Active target systems

Systemic administration of drugs in the form of nanoparticulates intravenously has been widely studied. Currently, there are some liposomal anticancer and antifungal medications in clinical use. These products show relative increase in drug bioavailability in the target sites. They are not, however, active targeting systems with recognition ligands on the surface. 

Other active targeting systems include specific peptides to target cells and organs that are selected from a phase display method [181-182] and aptamers, which are short molecules of double-stranded DNA or single-stranded RNA that bind to specific molecular targets [183]. 

A limitation of active target systems is that on-board electronics must be strapped to the subject with leads to each of the diodes. These wires, combined with the subject being tethered to the cameras, can interfere with certain movements. Tetherless systems (i.e., telemetered systems) are available however, wires to each diode are still necessary. 

L. Ilium and S. S. Davis, Passive and active targeting using colloidal carrier systems, in Drug Targeting (P. Buri and A. Gumma, eds.), Elsevier Science Publishers, Amsterdam, 1985, p. 65. 

The CRESST II setup will consist of up to 33 modules with both light and heat detection, reaching up to 10 kg of active target mass. The system is read out by a 66-channel SQUID system, two readout channels for each module. 

Individual user interface windows and the flow between them can be captured as a storyboard. Each window is often associated with a particular task, at some level of abstraction a flow sequence will refine a more abstract use case. Once again, users should be very actively involved in the actual design of the interface, even if that means teaching them a bit about what is achievable with the target system. 

Use of more specific in vitro assays to further assess effects on the pertinent target system and potential mechanism of activity ... 

A number of strategic research topics were pursued for fuel cell systems in the EU funded projects, ranging from basic research to validation and demonstration activities for gaining field experience . All activities were targeting systems which could be commercially viable by 2020 for many applications, with focus on the high temperature technologies (mainly Solid Oxide, SOFC) and... 

Special emphasis is placed on the carbohydrate-mediated cell - target system interaction by describing hints and pitfalls of assays for cytoadhesion, specificity, cytoinvasion, and cytoevasion. In addition, basic considerations are presented to discriminate between active and passive uptake as well as to detect lysosomal accumulation. Finally, the pros and cons of two useful analytical techniques, namely, flow cytometry and confocal laser scanning microscopy, are described in detail. 

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. 

The photoreceptor complex comprises cw-retinal and opsin (R-O) for which the regulatory signal is light. This interacts with the regulatory component of the complex R, which then dissociates (in the form ciT-R) from the O component. The free O is now catalytically active and catalyses the initial reaction in the visual cascade sequence which leads to activation of the target system (i.e. produces an action potential in the optic nerve). 

For practical purposes, measures of the effectiveness of drug targeting are required. Such measures have been derived based on the pharmacokinetic profiles of the drug targeting system and that of the active drug. 

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