S-100 beta has a neuronal localisation in the rat hindbrain revealed by an antigen retrieval method

A new model for diffuse brain injury by rotational acceleration: I model, gross appearance, and astrocytosis

Rapid head rotation is a major cause of brain damage in automobile crashes and falls. This report details a new model for rotational acceleration about the center of mass of the rabbit head. This allows the study of brain injury without translational acceleration of the head. Impact from a pneumatic cylinder was transferred to the skull surface to cause a half-sine peak acceleration of 2.1 x 10(5) rad/s2 and 0.96-ms pulse duration. Extensive subarachnoid hemorrhages and small focal bleedings were observed in the brain tissue. A pronounced reactive astrogliosis was found 8-14 days after trauma, both as networks around the focal hemorrhages and more diffusely in several brain regions. Astrocytosis was prominent in the gray matter of the cerebral cortex, layers II-V, and in the granule cell layer and around the axons of the pyramidal neurons in the hippocampus. The nuclei of cranial nerves, such as the hypoglossal and facial nerves, also showed intense astrocytosis. The new model allows study of brain injuries from head rotation in the absence of translational influences.

bFGF induces differentiation and death of olfactory neuroblastoma cells

Olfactory neuroblastoma (ONB) is a highly vascularized and malignant tumor arising in olfactory neuronal precursors from the paranasal sinuses. Previously, we showed that treatment of JFEN cells with transforming growth factor (TGF)-alpha caused them to differentiate and respond to chemical odorants, whereas basic fibroblast growth factor (bFGF) treated cells differentiated and died. In the present study we show that established ONB tumors treated with bFGF upregulate the bFGF receptor (FGFR1) prior to differentiation. This cellular differentiation was evidenced by bFGF-induced expression of the human runt homologue AML1 (PEBP2 alpha B, CBFA-2) that is highly expressed in developing olfactory neuroepithelium and TrkA, a preferred nerve growth factor receptor. Since TrkA is expressed in supporting cells, but not in mature olfactory neurons, we hypothesize that the expression of AML1 and TrkA in bFGF-treated JFEN cells induced supporting cell differentiation. Collectively, these results have implications for the treatment of patients afflicted with ONB.

Blast exposure causes redistribution of phosphorylated neurofilament subunits in neurons of the adult rat brain

There is little information on threshold levels and critical time factors for blast exposures, although brain damage after a blast has been established both clinically and experimentally. Moreover, the cellular pathophysiology of the brain response is poorly characterized. This study employs a rat model for blast exposure to investigate effects on the neuronal cytoskeleton. Exposure in the range of 154 kPa/198 dB or 240 kPa/202 dB has previously been shown neither to cause visual damage to the brain, nor to affect the neuronal populations, as revealed with routine histology. Here, the brains were investigated immunohistochemically from 2 h to 21 days after blast exposure. A monoclonal antibody was used which detects only the phosphorylated epitope of the heavy subunit of the neurofilament proteins (p-NFH). This epitope is normally restricted to axons, that is, not demonstrable in the perikarya. Eighteen hours after exposure in the 240-kPa/202-dB range, p-NFH immunoreactivity accumulated in neuronal perikarya in layers II-IV of the temporal cortex and of the cingulate and the piriform cortices, the dentate gyrus and the CA1 region of the hippocampus. At the same time, the p-NFH immunoreactivity disappeared from the axons and dendrites of cerebral cortex neurons. The most pronounced immunostaining of neuronal perikarya was found in the hemisphere, which faced the blast source. The perikaryal accumulation of p-NFH was present also at 7 days but the neuronal perikarya had become negative at 21 days, at which time the axons again displayed p-NFH immunoreactivity. Exposure in the range of 154 kPa/198 dB caused similar, although less marked accumulation of p-NFH immunoreactivity in the neuronal perikarya. The findings are interpreted to show a dephosphorylation of NFHs in axons and dendrites and a piling up of p-NFHs in the perikarya due to disturbed axonal transport.

Quantitative immunochemistry on neuronal loss, reactive gliosis and BBB damage in cortex/striatum and hippocampus/amygdala after systemic kainic acid administration

Cell specific markers were quantified in the hippocampus, the amygdala/pyriform cortex, the frontal cerebral cortex and the striatum of the rat brain after systemic administration of kainic acid. Neuron specific enolase (NSE) reflects loss of neurons, glial fibrillary acidic protein (GFAP) reflects reactive gliosis, and brain levels of serum proteins measures blood-brain-barrier permeability. While the concentration of NSE remained unaffected in the frontal cerebral cortex and the striatum, their GFAP content increased during the first three days. In the hippocampus and amygdala, NSE levels decreased significantly. GFAP levels in the hippocampus were unaffected after one day and decreased in the amygdala/pyriform cortex. After that, GFAP increased strikingly until day 9 or, in the case of amygdala/pyriform cortex, even longer. This biphasic time course for GFAP was accompanied by a decrease of S-100 during days 1-9 followed by a significant increase at day 27 above the initial level. The regional differences in GFAP and S-100 could result from the degree of neuronal degeneration, the astrocytic receptor set-up and/or effects on the blood-brain barrier.

Antiserum against S-100 protein prevents long term potentiation through a cAMP-related mechanism

Long term potentiation (LTP) was induced in the CA1 region of rat hippocampal slices by tetanization of the Schaffer collaterals. Local pretreatment of CA1 with serum of rabbits immunized against S-100 prevented the potentiation. However, treatment of the slices with a membrane permeant cAMP analogue, such as 8-Br-cAMP, could protect against the blocking effect of anti S-100 serum. We suggest that in the rat endogenous S-100b is involved in transduction mechanisms during LTP induction, via its ability to stimulate adenylate cyclase. Possible mechanisms of this action are discussed.

Ca2+-binding S100 proteins in the central nervous system

A number of neurodegenerative disorders have been attributed to abberrations of intracellular Ca2+ homeostasis regulated by Ca2+-binding proteins. This chapter will focus on the S100B and S100A6 proteins, which are highly expressed in the central nervous system. Their protein structures, localizations, and association with brain pathology as well as their potential use in clinical diagnostics will be discussed.

S100B and S100A1 proteins in bovine retina:their calcium-dependent stimulation of a membrane-bound guanylate cyclase activity as investigated by ultracytochemistry

The Ca2(+)-binding proteins of the EF-hand type, S100B and S100A1, were detected in the outer segment of bovine retina photoreceptors where they are localized to disc membranes, as investigated by immunofluorescence and immunogold cytochemistry. S100B and S100A1 stimulate a membrane-bound guanylate cyclase activity associated with photoreceptor disc membranes in dark-adapted retina in a Ca2(+)-dependent manner, although with different Ca2+ requirements, as investigated by an ultracytochemical approach. Other retinal cell types express S100B and S100A1 as well. S100B is detected in the outer limiting membrane, fine cell processes in the outer nuclear layer and the outer plexiform layer, cell bodies in the inner nuclear layer and the ganglion cell layer, and the inner limiting membrane, whereas S100A1 has a more discrete distribution. S100B and S100A1 also stimulate a membrane-bound guanylate cyclase activity in photoreceptor cell bodies and Muller cells, but their effect appears independent of the light- or dark-adapted state of the retina and is observed at relatively high Ca2+ concentrations. These data represent the ultrastructural counterpart of recent biochemical observations implicating S100B and, possibly, S100A1 in the Ca2(+)-dependent stimulation of a photoreceptor membrane-bound guanylate cyclase activity [T. Duda, R. M. Goraczniak and R. K. Sharma (1996) Molecular characterization of S100A1-S1000B protein in retina and its activation mechanism of bovine photoreceptor guanylate cyclast. Biochemistry 35, 6263-6266; A. Margulis, N. Pozdnyakov and A. Sitaramayya (1996) Activation of bovine photoreceptor guanylate cyclast by S100 proteins. Biochem. Biophys. Res. Commun. 218, 243-247]. Our data suggest that at least S100B may take part in the regulation of a membrane-bound guanylate cyclase-based signalling pathway in both photoreceptors and Muller cells.

The trophic factors S-100beta and basic fibroblast growth factor are increased in the forebrain reactive astrocytes of adult callosotomized rat

S-100 is a calcium-binding protein that is predominantly found in astrocytes of the central nervous system. In the present study, we investigated the temporal and spatial changes of S-100beta immunoreactivity after a stereotaxic mechanical lesion of the adult rat corpus callosum performed with an adjustable wire knife. Rats were killed 7, 14 and 28 days after surgery. S-100beta immunoreactivity was found within the cytoplasm and processes of quiescent putative astrocytes that were observed throughout the gray and white matters of the forebrain of sham-operated rats. Following callosotomy, the S-100beta immunoreactive profiles showed increased size and thick processes, as well as increased amount of S-100beta immunoreactivity. Unbiased stereologic analysis revealed a sustained and widespread increase of the Areal Fraction of S-100beta immunoreactive profiles in the medial and lateral regions of the white matter of callosotomized rats at the studied time-intervals. In the cerebral cortex of callosotomized rats, the estimated total number of S-100beta immunoreactive profiles was also increased 7 and 14 days after the lesion. Since the cellular and temporal changes in S-100beta immunoreactivity were closely similar to those described for basic fibroblast growth factor (bFGF) following brain lesions, we co-localized the S-100beta and bFGF immunoreactivities after callosotomy. bFGF immunoreactivity was found in the nuclei of S-100beta immunoreactive glial profiles throughout the forebrain regions of the sham-operated rats. bFGF immunoreactivity was increased in the nuclei of reactive S-100beta immunoreactive putative astrocytes in the forebrain white matter and in the cerebral cortex of callosotomized rats. These results indicate that after transection of the corpus callosum of adult rats, the reactive astrocytes may exert paracrine trophic actions through S-100beta and bFGF. Interactions between S-100beta and bFGF may be relevant to the events related to neuronal maintenance and repair following brain injury.

Functional roles of S100 proteins, calcium-binding proteins of the EF-hand type

A multigenic family of Ca2+-binding proteins of the EF-hand type known as S100 comprises 19 members that are differentially expressed in a large number of cell types. Members of this protein family have been implicated in the Ca2+-dependent (and, in some cases, Zn2+- or Cu2+-dependent) regulation of a variety of intracellular activities such as protein phosphorylation, enzyme activities, cell proliferation (including neoplastic transformation) and differentiation, the dynamics of cytoskeleton constituents, the structural organization of membranes, intracellular Ca2+ homeostasis, inflammation, and in protection from oxidative cell damage. Some S100 members are released or secreted into the extracellular space and exert trophic or toxic effects depending on their concentration, act as chemoattractants for leukocytes, modulate cell proliferation, or regulate macrophage activation. Structural data suggest that many S100 members exist within cells as dimers in which the two monomers are related by a two-fold axis of rotation and that Ca2+ binding induces in individual monomers the exposure of a binding surface with which S100 dimers are believed to interact with their target proteins. Thus, any S100 dimer is suggested to expose two binding surfaces on opposite sides, which renders homodimeric S100 proteins ideal for crossbridging two homologous or heterologous target proteins. Although in some cases different S100 proteins share their target proteins, in most cases a high degree of target specificity has been described, suggesting that individual S100 members might be implicated in the regulation of specific activities. On the other hand, the relatively large number of target proteins identified for a single S100 protein might depend on the specific role played by the individual regions that in an S100 molecule contribute to the formation of the binding surface. The pleiotropic roles played by S100 members, the identification of S100 target proteins, the analysis of functional correlates of S100-target protein interactions, and the elucidation of the three-dimensional structure of some S100 members have greatly increased the interest in S100 proteins and our knowledge of S100 protein biology in the last few years. S100 proteins probably are an example of calcium-modulated, regulatory proteins that intervene in the fine tuning of a relatively large number of specific intracellular and (in the case of some members) extracellular activities. Systems, including knock-out animal models, should be now used with the aim of defining the correspondence between the in vitro regulatory role(s) attributed to individual members of this protein family and the in vivo function(s) of each S100 protein.

Mapping of a neurovirulence determinant within the envelope protein of a polytropic murine retrovirus: induction of central nervous system disease by low levels of virus

Murine leukemia virus (MuLV) clone Fr98 is a recombinant polytropic virus that causes neurological disease characterized by ataxia in susceptible mouse strains. The envelope gene of Fr98 has been previously shown to encode at least two separate neurovirulence determinants. In the present study, the determinant encoded within the EcoRI/AvrII fragment of the envelope gene was further defined. In these experiments, neurovirulence was associated with a change from a serine to an arginine at position 195 and a glycine to an alanine at position 198 within the envelope protein. Neurovirulent and nonvirulent virus clones, which differed only at these two amino acid residues, showed no difference in the type or location of cells infected. Furthermore, equivalent levels of viral p30 capsid protein were detected in the brains of mice infected with either the neurovirulent or nonvirulent virus clones. These results were consistent with the interpretation that the envelope protein of the neurovirulent virus differed from that of the nonvirulent virus by having a greater toxic effect on central nervous system function.

Spatio-temporal patterns of ensheathing cell differentiation in the rat olfactory system during development

An immunocytochemical approach with specific glial markers was used to investigate the temporal and spatial patterns of differentiation of ensheathing glia wrapping axon fascicles along the primary olfactory pathway of the rat during development. The two glial markers tested, the proteins S-100 and glial fibrillary acidic protein, are known to be expressed at different stages of maturation in glial cells. The S-100 protein was first weakly expressed in cells accompanying the olfactory axons at embryonic day 14 (E14), while a first faint glial fibrillary acidic protein staining was detected along the olfactory axons at E15 and along the vomeronasal nerves at E16. A strong S-100 immunoreactivity was already present from E16 onwards along the axon fascicles through their course in both the nasal mesenchyme and the subarachnoid space before entering the olfactory nerve layer of the olfactory bulb. A gradual increase in glial fibrillary acidic protein expression was observed along this part of the developing olfactory pathway from E16 up to E20, when an adult-like pattern of staining intensity was seen. By contrast, most of the ensheathing cells residing in the olfactory nerve layer exhibited some delay in their differentiation timing and also a noticeable delayed maturation. It was only from E20 onwards that a weak to moderate S-100 expression was detected in an increasing number of cells throughout this layer, and only few of them appeared weakly glial fibrillary acidic protein positive at postnatal days 1 and 5. The immunocytochemical data indicate that there is a proximodistal gradient of differentiation of ensheathing cells along the developing olfactory pathway. The prolonged immaturity of ensheathing cells in the olfactory nerve layer, which coincides with the formation of the first glomeruli, might facilitate the sorting out of olfactory axons leading to a radical reorganization of afferents before they end in specific glomeruli.

Neuroblastoma cells can actively eliminate supernumerary MYCN gene copies by micronucleus formation--sign of tumour cell revertance?

Human neuroblastoma cell lines frequently exhibit MYCN amplification and many are characterised by the presence of morphologically distinct cell types. The neuronal cells (N-cells) and the so-called flat cells (F-cells) are thought to represent manifestations of different neural crest cell lineages and are considered to be the consequence of neuroblastoma cell pluripotency. In this study, various neuroblastoma cell lines were examined for micronuclei. In F-cells of neuroblastoma cell lines with extrachromosomally amplified MYCN, we observed the frequent occurrence of micronuclei. Using fluorescence in situ hybridisation (FISH) with a MYCN specific probe, we demonstrated that these micronuclei were packed with MYCN hybridisation signals. In addition, in a minor percentage of cells, MYCN signals occurred in clusters, adhered to the nuclear membrane and aggregated in nuclear protrusions. In F-cells, a substantial reduction or lack of amplified MYCN copies was observed. These observations let us conclude that extrachromosomally amplified genes can be actively eliminated from the nucleus resulting in a dramatic loss of amplified sequences in the F-cells. Moreover, reduction or loss of amplified sequences in F-cells was shown to be accompanied by downregulation of MYCN expression, by a decrease in proliferative activity and by upregulation of molecules of the major histocompatibility complex class I (MHC I). Interestingly, F-cells are not restricted to neuroblastoma cell cultures, but also occur in cell lines of other tissue origin. All F-cells share important biological features, interpreted as cell revertance, i.e. loss of the malignant phenotype and properties. This fact, together with the demonstration that neuroblastoma cells do not differentiate into Schwann cells in vivo [1] Ambros et al. NEJM 1996, 334, 1505-1511, do not support the hypothesis that F-cells represent Schwannian/glial differentiation in vitro. We therefore postulate that the elimination of amplified MYCN gene copies in cultivated neuroblastoma cells is in line with the phenomenon of tumour cell revertance.

Cytogenetic and immunohistochemical analysis of an adult anaplastic neuroblastoma

Neuroblastomas in children are common tumors and are characterized by a number of recurrent cytogenetic and molecular changes. Adult neuroblastomas are rare, and their relationship to pediatric neuroblastomas is not clear. We report an anaplastic neuroblastoma presenting in a 28-year-old man. Histopathologic identification of the tumor as a neuroblastoma was problematic, and the initial diagnosis was poorly differentiated sarcoma. Tumor cells expressed immunoreactivity for tyrosine hydroxylase in addition to generic neuroendocrine markers, consistent with catecholamine-synthesizing ability. They also extended long, branching neurites in vitro. The tumor was positive for immunoreactive trkA. The karyotype after 6 days in culture was found to be 42,XY with multiple chromosomal abnormalities. The only abnormality shared with pediatric neuroblastomas was a rearrangement of chromosome 17q. Double minute chromosomes or homogeneously staining regions associated with N-myc amplification were not present. To our knowledge, this is the first reported karyotype of an adult neuroblastoma. The cytogenetic findings, together with expression of trkA, suggest that the tumor was more closely related to the favorable prognosis neuroblastomas of infancy than to the poor prognosis tumors that occur in older children, despite its unfavorable histology.

Differential expression of manganese and copper-zinc superoxide dismutases in the olfactory and vomeronasal receptor neurons of rats during ontogeny

Superoxide dismutases (SODs) protect cells from damage by oxygen free radicals. Manganese (Mn) SOD is preferentially induced in terminally differentiating cells; induction of copper-zinc (CuZn) SOD is more closely associated with postnatal exposure to environmental sources of oxygen free radicals. The purpose of this study was to investigate ontogenetic changes in immunoreactivity for MnSOD and CuZnSOD relative to the expression of markers of neuronal and chemosensory differentiation in olfactory and vomeronasal receptor neurons (ORNs and VRNs, respectively), which mature with different time courses. Immunoreactivity for both SODs was detected in rat ORNs at embryonic day (E) 14, the earliest time point investigated, but not until E16 in vomeronasal neuroblasts. ORNs also expressed the neuronal marker protein gene product (PGP) 9.5 and the chemosensory cell marker olfactory marker protein (OMP) at E14; vomeronasal neuroblasts expressed PGP 9.5 at E16 but were not immunoreactive for OMP until postnatal day (P) 2. Immunoreactivity for MnSOD in ORNs and VRNs generally increased pre- and postnatally to a maximum at P11. Immunoreactivity for CuZnSOD did not increase markedly until after birth, reaching maximal levels at P11-P24. Within ORNs and VRNs, the most intense immunoreactivity was localized in the dendritic and supranuclear regions. The results indicate that in ORNs and VRNs, increases in MnSOD immunoreactivity during ontogeny parallel the ongoing differentiation and maturation of chemosensory receptor neurons; in contrast, the induction of immunoreactivity for CuZnSOD is associated with postnatal exposure to the ambient oxygen and xenobiotic environment.

S-100beta stimulates neurite outgrowth in the rat sciatic nerve grafted with acellular muscle transplants

S-100beta promotes neurite extension in vitro and motoneuron survival in the chicken embryo. We demonstrate here that local administration of S-100beta stimulates the sciatic nerve regeneration into acellular muscle grafts. Normally there is a 8-10 day delay in the regeneration of axons into such grafts. Local administration of S-100beta (0.5-1.0 microg/h) significantly stimulated regeneration into the grafts. In S-100beta treated grafts, the regeneration distance was increased with a factor of about 2.3 times as compared to vehicle treated grafts. The distance of regeneration was monitored with pinch test which detects sensory axons. Regenerating axons were growing outside the necrotic muscle cells as revealed with immunohistochemistry for the neurofilament light weight polypeptide. S-100beta was demonstrated immunocytochemically in motor neurons of the rat lumbar spinal cord and in large and medium sized neurons of the dorsal root ganglia. The results suggest that S-100beta is a physiological growth factor for peripheral nerve axons.

Delayed decrease of calbindin immunoreactivity in the granule cell-mossy fibers after kainic acid-induced seizures

Kainic acid (KA) administration induces an abnormal excitation and spontaneous recurrent seizures. Alterations of granule cell properties may be potential mechanisms. In this study, dynamic alterations of calbindin, a calcium binding protein particularly abundant in the granule cells, have been investigated immunocytochemically in the rat hippocampus after the KA-induced seizures. The calbindin immunoreactivity decreased slightly in the CA1/CA2 fields already after 1 and 3 days, and was lost partly or completely in the pyramidal layer after 10 days. From day 21, the calbindin immunoreactivity decreased in dendrites and soma of the granule cells and mossy fibers. The alterations remained at least to day 90, while no evident neuronal loss occurred in the granule cells. This may reflect a disturbance of calcium homostasis in the granule cells after seizures. The delayed decrease of calbindin has a time course similar to the occurrence of spontaneous recurrent seizures, suggesting a possible correlation between the two events.

Plasticity of granule cell-mossy fiber system following kainic acid induced seizures: an immunocytochemical study on neurofilament proteins

Abnormal reestablishment of mossy fibers with the CA3 pyramidal cells and granule cells is an important aspect of postlesional plasticity in epilepsy. However, basis for the structural reorganisation and functional consequences of the event remain uncertain. Therefore we have investigated alterations of neurofilaments, major cytoskeletal components of neurons, in the rat hippocampus after the kainic acid (KA) administration, an experimental model for the temporal lobe epilepsy. The immunoreactivity for phosphorylated heavy weight neurofilament (pNFH) and non-phosphorylated heavy weight neurofilament (npNFH), in particular the pNFH, decreased in the CA1 field and inner molecular layer of the dentate gyrus during 3 and 10 days after the KA administration. After 10 days, npNFH immunoreactivity appeared in the mossy fibers, in which it is normally absent, meanwhile the pNFH staining in the mossy fibers did not decrease. From day 21, the immunoreactivity of pNFH and npNFH was normal or above normal in the CA1 stratum lacunosum-moleculare, mossy fibers, hilus and inner molecular layer of the dentate gyrus. These alterations in the later phase remained at least to day 90. The reappearance and increase of the neurofilament immunoreactivity in the inner molecular layer of the dentate gyrus probably reflects a collateral extension of the granule cell axons known as mossy fiber sprouting. The results suggest that neurofilament changes in the granule cell-mossy fiber system may be a morphological basis for the structural reconstruction of granule cell axons, and neurofilaments are involved in the plasticity after the KA induced seizures.

Appearance of neuronal S-100 beta during development of the rat brain

In addition to being an astroglial protein, S-100 beta is localised in distinct populations of neurons in the adult rat hindbrain. We report, here, the expression of S-100 beta in both neurons and glia of the rat brain during development. Prenatally, S-100 beta immunoreactivity was confined to glial cells close to the germinal zone. After birth, S-100 beta positive glial cells were seen mainly in the brainstem and cerebellum, while only a few were detected in cerebral cortex and hippocampus. The number of S-100 beta containing glial cells increased steadily during the first 2 postnatal weeks after which the adult pattern was attained. No S-100 beta containing neurons were present prenatally. The first S-100 beta containing neurons were seen in the mesencephalic trigeminal nucleus at postnatal day 1 (P1), and in the motor trigeminal nucleus at P3. Neuronal S-100 beta immunoreactivity in other nuclei was mostly attained from the 10th to the 21st postnatal day. The neuronal S-100 beta immunoreactivity was first detected in the cell nuclei during development, then increased in the cytoplasm with ages. A nuclear staining in many immunoreactive neurons persisted until the adult. It usually took 1 to 2 weeks for neuronal S-100 beta to attain the adult staining pattern, i.e., heavy staining of the cytoplasm and processes, after its appearance. The forebrain never contained S-100 beta positive neurons. The S-100 beta is first expressed in glial cells, suggesting it is primarily of the glial origin. Coupled with neurotrophic effects of the protein, the time course of neuronal S-100 beta expression during the critical period of neuronal development implies that it may be involved in neuronal differentiation and maturation.

Comparison among different approaches for sampling cerebrospinal fluid in rats

Two approaches for time-resolved sampling of cerebrospinal fluid (CSF) in rats were compared regarding performance, reproducibility, and extent of the inevitable trauma caused by the implantation of a sampling tube. Several parameters were checked to evaluate the injury: blood cell contamination of CSF; concentrations in CSF of the cytosolic proteins neuron-specific enolase (NSE) and S-100 (chiefly present in astrocytes); blood-brain barrier leakage of a dye-protein complex; viability of nervous tissue cells as assessed by dye exclusion; light and electron microscopy. In one sampling method, a tube was forced epidurally into the cisterna magna via a hole in the calvarium, consistently damaging the meninges and the nervous tissue. When using the alternative sampling method, the tube was instead affixed to the posterior atlanto-occipital membrane and connected with the cisterna magna via a hole in the membrane. Such a procedure caused negligible damage. Both techniques induced an inflammatory response. We advocate the use of the second approach, i.e., to sample CSF via a hole in the atlanto-occipital membrane, as the method of choice due to its high reproducibility. It is fairly rapid, and associated with a negligible injury.

Phosphorylated and non-phosphorylated neurofilament proteins: distribution in the rat hippocampus and early changes after kainic acid induced seizures

The regional distribution of neurofilament proteins in the rat hippocampus and their early changes after kainic acid induced seizures were investigated immunocytochemically with antibodies against light weight neurofilament, phosphorylated and non-phosphorylated heavy weight neurofilament. The light weight and non-phosphorylated heavy weight neurofilaments were distributed more unevenly than the phosphorylated neurofilament. The perikarya and processes of pyramidal cells in the CA3 field contained the highest light weight and non-phosphorylated heavy weight neurofilaments, while the perikarya of granule cells contained only few light weight neurofilament and the perikarya of CA1 pyramidal cells were even devoid of immunoreactivity of both light and heavy weight neurofilaments. The fiber staining of the light weight and non-phosphorylated heavy weight neurofilaments, especially the former, was less in the CA1 field and molecular layer of dentate gyrus. The phosphorylated neurofilament immunoreactivity was identified only in axons. Mossy fibers, the axons of granule cells, contained the light weight and phosphorylated heavy weight neurofilaments, but not the non-phosphorylated neurofilament. Seven days after the kainic acid induced seizures, the phosphorylated neurofilament staining was greatly reduced in the CA1 and inner molecular layer of the dentate gyrus, probably resulting from the axonal degeneration of the Schaffer collaterals and the commissural/associational fibers. Furthermore, the nonphosphorylated neurofilament appeared in the mossy fibers of the CA3 stratum lucidum, which normally do not express such immunoreactivity. The results indicate that the neurofilaments are altered following the neuronal degeneration and postlesional plasticity caused by the kainic acid administration. Therefore, the examination of various phosphorylated neurofilaments may offer a comprehensive understanding of major hippocampal pathways, axonal plasticity and the possible roles of neurofilaments in the hippocampus following excitotoxic insults.