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A long-held dogma in radiation biology has been that the biological effects of exposure to ionizing radiation occur as a result of damage in directly irradiated cells and that no effect would occur in neighboring unirradiated cells. This paradigm has been frequently challenged by reports of radiation effects in unirradiated or ‘bystander’ cells receiving signals from directly irradiated cells, an issue that may have substantial impact on radiation risk assessment and development of radiation-based therapies. Radiation-induced bystander effects have been shown in single-cell systems in vitro for an array of cancer relevant endpoints, and may trigger damage in more complex 3-D tissue systems. They may be mediated by soluble factors released by irradiated cells into the extracellular environment and/or by the passage of mediator molecules through gap-junction intercellular communication. To date, evidence that radiation-associated bystander or abscopal responses are effectual in vivo has been limited, but new data suggest that they may significantly affect tumor development in susceptible mouse models. Further understanding of how the signal/s is transmitted to unirradiated cells and tissues and how it provokes long-range and significant responses is crucial. By summarizing the existing evidence of radiation induced bystander-like effects in various systems with emphasis on in vivo findings, we will discuss the potential mechanisms involved in these observations and how effects in bystander cells contribute to uncertainties in assessing cancer risks associated with radiation exposure.

Summary: Details given of the construction and electrical characteristics of a novel electrode for physiology using carbon and manganese dioxide as depolarizer. Comparisons made of its performance with that of more commonly used electrodes, showing that a MnO2 electrode being relatively non-polarizable may have some advantages as an electrode for recording biological d.c. potentials and as a stimulating electrode.

Abstract: The impedance measured by surface electrodes in impedance pneumography is partly that of lung and partly that of other tissues, notably the skin. The paper discusses the assessment of the relative contributions of these various tissues to the total impedance.

Abstract: The electrochemical and toxicological characteristics of manganese dioxide (MnO2) have been described. Details of the construction and testing of surface MnO2 electrode are presented. The reported data and the results of tests confirm that a MnO2 electrode sufficiently stable and free from polarization effects can be constructed.