On the multiplicity of the O-star Cyg OB2 #8A and its contribution to the gamma-ray source 3EG J2033+4118

We present the results of an intensive spectroscopic campaign in the optical waveband revealing that Cyg OB2 #8A is an O6 + O5.5 binary system with a period of about 21.9 d. Cyg OB2 #8A is a bright X-ray source, as well as a non-thermal radio emitter. We discuss the binarity of this star in the framework of a campaign devoted to the study of non-thermal emitters, from the radio waveband to gamma-rays. In this context, we attribute the non-thermal radio emission from this star to a population of relativistic electrons, accelerated by the shock of the wind-wind collision. These relativistic electrons could also be responsible for a putative gamma-ray emission through inverse Compton scattering of photospheric UV photons, thus contributing to the yet unidentified EGRET source 3EG J2033+4118.Comment: 8 pages, 4 figures, conference on "The Multiwavelength Approach to Gamma-Ray Sources", to appear in Ap&S

Ratios of anti-factor Xa to antithrombin activities of heparins as determined in recalcified human plasma

Anti-factor Xa and anti-thrombin activities of unfractionated (UF) and low molecular weight (LMW) heparins have been measured in human plasma and with purified human antithrombin III (ATIII) in the absence and presence of 1-5 mM calcium. The anti-factor Xa and antithrombin activities were measured directly, by assessing the heparin-dependent pseudo-first order rate constants of inactivation of human factor Xa or thrombin. These activities were studied with the 4th International Standard for UF heparin, the 1st International Standard for LMW heparin, CY216, enoxaparin, CY222, and the synthetic pentasaccharide. In plasma, calcium equally well increased the specific anti-factor Xa catalytic activities as compared to purified ATIII. That is, 1.5 mM calcium stimulated the UF standard heparin-catalysed inactivation of factor Xa 2.1-2.4 times. In the presence of the LMW heparins the effect of calcium was smaller (1.3-1.7 times), and in plasma there was no effect of calcium on the pentasaccharide-catalysed inactivation of factor Xa. Thus, the largest effects of calcium in the inactivation reaction of factor Xa is seen with UF standard heparin. Calcium reduced the anti-thrombin activities of all the heparin preparations studied about 1.5 times when purified ATIII was used, although in plasma this effect was less clear. Consequently, in the presence of 1.5 mM calcium the ratio of the anti-factor Xa to the anti-thrombin activities of UF standard heparin approximated those of the LMW heparins. The only exception was CY222, which under all conditions retained anti-factor Xa/anti-thrombin ratios significantly higher than those of UF standard heparin

In vitro amplification and detection of variant Creutzfeldt-Jakob disease PrPSc

Variant Creutzfeldt–Jakob disease (vCJD) poses a serious risk of secondary transmission and the need to detect infectivity in asymptomatic individuals is therefore of major importance. Following infection, it is assumed that minute amounts of disease‐associated prion protein (PrPSc) replicate by conversion of the host cellular prion protein (PrPC). Therefore, methods of rapidly reproducing this conversion process in vitro would be valuable tools in the development of such tests. We show that one such technique, protein misfolding cyclic amplification (PMCA), can amplify vCJD PrPSc from human brain tissue, and that the degree of amplification is dependent upon the substrate PRNP codon 129 polymorphism. Both human platelets and transgenic mouse brain are shown to be suitable alternative substrate sources, and amplified PrPSc can be detected using a conformation‐dependent immunoassay (CDI), allowing the detection of putative proteinase K sensitive forms of PrPSc

An Antibody to the aggregated synthetic prion protein peptide (PrP106-126) selectively recognizes disease-associated prion protein (PrPSc) from human brain specimens

Human prion diseases are characterized by the conversion of the normal host cellular prion protein (PrPC) into an abnormal misfolded form [disease‐associated prion protein (PrPSc)]. Antibodies that are capable of distinguishing between PrPC and PrPSc may prove to be useful, not only for the diagnosis of these diseases, but also for a better understanding of the molecular mechanisms involved in disease pathogenesis. In an attempt to produce such antibodies, we immunized mice with an aggregated peptide spanning amino acid residues 106 to 126 of human PrP (PrP106–126). We were able to isolate and single cell clone a hybridoma cell line (P1:1) which secreted an IgM isotype antibody [monoclonal antibody (mAb P1:1)] that recognized the aggregated, but not the monomeric form of the immunogen. When used in immunoprecipitation assays, the antibody did not recognize normal PrPC from non‐prion disease brain specimens, but did selectively immunoprecipitate full‐length PrPSc from cases of variant and sporadic Creutzfeldt–Jakob disease and Gerstmann–Straussler–Scheinker disease. These results suggest that P1:1 recognizes an epitope formed during the structural rearrangement or aggregation of the PrP that is common to the major PrPSc types found in the most common forms of human prion disease

Human platelets as a substrate source for the in vitro amplification of the abnormal prion protein (PrPSc) associated with variant Creutzfeldt-Jakob disease

BACKGROUND: Four recent cases of transfusion‐related transmission of variant Creutzfeldt‐Jakob disease (vCJD) highlight the need to develop a highly sensitive and specific screening test to detect infectivity in the blood of asymptomatic infected individuals. Protein misfolding cyclic amplification (PMCA), a method for the amplification of minute amounts of disease‐associated abnormal prion protein (PrPSc) to readily detectable levels, could be incorporated into such a test provided that a suitable substrate source for routine use in human PMCA reactions can be found. STUDY DESIGN AND METHODS: With the use of seed sources from individuals with variant and sporadic CJD, the use of human platelets (PLTs) as a PMCA substrate source was evaluated. The effects of seed/substrate prion protein gene (PRNP) codon 129 genotype compatibility on amplification efficiency and freeze‐thaw on a substrate's ability to support amplification and the degree of amplification achieved by serial PMCA (sPMCA) were investigated. RESULTS: Seed/substrate PRNP codon 129 compatibility was found to have a major influence on PrPSc amplification efficiency. Individual substrates, of the same PRNP codon 129 genotype, could be pooled and stored frozen for use in subsequent PMCA reactions. A consistent 10‐fold increase in PrPSc detection sensitivity was achieved after each round of sPMCA, resulting in a 10,000‐fold increase in detection sensitivity after four rounds, with no evidence of de novo PrPSc production detected in the unseeded PLT substrate. CONCLUSIONS: Providing issues of seed/substrate PRNP codon 129 compatibility are taken into consideration human PLTs are a suitable, readily available, renewable substrate source for use in human PMCA applications