Lipopolysaccharide Renders Transgenic Mice Expressing Human Serum Amyloid P Component Sensitive to Shiga Toxin 2

Transgenic C57BL/6 mice expressing human serum amyloid P component (HuSAP) are resistant to Shiga toxin 2 (Stx2) at dosages that are lethal in HuSAP-negative wild-type mice. However, it is well established that Stx2 initiates extra-intestinal complications such as the haemolytic-uremic syndrome despite the presence of HuSAP in human sera. We now demonstrate that co-administering purified Escherichia coli O55 lipopolysaccharide (LPS), at a dosage of 300 ng/g body weight, to HuSAP-transgenic mice increases their susceptibility to the lethal effects of Stx2. The enhanced susceptibility to Stx2 correlated with an increased expression of genes encoding the pro-inflammatory cytokine TNFα and chemokines of the CXC and CC families in the kidneys of LPS-treated mice, 48 hours after the Stx2/LPS challenge. Co-administering the glucocorticoid dexamethasone, but not the LPS neutralizing cationic peptide LL-37, protected LPS-sensitized HuSAP-transgenic mice from lethal doses of Stx2. Dexamethasone protection was specifically associated with decreased expression of the same inflammatory mediators (CXC and CC-type chemokines and TNFα) linked to enhanced susceptibility caused by LPS. The studies reveal further details about the complex cascade of host-related events that are initiated by Stx2 as well as establish a new animal model system in which to investigate strategies for diminishing serious Stx2-mediated complications in humans infected with enterohemorrhagic E. coli strains

Shiga Toxin and Lipopolysaccharide Induce Platelet-Leukocyte Aggregates and Tissue Factor Release, a Thrombotic Mechanism in Hemolytic Uremic Syndrome

BACKGROUND: Aggregates formed between leukocytes and platelets in the circulation lead to release of tissue factor (TF)-bearing microparticles contributing to a prothrombotic state. As enterohemorrhagic Escherichia coli (EHEC) may cause hemolytic uremic syndrome (HUS), in which microthrombi cause tissue damage, this study investigated whether the interaction between blood cells and EHEC virulence factors Shiga toxin (Stx) and lipopolysaccharide (LPS) led to release of TF. METHODOLOGY/PRINCIPAL FINDINGS: The interaction between Stx or LPS and blood cells induced platelet-leukocyte aggregate formation and tissue factor (TF) release, as detected by flow cytometry in whole blood. O157LPS was more potent than other LPS serotypes. Aggregates formed mainly between monocytes and platelets and less so between neutrophils and platelets. Stimulated blood cells in complex expressed activation markers, and microparticles were released. Microparticles originated mainly from platelets and monocytes and expressed TF. TF-expressing microparticles, and functional TF in plasma, increased when blood cells were simultaneously exposed to the EHEC virulence factors and high shear stress. Stx and LPS in combination had a more pronounced effect on platelet-monocyte aggregate formation, and TF expression on these aggregates, than each virulence factor alone. Whole blood and plasma from HUS patients (n = 4) were analyzed. All patients had an increase in leukocyte-platelet aggregates, mainly between monocytes and platelets, on which TF was expressed during the acute phase of disease. Patients also exhibited an increase in microparticles, mainly originating from platelets and monocytes, bearing surface-bound TF, and functional TF was detected in their plasma. Blood cell aggregates, microparticles, and TF decreased upon recovery. CONCLUSIONS/SIGNIFICANCE: By triggering TF release in the circulation, Stx and LPS can induce a prothrombotic state contributing to the pathogenesis of HUS

Direct observation of crystallization of amorphous Mg-bearing silicate grains into Mg

The crystallization of amorphous Mg-bearing silicate grains into Mg2SiO4 and its temperature dependence were clarified by observing the grains in situ while heating in a transmission electron microscope. The crystallization started from the grain surface at 800 °C. Before the crystallization at the grain surface, the formation of a rim-like layer due to prenucleation was observed. The characteristic structure change of the grains was recorded and indicated that prenucleation occurred before crystallization. This phenomenon probably corresponds to the “stall” idea suggested by Hallenbeck & Nuth (1998, Ap&SS, 255, 427) in the crystallization of silicate.

Crystalline Mg

A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains

Raised monocyte chemotactic protein‐1 (MCP‐1)/CCL2 in cerebrospinal fluid of patients with neuropsychiatric lupus

BACKGROUND: An imbalance in cytokine homoeostasis is thought to have a key role in the neuropsychiatric syndromes of systemic lupus erythematosus (NPSLE), and recently, a role for chemokines has been noted. OBJECTIVE: To compare concentrations of monocyte chemotactic protein‐1 (MCP‐1)/CCL2 in cerebral spinal fluid (CSF) of patients with SLE, and with and without neuropsychiatric symptoms. METHODS: CSF was obtained from 185 patients with SLE: 96 with NPSLE and 89 patients with SLE without neuropsychiatric symptoms (non‐NPSLE patients). MCP‐1/CCL2 concentrations were measured with an ELISA. RESULTS: The average concentration of CSF MCP‐1/CCL2 in patients with NPSLE was 1959 pg/ml, and in non‐NPSLE patients 712 pg/ml. The average MCP‐1/CCL2 concentration was significantly higher in the NPSLE group than in the non‐NPSLE group (p<0.001). In one representative patient with NPSLE, MCP‐1/CCL2 levels in the CSF decreased in parallel with a decline in neuropsychiatric symptoms. CONCLUSIONS: CSF MCP‐1/CCL2 levels are higher in patients with NPSLE than in non‐NPSLE patients. MCP‐1/CCL2 may have an important role in the expression of NPSLE. These results indicate that CSF MCP‐1/CCL2 reflects an inflammatory activity in the brain, suggesting that it might be used as a diagnostic tool and a monitor for therapeutic responses in patients with NPSLE

Direct observation of the metamorphism of silicon oxide grains

Experimental studies on the metamorphism of SiOx grains under heating at 10-6 Pa have been conducted using a high-resolution transmission electron microscope. Si crystallites were predominantly grown at 500 to 700 °C in SiOx grains. The Si crystallites disappeared at 800 °C and evaporated as the SiO phase

Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles

Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain­grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg2Si polyhedral grains were obtained in a Mg grain-rich atmosphere. Mg2SiO4 polyhedral grains were obtained in a SiO grain-rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202