Detection of surface-adsorbed (lipo)proteins by means of a two-step enzyme-immunoassay: a study on the Vroman effect

In view of reports on the involvement of high-molecular-weight (HMW) kininogen and high-density lipoprotein (HDL) in the Vroman effect, we studied the adsorption of fibrinogen, HMW kininogen, HDL and several other proteins from pooled human plasma and congenitally HMW kininogen-deficient plasma onto glass and low-density polyethylene, both as a function of the plasma concentration and the contact time. Mixtures of purified (lipo)proteins were also included in the study. Protein adsorption was determined by means of a two-step enzyme-immunoassay. Our results support the hypothesis that HMW kininogen is involved in the displacement of fibrinogen, which is almost instantly adsorbed from normal plasma onto glass. On hydrophobic polymers like polyethylene, the low amounts of adsorbed fibrinogen and HMW kininogen from plasma and concentrated plasma solutions may be due to a preferential adsorption of HDL

A savings based method for real-life vehicle routing problems

This paper describes a Savings Based algorithm for the Extended Vehicle Routing Problem. This algorithm is compared with a Sequential Insertion algorithm on real-life data. Besides the traditional quality measures such as total distance traveled and total workload, we compare the routing plans of both algorithms according to non-standard quality measures that help to evaluate the "visual attractiveness" of the plan. Computational results show that, in general, the Savings Based algorithm not only performs better with respect to these non-standard quality measures, but also with respect to the traditional measures.distribution;vehicle routing;road transport

Epigenetic regulation: DNA confers identity but is not enough to maintain it

A report on the conference 'Epigenetics and the dynamic genome', 30 June-2 July 2005, Babraham, Cambridge, UK

Dependence of endothelial cell growth on substrate-bound fibronectin

A better understanding of the mechanism of adhesion, spreading and proliferation of human endothelial cells (HEC) on polymeric surfaces may lead to the development of vascular prostheses which allow the formation of an endothelial lining on the luminal surface. In the present investigation the interaction of HEC with polyethylene precoated with monoclonal antibodies directed against HEC membrane antigens and against extracellular matrix compounds was studied. F(ab¿)2 fragments of a monoclonal antibody, directed against an endothelial cell membrane antigen, and F(ab')2 fragments of a monoclonal antibody, directed against cellular fibronectin, were also included in this study. Preadsorption of these antibodies and F(ab')2 fragments, including mixtures of antibodies and mixtures of F(ab')2 fragments, resulted in cell adhesion and spreading as well as moderate cell proliferation (or no proliferation) for several days. However, a good proliferation of HEC was only observed on polyethylene precoated with fibronectin or CLB-HEC-FN-140 (directed against fibronectin). These results strongly suggest that fibronectin, bound to a solid substrate, provides a biochemical signal necessary for the proliferation of HEC. The initial proliferation of HEC on other preadsorbed antibodies or F(ab')2 fragments may be explained by the fact that suspended HEC, used for cell seeding, still possess cell membrane-bound fibronectin

Impact analysis for the purpose of the introduction of DROPLET version 1.3.2

The user-friendly software tool DROPLET (acronym for DRinkwater uit OPpervlaktewater- Landbouwkundig gebruik Evaluatie Tool) assists the Dutch Board for the Authorisation of Plant Protection Products and Biocides (Ctgb) in evaluating whether pesticides may exceed the 0.1 μg/L standard in one of the Dutch surface water abstraction points for drinking water production. Based upon Good Agricultural Practice DROPLET uses the peak concentration in the FOCUS D3 ditch (with spray drift deposition according to Dutch numbers) as starting point for the final, expected concentrations at the abstraction points situated in the larger waterbodies downstream. Results of this impact analysis showed, that for the plant protection products which have been authorized in the period 2014-2018, for which the current version of DROPLET (1.2) was used in the risk assessment, the use of the new DROPLET version (1.3.2.) has no effect on the conclusion for the drinking water criterion. The predicted concentration in surface water at drinking water abstraction points was below the threshold of 0.1 μg/L for all products for all abstraction points for both the old and the new model suite. Therefore, we recommend implementing the new DROPLET version in the national authorization procedure

The role of cellular fibronectin in the interaction of human endothelial cells with polymers

During in-vitro adhesion, spreading and proliferation of human endothelial cells (HEC) on tissue culture polystyrene (TCPS), cellular fibronectin is deposited onto the surface of TCPS in spite of the fact that relatively large amounts of proteins have been adsorbed from the serum-containing culture medium to this surface. Evidence is presented that serum proteins, adsorbed to the TCPS surface, are displaced by cellular fibronectin. In addition, the interaction of HEC with polyethylene, precoated with monoclonal antibodies directed against HEC membrane antigens and against extracellular matrix compounds, was studied. F(ab')2 fragments of two monoclonal antibodies were also included in this study. Preadsorption of these antibodies and F(ab')2 fragments resulted in cell adhesion and spreading as well as moderate cell proliferation (or no proliferation) for several days. A good cell proliferation of HEC was only observed on polyethylene precoated with fibronectin or an antibody directed against fibronectin. The results indicate that the direct or indirect deposition of fibronectin is a prerequisite for the proliferation of HEC. It is suggested that fibronectin, bound to a solid substrate, provides a biochemical signal necessary for the proliferation of HEC

Schatting van in situ fluxen van organische microverontreinigingen uit waterbodems

Dit rapport beschrijft de resultaten van een onderzoek naar naleveringsfluxen van organische microverontreinigingen, ten behoeve van het Deltares koploperproject “Biobeschikbaarheid en gedrag van stoffen”, deelproject A “Nalevering van stoffen uit waterbodems”. Hierin wordt het belang van nalevering voor de kwaliteit van het oppervlaktewater onderzocht. Dit project moet leiden tot inzicht in de situaties waarin nalevering van stoffen uit de waterbodem naar het oppervlaktewater een significante (secundaire) verontreinigingbron vormt. Dit met het oog op normoverschrijding in het oppervlaktewater (chemische doelstelling KRW), of het niet bereiken van een goede ecologische toestand (ecologische doelstelling KRW). In het voorliggende rapport worden de resultaten van kolom flux-experimenten besproken. Aan de orde komen: (a) opzet meetprogramma voor zover afwijkend van het meetplan, (b) informatie met betrekking tot kwaliteitscontrole, (c) specificatie van gebruikte analysevoorschriften (d) analyseresultaten met korte toelichtin

Discrete-time quadrature feedback cooling of a radio-frequency mechanical resonator

We have employed a feedback cooling scheme, which combines high-frequency mixing with digital signal processing. The frequency and damping rate of a 2 MHz micromechanical resonator embedded in a dc SQUID are adjusted with the feedback, and active cooling to a temperature of 14.3 mK is demonstrated. This technique can be applied to GHz resonators and allows for flexible control strategies.Comment: To appear in Appl. Phys. Let

A savings based method for real-life vehicle routing problems

This paper describes a Savings Based algorithm for the Extended Vehicle Routing Problem. This algorithm is compared with a Sequential Insertion algorithm on real-life data. Besides the traditional quality measures such as total distance traveled and total workload, we compare the routing plans of both algorithms according to non-standard quality measures that h