Two Dimensional, Spatial Arrangement of Fibronectin Adsorbed to Biomaterials with Different Wettabilities

The effects of concentration, pH and substratum wettability on the two dimensional, spatial arrangement of adsorbed fibronectin are determined. Substrata with different wettability were exposed to a well defined flow of a fibronectin solution (0.1 or 1 mg/ml) in potassium phosphate buffer (pH 7.0 or 4.8) during 120 minutes at a shear rate of 20 s1. Rotary shadowed replicas of the surfaces were examined by transmission electron microscopy. Well defined structures, island-like in character on the low wettability substrata and knotted, reticulated on the high wettability substrata, could be seen in case of adsorption from pH 7.0 and the high concentration solution. Structures became more blurred upon lowering the solution pH and fibronectin concentration. Compared with bovine serum albumin, fibronectin shows smaller island-like structures, but the reticulated structure is thicker than for albumin

Factors determining a successful socioeconomic introduction of horticulture in foreign countries - Academic Consultancy Training Report

Course: Academic Consultancy Training (YMC 60809) Project: Sustainable development of greenhouse horticulture in developing countries (756) Commissioner: Wageningen UR Greenhouse Horticulture Contact person: Ir. C.J.M. van der Lans Coach: Dr. Ir. J.W. Hofstee Expert: Prof. Dr. O. van Kooten A lot of capital is attracted in the initiation of Dutch horticulture businesses abroad. There is however a lack of knowledge about what is known about the critical factors determining success or failure of a horticultural initiative in a foreign country. The goal of this project is to achieve socio-economic sustainability of the greenhouse horticulture in foreign countries. Therefore a model is presented which contains all the necessary factors that an entrepreneur should keep in mind to achieve socio-economic sustainability. In order to get an overview of all the important factors literature was studied and interviews were conducted. This led to a detailed description of all the issues that should be considered when setting-up businesses abroad. Those factors are represented in a ‘dial’ model pointing out what issues an entrepreneur should consider. The model is subdivided in three topics: market, production and trade & logistics. Important factors related to the market are whether there is a market and how to influence the whole production chain. Important factors for the production are the physical place and the employees. A very important factor of the trading is the legalization and the bureaucracy of the country you are producing in

On the relative importance of specific and non-specific approaches to oral microbial adhesion

In this paper, it is suggested that specificity and non-specificity in (oral) microbial adhesion are different expressions for the same phenomena. It is argued that the same basic, physico-chemical forces are responsible for so-called 'non-specific' and 'specific' binding and that from a physico-chemical point of view the distinction between the two is an artificial one. Non-specific interactions arise from Van der Waals and electrostatic forces and hydrogen bonding, and originate from the entire cell. A specific bond consists of a combination of the same type of Van der Waals and electrostatic forces and hydrogen bonding, now originating from highly localized chemical groups, which together form a stereo-chemical combination. The absence or presence of specific receptor sites on microbial cell surfaces must therefore be reflected in the overall, non-specific surface properties of cells as well. This point is illustrated by showing that glucanbinding lectins on mutans streptococcal strains may determine the pH dependence of the zeta potentials of these cells. When studying microbial adhesion, a non-specific approach may be better suited to explain adhesion to inert substrata, whereas a specific approach may be preferred in case of adhesion to adsorbed protein films. Adhesion is, however, not as important in plaque formation in the human oral cavity as is retention, because low shear force periods. during which adhesion presumably occurs, are followed by high shear force periods, during which adhering cells must withstand these detachment forces. Evidence is provided that such detachment will be through cohesive failure in the pellicle mass, the properties of which are conditioned by the overall, non-specific substratum properties. Therefore, in vivo plaque formation may be more readily explained by a non-specific approach.</p

Assessment of processing technologies which may improve the nutritional composition of dairy products – Overview of progress

Among consumers there is a growing demand for food products with a natural nutritional-physiological advantage over comparable conventional products. As part of an EU funded project, ALP is examining the possible impact of processing on nutritionally valuable milk components, using the example of conjugated linoleic acids (CLA). The extent to which processing influences the CLA content of the end product was determined by literature research and own investigations of organic and conventional butter. Furthermore, new chemical, sensory-based and bio crystallization methods were evaluated by ALP and the University of Kassel to determine the oxidation stability of butter. In a further step the storage stability of CLA enriched and conventional butter was examined and the different methods will be compared. As a third objective a process for low-input CLA enrichment of milk fat (with a focus on alpine butter) has been developed. Since the process selected for the work is a physical enrichment process, it is accepted by international organic farming and food groups. Among the many benefits ascribed to CLA, it is believed to be an effective agent against cancer. The demand for foods with properties that promote human health is growing. The dairy industry has the opportunity to meet this demand by developing new dairy products with a nutritional-physiological function for the functional food market

Vroege scheutontwikkeling bij tomaat

In opdracht van het Productschap Tuinbouw hebben onderzoekers van Plant Research International (onderdeel van Wageningen UR) een methode ontwikkeld om de trosaanleg bij jonge tomatenplanten eenduidig te meten. De methode is door zes deelnemende bedrijven in de praktijk getest en de plantontwikkeling is onder begeleiding van de onderzoekers gedurende vier seizoenen gevolgd gedurende de opkweek van de planten

How Do Bacteria Know They Are on a Surface and Regulate Their Response to an Adhering State?

Bacteria adhere to virtually all natural and synthetic surfaces [1,2]. Although there are a number of different reasons as to why bacteria adhere to a surface, the summarizing answer is brief: ‘‘Adhesion to a surface is a survival mechanism for bacteria’’. Nutrients in aqueous environments have the tendency to accumulate at surfaces [1,3], giving adhering bacteria a benefit over free floating, so-called planktonic ones. This is why mountain creeks may contain crystal clear, drinkable water, while stepping stones underneath the water may be covered with a slippery film of adhering microbes. In the oral cavity, adhesion to dental hard and soft tissues is life-saving to the organisms, because microbes that do not manage to adhere and remain planktonic in saliva are swallowed with an almost certain death in the gastrointestinal tract. Bacterial adhesion is generally recognized as the first step in biofilm formation, and for the human host, the ability of

Characterization of eukaryotic cell surfaces prior to and after serum protein adsorption by X-ray photoelectron spectroscopy - Fibroblasts, HELA epithelial, and smooth muscle cells

Elemental surface concentration ratios N/C, O/C, and P/C of fibroblasts, HELA epithelial cells, and smooth muscle cells, prior to and after washing in the absence or presence of serum proteins, were determined by X-ray photoelectron spectroscopy. Cell surfaces appeared to adsorb hardly any serum proteins, and the relatively high P/C, as compared to N/C and O/C, elemental surface concentration ratio indicated that the cell surfaces consisted mainly of the phospholipid bilayer, with little or no proteins present. The lack of adsorption of serum proteins to the cell surfaces seems at odds with the common notion that cells require adhesive proteins in order to adhere and spread. However, the adsorption behavior of cellularly produced proteins may be completely different, particularly since they seem to be able to displace adsorbed serum proteins from biomaterials surfaces. Interestingly, only HELA epithelial cells (a tumor cell line) appeared to adsorb a very small amount of proteins.</p

The role of surface free energy in the early in vivo formation of dental plaque on human enamel and polymeric substrata

Strips of teflon and cellulose acetate were glued to the upper lateral incisors of human volunteers in a split mouth, double blind study on the influence of the substratum surface free energy (s.f.e.) on supragingival dental plaque accumulation during a three day period of no oral hygiene. Plaque accumulation, microbial composition of the plaque and s.f.e. of the microorganisms were determined and compared to plaque developed on natural enamel surfaces. Significantly less microorganisms colonised the polymer surfaces (p &lt; 0.002). Streptococcus sanguis I was the predominant microorganism found in enamel samples, comprising about one-third of the total microflora, whereas it was recovered infrequently and in lower numbers from the polymeric surfaces, which predominantly contained Streptococcus sanguis II. Only on cellulose acetate sometimes high numbers of Streptococcus mitis and Streptococcus morbillorum were detected. The mean s.f.e. of the total plaque flora was lowest on teflon (84.5 mJ m-2) followed by cellulose acetate (86.0 mJm-2), whereas enamel harboured a microflora with a significantly higher mean s.f.e. (930 mJ m-2; p &lt; 0.05). Also within the same bacterial species lower s.f.e. strains were isolated from the polymer surfaces compared to enamel. The results conform to a previously postulated model in which the interfacial free energy is the driving force for adhesion of microorganisms to solid surfaces.</p

Influence of glutaraldehyde fixation of cells adherent to solid substrata on their detachment during exposure to shear stress

In order to determine the response of fixed and nonfixed cells adherent to a solid substratum to shear stress, human fibroblasts were allowed to adhere and spread on either hydrophilic glass or hydrophobic Fluoroethylene-propylene (FEP-Teflon) and fixed with glutaraldehyde. Then, the cells were exposed to an incrementally loaded shear stress in a parallel plate flow chamber up to shear stresses of about 500 dynes/cm2, followed by exposure to a liquid-air interface passage. The cellular detachment was compared with the one of nonfixed cells. In case of fixed cells, 50% of the adhering cells detached from FEP-Teflon at a shear stress of 350 dynes/cm2, whereas 50% of the adhering, nonfixed cells detached already at a shear stress of 20 dynes/cm2. No fixed cells detached from glass for shear stresses up to at least 500 dynes/cm2. More than 50% of the nonfixed cells were detached from glass at a shear stress of 350 dynes/cm2. Furthermore, the shape and morphology of fixed cells did not change during the incrementally loaded flow, in contrast to the ones of nonfixed cells, which clearly rounded up prior to detachment.</p