Towards cellular receptors for prions

Transmissible spongiform encephalopathies (TSE) are attributed to the conversion of the cellular prion protein (PrP(c)) into an abnormal isoform (PrP(sc)). This can be caused by the invasion of living organisms by infectious particles, or be inherited due to mutations on the PrP(c) gene. One of the most intriguing problems of prion biology is the inability to generate the infectious agent in vitro. This argues strongly that other cellular proteins besides those added in test tubes or found in cellular preparations are necessary for infection. Despite recent progress in the understanding of prion pathology, the subcellular compartments in which the interaction and conversion of PrP(c) into PrP(sc) take place are still controversial. PrP(c) interacts with various macromolecules at the cell membrane, in endocytic compartments and in the secretory pathway, all of which may play specific roles in the internalisation of PrP(sc) and conversion of PrP(c). A specific interacting protein required for the propagation of prions was originally proposed as a prion receptor, and later referred to as a ligand, a cofactor, protein X, or a partner. However, current studies indicate that PrP(c) associates with multi-molecular complexes, which mediate a variety of functions in distinct cellular compartments. It is proposed that a deeper understanding of the mechanics of such interactions, coupled to a better knowledge of the corresponding signalling pathways and ensuing cellular responses, will have a major impact on the prevention and treatment of TSE.     

Local and systemic antibody class responses to an infectious laryngotracheitis virus vaccine strain

Chickens infected with infectious laryngotracheitis virus (ILTV) responded by producing virus-specific IgG in their sera, which increased steadily in concentration, but with slight fluctuations, until peak titres were reached 40 days post-inoculation (pi), immediately prior to the second challenge. Thereafter, following an initial lag, concentrations continued to increase for 21 days before falling slightly at the end of the experiment. In contrast, peak concentrations of ILTV-specific IgM were reached 6 days pi falling to their lowest levels by day 16, before increasing to a second peak and trough on days 26 and 32, respectively. This cyclical production of ILTV-specific IgM was confirmed in a second experiment. The pattern of production of ILTV-specific IgG, IgM and IgA, detected in tracheal washings, occurred in the same cyclical manner. IgM was produced first, peak concentrations being detected 5 days pi, whereas IgG and IgA did not peak until 10 days pi, with second peaks of each class being detected 25-30 days pi. The possibility that the cyclical antibody class response to ILTV infection is related to the previously reported intermittent pattern of re-excretion of the virus is discussed.     

DADOS-Survey: an open-source application for CHERRIES-compliant Web surveys

Background  

The Internet has been increasingly utilized in biomedical research. From online searching for literature to data sharing, the Internet has emerged as a primary means of research for many physicians and scientists. As a result, Web-based surveys have been employed as an alternative to traditional, paper-based surveys. We describe DADOS-Survey, an open-source Web-survey application developed at our institution that, to the best of our knowledge, is the first to be compliant with the Checklist for Reporting Results of Internet E-Surveys (CHERRIES). DADOS-Survey was designed with usability as a priority, allowing investigators to design and execute their own studies with minimal technical difficulties in doing so.     

Hepatitis B virus transmission in Brazilian hemodialysis units: serological and molecular follow-up

A serological and molecular study of hepatitis B virus (HBV) infection was carried out in dialysis units in Central Brazil. Between 1995 and 1999, serum samples from all HBsAg-positive hemodialysis patients (n = 43) were tested for HBeAg/anti-HBe and subtyping by monoclonal ELISA. HBV DNA was detected by PCR and positive samples were genotyped by restriction fragment polymorphism pattern (RFLP) methodology. TheHBsAg prevalence declined in this population during the survey period (12-5.8%). HBeAg and anti-HBe were detected in 23 (53.5%) and 18 (41.9%) sera, respectively. Thirty-six samples could be HBsAg subtyped: 21 were subtype ayw(3), 14 belonged to adw(2) and one was identified as adw(4). HBV DNA was present in 30 serum samples. Of these, 20 (66.7%) were genotype D, 9 (30%) genotype A, and 1 (3.3%) genotype F. In addition, the RFLP pattern could be determined in samples from 18/20 genotype D patients: D3 (10 strains), D7 (7 strains) and D4 (1 strain); from 8/9 genotype A patients: A1 (6 strains) and A3 (2 strains); and from the patient infected with genotype F: F1. Patterns D3 and D7 were associated closely with HBV infection in the two largest hemodialysis units studied. These findings confirm the value of the RFLP method as an effective molecular epidemiological tool for elucidating HBV transmission in hemodialysis units.     

Platelet involvement in rat paw edema induced by 2-methoxy-PAF

PAF-acether (PAF) or 2-methoxy-PAF (2-MX) caused a dose-dependent paw edema showing a 1: 25 ratio between their inflammatory activities. 2-MX caused a thrombocytopenia, whereas PAF did not alter the number of these cells. Both phospholipids induced reductions in total leukocyte count. Rat antiplatelet serum produced platelet depletion by PAF-induced paw edema was unaffected. The edema of 2-MX was significantly reduced by antiplatelet serum, under conditions where normal serum was inactive against the edema induced by PAF or 2-MX. Histopathological analysis of PAF and 2-MX-induced edema showed, in the first case, a small infiltrate of neutrophils, some lymphocytes, and several mastocytes around the vessels and, in the second, a neutrophilic infiltrate. These results suggest that PAF and 2-MX may produce edema through different mechanisms and that 2-MX causes edema in part through platelet activation.     

Human and mouse sera recognize the same polypeptide associated with immunological resistance to Trypanosoma cruzi infection.

Effective immunological resistance to challenge with trypomastigotes of Trypanosoma cruzi has been linked to antibodies which are specific for determinants on live, but not fixed, trypomastigotes. In man and mouse, these antibodies can be detected specifically by viable immunofluorescence (VIF) and complement mediated lysis (CML) assays. VIF/CML positive sera from chagasic patients or experimentally infected mice recognize the same trypomastigote specific surface polypeptides of apparent Mr 70-160 kDa. VIF/CML negative chagasic sera fail to react with polypeptides of Mr 120, 145 and 160 kDa, whereas negative mouse sera lack antibodies to the 160 kDa component alone. Taken together, these clinical and experimental data suggest that the 160 kDa polypeptide should be tested for its potential in immunoprophylaxis.     

Albumin adsorption on alkanethiols self-assembled monolayers on gold electrodes studied by chronopotentiometry

Chronopotentiometry was used to study the adsorption of human serum albumin (HSA) to self-assembled monolayers with the following terminal functional groups: CH(3), COOH and OH. Surfaces were characterized by X-ray photoelectron spectroscopy, water contact angle measurements and cyclic voltammetry. HSA coverage of the different SAMs was investigated by chronopotentiometry and the total amount of adsorbed protein was determined using radiolabelled albumin. Both techniques have demonstrated that HSA adsorption to the different SAM-modified electrodes increases in the following order: OH相似文献   

Polysilanes fonctionnels, 3. Synthèse d'α,ω-bis(triméthylsilyl)oligo(méthylphénylsilane)s précurseurs des α,ω-bis(triméthylsilyl)oligo(chlorométhyl-silane)s. Charactérisation des heptaméthyl phényl-2 trisilane et octaméthyl diphényl-2,3 tétrasilane

Low-molecular-weight organosilane polymers were prepared by sodium coupling of dichloro-methylphenylsilane ( 1 ) with chlorotrimethylsilane ( 2 ). Gel permeation chromatography (GPC), IR and NMR (¹H, ¹³C and ²⁹Si) analysis of the crude product ( 3 ) were performed and compared with those of the isolated first oligomers, trisilane ( 3a ) and tetrasilane ( 3b ). The GPC characteristics, especially high resolution ones, in accordance with the α,ω-bis(trimethylsilyl)-oligo(methylphenylsilane) structure are compared with those of hydrocarbon polymers. The relations of the NMR characteristics of the methylphenylsilanediyl unit with the position along the chain and the configuration of the diads are approached. Some spectroscopic indications of the secondary structure are discussed.