Mouse macrophage development in the absence of the common γ chain: defining receptor complexes responsible for IL-4 and IL-13 signaling

The common γ chain (γ_c) forms a critical component of the receptors for interleukins (IL)-2, IL-4, IL-7, IL-9, and IL-15. We analyzed γ_c-deficient mice to define a role for γ_c signaling in the development and function of the macrophage lineage. No major differences in absolute cell numbers, cell surface phenotype, or in vitro function of γ^?_c compared to γ⁺_c macrophages were observed. We therefore conclude that signaling through the γ_c chain is not essential for the differentiation of mouse macrophages. Although B and T cells require γ_c for IL-4 responses, IL-4 up-regulated major histocompatibility class II molecules and inhibited nitric oxide production from γ^?_c macrophages following stimulation with lipopolysaccharide and interferon-γ. γ^?_c macrophages could also respond to IL-13, consistent with the model of a type II IL-4 receptor α/IL-13R which can function in the absence of γ_c. Both IL-4 and IL-13 responses could be completely inhibited with the mouse IL-4 antagonist QY, suggesting that all of the observed IL-13 responses pass through the type II receptor, making it the primary signaling receptor complex for IL-13 in mouse macrophages.     

The effect of sympathetic stimulation on proximal brachial artery mechanics in humans--differential behaviour within the length of the brachial artery?

AIMS: The mechanical properties of arteries play a major role in the regulation of blood pressure and cardiac performance. The effect of sympathetic stimulation on the mechanical properties of the proximal brachial artery was analysed in 18 healthy volunteers, nine young (25 +/- 2 years) and nine elderly (69 +/- 2 years). METHODS: A non-invasive ultrasonic echo-tracking system for measurement of systolic/diastolic variation of the proximal brachial artery diameter in combination with intra-arterial pressure measurements was used to determine wall mechanics. The pressure-diameter (P-D) relationship, distensibility coefficient (DC), compliance coefficient (CC) and stiffness(beta) were obtained at rest and during sympathetic stimulation induced by lower body negative pressure (LBNP). RESULTS: The peripheral vascular resistance increased by 100 and 72%, respectively in the young and elderly during LBNP (P < 0.001). Simultaneously, the mechanical properties of the proximal brachial artery remained unaltered, as estimated from both P-D relationship and stiffness in young (beta-index rest: 5.2 +/- 0.9, LBNP: 5.5 +/- 1.3, NS) as well as elderly (beta-index rest: 13.6 +/- 4.6, LBNP: 16.1 +/- 4.7, NS). CONCLUSIONS: LBNP-induced sympathetic activation does not change proximal brachial artery mechanics, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behaviour is within the length of the brachial artery, where the site of transition from elastic to muscular wall structure needs to be specified in future studies.     

Marked decrease in the levels of two inflammatory markers,hs-C-reactive protein and fibrinogen in patients with severe carotid atherosclerosis after eversion carotid endarterectomy

Objective and design: To study changes in the levels of two acute phase proteins, plasma fibrinogen and serum C-reactive protein (hs-CRP) in patients with severe carotid stenosis after eversion endarterectomy.Material and subjects: A total of 117 consecutive patients who underwent eversion endarterectomy were included in the study. Blood samples for acute phase protein measurement were taken before operation as well as 5.7 weeks and 13.8 months (median) post-surgery. Plasma fibrinogen and serum hs-CRP concentrations were promptly determined.Results: During the follow-up period sharp, highly significant (p < 0.0001) drop occurred in the serum concentrations of both acute phase proteins. The drop in the hs-CRP levels during the follow up period was mainly due to decrease in patients with highest baseline CRP levels.Conclusions: Our present findings indicate that removal of atherosclerotic plaques from the carotid arteries markedly decreases the production of two acute phase proteins due to the decrease of the inflammatory burden or the removal of the advanced plaques able to produce these proteins.Received 20 April 2004; returned for revision 9 June 2004; accepted by A. Falus 25 June 2004     

Hfq-dependent regulation of OmpA synthesis is mediated by an antisense RNA

This paper shows that the small RNA MicA (previously SraD) is an antisense regulator of ompA in Escherichia coli. MicA accumulates upon entry into stationary phase and down-regulates the level of ompA mRNA. Regulation of ompA (outer membrane protein A), previously attributed to Hfq/mRNA binding, is lost upon deletion of the micA gene, whereas overexpression of MicA inhibits the synthesis of OmpA. In vitro, MicA binds to the ompA mRNA leader. Enzymatic and chemical probing was used to map the structures of MicA, the ompA mRNA leader, and the complex formed upon binding. MicA binding generates a footprint across the ompA Shine-Dalgarno sequence, consistent with a 12 + 4 base-pair interaction, which is additionally supported by the effect of mutations in vivo and by bioinformatics analysis of enterobacterial micA/ompA homolog sequences. MicA is conserved in many enterobacteria, as is its ompA target site. In vitro toeprinting confirmed that binding of MicA specifically interferes with ribosome binding. We propose that MicA, when present at high levels, blocks ribosome binding at the ompA translation start site, which-in line with previous work-secondarily facilitates RNase E cleavage and subsequent mRNA decay. MicA requires the presence of the Hfq protein, although the mechanistic basis for this remains unclear.     

Cross-bridge movement and stiffness during the rise of tension in skeletal muscle – a theoretical analysis

Predictions for the time courses of cross-bridge attachment, N(t), stiffness, S(t), and force, T(t), during the tetanus rise were analysed for a special class of cross-bridge models where cross-bridges initially attach in a non-stereospecific weak-binding state, A _w. This state is in rapid equilibrium (equilibrium constant K) with detached states and the force generating transition (rate constant F ₊) is delayed. One model (model IA) which assumed step-function rise of activation at onset of tetanus, gave a poor fit to the experimental data (judged by root mean square error, RMSe 0.038) but the experimentally observed lead of N(t) over T(t) was reproduced qualitatively. An activation mechanism where K increased towards its maximum value according to an exponential function (Model IB) improved the fit considerably (RMSe 0.013). However, the activation time constant ( = 30 ms) derived in the fit was too high to reflect Ca²⁺ binding to troponin. In a further developed model (model II) both Ca²⁺-binding to troponin and cross-bridge attachment were assumed to be required for full activation. This more complex model gave a good fit to the experimental data (RMSe 0.013) with a realistic time constant for Ca²⁺ binding to troponin (9 ms). In both model IB and model II the best fit was obtained with F ₊ 40 s^–1 . An extended version of model IB, with distributed cross-bridge attachment and a series elastic element, gave a fit of similar quality (RMSe 0.009) as obtained with model IB and model II and with a similar value of F₊. The results support the view that weakly bound cross-bridges (state A _w) may account for the lead of cross-bridge movement over force during tension rise. It is also shown that, if the stiffness of the myofilaments is non-linear (stiffness increasing with tension) the experimentally observed lead of S(t) over T(t) may, to a significant degree, be attributed to cross-bridges in the state A _w.     

Multilocus sequence typing of Swedish invasive group B streptococcus isolates indicates a neonatally associated genetic lineage and capsule switching

Streptococcus agalactiae, also designated group B streptococcus (GBS), is an important pathogen in neonates, pregnant women, and nonpregnant adults with predisposing conditions. We used multilocus sequence typing (MLST) to characterize 158 GBS isolates that were associated with neonatal and adult invasive disease and that were collected in northern and western Sweden from 1988 to 1997. Five major genetic lineages (sequence type [ST] 19, ST-17, ST-1, ST-23, and ST-9 complexes) were identified among the isolates, including serotype Ia, Ib, and II to V isolates, indicating a highly clonal population structure among invasive GBS isolates. A number of STs were found to contain isolates of different serotypes, which indicates that capsule switching occurred rather frequently. Two distantly related genetic lineages were identified among isolates of serotype III, namely, clonal complex 19 (CC19), and CC17. CC19 was equally common among isolates from adult and neonatal disease (accounting for 10.3% of GBS isolates from adult disease and 18.7% from neonatal disease), whereas CC17 significantly appeared to be associated with neonatal invasive disease (isolated from 21.9% of neonatal isolates but only 2.6% of adult isolates). The distribution of the mobile elements GBSi1 and IS1548 reveals that they can act as genetic markers for lineages CC17 and CC19, respectively.     

Hyperglycaemia alters the endothelium-dependent relaxation of canine coronary arteries

The aim of the present study was to investigate the effects of experimental diabetes and hyperglycaemia per se on the endothelium-dependent relaxation of isolated canine coronary arteries and to analyse the possible involvement of the cyclooxygenase pathway in the alterations induced by hyperglycaemia. Rings from the left anterior descending coronary arteries of 18 metabolically healthy, six alloxan-diabetic and six insulin-treated alloxan diabetic dogs were set up for isometric tension recording. Diabetic coronaries as well as healthy vessels subjected to in vitro hyperglycaemia (25.5 mmol L-1 glucose) showed impaired (P < 0.05) relaxation to acetylcholine (3 nmol L-1-10 micromol L-1) compared with normoglycaemic, i.e. metabolically healthy and insulin-treated diabetic controls, either before or after indomethacin (3 micromol L-1) administration. The maximal dilation elicited by acetylcholine was further decreased (P < 0.05) by the cyclooxygenase inhibitor in the diabetic coronaries only. Relaxation to sodium nitroprusside did not differ among groups. These results suggest that hyperglycaemia may result in impaired endothelium-dependent dilation of coronary arteries. Diminished relaxation of diabetic coronaries is worsened by the inhibition of the synthesis of vasodilator cyclooxygenase products.     

Characteristics of anaerobic comma-shaped bacteria recovered from the female genital tract

Comma-shaped rods isolated from the vagina of women with signs of vaginitis were studied. Three types of rods were found: a long (length about 4μm), a medium-sized (about 3μm) and a short (about 1μm) variant. All three variants had a characteristic cork-screw motility. The long and the medium-sized variants had up to eight flagella, while the short had up to four. The bacteria only grew under anaerobic conditions, although after a great number of passages on artificial culture media the short variant, but not the other variants, could be grown in a microaerophilic atmosphere. In broth media growth of all three variants was stimulated by the addition of 0.3% formate-fumarate. On solid media colonies developed after incubation for 48 to 72 hours at 37 °C. The long and the medium-sized variants differed from the short variant in that they produced leucine arylamidase, while only the short variant produced α-galactosidase. None of the strains utilized carbohydrates; intravariant differences were found in the test results for gelatin and nitrate reduction. All strains of the short variant tested, but none of the long, hydrolysed sodium hippurate. Gas chromatographic analyses showed that all three variants produce acetic, lactic and succinic acids.