Factor XI activation by meizothrombin: stimulation by phospholipid vesicles containing both phosphatidylserine and phosphatidylethanolamine

The activation of factor XI by meizothrombin was investigated using recombinant meizothrombin (R155A meizothrombin) that is resistant to autocatalytic removal of fragment 1. Meizothrombin was capable of activating factor XI at an activation rate similar to that of thrombin. Dextran sulphate and heparin, known cofactors of thrombin-mediated factor XI activation, did not stimulate the activation of factor XI by meizothrombin. However, the activation of factor XI by meizothrombin was markedly enhanced by vesicles containing phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylethanolamine (PE), whereas PC/PS or PC/PE vesicles only had a minor effect on the activation. Thrombin-mediated factor XI activation was not influenced by phospholipids. The effect of PC/PS/PE and PC/PS vesicles was studied in a factor XI dependent clot lysis assay. In this assay, factor XI inhibits clot lysis by a feedback loop in the intrinsic pathway via thrombin-mediated factor XI activation. Removal of endogenous phospholipids in plasma by centrifugation resulted in an increased clot lysis, which could be restored to the pre-centrifugation level by the addition of PC/PS/PE vesicles, but not by PC/PS vesicles. When clot lysis was initiated by factor IXa in the presence of a factor XIa blocking antibody, there was no difference in inhibitory effect of PC/PS/PE or PC/PS vesicles. These data suggested that the differences in clot lysis inhibition observed between PC/PS/PE and PC/PS vesicles were caused by factor XI activation by meizothrombin. Meizothrombin-mediated factor XI activation may therefore play an important role in the antifibrinolytic feedback loop in the intrinsic pathway.     

New trends in rock slope stability analyses

 The paper discusses alternative approaches to stability analyses including the traditional deterministic principle, the so-called partial factor principle and the probabilistic approach which assesses the probability of failure rather than the factor of safety. To illustrate the different principles and approaches, stability analyses of road cuts near Trondheim, central Norway, are used as examples. It is concluded that although the traditional deterministic approach has the advantage of being well established and easy to understand, to conform with new standards and guidelines it is likely to be replaced by the partial factor principle. To obtain the best possible basis for evaluation it is useful to include a probabilistic analysis. Received: 5 August 1999 · 28 August 1999     

Indentation studies on two-phase bicrystals of alpha-beta brass with various phase boundary geometries

Indentation studies were carried out on a two-phase model system of alpha-beta brass so as to understand the role of phase boundary on the propagation of deformation. Unlike in the case of uniaxial loading, the phase boundary acts as a very effective barrier for slip propagation, irrespective of its geometry.     

Front-face fluorescence measurement of photosensitizers and lipid oxidation products during the photooxidation of butter

This paper shows that fluorescence spectroscopy can measure both degradation of photosensitizers and formation of lipid oxidation products in light-exposed butter. The photosensitizers were already notably degraded after 4 h of light exposure, whereas fluorescent lipid oxidation products were detected after 5 d. The fluorescence measurements were highly correlated with sensory assessments of acidic and rancid flavor. Photosensitizer degradation is therefore a promising indirect indicator of the onset of lipid oxidation in butter. Sensory analysis and measurement of peroxide value showed that the level of lipid oxidation was significantly higher for butter stored in air compared with butter stored in nitrogen (N₂). This might be explained by the formation of singlet oxygen from direct photooxidation and type II photosensitized oxidation. Addition of the singlet oxygen quencher β-carotene reduced the rancid flavor intensity in the air and N₂ packages from 9.0 to 4.9 and from 6.5 to 4.7, respectively. Results indicate that lipid oxidation in the butter stored in N₂ was mainly caused by type I photosensitized reactions, because addition of β-carotene had little effect on the rancid flavor intensity.     

Cases of instability caused by weakness zones in Norwegian tunnels

Cave-in and rock fall are rare occurrences in Norwegian tunnelling today. Despite all precautions that are taken to prevent such incidents from happening, a few serious cases have occurred during the last few years. In this paper, one recent case of cave-in during tunnelling (the Atlanterhav tunnel) and two cases of rock fall/cave-in after completion of the project (the Oslofjord and Hanekleiv tunnels) are discussed. The main focus is on discussion and comparison of the rock engineering aspects of these incidents, and on the lessons that may be learnt from them. It is concluded that the presence of swelling clay (smectite) has been a main cause of instability, although low internal friction may be a destabilizing factor at least as important as swelling, and that the most difficult situation is a combination of very poor quality material and high water pressure in faults/weakness zones.     

Cytokine profiles differ in newly recruited and resident subsets of mucosal macrophages from inflammatory bowel disease

BACKGROUND & AIMS: Most macrophages in the normal intestinal mucosa have a mature phenotype. In inflammatory bowel disease (IBD), a monocyte-like subset (CD14+ L1+) accumulates. The aim of this study was to characterize its potential with regard to cytokines. METHODS: Lamina propria mononuclear cells were adherence-separated, with or without depletion of CD14+ cells, and production of cytokines was investigated by bioassay, enzyme-linked immunosorbent assay, or immunocytochemistry. RESULTS: Tumor necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), and IL-1 receptor antagonist were found mainly in cells positive for myelomonocytic L1. In undepleted IBD cultures, TNF-alpha, IL-1alpha and beta, and IL-10 were markedly up-regulated by pokeweed mitogen stimulation; IL-1alpha and beta and IL-10 were also up-regulated by stimulation of interferon gamma and lipopolysaccharide in combination. The latter stimulation had no effect on normal control or CD14-depleted IBD cultures. Indomethacin caused a marked increase of TNF-alpha, particularly in undepleted IBD cultures, whereas IL-10 and IL-4 decreased TNF-alpha and IL-1beta in both CD14+ and CD14 macrophages. CONCLUSIONS: In IBD mucosa, macrophages with a monocyte-like phenotype are primed for production of TNF-alpha and IL-1alpha/beta and may therefore be of significant pathogenic importance [corrected]. However, this CD14+ subset, as well as the mucosal resident macrophages, have preserved responsiveness to several down-regulatory factors such as the macrophage deactivators IL-10 and IL-4.     

Identification of a specific binding site for the anabolic steroid stanozolol in male rat liver microsomes

Male rat liver microsomes contain a [3H]dexamethasone binding site, capable of binding glucocorticoids and progesterone. We have shown previously that the 17 alpha-alkylated androgen, stanozolol, can inhibit the [3H]dexamethasone binding to microsomes through a negative allosteric mechanism, which gives rise to the possibility of its interaction with a different binding site. In this study, the existence of a single-saturating binding site, capable of binding the radioactive steroid with a maximum number of the specific binding site of 49 +/- 2 pmol/mg of protein and a Kd of 37 +/- 1.3 nM was demonstrated by using [3H]stanozolol. In competition experiments, only stanozolol and danazol were able to compete with [3H]stanozolol for its binding to microsomes, among more than 60 steroids and other compounds tested. The binding of [3H]stanozolol was depressed after protease treatment of the microsomes, or after the administration of cycloheximide to adult male rats for 24 hr, which suggest its proteic nature. The [3H]stanozolol binding site was detected in many tissues of the rat, with the highest concentrations being found in the liver. It was detected from birth, increasing afterward in concentration and reaching a peak at 2 to 3 months of age. This is the first experimental verification of the existence in liver microsomes of a specific binding site for some 17 alpha-alkylate androgens, such as stanozolol and danazol, different from the androgen receptor or the [3H]dexamethasone binding site.