Surfactin is a lipopeptide produced by certain strains of Bacillus subtilis and has potent surface activity. Here, we present the first results showing that ion-conducting pores can be formed by ...surfactin in artificial lipid membranes. With a low aqueous concentration of surfactin (1 microM) and a restricted membrane area (5.10(-5) cm2) we observed conductance jumps that indicate the formation of individual ionic channels in the presence of K+, Rb+, Cs+, Na+ or Li+ chlorides. Although for every salt concentration (Ci), the distribution in amplitude of the conductance steps (lambda i) may be rather broad, there is always a step amplitude which is more frequent than the others. In addition, the channels corresponding to this most frequent step amplitude are the longest in duration. For Ci = 1 M, the cationic selectivity sequence deduced from these most frequent events is K+ greater than Rb+ greater than Na+ greater than Cs+ = Li+ with respective values for lambda Mi: 130, 110, 80 and 30 pS. In KCl solutions lambda MKCl increases as a function of Ci for low Ci, and shows a plateau for Ci greater than 0.5 M. When measured on larger area membranes (10(-2)cm2) with 1 M solutions of the monovalent salts KCl, NaCl, RbCl and CsCl or the divalent salt CaCl2, the macroscopic low voltage conductance (G0) increases with a slope of 2 on a log-log plot as a function of surfactin concentration. These results demonstrate that surfactin produces selective cationic channels in lipid bilayer membranes and suggest that at higher salt concentration, a dimer is involved in this functional channel-forming process.
The vasoconstrictor and mitogenic peptide endothelin-1 (ET-1) is believed to play a part in fibrosis and collagen production. We examined expression of ET-1 in lung tissue from 52 patients with ...interstitial lung fibrosis, of whom 45 had cryptogenic fibrosing alveolitis (CFA), 10 had CFA and concomitant pulmonary hypertension, and 7 had non-specific focal fibrosis. 17 normal unused donor lungs were studied as controls.
Immunohistochemistry and in-situ hybridisation were done with polyclonal antisera to ET-1 and its precursor big ET-1, and complementary RNA probes for preproET-1. Normal lung tissue and that from patients with focal fibrosis expressed very little ET-1. By contrast, there was striking expression of ET-1 in lung tissue from patients with CFA. Immunostains for ET-1 and big ET-1 and expression of ET-1 mRNA were most prominent in airway epithelium and type II pneumocytes, particularly those lining areas of young granulation tissue. ET-1-like immunoreactivity and mRNA were also present in pulmonary vascular endothelial cells, particularly in specimens from patients with pulmonary hypertension. In all patients, there was a significant correlation between ET-1-like immunoreactivity and histological parameters of disease activity (r=0·78, 95% CI 0·65-0·87, p< 0·001).
These findings suggest a possible role for cell-specific expression of ET-1 in the pathogenesis of CFA and associated pulmonary hypertension.
Angiogenesis is coordinated with follicular cell growth in goitrogenesis. The angiopoietins, Ang-1 and Ang-2, are angiogenic growth factors acting through Tie-2, a tyrosine kinase receptor. We have ...examined the expression and regulation of the angiopoietins and Tie-2 in human and rat thyroids. In human goiters there was increased Tie-2 immunostaining, compared with that in normal thyroids, on both follicular and endothelial cells. In an induced goiter in rats, in situ hybridization showed increased expression of messenger ribonucleic acids (mRNAs) for Tie-2 and Ang-1 in follicular cells. As Tie-2 has previously been believed to be restricted to cells of endothelial lineage in adults, we examined its expression further in isolated follicular cells. Tie-2 and Ang-1 mRNA expression in human thyrocytes was confirmed by ribonuclease protection assay. Ang-2 mRNA was not detected in human cultures or rat thyroids. In both human follicular cell cultures and FRTL-5 cells, immunoblotting showed that Tie-2 expression was increased by TSH and agents that increased intracellular cAMP. In conclusion, we have demonstrated the expression of Tie-2 and Ang-1 in thyroid epithelial and endothelial cells, and have shown the regulation of Tie-2 by TSH and cAMP in follicular cells. Tie-2 expression is increased in goiter in both humans and rats, consistent with a role in goitrogenesis.
The integrin alpha v beta 6 is only expressed in epithelial cells. In healthy adult epithelia, this receptor is barely detectable, but expression is rapidly induced following epithelial injury. Mice ...homozygous for a null mutation in the gene encoding the beta 6 subunit had juvenile baldness associated with infiltration of macrophages into the skin, and accumulated activated lymphocytes around conducting airways in the lungs. beta 6 super(-/-) mice also demonstrated airway hyperresponsiveness to acetylcholine, a hallmark feature of asthma. These results suggest that the epithelial integrin alpha v beta 6 participates in the modulation of epithelial inflammation. Genetic or acquired alterations in this integrin could thus contribute to the development of inflammatory diseases of epithelial organs, such as the lungs and skin.
Anderson-Fabry Disease (AFD) is a storage disease that mimics hypertrophic cardiomyopathy. Late gadolinium enhancement (LGE) by cardiovascular magnetic resonance occurs in approximately 50% of ...patients in the basal inferolateral LV wall, but how an intracellular storage disease causes focal LGE is unknown. We present a whole-heart histological validation that LGE is caused by focal myocardial collagen scarring. This scarring may be the substrate for electrical re-entry and sudden arrhythmic death. The reasons for this distribution of fibrosis are unclear, but may reflect inhomogeneous left ventricular wall stress.
A system is described for calculating volume from a sequence of multiplanar 2D ultrasound images. Ultrasound images are captured using a video digitising card (Hauppauge Win/TV card) installed in a ...personal computer, and regions of interest transformed into 3D space using position and orientation data obtained from an electromagnetic device (Polhemus, Fastrak). The accuracy of the system was assessed by scanning 10 water filled balloons (13–141 mL), 10 kidneys (147–200 mL) and 16 fetal livers (8–37 mL) in water using an Acuson
128XP
10
(5 MHz curvilinear probe). Volume was calculated using the ellipsoid, planimetry, tetrahedral and ray tracing methods and compared with the actual volume measured by weighing (balloons) and water displacement (kidneys and livers). The mean percentage error for the ray tracing method was 0.9 ± 2.4%, 2.7 ± 2.3%, 6.6 ± 5.4% for balloons, kidneys and livers, respectively. So far the system has been used clinically to scan fetal livers and lungs, neonate brain ventricles and adult prostate glands.
A set of nomograms based on the Dubbo Osteoporosis Epidemiology Study predicts the five- and ten-year absolute risk of fracture using age, bone mineral density and history of falls and low-trauma ...fracture. We assessed the discrimination and calibration of these nomograms among participants in the Canadian Multicentre Osteoporosis Study.
We included participants aged 55-95 years for whom bone mineral density measurement data and at least one year of follow-up data were available. Self-reported incident fractures were identified by yearly postal questionnaire or interview (years 3, 5 and 10). We included low-trauma fractures before year 10, except those of the skull, face, hands, ankles and feet. We used a Cox proportional hazards model.
Among 4152 women, there were 583 fractures, with a mean follow-up time of 8.6 years. Among 1606 men, there were 116 fractures, with a mean follow-up time of 8.3 years. Increasing age, lower bone mineral density, prior fracture and prior falls were associated with increased risk of fracture. For low-trauma fractures, the concordance between predicted risk and fracture events (Harrell C) was 0.69 among women and 0.70 among men. For hip fractures, the concordance was 0.80 among women and 0.85 among men. The observed fracture risk was similar to the predicted risk in all quintiles of risk except the highest quintile of women, where it was lower. The net reclassification index (19.2%, 95% confidence interval CI 6.3% to 32.2%), favours the Dubbo nomogram over the current Canadian guidelines for men.
The published nomograms provide good fracture-risk discrimination in a representative sample of the Canadian population.
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