DNA cross-link-dependent RAD50/MRE11/NBS1 subnuclear assembly requires the Fanconi anemia C protein

Fanconi anemia (FA) is a cancer-predisposition syndrome characterized by hypersensitivity to interstrand-cross-link (ICL) inducers. FA hypersensitivity to ICL has been correlated with alterations in homologous recombination, non-homologous end-joining, telomere maintenance, DNA-damage assessment and checkpoint regulation, processes in which the components of the RAD50/MRE11/NBS1 (RMN) complex are involved. To better characterize the mechanisms by which ICL are processed in human cells and to gain insight into their toxicity in FA, we examined (i). the RMN complex assembling in response to the ICL inducers mitomycin C (MMC) and photoactivated 8-methoxypsoralen and (ii). the proficiency of FA cells to perform RMN activation in response to ICL inducers. We show here that ICL activates the assembly of the RMN proteins into subnuclear foci, and that their formation proceeds independently of ICL incision, a step mainly dependent on XP-F/ERCC1 heterodimer activity. Interestingly, FA cells were unable to form RMN foci in response to either ICL inducer. Analysis by pulsed-field gel electrophoresis and single-cell gel electrophoresis of MMC-treated cells showed that FA cells from complementation group C (FA-C cells, defective in the FANCC gene) form double-strand breaks and unhook MMC-induced ICL similarly to FANCC wild-type cells. These observations imply that the absence of RMN assembly in FA-C cells is not simply due to the absence of DNA ends produced as intermediates of ICL processing, and indicates a direct role for FANCC in RMN focus assembly in response to ICL inducers. Moreover, we show that the formation of foci, including BRCA1 and/or RAD51 proteins, is significantly delayed in FA cells. These alterations in the assembly of DNA-repair proteins in FA provide an interpretation for the DNA-damage processing anomalies observed in FA cells and for the genetic instability and the cancer predisposition of the syndrome.     

Stabile polysauerstoff-radikale. I. Synthese von polymerisationsfähigen monomeren mit sterisch behinderter freier oder geschützter phenolischer hydroxylgruppe

New monomers with sterically hindered free or blocked phenolic hydroxyl groups were used as starting compounds for the preparation of stable oxygen polyradicals. In this paper the synthesis of these monomers is described: 2,6-Di-(tert-butyl)-4-vinylphenol was obtained by decarboxylation of 3-[3,5-di-(tert-butyl)-4-hydroxyphenyl]acrylic acid in yields of 80–;90%. 2,6-Di-(tert-butyl)-4-isopropenylphenol was prepared from 3,5-di-(tert-butyl)-4-hydroxyphenyl methyl ketone and methyl iodide by a GRIGNARD reaction followed by the dehydration of 2-[3,5-di-(tert-butyl)-4-hydroxyphenyl]-2-propanol. 2,6-Di-(tert-butyl)-4-isopropenylphenyl methyl ether was obtained with 64% yield from 3,5-di-(tert-butyl)-4-methoxybenzonitrile by two consecutive GRIGNARD reactions with methyl iodide via the unknown compounds 3,5-di-(tert-butyl)-4-methoxyphenyl methyl ketone and 2-[3,5-di-(tert-butyl)-4-methoxyphenyl]-2-propanol, followed by dehydration of the tertiary alcohol with 89% phosphoric acid.     

Pb2+ modulates the NMDA-receptor-channel complex

Summary The actions of Pb²⁺ on NMDA channel currents of acutely dissociated hippocampal CA1- and CA3-neurones from adult rats activated by aspartate plus glycine (asp/gly) were examined. A fast reversible and a slow irreversible response to Pb²⁺ were found. Pb²⁺ applied simultaneously with asp/gly decreased an inward current. The threshold concentration was below 2 M, the current was reduced > 90% at concentrations over 100 M, The decrease of the asp/gly activated current showed no voltage dependence. Opening of NMDA channels was not necessary for Pb²⁺-action, as preincubation in 50 M Pb²⁺-containing external solution for several seconds dramatically reduced the response to asp/gly/Pb²⁺. This effect was reversed within 2 to 5 s of wash. Presence of Pb²⁺ or asp/Pb²⁺ or glycine/Pb²⁺ in the external solution did not prevent recovery of the NMDA receptor/channel complex from desensitization. Prolonged perfusion of a cell with the asp/gly/Pb²⁺-containing external solution resulted in an irreversible decrease of the asp/gly current, whereas the amplitude of the asp/gly/Pb²⁺ response did not change over the duration of an experiment. We conclude that Pb²⁺ modulates NMDA channel activity via interaction with the NMDA/glycine receptor: as a result the channel current decreases.Abbreviations NMDA N-methyl-D-aspartate - LTP long-term potentiation - AP5 2-amino-5-phosphonovalerate - EGTA ethylene glycol bis(-aminoethylether)-N,N,N,N-tetraacetic acid - HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid Correspondence to H. L. Haas at the above address     

Hirntumorresektionen in einem offenen 0,5 T-MRT Zweijährige Erfahrungen aus neuroradiologischer Sicht

After two years clinical experience using an open 0.5 T-MRI, which make it possible to control all steps of a brain tumor resection, the high expense in relation to the effect is proofed. In 80 MRI-guided brain tumor resections the indication, the degree of resection, the appearance of operative induced changes, complications and clinical state are analysed. The advantage of the method consists in safety of localisation and detection especially of intra-axial cerebral tumors, recording of intraoperative invisible tumor parts and saving eloquent areas during tumor resection. To have optimal results, all over the operation time, the participation of a special experienced radiologist is necessary. The best results are shown in treatment of low grade gliomas and tumors near eloquent areas.     

Growing blood clot mimicking an aneurysm on postoperative computerized tomography and magnetic resonance imaging studies. Case report and review of the literature.

The authors describe the case of a 15-year-old boy who underwent resection of a large left temporal tumor. During a normal postoperative course, computerized tomography (CT) scanning demonstrated a spherically hyperdense structure near the internal carotid artery, enlarging on a control CT scan. A suspected false aneurysm was confirmed on magnetic resonance imaging; angiographic studies were negative. The authors believed they were dealing with a thrombosed false aneurysm and they performed operative revision. Intraoperatively the "aneurysm" could be dissected off the internal carotid artery and no lesion of the arterial wall was obvious. Histological findings showed a fresh blood clot. This case demonstrates that a blood clot may mimic an aneurysm on CT and magnetic resonance studies, which has not been described earlier. The origin of the blood clot remains unclear.