Faculty Bibliography

Background: Conformational transformation of a cellular prion protein (PrP^C) into the misfolded, proteinase K (PK)-resistant and self-replicating conformer PrP^Sc is considered to be the main pathological mechanism of prionoses. We and others have demonstrated that treatment with anti-PrP monoclonal antibodies (Mabs) stops replication of PrP^Sc in prion infected cell lines and significantly delays the clinical onset of disease in prion infected mice. This research was conducted to elucidate the mechanism(s) determining therapeutic efficacy of Mabs, which remains unknown. Methods: The effects of anti-PrP Mab on kinetics of PrP^Sc disappearance were investigated in N2A murine neuroblastoma line infected with 22L prion strain (N2A/22L), and in N2A/22L transfected with siRNA targeting Prnp mRNA. Trafficking of Cy3-6D11 in N2A and N2A/22L was tracked by a time-lapse fluorescent microscopy. Effects of Mabs and 3F4 on PrP solubility were studied in N2A clones over-expressing wild-type (WT) human PrP and Gerstmann-Straussler-Scheinker (GSS) mutant with either valine (V) or methionine (M) at position 129. Results: Mab treatment of N2A/ 22L resulted in total disappearance of PrP^Sc within 48hr, with PrP^Sc t_{1/ 2}=10.7hr. Mab treatment was associated with initial reduction in the level of total PrP and its unglycosylated fraction, which subsequently increased at 48hr, when PrP^Sc was no longer observed. Transfection of N2A and N2A/22L with siRNA resulted in 50% reduction of the total PrP after 17hr and 19.5hr, respectively. PrP^Sc level was diminished by 50% after 10.7hr in siRNA transfected N2A/22L, whereas Mab co-treatment shortened PrP^Sc t_1/2 to 7hr. Massive intracellular penetration of Cy3-6D11 was observed in N2A/22L but not in N2A cells, indicating that directs surface expressed PrP^Sc for intracellular degradation. Treatment of N2A clones over-expressing WT-M129 and WT-V129 human PrP and A117V/ M129, A117V/V129, and F198S/V129 GSS mutants with Mabs 3F4 and increased the detergent soluble PrP fraction from two to five folds (p< 0.05). Conclusions: Anti-PrP Mabs appear to exert their therapeutic effect by promoting degradation of PrP^Sc, but they do not affect PrP production. Anti- PrP Mabs increase the solubility of PrP aggregates, which likely exerts a complementary effect in promoting PrP^Sc degradation

A diagnostics capable of characterizing the runaway and superthermal electrons has been developing on the ISTTOK tokamak. In previous paper, a use of single-channel Cherenkov-type detector with titanium filter for runaway electron studies in ISTTOK was reported. To measure fast electron populations with different energies, a prototype of a four-channel detector with molybdenum filters was designed. Test-stand studies of filters with different thicknesses (1, 3, 7, 10, 20, 50, and 100 μm) have shown that they should allow the detection of electrons with energies higher than 69, 75, 87, 95, 120, 181, and 260 keV, respectively. First results of measurements with the four-channel detector revealed the possibility to measure reliably different fast electrons populations simultaneously.

The paper presents a schematic design and tests of a system applicable for measurements of fast electron pulses emitted from high-temperature plasma generated inside magnetic confinement fusion machines, and particularly in the TORE-SUPRA facility. The diagnostic system based on the registration of the Cherenkov radiation induced by fast electrons within selected solid radiators is considered, and electron low-energy thresholds for different radiators are given. There are some estimates of high thermal loads, which might be deposited by intense electron beams upon parts of the diagnostic equipment within the TORE-SUPRA device. There are some proposed measures to overcome this difficulty by the selection of appropriate absorption filters and Cherenkov radiators, and particularly by the application of a fast-moving reciprocating probe. The paper describes the measuring system, its tests, as well as some results of the preliminary measurements of fast electrons within TORE-SUPRA facility.

The paper presents an improved version of a miniature mass-spectrometer of the Thomson-type, which has been adopted for ion analysis near the dense plasma region inside a vacuum chamber. Problems connected with the separation of ions from plasma streams are considered. Input diaphragms and pumping systems, needed to ensure good vacuum inside the analyzing region, are described. The application of the miniature Thomson-type analyzer is illustrated by ion parabolas recorded in plasma-focus facility and rod plasma injector experiment. A quantitative analysis of the recorded ion parabolas is presented. Factors influencing accuracy of the ion analysis are discussed and methods of the spectrometer calibration are described.

The pathogenesis of prion diseases is related to conformational transformation of cellular prion protein (PrP(C)) into a toxic, infectious, and self-replicating conformer termed PrP(Sc). Following extracerebral inoculation, the replication of PrP(Sc) is confined for months to years to the lymporeticular system (LRS) before the secondary CNS involvement results in occurrence of neurological symptoms. Therefore, replication of PrP(Sc), in the early stage of infection can be targeted by therapeutic approaches, which like passive immunization have limited blood-brain-barrier penetration. In this study, we show that 6D11 anti-PrP monoclonal antibody (Mab) prevents infection on a FDC-P1 myeloid precursor cell line stably infected with 22L mouse adapted scrapie strain. Passive immunization of extracerebrally infected CD-1 mice with Mab 6D11 resulted in effective suppression of PrP(Sc) replication in the LRS. Although, a rebound of PrP(Sc) presence occurred when the Mab 6D11 treatment was stopped, passively immunized mice showed a prolongation of the incubation period by 36.9% (pb0.0001) and a significant decrease in CNS pathology compared to control groups receiving vehicle or murine IgG. Our results indicate that antibody-based therapeutic strategies can be used, even on a short-term basis, to delay or prevent disease in subjects accidentally exposed to prions

While cerebrospinal fluid (CSF) biomarkers are of use in the prediction and diagnosis of Alzheimer's disease our understanding of the background effects of age and the ApoE genotype is limited. Seventy-eight community-based normal volunteers (mean age 60+/-10 years, range 36-86) were examined to determine the relationships between CSF measures of total tau (T-tau), hyperphosphorylated tau (P-tau 231), amyloid beta (Abeta42/Abeta40 ratio), and isoprostane (IP) with age and ApoE genotype. The results showed that age by epsilon4 genotype interactions were found for P-tau231 (beta=1.82; p<0.05) and IP (beta=1.6; p<0.05). T-tau CSF concentration increased with age. The increasing CSF concentrations of P-tau and IP in epsilon4 carriers suggest that early tauopathy and oxidative stress may be related to the increased risk for AD. The data also suggest that T-tau changes are more age dependent than Abeta changes. The evidence that P-tau231 and IP are the earliest markers for the neuronal damage related to AD awaits longitudinal study.

Previous studies showed that memantine inhibits tau hyperphosphorylation in vitro. In this study, phosphorylated tau (P-tau) and total tau (T-tau) were measured before and after 6 month treatment with memantine in 12 subjects ranging from normal cognition with subjective memory complaints, through mild cognitive impairment to mild Alzheimer's disease. Thirteen non-treated individuals served as controls. Treatment was associated with a reduction of P-tau in subjects with normal cognition. No treatment effects were seen among impaired individuals, suggesting that longer treatment time may be necessary to achieve biomarker effect in this group

Central to the pathogenesis of Alzheimer's disease (AD) is the conversion of normal, soluble beta-amyloid (sAbeta) to oligomeric, fibrillar Abeta. This process of conformational conversion can be influenced by interactions with other proteins that can stabilize the disease-associated state; these proteins have been termed 'pathological chaperones'. In a number of AD models, intervention that block soluble Abeta aggregation, including beta-sheet breakers, and compounds that block interactions with pathological chaperones, have been shown to be highly effective. When combined with early pathology detection, these therapeutic strategies hold great promise as effective and relatively toxicity free methods of preventing AD related pathology