Elevated levels of fibrinogen-derived endogenous citrullinated peptides in synovial fluid of rheumatoid arthritis patients

Introduction

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation of the joints and the presence of autoantibodies directed against proteins containing the non-standard arginine-derived amino acid citrulline. The protein fibrinogen, which has an essential role in blood clotting, is one of the most prominent citrullinated autoantigens in RA, particularly because it can be found in the inflamed tissue of affected joints. Here, we set out to analyze the presence of citrullinated endogenous peptides in the synovial fluid of RA and arthritic control patients.

Methods

Endogenous peptides were isolated from the synovial fluid of RA patients and controls by filtration and solid phase extraction. The peptides were identified and quantified using high-resolution liquid chromatography-mass spectrometry.

Results

Our data reveal that the synovial fluid of RA patients contains soluble endogenous peptides, derived from fibrinogen, containing significant amounts of citrulline residues and, in some cases, also phosphorylated serine. Several citrullinated peptides are found to be more abundantly present in the synovial fluid of RA patients compared to patients suffering from other inflammatory diseases affecting the joints.

Conclusions

The increased presence of citrullinated peptides in RA patients points toward a possible specific role of these peptides in the immune response at the basis of the recognition of citrullinated peptides and proteins by RA patient autoantibodies.     

Parasite Pressures on Feral Honey Bees (Apis mellifera sp.)

Feral honey bee populations have been reported to be in decline due to the spread of Varroa destructor, an ectoparasitic mite that when left uncontrolled leads to virus build-up and colony death. While pests and diseases are known causes of large-scale managed honey bee colony losses, no studies to date have considered the wider pathogen burden in feral colonies, primarily due to the difficulty in locating and sampling colonies, which often nest in inaccessible locations such as church spires and tree tops. In addition, little is known about the provenance of feral colonies and whether they represent a reservoir of Varroa tolerant material that could be used in apiculture. Samples of forager bees were collected from paired feral and managed honey bee colonies and screened for the presence of ten honey bee pathogens and pests using qPCR. Prevalence and quantity was similar between the two groups for the majority of pathogens, however feral honey bees contained a significantly higher level of deformed wing virus than managed honey bee colonies. An assessment of the honey bee race was completed for each colony using three measures of wing venation. There were no apparent differences in wing morphometry between feral and managed colonies, suggesting feral colonies could simply be escapees from the managed population. Interestingly, managed honey bee colonies not treated for Varroa showed similar, potentially lethal levels of deformed wing virus to that of feral colonies. The potential for such findings to explain the large fall in the feral population and the wider context of the importance of feral colonies as potential pathogen reservoirs is discussed.     

A transcriptional network associated with natural variation in Drosophila aggressive behavior

Background  

Aggressive behavior is an important component of fitness in most animals. Aggressive behavior is genetically complex, with natural variation attributable to multiple segregating loci with allelic effects that are sensitive to the physical and social environment. However, we know little about the genes and genetic networks affecting natural variation in aggressive behavior. Populations of Drosophila melanogaster harbor quantitative genetic variation in aggressive behavior, providing an excellent model system for dissecting the genetic basis of naturally occurring variation in aggression.     

Aging in the post-genomic era: simple or complex?

A report on the Third Genetic Effects on Aging Meeting, The Jackson Laboratory, Bar Harbor, Maine, August 4-8, 2000.     

Characterization of Iron Uptake from Ferrioxamine B by Chlorella vulgaris

Iron uptake from two Fe³⁺-hydroxamate siderophores, ferrioxamine B and Fe³⁺-rhodotorulate, by iron-stressed Chlorella vulgaris (ATCC strain 11468) was evaluated with some comparison to iron uptake from synthetic and organic acid ferric chelates. Iron-stress induced iron uptake from ferrioxamine B. Dissipation of the electrochemical gradient, via uncouplers, inhibited iron uptake. Respiratory inhibitors gave variable results, an indication that a direct link to respiration was not apparent. Vanadate inhibition of iron uptake indicated that an ATPase or phosphate intermediate could be involved in the uptake mechanism. Divalent cations manifested variable effects dependent on the cation and chelator used. These data confirm that C. vulgaris has an inducible iron-uptake system for Fe³⁺-hydroxamic acid siderophores which may involve a different mechanism than that observed for other chelates.     

Sustained performance and some effects on the design and operation of complex systems

Man, increasingly the limiting element in the military man-machine system, must often operate for several days in a high-risk environment with little or no sleep. It is necessary, therefore, to have some knowledge of the likely effects of sleep deprivation to predict his behaviour and minimize the adverse effects of sleep loss. The early work of the Army Personnel Research Establishment (APRE) concentrated on studying the infantryman in field trials, characterized by more realism and of greater length than previously attempted. Although measures of cognitive functioning were included in these trials, continuous cognitive performance was not assessed, nor was performance on complex tasks. An opportunity to remedy this situation arose because of a newer study concerned with controlling a removely-piloted air vehicle from a ground control station (GCS). A 65-hour experiment was designed during which subjects performed continuously either on the GCS simulator or on a battery of cognitive tests, mood scales, and physiological assessments. Results showed that whereas performance showed the usual deterioration in the test battery, it held up remarkably well on the simulator. Several reasons for this difference are suggested.     

Chloroplast thylakoid proteins associated with sequestered proton-buffering domains. Plastocyanin contributes buffering groups to localized proton domains

Thylakoid membrane proteins are organized so as to shield 30–50 nmol H⁺ (mg Chl)^–1 from freely equilibrating with either the external or the lumen aqueous phases. Amine groups provide binding sites for this metastable buffering array and can be quantitatively measured by acetylation using [³H]acetic anhydride. The principle of the assay is that a metastable acidic domain will have relatively less of the reactive neutral form of the amine compared to the amount present after addition of an uncoupler. The extent of the acetylation reaction is strongly influenced by whether the lumen pH comes to complete equilibrium with the external pH prior to adding the acetic anhydride. Determination of the lumen pH by [¹⁴C]methylamine distribution after the standard 3 or 5 min equilibration in pH 8.6 buffer indicated that the lumen may have been 0.2 to 0.3 pH more acidic than the external phase. This effect was taken into account by determining the pH dependence, in the pH 8.2–8.6 range, of acetylation of the membrane proteins studied, and the labeling data were conservatively corrected for this possible contribution. Experiments were carried out to identify the thylakoid proteins that contribute such metastable domain amine groups, using the above conservative correction. Surprisingly, plastocyanin contributes buried amine groups, but cytochromef did not give evidence for such a contribution, if the conservative correction in the labeling was applied. If the correction was too conservative, cytochromef may contribute amines to the sequestered domains. The new methodology verified earlier results suggesting that three Tris-releasable photosystem II-associated proteins also contribute significantly to the sequestered amine-buffering array.