Transport-intensity, reducing

Short-term application of auxin to the apical cut surface of coleoptile sections, combined with an estimation of auxin accumulation with time in basal receivers which were replaced at brief intervals, was demonstrated by van der Weij (1932, p442ff) to be a means of calculating transport velocity. He observed that the auxin export rate (i.e., the transport intensity) increased initially to a maximum and then decreased. He assumed that the arrival time of the peak of transport intensity was the period of time needed by the auxin stream to traverse the segment. The velocity thus estimated (8mmh" ) was similar to the values of about 10mmh obtained with the intercept method. When labeled hormones became available, such pulse experiments were refined and modified. The duration of the pulse application could be reduced to 60 s (Shen-Miller 1973 a, b) and the receivers could be changed with great frequency to improve the estimation of the peak. 

If standard, generic products can be shipped in bulk from their point of origin and then assembled, customised or configured for local requirements nearer the point of use, there may be an opportunity to reduce overall transport-intensity. 

A further irncentive to reduce the transport-intensity arises from the continued upward pressure on oii-Pased fuei costs, which wiii oniy intensify as oii reserves become depieted. 

Producing, processing, transporting and disposing of these materials creates massive pollution. Reducing material intensity gives an immediate environmental benefit, and the potential for a significant economic benefit. 

Europe is still the main market for leather products and leather produced in the developing countries, e.g. Southeast Asia, may therefore end up on the European market and to European consumers. Chemicals that are added during the production, and which stay on/in the product, will hence be transported by the product to the final markets, and there will be a chemical flow around the world through the transport of leather and leather products containing chemicals. Since the tanning industry is a chemically intensive industry, an efficient chemical management in tanneries is necessary in order to minimise the overall use of chemicals and in particular also to reduce the amount of hazardous chemicals used in order to minimise eventual health effects on the consumer. 

Since active transport mechanisms require energy, the incubation temperature during the assay plays a crucial role. At 4°C, the fluidity of the cell membrane is reduced, the metabolism of the cell is downregulated, and energy-dependent transport processes are suppressed. Consequently, the amount of cell-associated target system refers mainly to the cytoadhesive fraction. In contrast, incubation at 37°C increases the fluidity of the cell membrane and the metabolic activity to an optimum, so both cytoadhesion and cytoinvasion occur at the same time. Thus, the uptake rate can be calculated from the difference in signal intensity measured upon incubation at both respective temperatures. 

Compared to in vivo studies, the Caco-2 model substantially increases the speed at which absorption potential can be estimated and reduces the amount of drug substance needed. However, manually performed assays are still too slow and labor intensive compared to biological high-throughput screening assays. Caco-2 cells take about 3 weeks to form monolayers of fully differentiated cells. At this point, Caco-2 monolayers are used to evaluate absorption potential under a variety of permeability protocols. In order to further expedite the process of absorption potential assessment, efforts have been made to increase the throughput of Caco-2 transport experiments. 

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