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We have examined 216 consecutive surgical specimens of patients with chronic pharmacoresistant temporal lobe epilepsy. Neoplasms were detected in 75 cases (34.7%). All but two of these tumors were of low histopathological grade (WHO-grade I or II). There were 34 gangliogliomas, 17 pilocytic astrocytomas, 9 oligodendrogliomas, 6 fibrillary astrocytomas, and 6 dysembryoplastic neuroepithelial tumors. Fifty-one specimens contained non-neoplastic focal lesions and an additional 13 cases had both tumors and non-neoplastic focal lesions within the same specimen. The most frequent non-neoplastic focal lesions were microscopic glioneuronal hamartias (32 cases), glioneuronal hamartomas (7 cases) and vascular malformations (13 cases). The hippocampal formation was structurally well preserved in 71 specimens and in 51 of these (71.8%) there was Ammon's horn sclerosis. The findings document that intractable temporal lobe epilepsy is associated with significant structural alterations in the great majority of patients.

Nervous system-specific transcription factors that bind to the octameric deoxyribonucleic acid sequence motif ATGCAAAT (or ATTTGCAT) are known as N-Oct proteins. Neurons and glia contain the ubiquitous Oct-1 protein and four polypeptide complexes termed N-Oct-2, N-Oct-3, N-Oct-4, and N-Oct-5. Previously, we showed that N-Oct proteins are differentially expressed by human neuroblastoma and glioblastoma cell lines in vitro. We have now extended this work to freshly isolated human primary and metastatic brain tumors. Contrary to brain tumor cell lines, of the five astrocytomas and three glioblastomas analyzed, all but two tumors displayed the complete N-Oct protein profile, irrespective of histopathological tumor grade. Two astrocytomas were negative for N-Oct-4. Ten of 13 ependymomas exhibited N-Oct-2, N-Oct-3, and N-Oct-4 but lacked the N-Oct-5 complex. In contrast, brain metastases of two patients with extracerebral carcinomas contained only Oct-1, and cerebral metastases from two cases of B cell lymphomas showed Oct-1 and Oct-2 complexes, the characteristic Oct protein pattern of B lymphocytes. Thus, metastatic carcinoma and lymphoma expressed a non-nervous system phenotype of Oct proteins.

Using a combination of transplacental carcinogen exposure and retrovirus-mediated oncogene transfer into fetal brain transplants, we have studied complementary transformation by N-ethyl-N-nitrosourea (NEU) and the v-myc oncogene in the nervous system. Previous experiments had demonstrated that both agents will not induce tumors independently whereas simultaneous expression of v-H-ras and v-gag/myc exerted a powerful transforming potential in neural grafts. In order to identify other genetic alterations that co-operate with an activated myc gene, the neurotropic carcinogen NEU was used to generate mutations of cellular genes. On embryonic day 14 (ED14), pregnant donor animals (F344 rats) received a single i.v. dose of NEU (50 mg/kg). Twenty-four hours later (ED15), the fetal brains were removed, triturated and incubated with a retroviral vector carrying the v-gag/myc oncogene. Subsequently, these primary cell suspensions were transplanted stereotactically into the caudate-putamen of syngenic adult recipients. After latency periods of 3-6 months, 5 of 10 recipients harboring ED15 fetal brain transplants developed malignant, poorly differentiated neuroectodermal tumors in the grafts. No tumor development was observed in seven recipients harboring ED16 neural grafts. Cell lines were established from three tumors and the 110 kd gag/myc fusion protein encoded by the retroviral construct was identified in the tumors by Western blotting. Several candidate genes for mutational activation by NEU including the H-ras, K-ras and neu oncogenes were analyzed for specific point mutations by polymerase chain reaction (PCR) and direct DNA sequencing of the PCR products. However, no mutations were found in any of these genes. These findings lend further support to the multistep hypothesis of neoplastic transformation in the brain. The tumors induced in this model provide an interesting tool for the identification of genes that co-operate with an activated myc gene in neurocarcinogenesis.

1954 to 1989, 33 patients with intracranial ependymomas had primary treatment in our hospital with surgery and postoperative radiotherapy. Five- and ten-year survival rates were 48% and 34% in 25 patients with a high-grade ependymoma and for low-grade ependymomas was maintained at 78% for both the five- and ten-year follow-up period. Cumulative frequency of local or intracranial recurrence was 70% (high-grade) and 20% (low-grade). Despite the fact, that only three of 25 patients with high-grade ependymomas had spinal irradiation with 19.5 to 30 Gy, there was only a single patient with clinical signs of spinal metastases simultaneously with an intracranial recurrence. Twelve out of 13 living patients without signs of tumor have been classified according to the neurological performance: Performance was good or very good in five patients, satisfying in three with an independent life, fair in two patients working in a sheltered office and dependent on some assistance and poor in two patients. Published results are discussed and compared with the own observations and our current treatment policy is given.

Using retrovirus-mediated gene transfer into neural transplants, we have expressed the human K-fgf/hst oncogene in the central nervous system. Single-cell suspensions of fetal rat brains were removed at embryonic days 13 and 14, exposed to a retroviral vector encoding the K-fgf oncogene and stereotaxically implanted into the caudate putamen of syngenic adult Fisher rats. Recipient animals were sacrificed at intervals of 6-16 months without evidence of neurological impairment. Mock-infected grafts showed the characteristic histopathological appearance of organotypically differentiated neural transplants. In contrast, grafts exposed to the K-fgf gene exhibited abundant capillary proliferation and capillary angiomas. By in situ hybridization analysis and immunohistochemistry, expression of K-fgf was detected in neural cells adjacent to vascular proliferations. Neurons and glia with abundant K-fgf transcripts were morphologically unaffected. In order to examine the transforming potential of the K-fgf gene in the nervous system, we combined retrovirus-mediated transfer of the K-fgf oncogene with a single transplacental exposure of the donor animals to the neurotropic carcinogen N-ethyl-N-nitrosourea (NEU). However, this combination of transforming agents did not result in tumor formation in the grafts. These results provide evidence for a powerful angiogenic effect of K-fgf on the developing brain in vivo.

✓ The central neurocytoma has recently been added to the differential diagnosis of intraventricular tumors. Histopathologically, this tumor is characterized by a uniform neoplastic cell population with features of neuronal differentiation. Central neurocytomas occur in young adults, develop in the area of the foramen of Monro, and are usually associated with the septum pellucidum. Initial reports appeared to indicate that these tumors are benign lesions with a favorable postoperative prognosis. The authors present clinical and neuropathological findings in a series of eight patients with central neurocytoma. An anterior transcallosal microneurosurgical approach yielded good outcomes. Postoperative radiation therapy was restricted to two patients with a malignant variant of central neurocytoma and one patient with a recurrent tumor. Observations of anaplastic variants of this neoplasm in two cases and local tumor recurrences in three indicate that the biological behavior and postoperative prognosis of central neurocytoma may not always be as favorable as previously assumed.

The incidence of HIV encephalopathies was determined in an ongoing consecutive autopsy study. Among 345 patients who died from AIDS in Switzerland during 1981-1990, 68 (19%) showed morphological evidence of HIV encephalopathy. Two major histopathological manifestations were observed. Progressive diffuse leukoencephalopathy (PDL) was present in 33 cases and is characterized by a diffuse loss of myelin staining in the deep white matter of the cerebral and cerebellar hemispheres, with scattered multinucleated giant cells but little or no inflammatory reaction. Multinucleated giant cell encephalitis (MGCE) was diagnosed in 32 cases; it's hallmarks are accumulations of multinucleated giant cells with prominent inflammatory reaction and focal necroses. In 3 patients both types of lesions overlapped. Brain tissue from 27 patients was analyzed for the presence of HIV gag sequences using the polymerase chain reaction (PCR) with primers encoding a 109 base pair segment of the viral gene. Amplification succeeded in all patients with clinical and histopathological evidence for HIV encephalopathy but was absent in AIDS patients with opportunistic bacterial, parasitic and/or viral infections. Potential mechanisms by which HIV exerts it's adverse effects on the human CNS are discussed.

Using a neural transplantation model which mimics structural and functional properties of the normal rat brain to a high extent, we have taken a novel approach to study the transforming potential of activated oncogenes in the developing brain. Single cell suspensions prepared from fetal rat brains were infected with replication-defective retroviral vectors encoding oncogenes and stereotaxically injected into the caudoputamen of adult F344 rats. Rats carrying transplants expressing the polyoma middle T antigen developed endothelial hemangiomas in the graft which in 70% of the recipient animals led to fatal cerebral hemorrhage within 13-50 days after transplantation. Expression of the v-src gene caused astrocytic and mesenchymal tumors with a 70% incidence after latency periods of 2-6 months, but no endothelial lesions. It was found by in situ hybridization that these oncogenes are expressed in all cell types present in the graft. This indicates that cell-type specific transformation is due to differential susceptibility of the respective target cell to the oncogenes, rather than selective integration or expression of the retroviral construct. The highly efficient gene transfer by retroviral vectors into fetal brain transplants provides a challenging experimental strategy to study differentiation and oncogenesis in the CNS.

This 6-year-old girl was admitted with insufficient involuntary breathing and generalized hypotonia. T2-weighted MR images showed bilateral symmetrical tubular hyperintense lesions in the medio-caudal part of the medulla oblongata that correlated well with demyelination and gliosis in the regions of the reticular formation and the nucleus solitarius found at autopsy. The typical lesions of Leigh's disease in the basal ganglia were not present, which made the diagnosis uncertain prior to the histopathological findings. MRI was very helpful in deciding on further management of the patient.

The expression of two forms of pp60c-src, pp60 and pp60+, was measured in the central nervous system (CNS) and the peripheral nervous system. Both forms were expressed in the CNS, whereas only pp60 was primarily detected in the peripheral nervous system. Our findings suggest that pp60+ may play a role in events important to the CNS.

Following oral or systemic (subcutaneous) administration to rats,N-nitroso -methylbenzylamine (NMBzA) causes a high incidence of oesophageal tumours. Methylation of DNA purines by a single oral dose of [14C-methyl]-NMBzA was most extensive in the oesophagus, followed by liver, forestomach and lung. After a single intravenous injection, alkylation levels were also highest in oesophageal DNA, followed by liver, lung and forestomach. These differences in the extent of alkylation were found to correlate with the autoradiographic distribution of tissue-bound 14C-radioactivity in in-situ preparations of the upper gastrointestinal tract following oral exposure to [14C-methyl]-NMBzA. In mice, systemic administration of NMBzA leads to the development of forestomach and lung tumours; in this species, DNA methylation after intraperitoneal injection of NMBzA is highest in liver, followed by lung and forestomach. Administration of [14C-methyl]-NMBzA to mice in the drinking-water led to very high concentrations of alkylated DNA bases in both oesophagus and forestomach. This finding is in good agreement with carcinogenicity studies, which showed 100% carcinoma incidence at these sites. Autoradiographic studies indicate that in rats and mice the metabolism of NMBzA in the oesophagus is largely restricted to the mucosa, whereas in lung, bioactivation occurs predominantly in the bronchial epithelium. In autoradiographs from liver, tissue-bound radioactivity showed a patchy distribution, with predominant reaction in the centrilobular region. In Mongolian gerbils, methylation of lung DNA by a similar subcutaneous dose of [14C-methyl]-NMBzA was greater than in rats and mice, whereas in the remaining tissues, levels of methylated purines were comparatively low. Chronic subcutaneous administration of NMBzA to gerbils caused no tumour within an observation period of two years.

The cytostatic drug procarbazine has previously been shown to be a potent transplacental neurotropic carcinogen in rats. Following a single IP administration of (14C-methyl)procarbazine (110 mg/kg) on day 22 of gestation, methylation products with cellular DNA were determined in fetal and maternal rat organs. The concentration of the major adduct N7-methylguanine was highest in the maternal liver (224 mumol/mol guanine). Fetal and nonhepatic maternal tissues exhibited significantly lower levels, but differed little from each other. In brain, lung, intestines, and placenta the O6-methylguanine/N7-methylguanine ratio was close to 0.11, indicating that procarbazine, like other methylating carcinogens, initiates malignant transformation via methyldiazonium hydroxide as the ultimate reactant. Following a single dose of (14C-methyl)procarbazine to newborn animals, methylpurine values were 30-60 times lower than after prenatal administration. This suggests that DNA alkylation in nonhepatic tissues occurs by systemic distribution of a proximate carcinogen formed in the adult rat liver.

The introduction of immunohistochemicar methods has had a profound impact both on the science and practice of neuropathology. In many ways it has changed our way of thinking about neuro-oncogenesis (Rubinstein 1987a), and in surgical pathology, it has led to a significantly higher level of diagnostic accuracy (Bonnin and Rubinstein 1984; Kleihues et al. 1987). However, the application of immunocytochemical markers has not profoundly affected our view on the current classification of brain tumors (Zulch 1979) although in a few cases it led to the abolishment of established entities (e.g., monstrocellular sarcoma) and the introduction of new diagnostic terms (e.g., the polymorphic xanthoastrocytoma). It should, however, be kept in mind that with respect to the histogenesis of neoplasms, the use of lineage-specific marker antigens may lead to erroneous interpretations. In contrast to their normal counterparts, neoplastic cells may undergo unpredictable changes in gene expression. This may result in the lack of a gene product typically present, or in the synthesis of a marker protein not usually expressed, in the cell of origin. Also, the panel of antibodies currently available offers no help in distinguishing normal from highly differentiated neoplastic cells. In this contribution we wish expand on two problems in which immunohistochemical markers have become increasingly useful, i.e. the assessment of cell kinetic parameters and analysis of the extent and direction of differentiation in embryonal CNS tumors.

Chronic administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water causes a high incidence of carcinomas of the glandular stomach in rats (SugimuraFujimura, 1967). Following a single oral dose of [14C-methyl]-MNNG (80 mg/L; 2.5 mg/kg b.w.), the extent of DNA methylation in the glandular stomach was 9 and 21 times higher than in forestomach and oesophagus, respectively. These differences were found to correlate with regional variations in the concentration of cellular thiols, which are known to accelerate the heterolytic decomposition of MNNG. When [14C-methyl]-MNNG was given intragastrically together with the thiol-blocking agent, N-ethylmaleimide, covalent binding of 14C-radioactivity to forestomach, glandular stomach and duodenum was almost completely abolished.

The promutagenic DNA lesion O6-alkylguanine can be enzymically removed from cellular DNA by an O6-alkylguanine-DNA alkyltransferase (O6-AT) which transfers the alkyl group from the O6-position of guanine to a cysteine residue contained within its sequence. We report that whole body X-irradiation induces the O6-AT activity in the liver of adult Wistar rats. In vivo repair activity was assessed by radiochromatographic determination of the persistence of O6-methylguanine in hepatic DNA of irradiated rats following a single i.p. injection of N-nitroso-[14C]dimethylamine (2 mg/kg). In addition, the O6-alkylguanine repair capacity was assayed in vitro by incubation of extracts from whole liver, hepatocytes, or hepatic cell nuclei with 3H-methylated DNA and high performance liquid chromatography analysis of this DNA substrate. We found that whole body X-irradiation increased in a dose-dependent manner the O6-AT activity over a range of 100-800 R. The repair induction was first detectable 12 h after X-ray exposure, reached a maximum level at 72 h, and declined to control values within 12 days. Deoxythymidine incorporation into hepatic DNA was significantly reduced during the initial 72 h following application of 500 R. In a split dose irradiation schedule with daily doses of 15 R, a delayed enzyme induction occurred after a 30-day treatment period. Pretreatment of rats with the translational inhibitor cycloheximide completely suppressed the O6-AT stimulation. This indicates that the induction of hepatic O6-alkylguanine repair is due to de novo synthesis of alkyltransferase molecules.

In a premature twin boy (gestational age 34 weeks) two-dimensional echoencephalography, computed tomography, and NMR tomography revealed a brain tumor. The exact diagnosis was confirmed by stereotactic biopsy from the brain. Up to now the clinical course of the child has been surprisingly benign.

Bilateral acoustic neurofibromatosis (neurofibromatosis 2, NF2) accounts for less than 10% of all cases of neurofibromatosis and manifests itself with bilateral acoustic schwannomas, multiple schwannomas of spinal nerve roots, meningiomas, glial tumors and hamartomatous CNS lesions. We have observed dysplastic foci of immature neuroectodermal cells in the cerebral cortex and basal ganglia of six patients afflicted with neurofibromatosis 2, ranging from occasional clusters of immature, dysplastic cells to numerous, confluent lesions. These cells, although often polymorphic and multinuclear did not show mitotic activity or a tendency for neoplastic transformation. To determine the histogenesis of these foci, extensive immunocytochemical reactions were carried out with antibodies to a variety of glial, neuronal and non-neural cell lineages. With the exception of S-100 protein, no immunoreactivity was detectable. S-100 was consistently expressed in these foci, irrespective of their size, location, and degree of polymorphism. On the basis of cytological appearance, distribution and immunoreactivity we tentatively designate these foci as glial micro-hamartomas. Although we did not systematically analyze the CNS of patients with von Recklinghausen neurofibromatosis (neurofibromatosis 1, NF1), the present study strongly suggests that these micro-hamartomas constitute a morphological hallmark of bilateral acoustic neurofibromatosis (NF2).

Two endothelial cell lines were derived from grafts of the central nervous system using retrovirus mediated gene transfer to introduce the polyoma middle-T oncogene into fetal rat brain endothelial cells and transplantation of these cells into adult rat brain. In this report, we further characterize these cells and the effect of dexamethasone on the expression of specific enzymatic markers. These cells take up acetylated low density lipoprotein, leucine, and glucose, and express Factor VIII-related antigen, angiotensin converting enzyme, alkaline phosphatase, gamma-glutamyltranspeptidase, and as yet undescribed aminopeptidase A and B-like enzymes. When grown on semi-permeable membranes, these transformed cells do not spontaneously retain small hydrophilic molecules. In culture, one of the lines (EC 193) forms a confluent monolayer of spindle-shaped cells homogenously expressing gamma-glutamyltranspeptidase at a level comparable to primary cells. The other cell line (EC 219) grows as clusters of elongated cells, and gamma-glutamyltranspeptidase activity is expressed mainly in cells forming the clusters. This clustered pattern changes to a confluent one after culture on type-I collagen. Dexamethasone increases angiotensin-converting enzyme activity, and decreases the expression of gamma-glutamyltranspeptidase and aminopeptidase A, whereas the aminopeptidase B activity is little modified. Inhibition of aminopeptidase A activity by amastatin, potentiates angiotensin II effects on DNA synthesis. These results indicate that retrovirally transformed brain endothelial cells are a useful model for studying the blood-brain barrier in vitro and that dexamethasone, an agent with the potential to reduce brain edema, directly affects some blood-brain barrier properties in these endothelial cell lines.