Neuronal glycolytic pathway impairment induced by HIV envelope glycoprotein gp120

Neurological impairment is a common feature of Acquired Immunodeficiency Syndrome (AIDS); functional alterations have been reported both in central and peripheral nervous system and the Human Immunodeficiency Virus (HIV) envelope glycoprotein gp120 has been proposed as a neurotoxin acting through a calcium-dependent mechanism. On the other hand it has been reported that gp120 treatment also induce about a 20% decrease in the cerebral glucose utilization and in the cellular ATP levels. The reported observations were performed on experimental system where also non-neuronal cells where present; in order to evaluate whether a direct interaction between HIV proteins and neuronal cells takes place, we used a neuroblastoma cultures where only neuronal cells are present. We analysed the effects of gp120 on the N18TG2 neuroblastoma clone. Treatments were performed both on growing and confluent cultures. Short time treatment with gp120 of confluent cultures causes a 25% reduction in the level of neuron-specific enolase, resulting in a similar decrease of oxygen consumption. Long time exposure of growing cells also causes a reduction in cell survival. Furthermore, using a membrane-specific fluorescent probe we observed that gp120 produces an increase of membrane trafficking. These observations suggest a direct interaction between the viral envelope protein and neuronal cells, which results in an alteration of glycolytic metabolism. This alteration may be related to the neurologic impairments observed in AIDS patients.

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.

Elevated S100 blood level as an early indicator of intraventricular hemorrhage in preterm infants. Correlation with cerebral Doppler velocimetry

The aim of this study was to assess the use of S100 protein in blood as a means of identifying preterm infants at risk of intraventricular hemorrhage. In 25 preterm newborns, S100 blood concentrations were measured by an immunoradiometric assay during the first 48 h. Cerebral Doppler velocimetry waveform patterns were also tested at the time the blood sample was taken, when clinical and cerebral ultrasound scanning were still normal. Of the 25 newborns studied, 14 were controls and 11 developed intraventricular hemorrhage as revealed by ultrasound scanning more than 72 h after birth, and clinically confirmed by neurological examination on the seventh day of follow-up. S100 blood concentrations were significantly higher (P<0.002) in infants with intraventricular hemorrhage than in control infants and also correlated significantly (r=0.81, P<0.003) with the grade of hemorrhage. A significant correlation (r=0.70, P<0.05) between the S100 blood concentration and the middle cerebral artery pulsatility index was also observed. The present data show that S100 blood concentrations offer a measurable parameter of brain lesion in preterm infants before a radiological assessment of hemorrhage can be performed, when clinical symptoms may be silent and preventive/therapeutic action could be especially useful.

Bcl-2 expression regulates cell sensitivity to S100beta-mediated apoptosis

The S100beta protein is overexpressed in the brain of patients with Alzheimer's disease and Down's syndrome and is able to induce apoptosis in neurons at high concentrations. The intracellular events that regulate the apoptotic effect are largely unknown. This study investigates the roles of the bcl-2 proto-oncogene, one of the best-defined apoptotic genes, on cell death induced by S100beta. Human neuronal precursor NT2/D1 cells showed a high degree of cell death by apoptosis after exposure to 2 microM S100beta in serum-free medium. Death was preceded by a down-regulation of the Bcl-2 protein. Gene transfer with a full-length bcl-2 cDNA under the control of a constitutive promoter in NT2 cells elevated Bcl-2 protein levels and repressed S100beta-mediated cell death. When exposed to retinoic acid, the NT2/D1 cells differentiated into a neuronal phenotype. The differentiated cells up-regulated their levels of Bcl-2 and became resistant to S100beta-induced cell death. Downregulation of Bcl-2 by an antisense oligonucleotide in the differentiated cells, however, increased their susceptibility to S100beta-related cytotoxicity. Therefore, apoptosis induced through S100beta signaling is subject to regulation by Bcl-2. A combined alteration such as up-regulation of S100beta together with down-regulation of Bcl-2 may be important in the pathogenesis of Alzheimer's disease and Down's syndrome.

An acquired sensitivity to H2O2-induced apoptosis during neuronal differentiation of NT2/D1 cells

Brief exposure of neuronally differentiated human NT2/D1 cells to hydrogen peroxide induced cell death by apoptosis with an ED50 of 30 microM, whereas a 70-fold higher concentration was required to obtain an ED50 effect in undifferentiated NT2/D1 neuronal precursor cells. This enhanced sensitivity in NT2/D1 neurons was correlated with an 8-fold lower level of intracellular glutathione. Pretreatment with N-acetyl-L-cysteine, an agent that is able to raise the levels of intracellular glutathione, promoted the survival of hydrogen peroxide-treated NT2/D1 neurons. Thus, the low glutathione level may contribute to the high sensitivity of NT2/D1 neurones to hydrogen peroxide-induced apoptosis. This study indicates that neuronal susceptibility to oxidative damage is developmentally regulated.

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.

Presence of S-100 beta in cholinergic neurones of the rat hindbrain

The double staining of S-100 beta and choline acetyltransferase (ChAT) revealed that S-100 beta immunoreactivity was localized in most, but not in all, cholinergic neurones in the somatomotor nuclei of the cranial nerves and in the ambiguus nucleus. S-100 beta was present in almost all cholinergic neurones in the brain stem reticular, red, vestibular (excluding medial), mesencephalic trigeminal and cerebellar nuclei. However, S-100 beta immunoreactivity was lacking in cholinergic neurones in the parabrachial complex, the dorsal motor nucleus of the vagal nerve and most sensory nuclei. No S-100 beta-positive neurones lacked ChAT immunoreactivity. Taken together with the fact that the vulnerability of motoneurones to axotomy is markedly reduced in the first 3 postnatal weeks, during which period neuronal S-100 beta appears and increases, a possible effect of S-100 beta on the survival of cholinergic motoneurones may be suggested.

Eliprodil prevents expression of the 70 kDa heat shock protein in MK801-injured neurones

The present study examined whether eliprodil (SL 82.0715), an N-methyl-D-aspartate (NMDA) receptor antagonist acting on the polyamine sites induced expression of the 70 kDa heat shock protein (HSP70) in the rat brain. Whereas the NMDA channel blocker MK801 consistently induced HSP70 in posterior cingulate and retrosplenial cortices, eliprodil had no such effects even at the highest dose (50 mg/kg, intraperitoneally), supporting the idea that injury to the cerebrocortical neurones by NMDA receptor antagonists is probably related to specific sites of the receptor. Furthermore, eliprodil, given immediately after injection of MK801, blocked the effects of MK801 on HSP70. The result is discussed in terms of high affinity of eliprodil for the sigma receptor.

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.

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

The localisation of S-100 in mammalian CNS neurons has been under debate for more than two decades. We address the question with two polyclonal and two new monoclonal antibodies. The specificity and the distribution in rat brain is based on an antigen retrieval method. We present evidence that aldehyde fixatives mask S-100 beta in neurons, and that the immunoreactivity is retrieved after trypsinisation. Neuronal S-100 beta is also detected in unfixed and ethanol fixed sections. The neuronal immunoreactivity is partly solubilised from unfixed tissue sections with 2.5 mM EDTA and is completely extracted with 2.5 mM EDTA and 1% Triton X-100. Most of the glial S-100 beta is washed out from unfixed tissue sections with saline. S-100 beta has distinct distribution in neurons of the hindbrain, i.e., the brainstem and cerebellum, but is not observed in the forebrain. One of the monoclonal antibodies immunostained neither neurons nor glia when it had been absorbed with S-100 crosslinked to nitrocellulose membranes. The distribution of neuronal S-100 beta differed from that of other neuronal calcium binding proteins, such as calbindin and parvalbumin. It was confined mainly to cholinergic neurons of the hindbrain. The presence of S-100 beta in distinct neuronal populations may indicate neurotrophic effects of S-100 beta. The notion is supported by the capability of S-100 to cause neurite outgrowth in vitro.

S-100 beta immunoreactivity in neurones of the rat peripheral sensory ganglia

S-100 beta, which is capable of exerting neurotrophic effects on cultured neurones and promoting the survival of motor neurones in vivo, has recently been found in distinct neurones of the rat hindbrain. Here we report that S-100 beta, as well as being present in satellite and Schwann cells, is also present in neurones of sensory ganglia (dorsal root ganglion, trigeminal, petrosal, jugular and nodose ganglia) but absent from neurones of the superior cervical ganglion. In the sensory ganglia, many neurones were immunoreactive, while the staining intensity varied among the neurones. Neuronal S-100 beta appeared in developing rats as early as postnatal day 1. No immunoreactive neurones were observed in the superior cervical ganglion during development. The results are suggestive of selective neurotrophic effects of S-100 beta.

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.

Excitotoxicity. Experimental correlates to human epilepsy

Neurochemical observations on cortical biopsies form 48 patients under surgical treatment for pharmacoresistant partial epilepsy showed a 70-80% increase in glutamate concentration when expressed in relation to neuron specific enolase. Intraperitoneal administration of one of its receptor agonists, kainic acid (KA), to the rat led to increased epileptogenic activity of the limbic type in a dose-dependent fashion. The KA injection also led to a neuronal cell death and a gliosis, closely correlated to the extent of seizure activity. In biopsies from human epileptogenic cortex, the concentration of neuron specific enolase correlated inversely to that of glial fibrillary acidic protein, a marker for astrocytic glial cells. Stimulation of the KA receptor decreased the extent of phosphorylation of the largest subunit of neurofilaments (NF-H) that have consequences for structural stability and axonal transport. Phosphorylated NF-H decreased also in human epileptic cortex, indicating either an overactivity of excitatory neurotransmitters or a loss of axonal compartments.

Changes in neurofilament protein NF-L and NF-H immunoreactivity following kainic acid-induced seizures

Postlesion plasticity of neuronal processes might contribute to secondary spontaneous seizures after kainic acid administration. In this study, neurofilament (NF) proteins were examined following intraperitoneal injection of kainic acid, and special reference was given to temporal changes in quantity and quality of the NF light (NF-L) and heavy (NF-H) subunits. A pronounced decrease in phosphorylation-related immunoreactivity of NF-H occurred as early as 1 day after the injection in the amygdala/pyriform cortex, hippocampus, striatum, and dorsal cerebral cortex. A shift of NF-H from the phosphorylated to nonphosphorylated form was evident in immunoblots, suggesting dephosphorylation contributed to the decrease. Decreases in NF-L and phosphorylated NF-H contents in the limbic structure at 3 days were correlated with the increasing kainic acid doses from 2.5 to 10 mg/kg. The degradation pattern in immunoblots with antibodies against NF-L indicated that the decrease in NF-L was probably due to calcium-activated proteolysis. NF-L and phosphorylated NF-H contents secondarily increased from 9 days onward, with approximately 20% above the control level of phosphorylated NF-H immunoreactivity at 27 days in the amygdala/pyriform cortex and ventral hippocampus. Immunohistochemical examination of the hippocampus revealed that an increase of NF staining in the mossy fiber system may contribute to the NF recovery in this region. Furthermore, the temporal changes of NF-L and phosphorylated NF-H contents were positively correlated with those of the neuronal cell adhesion molecule, a neuritic growth cone marker, substantiating postlesion regenerative reactions of NF proteins. Functional consequences of the NF plasticity remain to be identified.

Induction of glucose regulated protein (grp78) and inducible heat shock protein (hsp70) mRNAs in rat brain after kainic acid seizures and focal ischemia

Specific probes were obtained using PCR cloning from rat brain for the 78 kDa glucose regulated (grp78), inducible 72 kDa (hsp70) as well as constitutive 73 kDa (hsc73) heat shock mRNAs. Grp78 and hsc73 were expressed in normal rat brain whereas hsp70 was not. Subcutaneous injection kainic acid (10 mg/kg) produced seizures and induced all three mRNAs. The induction of grp78 and hsp70 mRNAs occurred within 2 h, peaked between 6-8 h, persisted for 48 h, and returned to control levels by 72 h. Expression of the grp78 and hsp70 mRNAs after focal ischemia progressively increased with occlusion durations from 15-120 min in the cerebral cortex. Though grp78 and hsp70 mRNAs were induced modestly in the striatum by 15 min of ischemia, longer durations of ischemia were characterized by little change in the grp78 mRNA levels and relatively lower levels of hsp70 expression. This result indicates that progressive increases in the duration of ischemia in brain, prior to infarction, may produce proportional increases in transcription of the heat shock genes. However, once the duration of ischemia is long enough to produce infarction, this severely limits the availability of ATP which blocks transcription of the heat shock genes. In conclusion, concurrent induction of the heat shock genes suggests that kainic acid seizures and focal ischemia induce several different stress responses in brain cells caused by denaturation of proteins, changes of protein synthesis, and changes of protein glycosylation.

Neuronal and glial marker proteins in encephalopathy associated with acute liver failure and acute hyperammonemia in the rabbit

Neuronal and glial cell marker proteins were quantified in order to evaluate the possibility of increased proteolysis in the brain of rabbits with acute liver failure and acute hyperammonemia. Acute liver failure was induced by a two-stage devascularization procedure. Acute hyperammonemia was induced by a prolonged infusion of ammonium acetate, which simulates the plasma ammonia level in acute liver failure. Control animals received an infusion of sodium/potassium acetate. After development of severe encephalopathy, the animals were sacrificed (13.7 +/- 1.3 hours for rabbits with acute liver failure and 20.2 +/- 0.8 hours for rabbits with hyperammonemia) (x +/- S.E.M./n = 6) and their brains were dissected into cerebral cortex, hippocampus, cerebellum and brain stem. The total protein content and the concentrations of the neuronal cell marker proteins NSE (neuron specific enolase), NF68 and NF200 (68 kD and 200 kD neurofilament polypeptides) and the glial cell marker proteins GFAP (glial fibrillary acidic protein) and S-100 were determined. Total protein content was decreased in the brain stem in acute hyperammonemia only. The content of neuronal and glial cell markers was not affected in either of the two conditions. However, low molecular weight proteolytic fragments of the NF 68 kD polypeptide were observed in the hippocampus of three out of six animals in both experimental groups. No proteolytic degradation of GFAP was observed. The results show that, in experimental encephalopathy due to acute liver failure and acute hyperammonemia, no major changes occur in the marker proteins. The finding of proteolytic fragments of the NF68 polypeptide indicates that the neuronal population is affected prior to glial alterations. These findings are in agreement with the concept that acute hepatic encephalopathy is reversible and induces only slight structural changes.

Biochemical correlates to cortical dysplasia, gliosis, and astrocytoma infiltration in human epileptogenic cortex

The study provides detailed biochemical correlates to the common histopathological diagnoses in epilepsy. A dot immunobinding procedure was used for quantification of NSE, GFA, S-100, NCAM, NF 68 and NF 200. The material consisted of samples from 48 patients either selected for surgical treatment of partial epilepsy or for disorders not related to epilepsy. The histopathological diagnosis of the epileptic cases was: MCD (mild cortical dysplasia, microdysgenesis), gliosis, astrocytoma, ganglioglioma, oligodendroglioma and single cases. The concentration in non-epileptic white matter, in per cent of that in grey matter was: NSE, 85; GFA, 175; S-100, 117; NCAM, 43; NF 68,227 and NF 200, 173. The concentration of NSE as well as of GFA was close to normal in the specimens of the MCD and gliosis groups and of one subgroup of the astrocytomas. There was a striking inverse relationship of the GFA vs the NSE concentrations in the whole material. The concentrations of S-100 showed no such inverse relationship to NSE levels. In all the epileptic groups, total NCAM was lower than 50% of that of the non-epileptic group. The mean NF 68 and NF 200 concentration in the gliosis and astrocytoma groups was 75% of that of the non-epileptic group while the corresponding value for the MCD group was 50%. There was a positive correlation of immunochemically determined GFA and the histopathological gliosis score in the samples of epileptogenic cortex. There was no correlation between the concentration of GFA in the samples and the duration of epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Glial and neuronal marker proteins in the silicone chamber model for nerve regeneration

In the present study, neuronal and Schwann cell marker proteins were used to biochemically characterize the spatiotemporal progress of degeneration/regeneration in the silicone chamber model for nerve regeneration. Rat sciatic nerves were transected and the proximal and distal stumps were inserted into a bridging silicone chamber with a 10-mm interstump gap. Using dot immunobinding assays, S-100 protein and neuronal intermediate filament polypeptides were measured in different parts of the nerve 0-30 days after transection. In the most proximal nerve segment, all the measured proteins were transiently increased. In the proximal and distal stumps adjacent to the transection, the studied proteins were decreased indicating degeneration of the nerve. Within the silicone chamber, the regenerating nerve expressed the Schwann cell S-100 protein already at 7 days, whereas the neurofilament polypeptides appeared later. These observations are corroborated by previous morphological studies. The biochemical method described provides a new and fast approach to the study of nerve regeneration.

Quantitative alterations of S-100 protein and neuron specific enolase in the rat nervous system after chronic 2,5-hexanedione exposure

The regional changes in quantities of the glial S-100 protein and the neuron specific enolase in the rat nervous system have been studied after long-term exposure to 2,5-hexanedione. The wet weights of most of the examined nervous tissues were found to be reduced, with an extensive effect seen in the brain stem. Using dot immunobinding assays, the concentrations of S-100 were found to be increased in most of the examined tissues, but unaffected in the brain stem. The total amount of S-100 per tissue was markedly reduced in the brain stem. The content of neuron specific enolase was reduced only in the brain stem. Thus the effects of 2,5-hexanedione on the nervous system varied regionally. The brain stem was severely atrophied with a reduction of neuronal as well as of glial marker proteins. Other brain regions contained increased glial cell marker proteins as signs of progressive astroglial reactions.

Biphasic changes in NCAM level after an NMDA lesion to the hippocampal formation: a quantitative dot-immunobinding assay

With a quantitative dot-immunobinding assay, the time course changes of neuronal cell adhesion molecule (NCAM) concentrations and total tissue content were monitored in the rat hippocampus after a 40 nmol NMDA injection. A biphasic alteration was observed; a decrease occurred at day 3, an increase at day 30. The time course of changes differed from that of the glial fibrillary acidic protein (GFAP), a marker for reactive astroglial cell, but was similar to that for the markers of sprouting neurites, i.e., low (L) and high (H) molecular weight subunits of the neurofilament polypeptides. It is suggested that NCAM is implicated in the onset of neurite sprouting in the hippocampus after an excitotoxic trauma.

Distinction of two different classes of small-cell lung cancer cell lines by enzymatically inactive neuron-specific enolase

Neuron specific enolase (NSE) is widely used as a neuro-endocrine marker. However the presence of NSE in many non-neuroendocrine tissues has raised questions on the specificity of NSE. We have investigated NSE immunoreactivity (NSA-ag), gamma-enolase activity and total enolase activity in small cell lung cancer (SCLC) cell lines. During well-controlled exponential growth comparison of NSE-ag content and gamma-enolase activity with the doubling-time (Td) and NSE-ag content with gamma-enolase and total enolase activity led to a clear distinction of two types of cell line: variant cell lines plus part of the classic cell lines (type I) and the remaining classic cell lines (type II). The distinction was based upon both an abrupt 6-fold increase of gamma-enolase activity and an 18-fold increase of NSE-ag, which for the larger part was enzymatically inactive. Within each group the increase of NSE-ag content was significantly correlated with the increase of gamma-enolase activity and both NSE-ag content and gamma-enolase activity increased linearly with Td. It is concluded that gamma-enolase seems to be associated with the regulation of growth rate and that a compound with the gamma-enolase antigen but without enzyme activity can distinguish two different classes of SCLC cell lines. Furthermore the demonstration that NSE-ag can represent the active enzyme as well as an enzymatically inactive compound may explain why a controversy about neuron- or non-specificity of NSE exists.

In vivo activation of kainate receptors induces dephosphorylation of the heavy neurofilament subunit

Injection of kainic acid (KA) into the rat hippocampus reduced the phosphorylation-related immunoreactivity of the heavy subunit of neurofilament proteins (NF-H). The effect was demonstrated quantitatively with a dot-immunobinding assay and qualitatively by immunoblotting with monoclonal antibodies against phosphorylation-dependent and nonphosphorylation-related epitopes of NF-H. The KA-induced reduction affected 50% of the phosphorylated NF-H in half of the hippocampus after 48 h. At the same time, the nonphosphorylation-related NF-H immunoreactivity increased as revealed by immunoblotting, indicating a shift from phosphorylated to nonphosphorylated NF-H. The effects on NF-H preceded a decrease in content of the neuron-specific enolase, a soluble neuronal cytoplasmic protein. No alterations of the light subunit of neurofilament proteins occurred, suggesting that KA has a preferential effect on NF-H phosphorylation. N-Methyl-D-aspartate administered similarly did not lead to a rapid dephosphorylation of NF-H. We propose that kainate receptor-mediated dephosphorylation in NF-H is involved in the signal transduction of excitatory amino acids with consequences for neuronal functions dependent on intermediary filament phosphorylation.

Proteolysis of filament proteins in glial and neuronal cells after in vivo stimulation of hippocampal NMDA receptors

An intrahippocampal injection of N-methyl-D-aspartate induced the appearance of degradation products of both the 68 kiloDalton neurofilament protein and the glial fibrillary acidic protein, as revealed by immunoblot techniques. The degradation of these two filament proteins was maximal at 10 days after the lesion. The degradation patterns were similar to those induced with calpains or calcium in vitro. There were no degradation effects on the 200 kD neurofilament protein as tested with both mono- and polyclonal antibodies. Consequently, the neuronal degeneration after excessive activation of NMDA receptors appears to involve calcium activation of proteolytic enzymes. The effects on the glial proteins are probably secondary to neuronal damage but could be related to calcium dependent processes.

A sensitive ELISA for glial fibrillary acidic protein: application in CSF of children

In the present study we describe a sensitive ELISA for determination of glial fibrillary acidic protein (GFAP). To validate the method combined determinations of GFAP and S-100 protein were performed in cerebrospinal fluid (CSF) of normal children and children with autism. The GFAP ELISA is of sandwich type and uses the biotin-avidin system. Sensitivity was 16 pg/ml. Between-day precision was 0.079 (coeff. of variance). S-100 protein concentrations were measured using a commercially available ELISA kit. Normal CSF from children and young adults were analysed. The CSF levels of GFAP in normal children were low (16-163 pg/ml). Both GFAP and S-100 protein concentrations correlated with age (P < 0.01 and P < 0.05, respectively), but the GFAP increment was more pronounced, probably reflecting the age-dependent expansion of the fibrillary astrocytes in the central nervous system (CNS). GFAP levels in children with infantile autism were higher than those in normal children of the same age range. S-100 protein concentrations were similar in both groups. High levels of GFAP in combination with normal S-100 protein concentrations in CSF indicates reactive astrogliosis in the CNS. In conclusion, the sensitive ELISA described makes it possible to measure low levels of GFAP present in the CSF of children. Combined assays of GFAP and S-100 protein can be used to discriminate between acute and chronic brain disorders in children.

Quantitative and qualitative alterations of neuronal and glial intermediate filaments in rat nervous system after exposure to 2,5-hexanedione

The precise mechanism for the neurotoxicity of 2,5-hexanedione is not known, but cross-linking of neurofilament proteins has been suggested as one possibility. In this study the effects of long-term exposure to 2,5-hexanedione were studied in the rat nervous system with special reference to regional changes in the quantities of neuronal and glial intermediate filaments. Using enzyme-linked immunosorbent assays the concentrations of 68- and 200-kDa neurofilament polypeptides were shown to be reduced in all brain regions studied. Similar results were obtained in the sciatic nerve. The concentration of glial fibrillary acidic protein was decreased in the cerebellar vermis and the dorsal cerebral cortex, whereas it was increased in the spinal cord, a result suggesting a regional variation in glial sensitivity. The intermediate filaments of the exposed animals were also immunoblotted using polyclonal antisera against the various neurofilament polypeptides and glial fibrillary acidic protein. In all tissues studied, several aggregates with molecular weights higher than those of the monomeric polypeptides were demonstrated. Contrary to clinical observations, these data indicate pronounced effects in both CNS and PNS and call for further studies on CNS effects in humans.

Determination of S-100 and glial fibrillary acidic protein concentrations in cerebrospinal fluid after brain infarction

BACKGROUND AND PURPOSE

We initiated the present study to evaluate the clinical value of consecutive concentration determinations of S-100 and glial fibrillary acidic proteins in cerebrospinal fluid from patients with brain infarction.

METHODS

We took sequential samples of cerebrospinal fluid from 28 patients within 48 hours, at 7 days, and at 18-21 days after the ictus. We measured astroglial protein concentrations using an enzyme-linked immunosorbent assay and also determined size of the infarction (computed tomography), clinical state of the patient (simplified activities of daily living test), blood-brain barrier dysfunction (cerebrospinal fluid/serum albumin ratio), and a myelin marker (myelin basic protein).

RESULTS

We found a transient increase of both proteins in the cerebrospinal fluid during the first week after the ischemic stroke (p less than 0.05). This increment was significantly correlated with the size of the infarction and the clinical state of the patients.

CONCLUSIONS

Transient release of astroglial proteins into the cerebrospinal fluid possibly reflects initial focal ischemic damage and, in the later phase, ongoing destruction of astroglial cells in the penumbra zone. We suggest that determinations of cerebrospinal fluid astroglial protein concentrations can be used to estimate ischemic brain damage, which should be of particular value in clinical trials of pharmacological agents, such as calcium antagonists, on stroke patients.

Neuronal and glial marker proteins in the evaluation of the protective action of MK 801

A quantitative dot immunobinding procedure was used to quantify glial [the S-100 protein and the glial fibrillary acidic (GFA) protein] and neuronal (the 68- and 200-kDa neurofilament polypeptides, neuron-specific enolase, and neuronal cell adhesion molecule) markers. A single intraperitoneal administration of 10 mg/kg of MK 801 blocked the increase of glial parameters and the decrease in content of neuronal marker proteins that occurred as the response to an N-methyl-D-aspartate (NMDA) lesion in the rat hippocampus. The degradation products of GFA protein and the 68-kDa neurofilament polypeptide that were induced by the NMDA lesion did not appear after MK 801 treatment. This study shows that brain-specific proteins are a set of precise tools for the evaluation of neuroprotective effects of antagonists to excitatory amino acids.

The effect of an N-methyl-D-aspartate lesion in the hippocampus on glial and neuronal marker proteins

The study employed an immunochemical quantification of brain cell marker proteins in addition to quantitative morphology in order to provide a more multifacetted and characterized model for an excitotoxic CNS lesion. The importance of the approach in the evaluation of the potential of neuroprotective agents is emphasized. The S-100 protein, the glial fibrillary acidic (GFA) protein, neuron specific enolase (NSE) and neuronal intermediary filament polypeptides (NF 68 and NF 200) were measured with a dot-immunobinding assay, 3-30 days after a unilateral injection of N-methyl-D-aspartate (NMDA) in the left dorsal hippocampus of the rat. After 3 days, the neuronal cell loss averaged 80% in the hippocampus. The S-100 content was reduced 3 days after injection, but was 150% of control at 30 days. GFA increased constantly from days 3 to 30. The neuronal marker proteins were all markedly reduced 7 days after injection. However, at 30 days, NF 68 and NF 200 were close to control (80%). Increasing content would reflect regeneration and sprouting of neurites. The content of the neuronal cytoplasmic marker, NSE, was significantly lower than control also at 10 and 30 days, although a gradual recovery could be traced.

Cerebrospinal fluid proteins in men with chronic encephalopathy after exposure to organic solvents

Cerebrospinal fluid was examined for 23 patients with chronic toxic encephalopathy after heavy exposure to organic solvents and 23 healthy age-matched referents. No differences were found between the patients and referents with respect to the levels of albumin, immunoglobulin, prealbumin, alpha-1-antitrypsin, beta-2-microglobulin, haptoglobin, or the astroglial cell proteins S100 and glial fibrillary acidic protein in the cerebrospinal fluid. The albumin ratio was normal for both the patients and the referents. The patient group had had heavy exposure to organic solvents, but its members had not been exposed for at least one year before the study. It was concluded that, if exposure to organic solvents affects proteins in cerebrospinal fluid, such effects are probably reversible.

Exposure of rats to high concentrations of 1,1,1-trichloroethane and its effects on brain lipid and fatty acid composition

Exposure of rats to 1,1,1-trichloroethane (TRI) (1200 p.p.m.) for 30 days resulted in changes in the fatty acid pattern of the brain ethanolamine phosphoglyceride. A decrease was observed in stearic acid (18:0) and arachidonic acid (20:4), while the 22-carbon (n-3) fatty acids were increased. These changes in the fatty acid pattern were similar to that observed previously in the rat for another solvent, perchloroethylene, at a lower exposure concentration (320 p.p.m). Both these solvents are little metabolised and it seems that a common mechanism exists whereby these solvents alter the fatty acid pattern of brain phospholipid upon exposure. The relatively low uptake of TRI makes a high exposure level (1200 p.p.m.) necessary to attain a blood concentration high enough for the changes to appear.

A simple quantitative dot-immunobinding assay for glial and neuronal marker proteins in SDS-solubilized brain tissue extracts

Immunoassays for quantitative determinations of the S-100 protein, the glial fibrillary acidic protein, the neuron specific enolase and the neurofilament proteins with molecular weight of 68 and 200 kDa in hot SDS sonicated rat brain extracts have been developed and characterized. The assays utilize a dot immunobinding technique, poly- or monoclonal antibodies and 125I-protein A. The SDS-sonication procedure was not found to affect the radioactivity recovery in the assay of the soluble S-100 protein or the neuron specific enolase. All 5 antigens can be measured with a within-assay variance below 10%. Even at a coefficient of variation less than or equal to 5%, the working ranges are approximately 30-100-fold with regard to the different antigens. It was found that gelatin-coated nitrocellulose membranes considerably increase the recovered radioactivity in the assay of the purified bovine S-100 protein, possibly by protein-protein interaction. This effect was not observed when SDS-sonicated rat brain extracts were assayed. The assay appears to be reproducible, convenient and rapid, and provides a high degree of precision in the determination of large number of samples.

Long-term exposure of rats to perchloroethylene, with and without a post-exposure solvent-free recovery period: effects on brain lipids

The effects of perchloroethylene were studied in the rat brain after continuous exposure for 90 days at 320 ppm. Animals were also allowed after exposure to recover in a solvent-free atmosphere for 30 days. Lipid and fatty acid compositions were studied in particular. Changes were observed in the fatty acid pattern of ethanolamine phosphoglyceride in the cerebral cortex. Fatty acids 18:0, 20:1 (n-7) and 20:4 (n-6) were decreased while very-long-chain polyunsaturated fatty acids were increased. Most fatty acid changes were normalized during the 30 days post-exposure solvent-free recovery period with the exception of the minor fatty acid 20:1 (n-7). However, the previously unchanged fatty acid 18:1 was found to be decreased after the recovery period. Cholesterol was also decreased at this time and a tendency to reduction of myelin-enriched lipids after exposure to perchloroethylene might indicate a persisting loss of myelin membranes.

Polyclonal antisera to the individual neurofilament triplet proteins: a characterization using ELISA and immunoblotting

In this article, the preparation and characterization of polyclonal rabbit antisera against the individual polypeptides of bovine neurofilament (68, 150, and 200 kilodaltons) is described. Selected antisera against the 68- and 150-kilodalton neurofilament polypeptides were specific for the corresponding antigen in homogenates of bovine, rat, and human brain as judged by immunoblots. The antisera against the 200-kilodalton neurofilament polypeptide cross-reacted to some extent with the 150-kilodalton neurofilament polypeptide, especially with the human antigen. The most specific antisera were used to develop an enzyme-linked immunosorbent assay (ELISA), and the cross-reactivities between the antisera and the different bovine and rat neurofilament polypeptides were determined. Contrary to the results in the immunoblots, the antiserum against the 200-kilodalton neurofilament polypeptide was subunit-specific, as was the 150-kilodalton antiserum. The 68-kilodalton antiserum displayed a minute cross-reactivity against bovine 150- and 200-kilodalton neurofilaments, but it cross-reacted somewhat more with the rat 150- and 200-kilodalton antigens. Even so, the subunit specificity of the antisera is high enough to enable the development of a quantitative ELISA for determination of the individual bovine or rat neurofilament polypeptides in a mixture. This study is the necessary preparation for such an assay.

Modulation of ATPase activities in the central nervous system by the S-100 proteins

The isomeric forms of bovine S-100a and S-100b have been shown to stimulate ATPase activities in fractions enriched in myelin and mitochondria isolated from the Gerbil brain and for S-100b more effectively than for calmodulin in erythrocytes or skeletal muscle. In the presence of Ca2+, S-100a produced a slight increase of ATPase activity in the mitochondrial fraction. However, S-100b in the presence of Zn2+ almost doubled the ATPase activity in brain myelin. S-100a, or S-100b, with or without Ca2+ and Zn2+ respectively, had no effect on the ATPase activity in mitochondria of the Gerbil liver. The observations may indicate a "second messenger" role for S-100b in the presence of Zn2+ in the Schwann cell.

Long term neurotoxicity of styrene. A quantitative study of glial fibrillary acidic protein (GFA) and S-100

Little information exists about the possible neurotoxicity of styrene. The present study was designed to explore whether long term inhalation exposure (three months) to styrene (90 and 320 ppm) could induce long lasting astroglial alterations in Sprague Dawley rats, traceable four months after exposure ceased. Styrene exposure at 320 ppm induced such alterations as shown by raised concentrations of the glial cell marker, glial fibrillary acidic protein (GFA) in the sensory motor cortex and in the hippocampus. GFA is the structural protein of the astroglial filaments and formation of these filaments has been shown after damage to the central nervous system from any cause. It is concluded that exposure to styrene at moderate exposure levels induces regional, long lasting astroglial reactions that serve as an indicator of solvent induced brain damage.

Parvalbumin increases in the caudate putamen of rats with vitamin D hypervitaminosis

The influence of chronic vitamin D3 application on the concentration of the four calcium-binding proteins parvalbumin, the 28-kDa calbindin-D, calmodulin, and S-100 was studied in various brain regions and in the kidney. Young rats were administered daily 20,000 international units of vitamin D3 per kg (body weight) over a period of 4 months. This chronic treatment resulted in a clinically mild hypervitaminosis that did not affect the content of calmodulin, the 28-kDa calbindin-D, and S-100. Also the concentration of parvalbumin in the cerebral cortex, hippocampus, and kidney remained unchanged. On the other hand, parvalbumin was increased about 50% in the caudate putamen of hypervitaminotic animals as compared to controls. Our results indicate that the metabolism of parvalbumin in the caudate putamen can be influenced by variations of the blood level of this steroid hormone.

The S-100 protein in cerebrospinal fluid: a simple ELISA method

A simple ELISA method is described for determinations of S-100 protein concentrations in CSF. The assay has a useful range of 200-3200 pmol/l. The precision of the ELISA was estimated using a pool of CSF. The coefficient of variation was 0.18 within assay, 0.17 between assay and 0.17 between day. The S-100 protein is stable in the CSF as no measurable differences in S-100 concentrations were observed in samples stored at room temperature for 2 days. No correlation between age and S-100 concentration was found when determinations were performed in CSF from neurologically healthy males. Furthermore, no changes of S-100 was observed in a lumbocisternal CSF gradient from patients with normal pressure hydrocephalus. Thus, the described ELISA represents an easy to handle and reliable method, well suited for routine determinations of S-100 protein concentration in the CSF.

Effects of exposure to Freon 11, 1,1,1-trichloroethane or perchloroethylene on the lipid and fatty-acid composition of rat cerebral cortex

Organic solvents are often present as mixtures in various industrial and house-hold products. The adverse effects arising from exposure to these solvents have often been generalized to concern the whole group of solvents. In an examination of the possibility that organic solvents have general effects on experimental animals, rats were continuously exposed to vapors of the halogenated solvents Freon 11, perchloroethylene, and 1,1,1-trichloroethane. The lipid composition and fatty-acid pattern of ethanolamine phosphoglyceride from the cerebral cortex were analyzed. It was observed that only perchloroethylene had effects on the brain lipid composition. Cholesterol and total phospholipids were slightly reduced. Among the fatty acids the proportion of stearic acid was reduced and those of docosapentanoic, 22:5 (N = 6), and of docosahexanoic, 22:6 (N = 3), acids were increased. The changes in the fatty-acid pattern indicate that an alteration occurs in the desaturation of fatty acids. It seems probable that the chloroethylenes have specific effects on the fatty-acid pattern of brain phospholipids not shared by other solvents.

A rapid HPLC method to separate the triplet proteins of neurofilament

In this article a fast HPLC technique to separate the individual neurofilament proteins is described. Highly pure fractions of the three neurofilament proteins can be obtained. As much as 50 mg of each neurofilament polypeptide can be separated from a crude neurofilament protein preparation in one step in less than 2 h. The short separation time is of importance in minimizing degradation, especially of the 150-kilodalton neurofilament polypeptide.

Effects of low-dose inhalation of three chlorinated aliphatic organic solvents on deoxyribonucleic acid in gerbil brain

Young adult Mongolian gerbils (Meriones ungiculatus) were continuously exposed by inhalation to 1,1,1-trichloroethane at the Swedish occupational exposure limit (70 ppm), to methylene chloride at three times (210 ppm) the Swedish occupational exposure limit (70 ppm), and to perchloroethylene at three times (60 ppm) the Swedish occupational exposure limit (20 ppm), for three months, followed by a four-month postexposure solvent-free period. The concentrations of deoxyribonucleic acid (DNA) were then determined in different regions of the gerbil central nervous system. It was observed that the DNA concentrations in several brain regions were decreased in the exposed animals. It was found that 1,1,1-trichloroethane induced these alterations in many more brain areas at its Swedish occupational exposure limit than the other solvents studied at threefold their Swedish occupational exposure limits. The results suggest that all the solvents decrease cell density by inhibiting the slow acquisition of DNA or by inducing cell death in some sensitive brain areas and that 1,1,1-trichloroethane should not be regarded as harmless as previously stated.

Lipid composition and fatty acid pattern of the gerbil brain after exposure to perchloroethylene

Continuous inhalation of perchloroethylene (PCE) (320 ppm) for 3 months by Mongolian gerbils resulted in an altered fatty acid pattern of a brain phospholipid. A minor decrease in the brain weight was also observed. In ethanolamine phosphoglyceride of the cerebral cortex and the hippocampus, a decrease was found among the minor fatty acids derived from linolenic acid with a corresponding increase in several fatty acids of the linoleic acid family. Linoleic acid itself was decreased. Stearic acid was also decreased in both the cerebral cortex and the hippocampus. These changes in the fatty acid pattern indicate increased desaturation. PCE might alter the desaturase activity either directly by interfering with the protein moieties of the enzyme system, or indirectly by changing the properties of the lipid matrix. The observed changes in fatty acid composition are also consistent with the current hypothesis that solvents and anesthetics perturb the lipid matrix of membranes, possibly inducing complex compensatory changes in the membrane lipid composition.

Fatty acid changes in rat brain ethanolamine phosphoglycerides during and following chronic exposure to trichloroethylene

Rats were exposed by continuous inhalation to a moderate level of trichloroethylene (1720 mg/m3). The fatty acid pattern of brain ethanolamine phosphoglycerides was examined during exposure and after an additional exposure-free period. Alterations in the fatty acid pattern were noted after 30 days of exposure. An increased ratio of linoleic acid-derived (n-6) to linolenic acid-derived (n-3) fatty acids was observed in the cerebral cortex, the hippocampus, and the brain stem. Of the major fatty acids, arachidonic acid (20:4(n-6)) was increased in the cerebral cortex and the brain stem, while docosahexenoic acid (22:6(n-3)) was decreased in the cerebral cortex and the hippocampus. A further change in these fatty acids was observed in the cerebral cortex following a longer exposure period of 90 days. The 22-carbon linoleic acid-derived fatty acids were also increased after 90 days of exposure. These findings imply that trichloroethylene affects the metabolism of ethanolamine phosphoglyceride fatty acids in the rat brain by inhibiting desaturation of the linolenic acid family and by increasing desaturation of the linoleic acid family. The effect of trichloroethylene was partially reversible, since a postexposure solvent-free period revealed a rapid partial normalization of 22:6(n-3), which is the most important fatty acid of the linolenic acid family in the rat brain. However, the precursor of this fatty acid, 22:5(n-3), was decreased during the first 10 exposure-free days. This suggests that desaturation over the first steps was still impaired. A complete normalization of the fatty acid pattern was not observed during the 30-day solvent-free period. The decreased number of double bonds and shorter chain lengths detected after solvent exposure is consistent with the idea of a compensatory remodeling of membrane lipid composition based on membrane stability with regard to phase preference.

Chronic effects of dichloromethane on amino acids, glutathione and phosphoethanolamine in gerbil brain

Mongolian gerbils were exposed to dichloromethane for three months by continuous inhalation at 210 ppm. Total free tissue amino acids, glutathione, and phosphoethanolamine were determined in the vermis posterior of the cerebellum and the frontal cerebral cortex. These two brain areas were chosen because humans occupationally exposed to dichloromethane have shown abnormalities in the electroencephalogram of the frontal part of the cerebral cortex. This study showed that long-term exposure of gerbils to dichloromethane (210 ppm) for three months leads to decreased levels of glutamate, gamma-aminobutyric acid, and phosphoethanolamine in the frontal cerebral cortex, while glutamine and gamma-aminobutyric acid are elevated in the posterior cerebellar vermis.

Irreversible effects of dichloromethane on the brain after long term exposure: a quantitative study of DNA and the glial cell marker proteins S-100 and GFA

Two astroglial proteins S-100 and GFA, as well as DNA, were quantitatively determined in different regions of the gerbil brain after continuous long term exposure to moderate concentrations of dichloromethane. The intention of the experiment was to expose three groups of animals at three different solvent concentrations (210, 350, or 700 ppm) for three months. Because of the high mortality rate, however, the 700 ppm experiment was terminated after seven weeks. In the 350 ppm experiment half the exposed animals died and the exposure period was terminated after ten weeks. After the exposure period, the surviving gerbils in the 350 ppm exposure group and those from the 210 ppm group were allowed a postexposure solvent free period of four months. After exposure to 350 ppm, increased concentrations of the two astroglial proteins were found in the frontal and sensory motor cerebral cortex, compatible with astrogliosis in these regions. Exposure to 350 ppm and 210 ppm decreased the concentrations of DNA in the hippocampus. Moreover, after exposure at 350 ppm, DNA concentrations were also decreased in the cerebellar hemispheres. These results indicate a decreased cell density in these brain regions, probably due to cell loss. The neurotoxic effects were not found to correlate with the endogenous formation of carbon monoxide.

Tetrachloroethylene: levels of DNA and S-100 in the gerbil CNS after chronic exposure

Concentrations of the astroglial protein S-100, DNA and protein were studied in different regions of the gerbil CNS after chronic tetrachloroethylene exposure. The animals were exposed by continuous inhalation at 60 or 320 ppm for three months, followed by a four month solvent-free period. Increased concentrations of S-100, indicative of astroglial hypertrophy and/or proliferation, were found not only in the hippocampus and in the cerebral occipital cortex, but also in the cerebellar areas. In the frontal cerebral cortex, decreased S-100 and DNA concentrations were found to be concomitant with a decreased wet weight of the area, suggesting an atrophy which also affects the astroglial cells. This atrophy also is reflected in decreased DNA concentrations found after exposure at 60 ppm in this region of the brain. These results are consistent with the observation that tetrachloroethylene is a potent neurotoxin, as changes in the gerbil brain were found even at exposure levels as low as 60 ppm.

Membrane lipid changes in organic solvent tolerant neural cells

Although, organic solvents are known to interact with neural membranes and to possess acute anesthetic properties, very little is known about the chronic effects of organic solvents on neural membranes. In the present study lipid compositional changes were examined after chronic exposure to the chlorinated organic solvents, trichloroethylene (TCE) and perchloroethylene (PCE). Animals were exposed continuously in inhalation chambers. Each experimental group had its own control group exposed simultaneously to air under identical conditions. Exposure to these organic solvents had only minor effects on lipid class composition. A tendency towards a decreased cholesterol to phospholipid ratio was observed, whereas the content of cerebrosides was unaffected. However, the proportions of the polyunsaturated fatty acids of ethanolaminephosphoglyceride (EPG) was consistently changed after exposure to either of these solvents for three months at (320 ppm). After longer exposure periods such alterations were observed at even lower solvent concentrations. This change in fatty acid pattern was characterized by an increase in linolenic acid derived fatty acids, with a concomitant decrease in fatty acids of the linolenic acid family. These changes may be an effort to compensate for the increased hydrophobic volume of membranes induced by dissolved solvent molecules. This compensation could be achieved by insertion of less coned lipid components into the membrane. The observed decrease in cholesterol to phospholipid ratio and the increase in the less saturated linoleic acid derived fatty acids could serve this function. Another possibility could be that chlorinated organic solvents interfere with the protein structure of desaturases, resulting in an alteration in the speed of desaturation and a changed fatty acid composition.

Astrogliosis in the cerebral cortex of gerbils after long-term exposure to 1,1,1-trichloroethane

Mongolian gerbils (Meriones ungiculatus) were continuously exposed by inhalation to 1,1,1-trichloroethane at 70, 210, or 1 000 ppm for three months, followed by a four-month postexposure solvent-free period. Concentrations of two astroglial proteins, S-100 and glial fibrillary acidic (GFA) protein, were then determined in different regions of the cerebral cortex. The main biochemical alterations induced after exposure to 210 and 1 000 ppm of 1,1,1-trichloroethane demonstrated a pronounced change in gerbil brain; increased concentrations of GFA protein were found in the cerebral sensorimotor cortex at both these exposure levels, an occurrence indicating astrogliosis in this brain region. These results suggest that 1,1,1-trichloroethane should not be regarded as harmless, particularly regarding neurotoxicity, as previously claimed.