 4 different types of Ca2+ responses could be obtained: a sharp spike, which declined back to baseline; an initial sharp spike, which declined to a smaller but sustained Ca2+ elevation; an initial sharp spike which declined and showed low amplitude oscillations; and a sharp spike which declined back to baseline with baseline oscillations. Applications of the alpha 2 adrenoceptor agonist clonidine to individual astroglial cells evoked Ca2+ transients mostly in young cultures (cultivated for 7-10 days), while applications of the alpha 1 adrenoceptor agonist phenylephrine evoked Ca2+ transients mostly in older cultures (17-21 days of cultivation). Applications of the beta adrenoceptor agonist isoproterenol evoked Ca2+ transients in both young and older cultures, however, more frequent in older cultures. The alpha 2 and beta receptor responses were dependent on external Ca2+ levels. The NA-evoked Ca2+ responses were seen in cultivated cells at all ages, but were more frequent in older cultures. Approximately 50% of the astroglial cells in 8 day old cultures responded to 5-HT with a cytosolic Ca2+ mobilization and 80% of the cells in 21 day old cultures responded.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Receptor regulation of the glutamate, GABA and taurine high-affinity uptake into astrocytes in primary culture.

From experiments using dissociated primary astroglial cultures from newborn rat cerebral cortex, the stimulation of monoamine receptors (alpha, beta and 5HT) was shown to affect the high-affinity uptake kinetics of glutamate, GABA and taurine. In the presence of the alpha 1 agonist phenylephrine, there was an increased uptake (Vmax) of glutamate, while beta adrenoceptor activation slightly inhibited the glutamate uptake and stimulated the GABA and taurine uptakes. 5HT2 receptor stimulation caused a slight inhibition of the taurine uptake. The uptake rate of GABA was not affected by 5HT, alpha 1 or alpha 2 receptor agonists and the glutamate uptake was not affected by 5HT or alpha 2 receptor agonists. Nor was the taurine uptake affected by alpha 1 or alpha 2 receptor agonists. The active uptake of aspartate was unaffected by the presence of any of the monoamine receptor agonists used in this study. When the mechanisms behind these effects were studied, the GABA uptake seemed to be mediated via the G protein-adenylate cyclase complex in the receptor domain. Moreover, the K+ channels seemed to be involved. The taurine uptake, however, did not seem to be regulated by the same mechanism. It seems more probable that there is a direct interaction between the receptor and carrier of taurine at the membrane level. The mechanism underlying the receptor-regulated glutamate uptake is at present unclear, although it does not seem to involve protein kinase C.

Animals↗

PubMed1991

The presence of glutathione in primary neuronal and astroglial cultures from rat cerebral cortex and brain stem.

The concentration of the tripeptide glutathione (GSH) was measured in primary cultures of neurons and astroglial cells from rat cerebral cortex and brain stem. The concentration of GSH was found to be approximately 20 nmol/mg protein in the neuronal culture from the cerebral cortex and ca. 40 nmol/mg protein in the neuronal brain stem cultures. A GSH concentration of approximately 20 nmol/mg was observed in the astrocyte cultures from both brain regions. The possibility to increase the GSH concentration was tested by incubating the cultures in the presence of the GSH precursor gamma-glutamylcysteine (gamma-GC). In the cultured astrocytes gamma-GC produced a dose-dependent increase in GSH. A similar increase was observed in the neuronal cultures, but this effect failed to reach statistical significance.

Animals↗

PubMed1991

Heterogeneity among astroglial cells with respect to 5HT-evoked cytosolic Ca2+ responses. A microspectrofluorimetric study on single cells in primary culture.

The effect of 5-hydroxytryptamine (5HT) on cytoplasmic Ca2+ concentration was examined at the single cell level in astroglial enriched primary cultures from newborn rat cerebral cortex. Type 1 astroglial cells were identified and the Ca2+ indicator dye fura 2/AM was used in a microspectrofluorimetric system. Pharmacological studies indicated that the Ca2+ responses were mediated by 5HT2 receptors. Four different patterns of 5HT evoked cytosolic Ca2+ responses were identified including two different types of spike patterns and two types of Ca2+ oscillations (low amplitude and base-line spiking behaviour). In addition, cells with spontaneous Ca2+ oscillations were of two types, those responding to 5HT and those not responding to 5HT. The different responses were identified already on day 7 in culture and were followed up to day 21 with a concomitant increase in the number of responding cells, although the response patterns did not differ during culture. The triggering 5HT concentration was 1 microM. The results suggest that subpopulations of astrocytes exist with respect to 5HT2-evoked cytosolic Ca2+ mobilization.

Animals↗

PubMed1991

Mu and delta opiate receptors in neuronal and astroglial primary cultures from various regions of the brain--coupling with adenylate cyclase, localisation on the same neurones and association with dopamine (D1) receptor adenylate cyclase.

Primary cultures, enriched in neurones or astroglial cells, from three phylogenetically different regions of the brain of the rat, the cerebral cortex, the striatum and the brain stem, were used to investigate the presence of opiate receptors, coupled to adenylate cyclase. Morphine was used as a mu-receptor agonist and [D-Ala2, D-Leu5]-enkephalin (DADLE) was used as a delta-receptor agonist. In the neuronal cultures, both ligands inhibited the prostaglandin (PG)E1-stimulated intracellular accumulation of cyclic AMP dose-dependently, with the most prominent effects seen in the cultures of striatum and with DADLE being more potent than morphine. The opiate receptor antagonist, naloxone reversed the effects. Morphine and DADLE, added together, inhibited the PGE1-stimulated accumulation of cyclic AMP, less than the sum of the effects of each drug. Therefore, it might be that these opioid receptors are localized together on the same neurone. Striatal neurones contained dopamine receptors coupled to cyclic AMP, as second messenger. It was shown that the D1 (dopamine) receptor-stimulated activity of adenylate cyclase was inhibited by the mu and delta opioid receptor ligands. Thus, interactions at the level of adenylate cyclase seem to exist between D1, mu and delta opiate receptors. In the astroglial enriched cultures, DADLE inhibited the PGE1-induced accumulation of cyclic AMP, however, with a less prominent effect in the brain stem cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗