Intercellular communication in spheroids

This chapter has shown that the response of spheroid cells to gap junctional communication may lead to certain metabolic and cell physiological changes. It has also become apparent that the functions of the gap junctions are very complex. They may, for example, be related to the fundamental effects of cAMP and/or Ca 2+. These lines of evidence should be pursued further. However, further insight into these functions may also be gained from a study of the structure and function of the gap-junctional proteins, as well as from a genetic approach (e.g., Willecke et al. 1982, 1983). In this context, the spheroids are of particular importance as test systems, since they perfectly simulate the three dimensional arrangement of cells encountered in a tissue. Indeed, the results presented in the sections "Biophysical and Biochemical Effects Associated with Intercellular Communications" and "Intercellular Communication and Radiosensitivity" have revealed clear cut differences between cells growing as spheroids or as monolayers in response to communication dependent processes, which indicate that the response of the monolayers could be somewhat trivial. The advantage of multicellular spheroid systems with three-dimensional growth over monolayer cultures is unquestionable. Cells growing in three-dimensional multicell spheroids may re-establish their regulatory activities and, therefore, match the in vivo conditions more closely. Multicell spheroids allow in vitro investigations on differentiating systems and on interactions between normal and malignant cells, thus substituting costly in vivo experiments

Electrochemical monitoring of subcutaneous tissue pO2 fluctuations during exercise using a semi‐implantable needle electrode

Semi‐implantable needle oxygen electrodes were used for forearm subcutaneous monitoring in human subjects undertaking high intensity cycling and fist clenching exercise. pO2 variations in the range between 40 and 100 mm Hg oxygen were seen. Superimposed on these were paradoxical rises in subcutaneous pO2, of up to 100 mm Hg which paralleled the scale of the exercise. This was indicative of increased blood flow through skin. Triton X‐100 incorporated into the sensor polyurethane membranes helped to give faster responses and reduced the possibility of biofouling and drift. The sterilizable system, free from internal electrolyte film appears promising for future clinical monitoring