Neural crest stem cells protect spinal cord neurons from excitotoxic damage and inhibit glial activation by secretion of brain-derived neurotrophic factor.

The acute phase of spinal cord injury is characterized by excitotoxic and inflammatory events that mediate extensive neuronal loss in the gray matter. Neural crest stem cells (NCSCs) can exert neuroprotective and anti-inflammatory effects that may be mediated by soluble factors. We therefore hypothesize that transplantation of NCSCs to acutely injured spinal cord slice cultures (SCSCs) can prevent neuronal loss after excitotoxic injury. NCSCs were applied onto SCSCs previously subjected to N-methyl-D-aspartate (NMDA)-induced injury. Immunohistochemistry and TUNEL staining were used to quantitatively study cell populations and apoptosis. Concentrations of neurotrophic factors were measured by ELISA. Migration and differentiation properties of NCSCs on SCSCs, laminin, or hyaluronic acid hydrogel were separately studied. NCSCs counteracted the loss of NeuN-positive neurons that was otherwise observed after NMDA-induced excitotoxicity, partly by inhibiting neuronal apoptosis. They also reduced activation of both microglial cells and astrocytes. The concentration of brain-derived neurotrophic factor (BDNF) was increased in supernatants from SCSCs cultured with NCSCs compared to SCSCs alone and BDNF alone mimicked the effects of NCSC application on SCSCs. NCSCs migrated superficially across the surface of SCSCs and showed no signs of neuronal or glial differentiation but preserved their expression of SOX2 and Krox20. In conclusion, NCSCs exert neuroprotective, anti-apoptotic and glia-inhibitory effects on excitotoxically injured spinal cord tissue, some of these effects mediated by secretion of BDNF. However, the investigated NCSCs seem not to undergo neuronal or glial differentiation in the short term since markers indicative of an undifferentiated state were expressed during the entire observation period.

Coping with multiple sclerosis-the role of social support.

OBJECTIVE: The aim of this study was to get insights in mechanisms of coping and social support in multiple sclerosis (MS). BACKGROUND: Multiple sclerosis is the most common chronic inflammatory disease of the central nervous system in young adults. MS strains the patient through its unpredictable course and increasing disability. MATERIAL AND METHODS: A cross-sectional study was conducted. Two hundred and forty-three patients with MS were consecutively examined at two neurological hospitals. Besides sociodemographic variables, the level of impairment, depression, social support, and coping behavior was assessed. RESULTS: Researched patients were on average 44.0 years old (SD=11.6), were diagnosed for 8.2 years (SD=7.1), and had a mean EDSS of 4.0 (SD=2.2). Patients with MS with an EDSS of 3.0-6.0 are using more intensively cognitive or behavioral coping techniques than less (EDSS≤2.5) or stronger impaired patients (EDSS≥6.5). The level of impairment was further correlated with the amount of reported social support. CONCLUSION: Differences in coping behavior could be observed for different levels of impairment through MS. Patients tackle more intensively and more actively with their disease when trying to adapt to increasing disability with an EDSS range between 3.0 and 6.0. In addition, the coping behavior of patients with MS was connected to social support, especially support by family, friends, or other patients with MS. Results refer to the importance of special trainings to enhance coping abilities of patients with MS.

[Genetic methods for analysis of autoinflammatory diseases]. / Genetische Methoden für die Analyse autoinflammatorischer Erkrankungen.

Over the past years the phenotypic and genetic spectrum of autoinflammatory diseases has continuously increased. Moreover, several monogenic autoinflammatory disorders have now been identified where febrile episodes are not among the leading symptoms and which can be accompanied by autoimmune phenomena and susceptibility to infections. Autoinflammatory conditions that are characterized by uncontrolled activity of cytokines, such as interleukin-1 beta (IL1ß), tumor necrosis factor alpha (TNF-α) and type 1 interferons (1-IFN), are amenable to specific therapeutic interventions. Thus, identification of the underlying genetic cause is important. During diagnostic work-up, genetic testing of a patient with autoinflammation should be carried out depending on the clinical presentation. If a distinct disorder is suspected, sequencing of the causative gene should be performed. Genetic tests using next generation sequencing (NGS), such as panel sequencing, exome sequencing and array comparative genomic hybridization (CGH) can be carried out if symptoms cannot be assigned to a specific disease entity.

[Type I interferonopathies. Systemic inflammatory diseases triggered by type I interferons]. / Typ-I-Interferonopathien. Durch Typ-1-Interferone bedingte entzündliche Systemerkrankungen.

Type I interferons mediate immune defense against viral infections. The induction of type I interferons has stimulating and modulating effects on the innate and adaptive immune systems thereby reducing tolerance against self-antigens. Genetic defects that result in an inadequate activation of the type I interferon system can cause a group of inflammatory disorders, which are collectively referred to as type I interferonopathies. While the clinical spectrum of type I interferonopathies is broad and heterogeneous, neurological and cutaneous symptoms are the most frequent manifestations. Some clinical and genetic features of type I interferonopathies are shared by multifactorial diseases, such as systemic lupus erythematosus and systemic vasculitis. Advances in understanding the disease mechanisms underlying type I interferonopathies have pinpointed novel targets for therapeutic interventions.

Effects of repeated embryo collection on embryo recovery rate in fertile mares.

In mares, repeated embryo collection in successive oestrous cycles is necessary if a greater number of foals should be produced. We investigated effects of repeated embryo collection in fertile donor mares on embryo recovery rates. In addition, an influence of the individual mare and season on embryo recovery rates was studied. In nine mares, a total of 153 embryo collections were performed during 30 months (17 ± 2.2 embryo collections per mare). The overall embryo recovery rate was 64% and did not differ among mares. Between successive embryo collection procedures, recovery rate varied significantly; however, no increase or decrease in the embryo recovery rate with increasing number of successive embryo collections was seen. In three mares, ovulation ceased from November to February. In the remaining six mares, embryo production was successfully continued throughout winter and no influence of the month on embryo recovery rates was detected.

Receptive music therapy and salivary histamine secretion.

INTRODUCTION: Receptive music therapy (rMT) not only provides a good feeling but also a more effective healing process and mastery of stress. METHODS AND RESULTS: In a preliminary study it could be shown that American Doudouk-music (feel-good music) suppressed salivary histamine secretion in two groups (n = 4) of allergic and non-allergic young volunteers. Stress was induced by eating adverse food/allergenic food during music exposure. There was no response in the vein blood samples and no significant difference between the allergic and non-allergic groups. CONCLUSION: It can be concluded that saliva is an appropriate medium for histamine measurements during music exposure.

ABC-transporter gene-polymorphisms are potential pharmacogenetic markers for mitoxantrone response in multiple sclerosis.

Escalation therapy with mitoxantrone (MX) in highly active multiple sclerosis is limited by partially dose-dependent side-effects. Predictors of therapeutic response may result in individualized risk stratification and MX dosing. ATP-binding cassette-transporters ABCB1 and ABCG2 represent multi-drug resistance mechanisms involved in active cellular MX efflux. Here, we investigated the role of ABC-gene single nucleotide polymorphisms (SNPs) for clinical MX response, corroborated by experimental in vitro and in vivo data. Frequencies of ABCB1 2677G>T, 3435C>T and five ABCG2-SNPs were analysed in 832 multiple sclerosis patients (Germany, Spain) and 264 healthy donors. Using a flow-cytometry-based in vitro assay, MX efflux in leukocytes from individuals with variant alleles in both ABC-genes (designated genotype ABCB1/ABCG2-L(ow), 22.2% of patients) was 37.7% lower than from individuals homozygous for common alleles (ABCB1/ABCG2-H(igh), P < 0.05, 14.8% of patients), resulting in genotype-dependent MX accumulation and cell death. Addition of glucocorticosteroids (GCs) inhibited MX efflux in vitro. ABC-transporters were highly expressed in leukocyte subsets, glial and neuronal cells as well as myocardium, i.e. cells/tissues potentially affected by MX therapy. In vivo significance was further corroborated in experimental autoimmune encephalomyelitis in Abcg2(-/-) animals. Using a MX dose titrated to be ineffective in wild-type animals, disease course and histopathology in Abcg2(-/-) mice were strongly ameliorated. Retrospective clinical analysis in MX monotherapy patients (n = 155) used expanded disability status scale, relapse rate and multiple sclerosis functional composite as major outcome parameters. The clinical response rate [overall 121 of 155 patients (78.1%)] increased significantly with genotypes associated with decreasing ABCB1/ABCG2-function [ABCB1/ABCG2-H 15/24 (62.5%) responders, ABCB1/ABCG2-I(ntermediate) 78/98 (79.6%), ABCB1/ABCG2-L 28/33 (84.8%), exact Cochran-Armitage test P = 0.039]. The odds ratio for response was 1.9 (95% CI 1.0-3.5) with each increase in ABCB1/ABCG2 score (from ABCB1/ABCG2-H to -I-, and -I to -L). In 36 patients with severe cardiac or haematological side effects no statistically relevant difference in genotype frequency was observed. However, one patient with biopsy proven cardiomyopathy only after 24 mg/m2 MX exhibited a rare genotype with variant, partly homozygous alleles in 3 ABC-transporter genes. In conclusion, SNPs in ABC-transporter genes may serve as pharmacogenetic markers associated with clinical response to MX therapy in multiple sclerosis. Combined MX/GC-treatment warrants further investigation.

Intracellular distribution of mammalian protein kinase A catalytic subunit altered by conserved Asn2 deamidation.

The catalytic (C) subunit of protein kinase A functions both in the cytoplasm and the nucleus. A major charge variant representing about one third of the enzyme in striated muscle results from deamidation in vivo of the Asn2 residue at the conserved NH(2)-terminal sequence myrGly-Asn-Ala (Jedrzejewski, P.T., A. Girod, A. Tholey, N. König, S. Thullner, V. Kinzel, and D. Bossemeyer. 1998. Protein Sci. 7:457-469). Because of the increase of electronegativity by generation of Asp2, it is reminiscent of a myristoyl-electrostatic switch. To compare the intracellular distribution of the enzymes, both forms of porcine or bovine heart enzyme were microinjected into the cytoplasm of mouse NIH 3T3 cells after conjugation with fluorescein, rhodamine, or in unlabeled form. The nuclear/cytoplasmic fluorescence ratio (N/C) was analyzed in the presence of cAMP (in the case of unlabeled enzyme by antibodies). Under all circumstances, the N/C ratio obtained with the encoded Asn2 form was significantly higher than that with the deamidated, Asp2 form; i.e., the Asn2 form reached a larger nuclear concentration than the Asp2 form. Comparable data were obtained with a human cell line. The differential intracellular distribution of both enzyme forms is also reflected by functional data. It correlates with the degree of phosphorylation of the key serine in CREB family transcription factors in the nucleus. Microinjection of myristoylated recombinant bovine Calpha and the Asn2 deletion mutant of it yielded N/C ratios in the same range as encoded native enzymes. Thus, Asn2 seems to serve as a potential site for modulating electronegativity. The data indicate that the NH(2)-terminal domain of the PKA C-subunit contributes to the intracellular distribution of free enzyme, which can be altered by site-specific in vivo deamidation. The model character for other signaling proteins starting with myrGly-Asn is discussed.

Controlling the structure of sequence-defined poly(phosphodiester)s for optimal MS/MS reading of digital information.

Digital polymers are monodisperse chains with a controlled sequence of co-monomers, defined as letters of an alphabet, and are used to store information at the molecular level. Reading such messages is hence a sequencing task that can be efficiently achieved by tandem mass spectrometry. To improve their readability, structure of sequence-controlled synthetic polymers can be optimized, based on considerations regarding their fragmentation behavior. This strategy is described here for poly(phosphodiester)s, which were synthesized as monodisperse chains with more than 100 units but exhibited extremely complex dissociation spectra. In these polymers, two repeating units that differ by a simple H/CH3 variation were defined as the 0 and 1 bit of the ASCII code and spaced by a phosphate moiety. They were readily ionized in negative ion mode electrospray but dissociated via cleavage at all phosphate bonds upon collisional activation. Although allowing a complete sequence coverage of digital poly(phosphodiester)s, this fragmentation behavior was not efficient for macromolecules with more than 50 co-monomers, and data interpretation was very tedious. The structure of these polymers was then modified by introducing alkoxyamine linkages at appropriate location throughout the chain. A first design consisted of placing these low dissociation energy bonds between each monomeric bit: while cleavage of this sole bond greatly simplified MS/MS spectra, efficient sequencing was limited to chains with up to about 50 units. In contrast, introduction of alkoxyamine bonds between each byte (i.e. a set of eight co-monomers) was a more successful strategy. Long messages (so far, up to 8 bytes) could be read in MS3 experiments, where single-byte containing fragments released during the first activation stage were further dissociated for sequencing. The whole sequence of such byte-truncated poly(phosphodiester)s could be easily re-constructed based on a mass tagging system which permits to determine the original location of each byte in the chain. Copyright © 2017 John Wiley & Sons, Ltd.

The structure of OmpF porin in a tetragonal crystal form.

BACKGROUND: OmpF porin is a trimeric integral membrane protein responsible for the passive transport of small hydrophilic molecules, such as nutrients and waste products, across the outer membrane of Escherichia coli. Very few membrane proteins have been crystallized in three dimensions, yet this stable protein can be obtained in several crystal forms. Comparison of the structures of the same membrane protein in two different packing environments is of major interest, because it allows us to explore the integrity of the structure outside the natural membrane environment. RESULTS: The structure of OmpF porin in a tetragonal crystal form with two trimers per asymmetric unit has been determined at 3.2 A resolution and compared with that obtained previously in a trigonal crystal form. The lattice contacts involve only polar atoms, whereas extensive hydrophobic protein-protein interactions were found in the trigonal lattice. The trimer structure is virtually identical in both. CONCLUSIONS: Our comparison reveals that the overall structure of OmpF is not influenced by crystal lattice constraints and, thus, presumably bears close resemblance to the in vivo structure. The tetragonal crystal structure has provided the starting model for the phasing of neutron diffraction data obtained from this crystal form, as described in an accompanying article.

Costs and quality of life of multiple sclerosis in Germany.

This cost-of-illness analysis based on information from 2973 patients with multiple sclerosis (MS) in Germany is part of a Europe-wide study on the costs of MS. The objective was to analyze the costs and quality of life (QOL) related to the level of disease severity. Patients from six centres (office- and hospital-based physicians) and patients enrolled in a database were asked to participate in the survey; 38% answered a mail questionnaire. In addition to details on the disease (type of disease, relapses, level of functional disability), the questionnaire asked for information on all resource consumption, medical, non-medical, work absence, informal care, as well as QOL (measured as utility). The mean age of the cohort was 45 years, and 18% of patients were 65 years of age or older. Forty-seven percent of patients had mild disease (Expanded Disability Status Scale [EDSS] score 0-3), 36% had moderate disease (EDSS score 4-6.5) and 12% had severe disease (EDSS score > or =7). The mean EDSS score in the sample was 3.8 (median 4.0), with a mean utility of 0.62. Costs and utility are highly correlated with disease severity. Workforce participation decreases from 73% in very early disease to less than 10% in the very late stages, leading to a tenfold rise in productivity losses in the late stages of disease. Hospitalisation and ambulatory visits rise by a factor of 5-6 between early and late disease; investments and services increase from basically no cost to euro 2700; and informal care increases by a factor of 27 for patients with an EDSS score of 7 and by a factor of 50 for patients at the very severe end of the EDSS scale (8-9). Hence, total mean costs per patient are determined essentially by the distribution of the severity levels in the sample, increasing from approximately euro 18 500 at an EDSS score of 0-1 to euro 70 500 at an EDSS score of 8-9. The same is true for utility, which decreases from 0.86 to 0.10 as the disease becomes severe. However, the utility loss compared to the general population is high at all levels of the disease, leading to an estimated loss of 0.2 quality-adjusted life-years per patient. Relapses are associated with a cost of approximately euro 3 000 and a utility loss of 0.1 during the quarter in which they occur. Compared with a similar study performed in 1999, resource consumption, with the exception of drugs, is somewhat lower. This is most likely due to a difference in the severity distribution of the two samples and to changes in health-care consumption overall in the country, such as the introduction of diagnosis-related groups (DRGs, Fallpauschalen).

Revealing the quality of movement: A meta-analysis review to quantify the thresholds to pathological variability during standing and walking.

Neuromotor processes are inherently noisy, which results in variability during movement and fluctuations in motor control. Although controversial, low levels of variability are traditionally considered healthy, while increased levels are thought to be pathological. This systematic review and meta-analysis of the literature investigates the thresholds between healthy and pathological task variability. After examining 13,195 publications, 109 studies were included. Results from over 3000 healthy subjects and 2775 patients revealed an overall positive effect size of pathology on variability of 0.59 for walking and 0.80 for sway. For the coefficient of variation of stride time (ST) and sway area (SA), upper thresholds of 2.6% and 265mm(2) discriminated pathological from asymptomatic performance, while 1.1% and 62mm(2) identified the lower thresholds for pathological variability. This window of healthy performance now provides science based evidence for the discrimination of both extremely low and extremely high levels of variability in the identification as well as standardised monitoring of functional status in neurological cases.

Characterisation of the major intrinsic protein (MIP) from bovine lens fibre membranes by electron microscopy and hydrodynamics.

The major intrinsic protein (MIP) from bovine lens fibre membranes has been purified from unstripped membranes using a single ion-exchange chromatography step (MonoS) in the non-ionic detergent octyl-beta-D-glucopyranoside (OG). SDS-PAGE has confirmed the purity of the preparation and thin-layer chromatographic analysis has shown that the protein is virtually lipid-free. To establish a stable and monodisperse protein sample, we exchanged OG with decyl-beta-D-maltopyranoside (DeM), another non-ionic detergent, by gel-filtration column chromatography. We conclude that the resulting protein/detergent complex is composed of four copies of MIP (a tetramer) and a detergent micelle. This conclusion is based on: (1) measurement of the weight-average molecular mass (Mw,app) of the protein moiety in the protein/detergent complex by sedimentation equilibrium; (2) measurement of the apparent molecular mass of the complexes formed by MIP in OG, in DeM, in dodecyl-beta-D-maltopyranoside (DoM) and in sodium dodecylsulphate (SDS) by gel filtration; (3) measurement of the apparent molecular mass of pure detergent micelles; (4) measurement of the predicted change in the molecular mass of the MIP/DeM complex after partial enzymatic proteolysis; and (5) measurement of the size and shape of the MIP/detergent complex by electron microscopy and single-particle analysis. Therefore, the tetragonal arrangement of MIP observed in both plasma membranes and junctional membranes in lens fibre cells is maintained in solution with non-ionic detergents.

The amino terminus of PKA catalytic subunit--a site for introduction of posttranslational heterogeneities by deamidation: D-Asp2 and D-isoAsp2 containing isozymes.

Conserved deamidation of PKA catalytic subunit isozymes Calpha and Cbeta--more than 25% at Asn2 in vivo in both cases--has been shown to yield Asp2- and isoAsp2-containing isozymes (Jedrzejewski PT, Girod A, Tholey A, König N, Thullner S, Kinzel V, Bossemeyer D, 1998, Protein Sci 7:457-469). Isoaspartate formation in proteins in vivo is indicative of succinimide intermediates involved in both the initial deamidation reaction as well as the "repair" of isoAsp to Asp by the action of protein L-isoaspartyl (D-aspartyl) O-methyl transferase (PIMT). L-Succinimide is prone to racemization to D-succinimide, which may hydrolyze to D-isoAsp- and D-Asp-containing diastereomers with, respectively, no and poor substrate character for PIMT. To analyze native PKA catalytic subunit from cardiac muscle for these isomers the N-terminal tryptic peptides (T1) of the enzyme were analyzed following procedures refined specifically with a set of corresponding synthetic peptides. The methods combined high resolution high-performance liquid chromatography and a new mass spectrometric procedure for the discrimination between Asp- and isoAsp-residues in peptides (Lehmann et al., 2000). The results demonstrate the occurrence of D-isoAsp- and D-Asp-containing T1 fragments in addition to the L-isomers. The small amount of the L-isoAsp isomer, representing only part of the D-isoAsp isomer, and the relatively large amounts of the L-Asp and D-Asp isomers argues for an effective action of PIMT present in cardiac tissue.

A conserved deamidation site at Asn 2 in the catalytic subunit of mammalian cAMP-dependent protein kinase detected by capillary LC-MS and tandem mass spectrometry.

The N-terminal sequence myr-Gly-Asn is conserved among the myristoylated cAPK (protein kinase A) catalytic subunit isozymes Calpha, Cbeta, and Cgamma. By capillary LC-MS and tandem MS, we show that, in approximately one third of the Calpha and Cbeta enzyme populations from cattle, pig, rabbit, and rat striated muscle, Asn 2 is deamidated to Asp 2. This deamidation accounts for the major isoelectric variants of the cAPK C-subunits formerly called CA and CB. Deamidation also includes characteristic isoaspartate isomeric peptides from Calpha and Cbeta. Asn 2 deamidation does not occur during C-subunit preparation and is absent in recombinant myristoylated Calpha (rCalpha) from Escherichia coli. Deamidation appears to be the exclusive pathway for introduction of an acidic residue adjacent to the myristoylated N-terminal glycine, verified by the myristoylation negative phenotype of an rCalpha(Asn 2 Asp) mutant. This is the first report thus far of a naturally occurring myr-Gly-Asp sequence. Asp 2 seems to be required for the well-characterized (auto)phosphorylation of the native enzyme at Ser 10. Our results suggest that the myristoylated N terminus of cAPK is a conserved site for deamidation in vivo. Comparable myr-Gly-Asn sequences are found in several signaling proteins. This may be especially significant in view of the recent knowledge that negative charges close to myristic acid in some proteins contribute to regulating their cellular localization.

Structural analysis of hnRNP particles approached by in vitro phosphorylation using exogenous protein kinase and l gamma 32 P1 ATP.

Using an exogenous kinase, nuclear ribonucleoprotein complexes with sedimentation coefficients greater than 100S were phosphorylated in vitro before and after treatment with increasing concentrations of NaC1. The phosphorylation pattern of the proteins before raising the NaC1 concentration shows a major group of labelled proteins in the 30 000 to 40 000 MW range. Treatment of the complexes with 400 and 800 mM NaC1 produces a relative increase in the labelling of some polypeptides with the appearance of new labelled bands and the concomitant disappearance of several proteins. Even at the highest salt concentration used (1.2 M), it is still possible to identify a group of labelled polypeptides which are suggested to form the backbone structure of the nuclear RNP complexes.

CSF and serum levels of soluble interleukin-6 receptors (sIL-6R and sgp130), but not of interleukin-6 are altered in multiple sclerosis.

Interleukin-6 (IL-6) has recently been implicated in multiple sclerosis (MS), since IL-6 deficient mice were resistant to a demyelinating form of experimental autoimmune encephalomyelitis and IL-6 expression was upregulated in MS. The cytokine IL-6 and its action mediating soluble receptors (sIL-6R and sgp130) were measured in cerebrospinal fluid (CSF) and serum of 61 MS patients and 39 controls. In the presence of unchanged IL-6 concentrations, sIL-6R and sgp130 serum levels were significantly increased in MS and correlated with disease severity. Furthermore, sgp130 CSF levels were decreased in MS, suggesting a possibly altered IL-6 regulation in the CSF.

Functional AMPA/kainate receptors in human embryonic and foetal central nervous system.

Here, functional AMPA/kainate receptors in human embryonic (5.5-7.5 gestational weeks) and foetal (8-10 gestational weeks) central nervous system tissue, shown by the cobalt labeling method, are reported. Specific agonist-induced cobalt incorporation was detected in brainstem and spinal cord cells, even in the youngest embryo studied. T-AMPA or kainate, but also vegetal toxins such as L-BOAA or acromelate, induced accumulation of cobalt. In contrast, no labeling was observed after exposure to KCl or NMDA. Cobalt labeled cells were particularly prominent in motor regions of brainstem and spinal cord. Co-application of the diuretic agent cyclothiazide, a desensitization blocker at AMPA receptors, dramatically increased the number of stained cells, which was particularly obvious in sensory regions, suggesting different receptor properties in motor versus sensory regions. This is the first study providing evidence for functional AMPA/kainate receptors, permeable to divalent cations, in brainstem and spinal cord at an early stage of human central nervous system development. Since many developmental processes are influenced by the modulation of cytosolic calcium, exposure at critical stages of embryogenesis to food or drug substances modifying the activity of AMPA/kainate receptors may alter brain development.

AMPA elicits long-lasting, partly hypothermia-sensitive calcium responses in acutely dissociated or cultured embryonic brainstem cells.

This study aimed at testing if, and under which conditions, long-lasting cytosolic calcium responses can be induced in dissociated embryonic brain cells exposed to alpha-amino-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor agonists. Rat brainstem cells (gestation days 13-14; mean crown-rump lengths 8-11 mm) were mechanically dissociated and loaded with the fluorescent calcium marker Fluo-3 after in vitro delays ranging from 20 min to 6 days. The cells were exposed to various concentrations of AMPA, domoic acid or kainic acid. The evoked fluorescence changes, indicating variations of cytosolic calcium, were recorded and analysed either with a video-microscope or a laser cytometer. Even at the earliest stages, non-desensitizing (or partly desensitizing) calcium responses to AMPA were found. In addition, sequential exposure to AMPA followed either by domoic acid, or by AMPA in the presence of aniracetam, revealed the existence of cells bearing predominantly desensitizing receptors. The non-desensitizing as well as desensitizing response components were blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX). When the experiments were conducted at 24 degrees C, the cytosolic calcium levels generally returned close to pre-stimulus baseline levels after washout. In contrast, when the working temperature was slightly raised (to 27 degrees C), complex secondary calcium rises were observed not only during prolonged stimulation, but also after short agonist application. The calcium modulation might be correlated with some form of cellular "learning" in the embryonic brain. Under particular conditions, where the regulation processes are either switched off by cell programmes or simply overloaded, the cascade of events comprising secondary calcium rises may lead to cell death.

Blockade of AMPA/kainate receptors can either decrease or increase the survival of cultured neocortical cells depending on the stage of maturation.

Neurotoxicity has often been associated with glutamate receptor stimulation and neuroprotection with glutamate receptor blockade. However, the relationship may be much more complex. We dissociated cells from the rat neocortical anlage at an early stage of prenatal development (embryonic day 14). The cells were exposed in vitro to agonists and antagonists of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)/kainate and N-methyl-D-aspartate (NMDA) receptors and the effects on differentiation and survival have been quantitatively and qualitatively evaluated. NMDA and the non-competitive antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801) had the expected effects (the agonist decreasing and the antagonist increasing neuronal survival) when applied at a relatively advanced stage of in vitro maturation, but no significant effect in either direction at earlier stages. Kainate also had an effect on cell survival only at an advanced stage (where it decreased the number of cells). However, this cannot be attributed to the absence of functional AMPA/kainate receptors at earlier stages, since: (1) cells could be loaded with cobalt; and (2) early application of kainate dramatically reduced the number of cobalt-positive cells. Furthermore, exposure at early stages to 6,7-dinitroquinoxaline-2,3-dione (DNQX), or GYKI 53655, (competitive and non-competitive AMPA receptor antagonists, respectively) strongly reduced cell survival. The effects were concentration- and time-dependent with a complex time--curve. The decrease in cell number was maximal after antagonist application from 2 to 5 days in vitro. The effects of DNQX could be cancelled by co-application of kainate. When exposed to an antagonist at later stages of development, the number of surviving cells gradually approached control values and finally became significantly higher. Our results suggest that cells of the developing neocortex (and perhaps newly generated cells in the adult brain) require at different stages of their development, an appropriate level of AMPA/kainate receptor activation.