Hans-Dieter Mennel

Neuroprotective effect of memantine demonstrated in vivo and in vitro

The purpose of the present study was to test whether the anticonvulsant, memantine (1-amino-3,5-dimethyladamantane), can protect neurons against hypoxic or ischemic damage. To this end, we used a rat model of transient forebrain ischemia and cultured neurons from chick embryo cerebral hemispheres. Ischemia was induced for 10 min by clamping both carotid arteries and lowering the mean arterial blood pressure to 40 mm Hg; the rats were allowed to recover for 7 days. Cultured neurons were made hypoxic with 1 mmol/l NaCN added to the incubation medium for 30 min followed by a recovery period of 3 days. The possible effects of memantine were compared with those produced by a typical non-competitive NMDA antagonist, dizocilpine. Similar effects were obtained with both drugs. The drugs reduced the damage caused by transient ischemia to neurons of the hippocampal CA1 subfield. Memantine (10 and 20 mg/kg) had a dose-dependent effect when administered intraperitoneally to the rats 1 h before ischemia. Dizocilpine was active in this model at a dosage of 1 mg/kg. When administered after ischemia, 10 mg/kg memantine significantly protected CA1 neurons against ischemic damage. Furthermore, the drugs protected cultured neurons against hypoxic damage. The lowest effective concentration was 0.1 mumol/l for dizocilpine and 1 mumol/l for memantine. Thus, memantine possesses neuroprotective activity but is less potent than dizocilpine.

PAF Antagonist Ginkgolide B Reduces Postischemic Neuronal Damage in Rat Brain Hippocampus

We investigated the effect of the known antagonist of platelet-activating factor (PAF), ginkgolide B, on postischemic neuronal damage in the rat. Neuronal necroses were evaluated in the hippocampus 7 days after a 10-min forebrain ischemia. Preischemic application of ginkgolide B (50 mg/kg p.o.) significantly reduced neuronal damage. It is suggested that the antagonism of PAF is responsible for this beneficial effect of ginkgolide B.

Vinpocetine prevents ischemic cell damage in rat hippocampus

The effects of vinpocetine on hippocampal cell damage and local cerebral blood flow (LCBF) were measured in a rat model of forebrain ischemia (2-vessel occlusion and hypotension). Duration of ischemia was 10 min. LCBF was determined after 2 min of recirculation using the 14C-iodoantipyrine technique. Hippocampal cell loss was quantified histologically 7 days post-ischemia. Intraperitoneal application of vinpocetine (10 mg/kg) 15 min prior to ischemia significantly reduced neuronal cell loss in hippocampal CA 1 sector from 60% to 28%. The drug led to a marked increase in blood flow in cortical areas, whereas LCBF remained unchanged in hippocampus and all other structures measured. It is suggested that the protective effect of vinpocetine does not depend on increased postischemic blood flow.

Clinicopathologic Features of Aggressive Meningioma Emphasizing the Role of Radiotherapy in Treatment

Background and Purpose:Although meningiomas are typically benign, they occasionally behave in an aggressive fashion and carry a less favorable prognosis. The aim of this study was to review the clinical, radiologic and histopathologic features of these aggressive variants as well as the outcome after multimodality therapy.Patients and Methods:16 patients with atypical meningiomas (n = 11) and anaplastic meningiomas (n = 5) were treated in the Departments of Neurosurgery and Radiation Oncology at the University Hospital of Philipps University Marburg, Germany, between 1997 and 2003. Tumor grading was based on new WHO criteria. There were eleven men and five women with a mean age of 54 years. The median follow-up period was 34 months.Results:A total of 24 surgical procedures were performed for these 16 patients. Only seven patients underwent postoperative fractionated stereotactic radiotherapy. Patients with atypical meningioma received radiotherapy only for the recurrent disease. Six patients (37.5%) experienced tumor recurrence after a mean period of 27.2 months in spite of gross total resection. Radiographic findings suggestive of aggressiveness were observed mostly with WHO grade III meningiomas. By comparing the proliferation rate in four cases with atypical meningioma operated twice, the recurrent tumor had a higher proliferation rate than the first tumor in three cases. A special proliferation pattern was noticed in MIB-1 with anaplastic meningiomas. The mean overall survival period was 66.5 months. There was no mortality among patients with atypical meningioma, while four out of five patients with anaplastic meningioma died during follow-up.Conclusion:Considering the higher rate of recurrence in aggressive meningiomas even after radical surgical excision and the possibility that the recurrent tumor is more aggressive than the original one, surgery should be combined with postoperative fractionated radiotherapy to improve local tumor control. The peculiar focal expression patterns of anaplastic meningioma in MIB-1 might be a marker of such malignant development.Hintergrund und Ziel:Obwohl Meningeome in der Regel gutartig sind, weisen sie gelegentlich ein aggressives Wachstumsverhalten mit einer weniger günstigen Prognose auf. Ziel dieser Studie war es, rückblickend diese aggressive Variante nach klinischen, radiologischen und histopathologischen Kriterien zu untersuchen und das Ergebnis nach multimodaler Therapie darzustellen.Patienten und Methodik:16 Patienten mit atypischen Meningeomen (n = 11) und anaplastischen Meningeomen (n = 5) wurden zwischen 1997 und 2003 in den Kliniken für Neurochirurgie und Strahlentherapie der Philipps-Universität Marburg behandelt. Die Tumorgraduierung erfolgte nach den neuen WHO-Kriterien. Es handelte sich um elf Männer und fünf Frauen mit einem Durchschnittsalter von 54 Jahren. Der mittlere Nachbetrachtungszeitraum betrug 34 Monate.Ergebnisse:Insgesamt wurden 24 chirurgische Eingriffe bei diesen 16 Patienten durchgeführt. Lediglich sieben Patienten wurden einer fraktionierten stereotaktischen Nachbestrahlung unterzogen. Die Patienten mit atypischen Meningeomen erhielten erst im Fall eines Rezidivwachstums eine Strahlentherapie. Sechs Patienten (37,5%) entwickelten trotz vollständiger Resektion nach durchschnittlich 27,2 Monaten ein Tumorrezidiv. Zeichen für aggressives Wachstum fanden sich in der radiologischen Befundung überwiegend bei Meningeomen des WHO-Grads III. Beim Vergleich der Proliferationsraten bei vier Patienten mit atypischen Meningeomen, die zweimal operiert wurden, wies der Rezidivtumor bei drei Präparaten eine höhere Proliferationsrate auf als der ursprüngliche Tumor. Bei den anaplastischen Meningeomen wurde ein auffälliges Muster der mit dem Proliferationsmarker MIB-1 markierten Tumorzellen beobachtet. Die mittlere Überlebenszeit des Gesamtkollektivs betrug 66,5 Monate. Alle Patienten mit atypischen Meningeomen leben, wohingegen vier der fünf Patienten mit anaplastischen Meningeomen in der Nachbeobachtungszeit verstarben.Schlussfolgerung:Berücksichtigt man die trotz radikaler Tumorexzision erhöhte Rezidivrate bei aggressiven Meningeomen und die Möglichkeit der Malignisierung des Rezidivtumors, sollte die postoperative Strahlentherapie Teil des multimodalen Behandlungskonzepts sein, unabhängig vom Ausmaß der Tumorresektion. Das eigenartige fokale Verteilungsmuster von MIB-1-markierten Tumorzellen anaplastischer Meningeome könnte ein typisches Merkmal dieser Malignisierung sein.

Phencyclidine reduces postischemic neuronal necrosis in rat hippocampus without changing blood flow

In this report the effects of phencyclidine (PCP) on physiologic variables, local cerebral blood flow (LCBF), and on hippocampal cell damage were measured in a rat model of forebrain ischemia (2-vessel occlusion and hypotension). Ischemia was induced for 10 min. LCBF was determined after 2 min of recirculation, using the [14C]iodoantipyrine technique. Hippocampal cell loss was quantified histologically 7 days postischemia as the percentage of acidic stainable neurons. Intravenous application of PCP (2 mg/kg) at 15 min prior to ischemia left postischemic LCBF unchanged, but neuronal damage was significantly reduced in hippocampal CA1 sector from 46 to 15.7%. PCP is concluded to reduce ischemic damage of neurons mainly via a direct effect on brain tissue.

Endoscopic Anatomy of the Third Ventricle

42 cadaver brains in situ were examined endoscopically to work out topographical anatomical landmarks for orientation. The endoscopic route from the chosen precoronal trepanation point to the defined ventricular landmarks has been measured in 22 cases. The identification and measurements of the anatomical landmarks are helpful for safe and atraumatic endoscopical navigation within the ventricular system. Furthermore this article describes and discusses cerebral lesions during ventriculoscopy.

Secretory meningioma: immunohistochemical findings and evaluation of mast cell infiltration

Secretory meningiomas constitute a relatively rare subtype of meningiomas, accounting for only 1.1% at our institution, with a 6:1 predominance of female patients. This study aimed to obtain more information about the immunohistochemical characteristics of this histological entity, and to analyse the effects of histological factors such as the presence of mast cells on the radiological evidence of surrounding tumour oedema that frequently occurred in this subtype of meningioma. Fourteen cases of secretory meningioma were examined. Relevant clinical information was obtained from the patient files. Peritumoural oedema was determined either by CT or MRI scans and graded as small, moderate and severe. In order to perform the quantitative evaluation of mast cells in secretory meningiomas in a comparison with other meningiomas, 14 non-secretory meningiomas were randomly selected and used as a control group. The immunohistochemical staining of carcinoembryonic antigen was positive within the secretory droplets and the cells surrounding them in all cases. Ki 67 (MIB 1) proliferative index mean values were 2.4%, indicating low expression in all secretory meningiomas. Moreover, from our statistical analysis, there is no clear-cut pattern of various types of cytokeratins emerging in secretory meningiomas. The secretory meningiomas were characterized by a significantly increased number of mast cells as compared with non-secretory meningiomas of different grades. As the present clinical findings and laboratory results could not confirm a correlation between mast cell density and radiological evidence of oedema, further studies of mediators are warranted.

Naftidrofuryl Protects Neurons against Ischemic Damage

The effects of naftidrofuryl on postischemic neuronal damage and on local cerebral blood flow (LCBF) were examined in a rat model of forebrain ischemia (occlusion of carotid arteries and hypotension). Ischemia was induced for 10 min. LCBF was measured after 2 and 10 min of recirculation. A histological evaluation of cell loss in the hippocampal areas was performed 7 days after ischemia. Naftidrofuryl (10 mg/kg) was administered intraperitoneally 15 min before ischemia. The drug reduced the percentage of necrotic neurons in the CA1 and CA4 sector of the hippocampus, while the LCBF of these hippocampal sections was not significantly altered. Thus, naftidrofuryl is suggested to protect hippocampal neurons against ischemic damage mainly by a direct effect on brain parenchyma.

Preconditioning-induced protection against cyanide-induced neurotoxicity is mediated by preserving mitochondrial function.

The central nervous system is one of the main target organs in cyanide toxicity. In this study, primary cultures of chick embryonic neurons were used to characterize sodium cyanide (NaCN)-induced cell death and to investigate the mechanism of NaCN-mediated preconditioning. After treatment of the cells with 1mM NaCN for 1h followed by a NaCN-free incubation period of 23 h, we observed features of apoptosis such as a reduction in nuclear size, chromatin condensation and nuclear fragmentation as evaluated by nuclear staining with Hoechst 33258 and electron microscopy. In addition, NaCN-induced neurotoxicity was reduced by the protein synthesis inhibitor cycloheximide (CHX) suggesting an active type of cell death. Most of the neurons with condensed chromatin and a shrunken nuclei also showed membrane damage at a late stage. Mitochondrial membrane potential as well as the protein levels of Bcl-2 and Bcl-x(L) decreased 15-60 min and 1-3 h after the exposure to NaCN (1mM, 1h), respectively. Preconditioning caused by incubating chick neurons with 100 microM NaCN for 30 min followed by a NaCN-free interval of 24h significantly protected the neurons against subsequent NaCN (1mM, 1h)-induced damage. Preconditioning prevented NaCN-induced decrease in the mitochondrial membrane potential as well as in the protein levels of Bcl-2 and Bcl-x(L) suggesting that preconditioning-induced neuroprotection is mediated by preserving mitochondrial function.

Expression of p53 and p21 in Primary Glioblastomas.

Background and Purpose:Primary glioblastomas (GBMs) are highly radioresistant, and in contrast to secondary GBMs, they bear wild-type (wt) p53 protein, which is stabilized in a proportion of these tumors. Therefore, it was investigated in vivo whether p53 expression has prognostic value in patients undergoing radiochemotherapy. Additionally, the authors tried to identify, in vitro, subgroups of primary GBM with different susceptibilities to irradiation, on the basis of their p53 and p21 responses to ionizing radiation.Material and Methods:Tumor tissue samples from 31 patients suffering from primary GBM undergoing a combined radiochemotherapy with topotecan were investigated. The percentage of cells expressing p53 protein was determined immunohistochemically. Additionally, primary cultures from eleven primary GBMs were established and investigated. p53 and p21 expressions were evaluated before irradiation with 10 Gy and at 2 and 8 h after irradiation. p53 protein expression was measured by Western analysis and p21 mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR).Results:The percentage of p53-positive cells within the tumor specimens obtained from the 31 patients ranged from 0% to 28%, the median value being 4.3%. No significant correlation with disease-free survival or overall survival was found. In vitro, p53 protein was detected in seven of eleven cultures from primary GBM. After irradiation a decrease in p53 protein expression was seen in six of the seven p53-positive cultures. Half of the cultures (two of four) without basal p53 expression showed an increase in p53 expression after irradiation. Basal overexpression of p21 was detected in six of the eleven cultures; in four out of six irradiation led to a decrease in p21 expression. In all cell lines (five of eleven) initially showing absent p21 expression, irradiation induced p21 expression. Despite these responses, G1 arrest was not detectable in any of the GBM cultures.Conclusion:p53 protein expression in vivo does not correlate with the outcome of patients with primary GBM. Therefore, p53 protein content per se does not appear to be a helpful prognostic factor for prognosis-adapted therapy in primary GBM. By contrast, primary GBM cells in vitro show different and independent responses in their p53 and p21 pathways to ionizing radiation. The failure of G1 arrest seems to be due to a functional defect in the p53 pathway, either because p21 was not induced or because of an unidentified defect downstream from p21.Hintergrund und Ziel:In primären Glioblastomen (GBM) liegt die Wildtyp-(wt-)Form des TP53-Gens mit Stabilisierung des Proteins in einem Teil der Tumoren vor. Kann die p53-Expression in vivo Aussagen über das Ansprechen auf eine Radiochemotherapie liefern, und lassen sich auf dem Boden der p53- und p21-Antwort auf Bestrahlung prognostisch differente Subgruppen primärer GBM in vitro identifizieren?Material und Methodik:Tumorgewebe von 31 GBM-Patienten, die mit Topotecan kombiniert radiochemotherapiert wurden, wurde immunhistochemisch auf p53-Protein ausgewertet. Der Anteil p53-positiver Zellen wurde mit lokaler Kontrolle und Überleben korreliert. Zusätzlich wurden in vitro elf Primärkulturen primärer GBM ausgewertet. p53-Protein-Gehalt und p21-mRNA wurden mittels Western-Blot bzw. Polymerase-Kettenreaktion (PCR) bestimmt. Basales p53 und p21 sowie deren Aktivierung 2 und 8 h nach Bestrahlung mit 10 Gy wurden untersucht.Ergebnisse:Der Prozentsatz p53-positiver Zellen in den Tumorproben der 31 Patienten betrug zwischen 0% und 28% mit einem Median von 4,3%. Eine signifikante Korrelation zwischen p53-Markierung und progressionsfreiem Überleben oder Gesamtüberleben konnte nicht festgestellt werden. In vitro konnte ein basaler p53-Protein-Nachweis in sieben von elf Kulturen erfolgen. Nach der Bestrahlung zeigte sich in sechs dieser sieben Kulturen eine Proteinabnahme. In der Hälfte (zwei von vier) der GBM ohne basalen Proteinnachweis konnte nach Bestrahlung das p53-Protein nachgewiesen werden. Basale p21-Expression bestand in sechs der elf Kulturen, von denen vier mit einer Abnahme auf die Bestrahlung reagierten. Alle Zelllinien (fünf von elf) ohne basalen p21-RNA-Nachweis exprimierten nach Bestrahlung p21. Trotz der Reagibilität von p53 und p21 kam es bei keiner Zelllinie zu einem G1-Arrest.Schlussfolgerung:In vivo korreliert der p53-Protein-Gehalt der GBM nicht mit den Therapieergebnissen, so dass der p53-Nachweis keine prognostische Relevanz aufweist. In vitro zeigten sich für p53 und p21 unterschiedliche und voneinander unabhängige Reaktionsmuster nach der Bestrahlung. Das Fehlen eines G1-Arrests in allen Zelllinien könnte in einer Gruppe durch einen Defekt im p53-Signalweg und Fehlen der p21-Induktion erklärt werden. In einer anderen Subgruppe scheint, p21 nachgeschaltet, ein noch unidentifizierter Defekt vorzuliegen.