In adult onset myositis, the presence of interstitial lung disease and myositis specific/associated antibodies are governed by HLA class II haplotype, rather than by myositis subtype

The Fcγ receptors play important roles in the initiation and regulation of many immunological and inflammatory processes, and genetic variants (FCGR) have been associated with numerous autoimmune and infectious diseases. The data in rheumatoid arthritis (RA) are conflicting and we previously demonstrated an association between FCGR3A and RA. In view of the close molecular proximity with FCGR2A, FCGR2B and FCGR3B, additional polymorphisms within these genes and FCGR haplotypes were examined to refine the extent of association with RA. Biallelic polymorphisms in FCGR2A, FCGR2B and FCGR3B were examined for association with RA in two well characterized UK Caucasian and North Indian/Pakistani cohorts, in which FCGR3A genotyping had previously been undertaken. Haplotype frequencies and linkage disequilibrium were estimated across the FCGR locus and a model-free analysis was performed to determine association with RA. This was followed by regression analysis, allowing for phase uncertainty, to identify the particular haplotype(s) that influences disease risk. Our results reveal that FCGR2A, FCGR2B and FCGR3B were not associated with RA. The haplotype with the strongest association with RA susceptibility was the FCGR3A–FCGR3B 158V-NA2 haplotype (odds ratio 3.18, 95% confidence interval 1.13–8.92 [P = 0.03] for homozygotes compared with all genotypes). The association was stronger in the presence of nodules (odds ratio 5.03, 95% confidence interval 1.44–17.56; P = 0.01). This haplotype was also more common in North Indian/Pakistani RA patients than in control individuals, but not significantly so. Logistic regression analyses suggested that FCGR3A remained the most significant gene at this locus. The increased association with an FCGR3A–FCGR3B haplotype suggests that other polymorphic variants within FCGR3A or FCGR3B, or in linkage disequilibrium with this haplotype, may additionally contribute to disease pathogenesis.     

The bacterial flagellar switch complex is getting more complex

The mechanism of function of the bacterial flagellar switch, which determines the direction of flagellar rotation and is essential for chemotaxis, has remained an enigma for many years. Here we show that the switch complex associates with the membrane-bound respiratory protein fumarate reductase (FRD). We provide evidence that FRD binds to preparations of isolated switch complexes, forms a 1:1 complex with the switch protein FliG, and that this interaction is required for both flagellar assembly and switching the direction of flagellar rotation. We further show that fumarate, known to be a clockwise/switch factor, affects the direction of flagellar rotation through FRD. These results not only uncover a new component important for switching and flagellar assembly, but they also reveal that FRD, an enzyme known to be primarily expressed and functional under anaerobic conditions in Escherichia coli, nonetheless, has important, unexpected functions under aerobic conditions.     

Treadmill exercise reduces obestatin concentrations in rat fundus and small intestine

Ghrelin and obestatin both are orexigenic/anorexigenic peptides which are secreted from gastrointestinal tracts (fundus submucosa cells). Obestatin is a 23 amino acid peptide recently isolated from rat stomach, is encoded by the same gene that encodes ghrelin. It has been suggested that ghrelin/obestatin stimulate growth hormone release and have opposite actions on food intake. Distribution and biological activity of obestatin and its role in energy balance were studied in rodents. The purpose of the present study was to investigate fundus and intestine obestatin concentrations and selected hormonal responses to a treadmill exercise running program. Fourteen adult Wistar male rats (12-14 weeks old, 235-250 g) were used for this study. Animals were divided into control (n = 7) and training (n = 7) groups. Training group was given exercise on a motor-driven treadmill at 25 m/min (0% grade) for 60 min/day, 5 days/week for 6 weeks. Rats were sacrificed 48 h after the last session of exercise fundus, small intestine, and liver were excised, immediately washed in ice-cold saline, and frozen in liquid nitrogen for determination of obestatin and ATP concentrations and liver glycogen content. Plasma was collected for glucose, growth hormone (GH), insulin, and cortisol measurements. Total obestatin concentrations were significantly (P < 0.045, P < 0.032, respectively) low in trained rat fundus and intestine at rest. Fundus and intestine ATP content remained unchanged. Liver glycogen content was significantly (P < 0.039) higher in trained rats. Changes in plasma total obestatin, glucose, insulin, cortisol levels were not significant. Plasma GH concentrations was significantly (P < 0.001) higher in trained animals when compared with control rats. The data indicate that moderate treadmill exercise was able to reduce fundus and small intestine total obestatin concentrations and this reduction was accompanied with a higher plasma GH and liver glycogen content in trained rats. Exercise training might modulate fundus and intestine total obestatin levels via an improvement of energy source and a negative feedback action of GH on this peptide.     

Subfornical organ differentially modulates baroreflex function in normotensive and two-kidney, one-clip hypertensive rats

During activation of the renin-angiotensin system, hindbrain circumventricular organs such as the area postrema have been implicated in modulating the arterial baroreflex. This study was undertaken to test the hypothesis that the subfornical organ (SFO), a forebrain circumventricular structure, may also modulate the baroreflex. Studies were performed in rats with two-kidney, one-clip (2K,1C) hypertension as a model of endogenously activated renin-angiotensin system. Baroreflex function was ascertained during ramp infusions of phenylephrine and nitroprusside in conscious sham-clipped and 5-wk 2K,1C rats with either a sham or electrolytically lesioned SFO. Lesioning significantly decreased mean arterial pressure in 2K,1C rats from 158 +/- 7 to 131 +/- 4 mmHg but not in sham-clipped rats. SFO-lesioned, sham-clipped rats had a significantly higher upper plateau and range of the renal sympathetic nerve activity-mean arterial pressure relationship compared with sham-clipped rats with SFO ablation. In contrast, lesioning the SFO in 2K,1C rats significantly decreased both the upper plateau and range of the baroreflex control of renal sympathetic nerve activity, but only the range of the baroreflex response of heart rate decreased. Thus, during unloading of the baroreceptors, the SFO differentially modulates the baroreflex responses in sham-clipped vs. 2K,1C rats. Since lesioning the SFO did not influence plasma angiotensin II (ANG II), the effects of the SFO lesion are not caused by changes in circulating levels of ANG II. These findings support a pivotal role for the SFO in the sympathoexcitation observed in renovascular hypertension and in baroreflex regulation of sympathetic activity in both normal and hypertensive states.     

Control of the endonuclease activity of type I restriction-modification systems is required to maintain chromosome integrity following homologous recombination

A type I restriction-modification enzyme will bind to an unmethylated target sequence in DNA and, while still bound to the target, translocate DNA through the protein complex in both directions. DNA breakage occurs when two translocating complexes collide. However, if type I restriction-modification systems bind to unmodified target sequences within the resident bacterial chromosome, as opposed to incoming 'foreign' DNA, their activity is curtailed; a process known as restriction alleviation (RA). We have identified two genes in Escherichia coli, rnhA and recG, mutations in which lead to the alleviation of restriction. Induction of RA in response to these mutations is consistent with the production of unmodified target sequences following DNA synthesis associated with both homologous recombination and R-loop formation. This implies that a normal function of RA is to protect the bacterial chromosome when recombination generates unmodified products. For EcoKI, our experiments demonstrate the contribution of two pathways that serve to protect unmodified DNA in the bacterial chromosome: the primary pathway in which ClpXP degrades the restriction endonuclease and a mechanism dependent on the lar gene within Rac, a resident, defective prophage of E. coli K-12. Previously, the potential of the second pathway has only been demonstrated when expression of lar has been elevated. Our data identify the effect of lar from the repressed prophage.     

The Drosophila epsin 1 is required for ubiquitin-dependent synaptic growth and function but not for synaptic vesicle recycling

The ubiquitin-proteasome system plays an important role in synaptic development and function. However, many components of this system, and how they act to affect synapses, are still not well understood. In this study, we use the Drosophila neuromuscular junction to study the in vivo function of Liquid facets (Lqf), a homolog of mammalian epsin 1. Our data show that Lqf plays a novel role in synapse development and function. Contrary to prior models, Lqf is not required for clathrin-mediated endocytosis of synaptic vesicles. Lqf is required to maintain bouton size and shape and to sustain synapse growth by acting as a specific substrate of the deubiquitinating enzyme Fat facets. However, Lqf is not a substrate of the Highwire (Hiw) E3 ubiquitin ligase; neither is it required for synapse overgrowth in hiw mutants. Interestingly, Lqf converges on the Hiw pathway by negatively regulating transmitter release in the hiw mutant. These observations demonstrate that Lqf plays distinct roles in two ubiquitin pathways to regulate structural and functional plasticity of the synapse.     

Homology Modeling of Hemagglutinin/Protease [HA/P (vibriolysin)] from <Emphasis Type="Italic">Vibrio Cholerae</Emphasis>: Sequence Comparision,Residue Interactions and Molecular Mechanism

Vibrio cholerae produces a zinc-containing and calcium-stabilized soluble hemagglutinin/protease, which has been earlier shown to have the ability to cleave several physiologically important substrates including mucin, fibronectin and lactoferin. This study presents homology modeling of hemagglutinin/protease (vibriolysin) from Vibrio cholerae in the presence of inhibitor HPI [N-(1-carboxy-3-phenylpropyl)-phenylalanyl-alpha-aspargine]. The 3D structure was predicted based on its sequence homology with Pseudomonas aeruginosa elastase (PAE). Comparison of the 3D structures of PAE and HA/P reveals a remarkable similarity having a conserved α + β domain. The inhibitor shows similar binding features as seen in other metalloproteases of M4 peptidase family. The study also highlights the key catalytic residues as well as the residues at the S₁ and binding sub-sites. The similarities between the two proteins provide support for the hypothesis that the two enzymes have similar three-dimensional structures and a common mechanism of action. The fact that both enzymes are secreted as zinc-containing proteases, led us to further hypothesize that they may play similar role in pathogenesis.     

Transforming growth factor-beta1 (TGF-beta1) regulates ATDC5 chondrogenic differentiation and fibronectin isoform expression

Regulated splicing of fibronectin (FN) occurs during the mesenchymal to chondrocyte transition and ultimately results in the relative enrichment of an extra domain B (EDB) exon-containing FN isoform with the suggestion that FN isoforms may play a functional role in chondrogenesis. Promotion of chondrogenesis can also be achieved by treatment with transforming growth factor-beta (TGF-beta), which also regulates FN isoform expression. We have examined the effects of TGF-beta treatment on the assumption of the chondrogenic phenotype in the teratoma-derived cell line ATDC5 and tested whether these effects on chondrogenesis are paralleled by appropriate changes in FN isoform expression. ATDC5 cells were maintained in a pre-chondrogenic state and, in this state, treated with 10 ng/ml TGF-beta. The cells started to elaborate a matrix rich in sulfated proteoglycans, such that within the first 12 days of culture, TGF-beta1 treatment appeared to slightly accelerate early acquisition of an Alcian blue-stained matrix, and caused a dose- and time-dependent decrease in collagen type I expression; changes in collagen type II expression were variable. At later times, cells treated with TGF-beta became indistinguishable from those of the controls. Interestingly, TGF-beta treatment caused a significant dose- and time-dependent decrease in the proportion of FN containing the extra domain A (EDA) and the EDB exons. These data suggest that TGF-beta induces the early stages of chondrogenic maturation in this pre-chondrogenic line and that TGF-beta treatment increases expression of FN isoforms that lack the EDA and EDB exons.     

Social linkages to biological markers of health among the elderly

The social environment and exposure to life challenge affect a person's physical and emotional well-being. The present research uses a population-based study of the elderly in Taiwan to elaborate the cumulative physiological costs--as reflected in biological markers of risk factors known to have adverse consequences for health--of challenge and unfavourable position in social hierarchies and networks. Overall, biological markers of risk among the elderly are similar in Taiwan and the United States. However, male and female Taiwanese elderly are at lower risk for illness associated with indicators of DHEA-S, while women are at higher risk for illness associated with elevated blood pressure, and men at lower risk for illness associated with total/HDL cholesterol, and glycosylated haemoglobin. There are strong and statistically significant effects of position in social hierarchy (education) and challenge (recent widowhood and a perception of high demands) on an index of cumulative risk (allostatic load). Membership in social networks and participation in social activities have expected, but not statistically discernible, effects.