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Biomedical subjects

W Frick

Publications and source records attributed to W Frick.

At least 19 recordsLinked to original sources
PubMed2003

Proliferation of myocytes on different ECM-components of animal/human origin in vitro.

For the purpose of tissue regeneration gels of reconstituted basement membrane have been suggested as a vehicle to transfer autologous cells. Results do look promising, but it should be considered that extracellular matrix (ECM) gel (Matrigel) is a soluble extract of Engelbreth-Holm-Swarm (EHS) mouse tumor. Therefore objections arising concerning possible risks complicate clinical use in human subjects. Aim of this study was to determine whether ECM-components of human origin can be used as substitutes for tissue engineering tasks as proposed previously. Proliferation capability and viability of primary rat myocytes and rat myocyte cell lines were determined on days 1, 2, 4 and 8 after inocculation of the cells. Pooled data suggest that an appropriate combination of human ECM and human Collagen Type IV may represent an approach with good prospects.

Animals↗
PubMed2001

Insulin-mimetic signaling by the sulfonylurea glimepiride and phosphoinositolglycans involves distinct mechanisms for redistribution of lipid raft components.

The insulin signal transduction cascade provides a number of sites downstream of the insulin receptor (IR) for cross-talk from other signaling pathways. Tyrosine phosphorylation of the IR substrates IRS-1/2 and metabolic insulin-mimetic activity in insulin-responsive cells can be provoked by soluble phosphoinositolglycans (PIG), which trigger redistribution from detergent-insoluble glycolipid-enriched raft domains (DIGs) to other areas of the plasma membrane and thereby activation of nonreceptor tyrosine kinases (NRTK) [Müller, G., Jung, C., Wied, S., Welte, S., Jordan, H., and Frick, W. (2001) Mol. Cell. Biol. 21, 4553-4567]. Here we describe that stimulation of glucose transport in isolated rat adipocytes by a different stimulus, the sulfonylurea glimepiride, is also based on IRS-1/2 tyrosine phosphorylation and downstream insulin-mimetic signaling involving activation of the NRTK, pp59(Lyn), and pp125(Fak), as well as tyrosine phosphoryation of the DIGs component caveolin. As is the case for PIG 41, glimepiride causes the concentration-dependent dissociation of pp59(Lyn) from caveolin and release of this NRTK and the glycosyl-phosphatidylinositol-anchored (GPI) proteins, Gce1 and 5'-nucleotidase, from total and anti-caveolin-immunoisolated DIGs. This results in their movement to detergent-insoluble raft domains of higher buoyant density (non-DIGs areas). IRS-1/2 tyrosine phosphorylation and glucose transport activation by both glimepiride and PIG are blocked by introduction into adipocytes of the caveolin scaffolding domain peptide which mimicks the negative effect of caveolin on pp59(Lyn) activity. Tyrosine phosphorylation of the NRTK, IRS-1/2, and caveolin as well as release of the NRTK and GPI proteins from DIGs and their redistribution into non-DIGs areas in response to PIG is also inhibited by treatment of intact adipocytes with either trypsin plus salt or N-ethylmaleimide (NEM). In contrast, the putative trypsin/salt/NEM-sensitive cell surface component (CIR) is not required for glimepiride-induced glucose transport, IRS-1/2 tyrosine phosphorylation, and redistribution of GPI proteins and NRTK. The data suggest that CIR is involved in concentrating signaling molecules at DIGs vs detergent-insoluble non-DIGs areas. These inhibitory interactions are relieved in response to putative physiological (PIG) or pharmacological (sulfonylurea) stimuli via different molecular mechanisms (dependent on or independent of CIR, respectively) thereby inducing IR-independent positive cross-talk to metabolic insulin signaling.

Adipocytes↗
PubMed2001

Nine-year results of Müller cemented titanium Straight Stems in total hip replacement.

At the Orthopaedic Department of the University of Basel, a total of 540 cemented Müller titanium alloy (Ti6Al7Nb) Straight Stems were inserted between 1989 and 1993. A cohort of 120 consecutive patients (66 women, 54 men) with 126 prostheses operated on between March and December 1989 were followed clinically and radiologically in a prospective manner for a mean observation time of 9.1 years. In all cases, the Müller titanium alloy Straight Stem was combined with the senior author's (E.W.M.) Press-Fit Cup. The mean age of the patients at surgery was 66 (range 43-93) years. Fourty patients (41 hips) died, 9 were interviewed by telephone, none was 'lost to follow-up'. Seventy-one patients with 76 hip replacements were available for the follow-up. Four hips had been revised: two of them due to aseptic loosening of the femoral component, one because of a late infection--all after 9 years--and one owing to a periprosthetic fracture after 6 years. The 9-year overall survivorship is 96.8%, and for aseptic loosening of the stem 98.4%. None of the cups had to be revised for aseptic loosening. The clinical result (according to Merle d'Aubigné) was excellent and good in 88%, moderate in 8%, and poor in 4%. The radiological analysis showed no osteolysis or radiolucent lines in 59 prostheses (78%). Nine stems (12%) showed a radiolucent line. Focal osteolysis was detected in 8 cases (10%) in one or more Gruen zones. The distribution of the osteolyses shows that predominantly zones VII, VI, V, and II are affected in decreasing frequency. No osteolysis was detected on the acetabular side. Our results do not confirm the high rate of osteolysis and revisions with the Müller titanium alloy Straight Stem presented by some other institutions. The verdict on a specific endoprosthetic implant must be made by combined assessment of the design, the implant surface condition, the material, the cement, the cementing procedure and the operative technique. The statement made in earlier publications that cemented titanium alloy should not be used as a femoral stem prosthesis should be reconsidered.

Adult↗
PubMed2001

Redistribution of glycolipid raft domain components induces insulin-mimetic signaling in rat adipocytes.

Caveolae and caveolin-containing detergent-insoluble glycolipid-enriched rafts (DIG) have been implicated to function as plasma membrane microcompartments or domains for the preassembly of signaling complexes, keeping them in the basal inactive state. So far, only limited in vivo evidence is available for the regulation of the interaction between caveolae-DIG and signaling components in response to extracellular stimuli. Here, we demonstrate that in isolated rat adipocytes, synthetic intracellular caveolin binding domain (CBD) peptide derived from caveolin-associated pp59(Lyn) (10 to 100 microM) or exogenous phosphoinositolglycan derived from glycosyl-phosphatidylinositol (GPI) membrane protein anchor (PIG; 1 to 10 microM) triggers the concentration-dependent release of caveolar components and the GPI-anchored protein Gce1, as well as the nonreceptor tyrosine kinases pp59(Lyn) and pp125(Fak), from interaction with caveolin (up to 45 to 85%). This dissociation, which parallels redistribution of the components from DIG to non-DIG areas of the adipocyte plasma membrane (up to 30 to 75%), is accompanied by tyrosine phosphorylation and activation of pp59(Lyn) and pp125(Fak) (up to 8- and 11-fold) but not of the insulin receptor. This correlates well to increased tyrosine phosphorylation of caveolin and the insulin receptor substrate protein 1 (up to 6- and 15-fold), as well as elevated phosphatidylinositol-3' kinase activity and glucose transport (to up to 7- and 13-fold). Insulin-mimetic signaling by both CBD peptide and PIG as well as redistribution induced by CBD peptide, but not by PIG, was blocked by synthetic intracellular caveolin scaffolding domain (CSD) peptide. These data suggest that in adipocytes a subset of signaling components is concentrated at caveolae-DIG via the interaction between their CBD and the CSD of caveolin. These inhibitory interactions are relieved by PIG. Thus, caveolae-DIG may operate as signalosomes for insulin-independent positive cross talk to metabolic insulin signaling downstream of the insulin receptor based on redistribution and accompanying activation of nonreceptor tyrosine kinases.

Adipocytes↗
PubMed2000

Cross talk of pp125(FAK) and pp59(Lyn) non-receptor tyrosine kinases to insulin-mimetic signaling in adipocytes.

Signaling molecules downstream from the insulin receptor, such as the insulin receptor substrate protein 1 (IRS-1), are also activated by other receptor tyrosine kinases. Here we demonstrate that the non-receptor tyrosine kinases, focal adhesion kinase pp125(FAK) and Src-class kinase pp59(Lyn), after insulin-independent activation by phosphoinositolglycans (PIG), can cross talk to metabolic insulin signaling in rat and 3T3-L1 adipocytes. Introduction by electroporation of neutralizing antibodies against pp59(Lyn) and pp125(FAK) into isolated rat adipocytes blocked IRS-1 tyrosine phosphorylation in response to PIG but not insulin. Introduction of peptides encompassing either the major autophosphorylation site of pp125(FAK), tyrosine 397, or its regulatory loop with the twin tyrosines 576 and 577 inhibited PIG-induced IRS-1 tyrosine phosphorylation and glucose transport. PIG-induced pp59(Lyn) kinase activation and pp125(FAK) tyrosine phosphorylation were impaired by the former and latter peptide, respectively. Up-regulation of pp125(FAK) by integrin clustering diminished PIG-induced IRS-1 tyrosine phosphorylation and glucose transport in nonadherent but not adherent adipocytes. In conclusion, PIG induced IRS-1 tyrosine phosphorylation by causing (integrin antagonized) recruitment of IRS-1 and pp59(Lyn) to the common signaling platform molecule pp125(FAK), where cross talk of PIG-like structures and extracellular matrix proteins to metabolic insulin signaling may converge, possibly for the integration of the demands of glucose metabolism and cell architecture.

Adipocytes↗
PubMed2000

[Concerning cell cultures for biocompatibility-testing: monitoring by DNA-fingerprinting].

Cell cultures are innovative tools for e.g. biocompatibility testing of biomaterials in vitro. In our studies we used fibroblast, endothelial cell and chondrocyte cultures of human origin and of the test animal species most common for this purpose in vivo. Verification of the identity of these cells is obligatory for reproducibility of the tests and valid interpretation of the results. Cultured cells have to be checked for identity, contaminations of various origins and also for genomic mutations occuring during prolonged cultivation in vitro or due to exposition to biomaterials. Furthermore, the risk of genetic cross-contamination with other cells increases with the number of cell cultures passaged parallel in the same laboratory. Therefore, we generated reference fingerprints of the cultures in varying passages for comparative monitoring of cells purposed for in vitro tests. Minisattelite DNA polymorhism resulting in reproducible individual DNA fingerprints is very discriminatory and can be used for cell culture monitoring. The patterns are stable over several passages, although sudden changes did happen in two cases, i.e. loss/gain of bands or changes in band-intensity, indicating massive genomic mutations of the cultures in vitro. Influences of biomaterials on the prints could not be detected. Several tasks can be followed at the same time: detection of contaminant cells, identification of these cells of primary culture origin used for in vitro testing and finally, monitoring for eventual genomic mutations due to prolonged cultivation or contact to biomaterials. Inconclusive results in just one of these aspects should lead to the disqualification of the monitored cultures from usage in vitro.

Animal Testing Alternatives↗
PubMed1999

Signalling via caveolin: involvement in the cross-talk between phosphoinositolglycans and insulin.

In recent years, a number of cross-talk systems have been identified which feed into the insulin signalling cascade at the level of insulin receptor substrate (IRS) tyrosine phosphorylation, e.g., receptor and non-receptor tyrosine kinases and G-protein-coupled receptors. At the molecular level, a number of negative modulator and feedback systems somehow interacting with the beta-subunit (catecholamine-, phorbolester-, or tumor necrosis factor-alpha-induced serine/threonine phosphorylation, carboxy-terminal trimming by a thiol-dependent protease, association of inhibitory/regulatory proteins such as RAD, PC1, PED, alpha2-HS-glycoprotein) have been identified as candidate mechanisms for the impairment of insulin receptor function by elevations in the activity and/or amount of the corresponding modification enzymes/inhibitors. Both decreased responsiveness and sensitivity of the insulin receptor beta-subunit for insulin-induced tyrosine autophosphorylation have been demonstrated in several cellular and animal models of metabolic insulin resistance as well as in the adipose tissue and skeletal muscle of diabetic patients and obese Pima Indians compared to non-obese subjects. Therefore, induction of the insulin signalling cascade by bypassing the defective insulin receptor kinase may be useful for the therapy of non-insulin dependent diabetes mellitus. During the past two decades, phosphoinositolglycans (PIGs) of various origin have been demonstrated to exert potent insulin-mimetic metabolic effects upon incubation with cultured or isolated muscle and adipose cells. However, it remained to be elucidated whether these compounds actually manage to trigger insulin signalling and if so at which level of hierarchy within the signalling cascade the site of interference is located. Recent studies using isolated rat adipocytes and chemically synthesized PIG compounds point to IRS1/3 tyrosine phosphorylation by p59Lyn kinase as the site of cross-talk, the negative regulation of which by interaction with caveolin is apparently abrogated by PIG. This putative mechanism is thus compatible with the recently formulated caveolin signalling hypothesis, the supporting data for which are reviewed here. Though we have not obtained experimental evidence for the involvement of PIG in physiological insulin action, the potential cross-talk between insulin and PIG signalling, including the caveolae/detergent-insoluble glycolipid-enriched rafts as the compartments where the corresponding signalling components are concentrated, thus represent novel targets for signal transduction therapy.

Amino Acid Sequence↗
PubMed1998

Insulin-mimetic signalling of synthetic phosphoinositolglycans in isolated rat adipocytes.

A set of synthetic phosphoinositolglycan (PIG) compounds has been demonstrated to exert insulin-mimetic activity on glucose and lipid metabolism in rat adipocytes differing considerably in potency [compound 41>37>45>>7>1; W. Frick, A. Bauer, J. Bauer, S. Wied and G. Müller, G. (1998) Biochemistry 37, 13421-13436]. In the present study we examine whether these differences are based on the capability of the PIG compounds to stimulate signalling components which are thought to mediate metabolic insulin action. Studies using a tyrosine kinase inhibitor and introduction into adipocytes of anti-phosphotyrosine or inhibitory anti-insulin receptor beta-subunit antibodies demonstrated dependence on tyrosine phosphorylation but independence of insulin receptor kinase activation of the insulin-mimetic signalling and metabolic activity of the PIG compounds. The five compounds elicited in rat adipocytes a significant increase in tyrosine phosphorylation of both insulin receptor substrate 1 (IRS-1) and IRS-3 and, to a minor degree, IRS-2, in IRS-1/3-associated phosphatidylinositol 3-kinase (PI 3-K) protein as well as activity, and in protein kinase B (PKB) activity as well as phosphorylation. This was most pronounced for compound 41, approaching 65-95% of the maximal insulin response (MIR) at 20 microM, and declined in the order of compounds 37, 45, 7 and 1. The same ranking was true for the maximal inhibition of glycogen synthase kinase 3 activity (GSK-3) (41, 75% of MIR; compound 37, 65%; compound 7, 25%; compound 1, 10%) and GSK-3 autophosphorylation. The half-maximal concentrations effective for signalling (compound 41, 2-5 microM; compound 37, 10-20 microM) corresponded well to those stimulating glucose and lipid metabolism. Interestingly, compounds 37 and 41 stimulated mitogen-activated protein kinase (MAPK) and protein synthesis in rat adipocytes to only about 20-30% (at 50 microM) of MIR. We conclude that in rat adipocytes: (i) the potency of PIG compounds to regulate glucose/lipid metabolism depends on the activation of PI 3-K and PKB and inhibition of GSK-3; (ii) initiation of tyrosine phosphorylation of IRS-1/3 is sufficient and activation of the PI 3-K cascade is required for insulin-mimetic metabolic signalling; and (iii) PIG compounds are quite selective for the PI 3-K compared to the MAPK cascade, (iv) PIG compounds seem to use the same signalling components downstream of PI 3-K (including Rab4) for stimulation of glucose transport as does insulin. Thus the early signalling step(s) used by PIG, but not by insulin, may represent a target for the treatment of insulin-resistant states.

Adipocytes↗
PubMed1998

Structure-activity relationship of synthetic phosphoinositolglycans mimicking metabolic insulin action.

Phosphoinositolglycan (PIG) molecules have been implicated to stimulate glucose and lipid metabolism in insulin-sensitive cells and tissues in vitro and in vivo. The structural requirements for this partial insulin-mimetic activity remained unclear so far. For establishment of a first structure-activity relationship, a number of PIG compounds were synthesized consisting of the complete or shortened/mutated glycan moiety derived from the structure of the glycosylphosphatidylinositol (GPI) anchor of the GPI-anchored protein, Gce1p, from yeast. The PIG compounds were divided into four classes according to their insulin-mimetic activity in vitro with the typical representatives: compound 41, HO-SO2-O-6Manalpha1(Manalpha1-2)-2Manalpha1 (6-HSO3)- -6Manalpha1-4GluNb eta1-6(D)inositol-1,2-(cyclic)-phosphate; compound 37, HO-PO(H)O-6Manalpha1(Manalpha1-2)-2Manalpha1-6Manal pha1-4GluNbeta1-6( D)inositol-1,2-(cyclic)-phosphate; compound 7, HO-PO(H)O-6Manalpha1-4GluN(1-6(L)inositol-1,2-(cyclic)-ph osp hate; and compound 1, HO-PO(H)O-6Manalpha1-4GluN(1-6(L)inositol. Compounds 41 and 37 stimulated lipogenesis up to 90% (at 20 microM) of the maximal insulin response but with differing concentrations required for 50% activation (EC50 values 2.5 +/- 0.9 vs 4.9 +/- 1.7 microM) as well as glycogen synthase (4.7 +/- 1 vs 9.5 +/- 1.5 microM) and glycerol-3-phosphate acyltransferase (3.5 +/- 0.8 vs 8.0 +/- 1.1 microM). Compound 7 was clearly less potent (20% of the maximal insulin response at 100 microM), whereas compound 1 was almost inactive. This relative ranking in the insulin-mimetic potency between members of the PIG classes (e.g., 41 > 37 >> 7 > 1) was also observed for the (i) activation of glucose transport and glucose transporter isoform 4 translocation in isolated normal and insulin-resistant adipocytes, (ii) inhibition of lipolysis in adipocytes, (iii) stimulation of glucose transport and glycogen synthesis in isolated normal and insulin-resistant diaphragms, and (iv) induction of tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) in diaphragms. The complete glycan core structure (Man3-GluN) of typical GPI anchors including a mannose side chain and the inositolphosphate moiety was required for maximal insulin-mimetic activity of the PIG compounds with some variations possible with respect to the type of residues coupled to the terminal mannose/inositol as well as the type of linkages involved. These data argue for the potency and specificity of the interaction of PIG molecules with putative signaling component(s) (presumably at the level of the IRS proteins) in adipose and muscle cells which finally lead to insulin-mimetic metabolic activity even in insulin-resistant states.

Adipocytes↗
PubMed1998

Convergence and divergence of the signaling pathways for insulin and phosphoinositolglycans.

Phosphoinositolglycan molecules isolated from insulin-sensitive mammalian tissues have been demonstrated in numerous in vitro studies to exert partial insulin-mimetic activity on glucose and lipid metabolism in insulin-sensitive cells. However, their ill-defined structures, heterogeneous nature, and limited availability have prohibited the analysis of the underlying molecular mechanism. Phosphoinositolglycan-peptide (PIG-P) of defined and homogeneous structure prepared in large scale from the core glycan of a glycosyl-phosphatidylinositol-anchored membrane protein from Saccharomyces cerevisiae has recently been shown to stimulate glucose transport as well as a number of glucose-metabolizing enzymes and pathways to up to 90% (at 2 to 10 microns) of the maximal insulin effect in isolated rat adipocytes, cardiomyocytes, and diaphragms (G. Müller et al., 1997, Endocrinology 138: 3459-3476). Consequently, we used this PIG-P for the present study in which we compare its intracellular signaling with that of insulin. The activation of glucose transport by both PIG-P and insulin in isolated rat adipocytes and diaphragms was found to require stimulation of phosphatidylinositol (PI) 3-kinase but to be independent of functional p70S6kinase and mitogen-activated protein kinase. The increase in glycerol-3-phosphate acyltransferase activity in rat adipocytes in response to PIG-P and insulin was dependent on both PI 3-kinase and p70S6kinase. This suggest that the signaling pathways for PIG-P and insulin to glucose transport and metabolism converage at the level of PI 3-kinase. A component of the PIG-P signaling pathway located up-stream of PI 3-kinase was identified by desensitization of isolated rat adipocytes for PIG-P action by combined treatment with trypsin and NaCl under conditions that preserved cell viability and the insulin-mimetic activity of sodium vanadate but completely blunted the insulin response. Incubation of the cells with either trypsin or NaCl alone was ineffective. The desensitized adipocytes were reconstituted for stimulation of lipogenesis by PIG-P by addition of the concentrated trypsin/salt extract. The reconstituted adipocytes exhibited 65-75% of the maximal PIG-P response and similar EC50 values for PIG-P (2 to 5 microns) compared with control cells. A proteinaceous N-ethylmaleimide (NEM)-sensitive component contained in the trypsin/salt extract was demonstrated to bind in a functional manner to the adipocyte plasma membrane of desensitized adipocytes via bipolar interactions. An excess of trypsin/salt extract inhibited PIG-P action in untreated adipocytes in a competitive fashion compatible with a receptor function for PIG-P of this protein. The presence of the putative PIG-P receptor protein in detergent-insoluble complexes prepared from isolated rat adipocytes suggests that caveolae/detergent-insoluble complexes of the plasma membrane may play a role in insulin-mimetic signaling by PIG-P. Furthermore, treatment of isolated rat diaphragms and adipocytes with PIG-P as well as with other agents exerting partially insulin-mimetic activity, such as PI-specific phospholipase C (PLC) and the sulfonylurea glimepiride, triggered tyrosine phosphorylation of the caveolar marker protein caveolin, which was apparently correlated with stimulation of lipogenesis. Strikingly, in adipocytes subjected to combined trypsin/salt treatment, PIG-P, PI-specific PLC, and glimepiride failed completely to provoke insulin-mimetic effects. A working model is presented for a signaling pathway in insulin-sensitive cells used by PIG(-P) molecules which involves GPI structures, the trypsin/salt- and NEM-sensitive receptor protein for PIG-P, and additional proteins located in caveolae/detergent-insoluble complexes.

Adipocytes↗
PubMed1991

The structure of bergenin.

X-ray analysis of the 3,4,8,10,11-penta-acetate (3) of bergenin has confirmed the earlier structural assignments.

Benzopyrans↗
PubMed1986

Pharmacological profile of the abeorphine 201-678, a potent orally active and long lasting dopamine agonist.

The central dopaminergic effects of an abeorphine derivative 201-678 were compared to those of apomorphine and bromocriptine in different model systems. After oral administration, this compound induced contralateral turning in rats with 6-hydroxydopamine induced nigral lesions and exhibited strong anti-akinetic properties in rats with 6-hydroxydopamine induced hypothalamic lesions. It decreased dopamine metabolism in striatum and cortex, but did not modify noradrenaline and serotonin metabolism in the rat brain. 201-678 counteracted the in vivo increase of tyrosine hydroxylase activity induced by gamma-butyrolactone. In vitro it stimulated DA-sensitive adenylate cyclase and inhibited acetylcholine release from rat striatal slices. This compound had high affinity for 3H-dopamine and 3H-clonidine binding sites. These results indicate that 201-678 is a potent, orally active dopamine agonist with a long duration of action. Furthermore it appears more selective than other dopaminergic drugs.

Acetylcholine↗
PubMed1986

Structure-activity relationships of dopaminergic 5-hydroxy-2-aminotetralin derivatives with functionalized N-alkyl substituents.

5-Hydroxy-2-aminotetralin derivatives in which one N-alkyl substituent carries a functional group have been prepared and their dopaminergic activities compared with those of 5-hydroxy-2-(di-n-propylamino)tetralin (5-OH-DPAT) and known ergolines. Several members of the series demonstrated high affinities in dopamine (DA) receptor binding and DA agonist properties in the rotational behavior model in the range of known potent ergolines. The results suggest that the accessory binding site for the larger N-alkyl substituent of the 5-hydroxy-2-aminotetralins can accommodate various neutral and bulky functionalities and is probably identical with the site(s) to which the 8-substituents of the ergolines bind.

Animals↗
PubMed1985

[3H]205-501, a non-catechol dopaminergic agonist, labels selectively and with high affinity dopamine D2 receptors.

[3H]205-501, a noncatechol dopaminergic agonist, is presented as a ligand with high affinity (KD approximately 1 nM) and high selectivity for dopamine receptors. pKi values of dopaminergic agonists derived from competition isotherms in the [3H]205-501 binding assay correlate very well with their potency in the acetylcholine release assay, which is controlled by dopamine D2 receptors. There is however no correlation with their potency stimulating adenylate cyclase, a process controlled by dopamine D1 receptors. Thus [3H]205-501 is the first agonist ligand selective for dopamine D2 receptors.

Acetylcholine↗
PubMed1985

Gangliosides alter morphology and growth of astrocytes and increase the activity of choline acetyltransferase in cultures of dissociated septal cells.

Administration of gangliosides has been reported to stimulate regeneration of motoneurons and of central dopaminergic and cholinergic neurons. To shed light on the mechanism by which gangliosides mediate the effects on cholinergic neurons, we studied their actions on cultures of cells dissociated from the septal area of fetal rat brains. These cultures contain cholinergic neurons, which, in vivo, give rise to the cholinergic septo-hippocampal pathway. Gangliosides produced prominent changes in the morphological appearance of the cultures. In contrast to control cultures, which contained many process-bearing cells and a confluent layer of flat cells, there were no flat cells in cultures grown in the presence of gangliosides (0.2 to 0.8 mg/ml of medium). Using immunocytochemical visualization of the astrocytic marker glial fibrillary acid protein, it was shown that all astrocytes in cultures grown in the presence of gangliosides exhibited the morphology of process-bearing cells, whereas in control cultures astrocytes represented the majority of the flat cells. Furthermore, gangliosides attenuated astrocytic proliferation. The effects of gangliosides apparently were not mediated by cAMP, since they could be differentiated from actions of forskolin, an activator of adenylate cyclase. Astrocytic growth and morphology were affected by ganglioside mixtures of various sources and composition and also by the pure gangliosides GM1 and GD1a, whereas lipid and carbohydrate components of gangliosides were ineffective. In contrast to the prominent effects on astrocytes, gangliosides failed to significantly alter survival or fiber growth of cholinergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗