Cell function monitoring

Patients with metastatic renal cell carcinoma commonly develop mild biochemical thyroid function test abnormalities while taking sorafenib. However, compared with sunitinib, which is associated with a high incidence of thyroid dysfunction, making routine monitoring necessary, patients taking sorafenib need thyroid function monitoring only if clinically indicated (1074). 

Ultimately multiple imaging modalities as well as newer more sensitive approaches to track live cells may be needed for complete functional monitoring of the various cellular repair processes. 

Fig. 7.4 (a) Dose-response of the lamellarin M-induced mitochondrial depolarization in P388 cells, (b) Monitoring of the mitochondrial membrane potential (A rm) by realtime flow cytometry, using functional mitochondria isolated from P388 cells and the fluorescent probe JC-1. 

It is often possible to address function more specifically in in vitro assays, where functional parameters are usually very sensitive readouts of adverse effects. For example trans-epithelial electrical resistance (TEER) is a very sensitive marker of epithelial disturbances. TEER measures the barrier function of the entire mono-layer and is utilized to study functional disturbances of many epithelial/endothelial cell types including blood-brain barrier, pulmonary, renal, and gastrointestinal cells. Its sensitivity lies in the fact that only a small proportion of cell death has a very large impact on barrier function. Additionally, cell stress can interfere with the arrangement and population of tight junction proteins [16] thus, TEER can in certain conditions measure functional disturbances in the absence of cell death [13]. Also since TEER can be measured noninvasively, it is nondestructive and can be used to monitor the effects of treatment over days and weeks [13, 17]. For excitable cells, electrical activity has also been proven to be an extremely sensitive parameter of adverse drug reactions and microelectrode arrays have been employed successfully to monitor neurotoxicity in vitro [18]. Also, for contractile cells, such as cardiomyocytes, the use of impedance measurements to measure the effects of compounds on spontaneous contraction has been demonstrated to be a very sensitive functional monitoring parameter in vitro [19, 20], Admittedly, none of the aforementioned techniques are true biomarkers per se however, such measurements illustrate the fact that in vitro techniques allow certain possibilities that are not practically tenable in the whole body. 

The value of Fmax for a given experiment can be measured very accurately, with an error of less than 5%. Thus, for the purpose of simulation, the amplitude is a very informative parameter. However, as demonstrated in Figure 29, Fmax is highly dependent on X0, which is a function of the excitation laser output, pulse-beam dimensions, and observation cell and monitoring-beam geometries. The other parameters, rmax, yi, and y2 are much less affected by Xq. Thus, the amplitude is a... 

The instrumentation and probes for fluorescence analysis and imaging are now available to perform multiple biochemical analyses in living cells. The interplay between cellular structures and differentiated cell function can now be dynamically visualized and monitored to provide topologically specific information about the biology of the cell. 

Biomimetic systems and devices as nonspecific indicators of threat and response might take the form of a nanocanary, in which a few living cells are harnessed to monitor biological responses to a variety of biologically active test agents. Such biomarker systems would enable a wide spectrum of applications that are adaptable to a broad range of unknown threats, including implantable sensor devices with presymptomatic sensitivity to biomarkers. Therefore, one key to the development of biomimetic systems is to develop analytical tools that can probe in vivo and in vitro cellular processes at the molecular scale with minimal disruption of normal cell function. 

Because of this, GFP can be fused to almost any protein of interest to analyze protein location, movement, and chemistry in living cells. GFP has been used to probe protein function, monitor protein interactions, and act as biosensors for protein presence. GFP can be attached to specific antibodies to detect the presence of foreign antigens (Ryan, 2003), or attached to viruses to track their movement throughout the body. 

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