Wilfried Seifert

Fibroblast Growth Factor Enhances Long-term Potentiation in the Hippocampal Slice.

Recently we reported that perfusion of hippocampal slices with epidermal growth factor (EGF) lead to enhancement of potentiated responses after tetanic stimulation. In the present study we report that basic fibroblast growth factor (FGF) can also lead to an enhancement of potentiated responses. FGF is a mitogen for several cell types and exhibits neurotrophic effects on neurons of the central nervous system (CNS). Rat hippocampal slices were perfused with FGF at a concentration of 10−9 M. During extra‐ and intracellular recordings in the CA1 ‐region, the addition of FGF to the perfusing medium produced no change in evoked responses if single pulse or paired pulse stimulation was used. Furthermore FGF had no influence on the resting membrane potential and input resistance. However, after tetanic stimulation, FGF‐treated slices showed an increase in the magnitude of potentiation compared to control slices. Taken together with the EGF data these results support the hypothesis that growth factors like FGF with neurotrophic potential on CNS‐neurons can influence synaptic efficacy. Furthermore these results show that factors which are able to modulate developmental plasticity and regenerative plasticity can also modulate synaptic plasticity.

Free radicals induce gene expression of NGF and bFGF in rat astrocyte culture.

Hydrogen peroxide (H2O2) is a type of active oxygen species produced mainly in blood by inflammation, ischemia or anoxia. Treatment of rat neonatal cortical astrocytes in culture with 0.2-1.0 mM H2O2 which is lethal for hippocampal neurons, increases nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) mRNA content in a time dependent manner. H2O2 also increases c-fos mRNA expression, which is probably involved in the gene regulation of both NGF and bFGF. Maximal induction was reached after 6 h of incubation (5.7-fold increase in NGF and 2.4-fold induction of bFGF mRNA). Hydrogen peroxide induced bFGF and NGF gene expression suggests that neurotrophic factors in astrocytes could be induced by lesion, consistent with their protective function in the CNS.

Glutamate induces the growth factors NGF, bFGF, the receptor FGF-R1 and c-fos mRNA expression in rat astrocyte culture.

The effect of glutamate on primary cultures of rat cortical astrocytes was studied using Northern blot hybridization. Incubation with glutamate (100 microM, 15 min) induced nerve growth factor (NGF), basic fibroblast growth factor (bFGF), FGF receptor (FGF-R1) and proto-oncogene c-fos gene expression in a time dependent manner. Maximal induction of NGF, bFGF and FGF-R1 mRNA was reached after 4 h of incubation (7.2-fold induction of NGF, 3-fold increase in bFGF and 3.6-fold induction of FGF-R1 mRNA). The induction kinetics of NGF, bFGF and FGF-R1 mRNA are similar. The rapid (1 h) 77-fold induction of the c-fos transcript precedes the induction of the other genes tested.

The role of monosialoganglioside GM1 in the synaptic plasticity: In vitro study on rat hippocampal slices.

Rat hippocampal slices were incubated with neuraminidase from Vibrio Cholerae. This enzyme liberates sialic acid from polysialogangliosides converting them into monosialoganglioside GM1. Thus, the tissue is enriched in GM1 content. Another set of slices was incubated with GM1 itself. Both treatments increased the magnitude of potentiation of synaptic response recorded from pyramidal cell layer following high frequency stimulation of Schaffer collateral-commissural fibers. It is concluded that enrichment of synaptic membranes in GM1 enhances the ability of these nerve endings to be potentiated.

Influence of epidermal growth factor on long-term potentiation in the hippocampal slice

Rat hippocampal slices were perfused with epidermal growth factor (EGF) at a concentration of 10(-8) M. EGF is a well known mitogen which exhibits neurotrophic action on neurons of the CNS. During extra- and intracellular recordings in the pyramidal cell body layer of the CA1-region no influence of EGF on evoked potentials was seen if single-pulse or paired-pulse stimulation was used. Furthermore EGF has no influence on the resting membrane potential of the cells investigated. However after tetanic stimulation a significant increase in the magnitude of long-term potentiation was observed. Therefore it is concluded, that EGF might be involved in modulation of neuronal plasticity.

bFGF induces its own gene expression in astrocytic and hippocampal cell cultures

Basic FGF mRNA induction by bFGF was investigated in cell cultures from rat brain, i.e. postnatal day 2 cortex and embryonic day 18 hippocampus. In situ hybridization shows that after bFGF treatment (10(-10) M) for 14 h neurones and glial cells show a remarkable increase in bFGF mRNA production. Incubation of astrocytes with antisense bFGF phosphorothioate oligodeoxynucleotides (bFGF-PTOs) resulted in an inhibition of both bFGF induced and serum induced proliferation. The results indicate that bFGF is capable of inducing its own mRNA production. This induction, i.e. new synthesis of bFGF mRNA, seems to be essential for the mitogenic effect of both bFGF and serum components.

On the chemical nature of alteration and modification of DNA dependent RNA polymerase of E. coli after T4 infection

After infection of E. coli with bacteriophage T4 the host DNA dependent RNA polymerase is changed by two consecutive processes [ 1,2] . The first of them, termed alteration is very rapid and coincides with the shut off of host transcription [3] . It requires neither protein synthesis nor the phage genome ]2] and therefore might reflect a dormant capacity of the host which is triggered by phage adsorption. The second process, termed modification, leads to a structural change of subunits f3’ and f3, a further change of (Y and the absence of u factor in the purified enzyme [ 1,2,4,5,6,7]. It requires protein synthesis and might be phage gene dependent. The work reported here aims at the understanding of the chemical nature of alteration and modification.

Survival-promoting and protein kinase C-regulating roles of basic FGF for hippocampal neurons exposed to phorbol ester, glutamate and ischaemia-like conditions

Recent evidence suggests that protein kinase C (PKC) is involved in the pathophysiology of neurodegenerative diseases. We examined the effect of basic fibroblast growth factor (bFGF) on the survival of cultured rat hippocampal neurons exposed to conditions in which PKC is likely to play a role. bFGF reduced neuron damage caused by the PKC‐activating phorbol ester 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), glutamate and ischaemia‐like culture conditions. bFGF was able to counteract the excessive activation of PKC caused by these treatments. Moreover, bFGF prevented the loss of PKC occurring after prolonged exposure to TPA or ischaemia‐like conditions. These results indicate that both the overactivation and the abnormal degradation of PKC can lead to neuron degeneration, and that the neurotrophic competence of bFGF may reside in its ability to regulate and normalize the PKC phosphorylating system.

Evidence for the functional role of monosialoganglioside GM1 in synaptic transmission in the rat hippocampus

The hippocampal slices were incubated with compounds which hydrolyze, modify or bind with sialic acid containing molecules. The efficiency of synaptic transmission was tested in the presence of these compounds. The size of the evoked extracellularly recorded potential following Schaffer collateral stimulation was used as an indicator of synaptic transmission efficiency. Sodium periodate (10 mM) and sodium perchlorate (59.2 mM) evoked a reversible (after washout) decrease in the size of the population spike. Higher concentration of sodium periodate (60 mM) abolished the size of the population spike, which was only poorly reversible after washout. Tetanus toxin, which binds to polysialogangliosides, and neuraminidase from Vibrio cholerae (an enzyme which splits off sialic acid from polysialogangliosides, leaving GM1 intact, and splits off sialic acid from sialoglycoproteins) had no influence on the size of the population spike. Cholera toxin, which binds to GM1, slightly reduced the size of the population spike. Incubation of the slices with neuraminidase from Arthrobacter ureafaciens (an enzyme which splits off sialic acid from all gangliosides, including GM1, and from sialoglycoproteins) abolished the population spike after 5 h. GM1 antiserum abolished the potential after approximately 100 min. The conclusion is drawn that of all gangliosides only GM1 is necessary to support synaptic transmission in Schaffer collateral-pyramidal cell synapses.

Immunological cross-reactivity of cultured rat hippocampal neurons with goldfish brain proteins synthesized during memory consolidation

Ependymins are goldfish brain glycoproteins exhibiting a specifically enhanced rate of synthesis when the animals adopt a new pattern of swimming behavior. With specific antisera against ependymins it has become possible to look for ependymin-like immunoreactivity in other animal species, both qualitatively by immunofluorescence staining and quantitatively by radioimmunoassay. Ependymin-like immunoreactivity was detected not only in other fish but also in rat brain. In the rat radioimmunoassay measurements were highest for the hippocampal formation and for cultured neurons derived from the embryonic hippocampus. Immunofluorescence staining was performed on various cell culture systems derived from rat brain, in order to establish which cell type contains the antigen. Only neuronal cell populations reacted with the anti-ependymin antisera. Cells derived from embryonic rat brain hippocampus which resembled pyramidal neurons stained particularly bright for ependymin-like immunoreactivity. The antigenic material was distributed throughout the cytoplasm including the neuronal extensions. Various neuron-specific antisera have been used to counterstain the cells containing ependymin-like immunoreactivity.