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The physical meaning of the observed critical electric potential difference necessary for photophosphorylation is discussed. An interpretation of this phenomenon on the basis of the equilibrium thermodynamic formulation of the chemiosmotic hypothesis requires a reversible ATPase system. Contrary to this, ATP hydrolysis experiments seem to corm that the Mg++. dependent ATPase system of class II-chloroplasts is irreversible m the absence of SH-compounds. This sheds doubt on the equilibrium thermodynamic interpretation of the critical electric potential difference for phosphorylation. However it can be shown, that the seeming irreversibility may be due to some trigger requirements of an intrinsically reversible ATPase system. This leads to an identification of the critical electric potential difference with the triggering level of the enzyme system. Two operational models for an ATPase system, whose activity is modulated by the electric potential difference, are derived. These account quantitatively for a set of experiments on the critical electric potential difference. [ABSTRACT FROM AUTHOR]

The ATP-synthesis and the electric phenomena on the thylakoid membrane have been studied under excitation of photosynthesis with short flash groups. The light induced electric potential difference has been measured by means of field indicating absorption changes around 523 nm. It is shown that upon excitation with short flash groups a certain electric potential difference required before ATP can be synthesized. Moreover it is confirmed that the ATP-synthesis accompanied by an additional flux of protons down their electrochemical potential gradient. Correlation between the number of protons which have flowed across the ATPase coupled pathway, and the number of ATP-molecules which have been formed, yields a ratio H+/ATP = 3. Since this ratio includes only those protons, which have interacted with the ATPase complex, it represents the lower limit for H+/ATP-ratios determined by any other method. The necessity of a certain electric potential difference and the fact that 3 H+ have to be translocated down their electrochemical potential difference before one molecule of ATP can be synthesized is consistent with the chemiosmotic postulate, that the ADP ~ P bond energy derived from the electrochemical potential difference of the proton across the coupling membrane. With respect to the alternative hypothesis for phosphorylation, the results impose grave restriction on a phosphorylation driven only by the free energy of a chemical intermediate, if this does exist at all. [ABSTRACT FROM AUTHOR]

The article discusses the use of magnetism in medicine. Magnetism has been used in various diagnostic and therapeutic process in medicine and physiology. Some of the advanced research at the Wiezmann Institute and other institutions regarding the magnetic fields is discussed and evaluated including the electric potentials or magnetic phosphenes, muscle stimulation, and magnetic controls. The development of magnetic tools are also discussed including magnetic catheters, and the improvement of contrast materials for X-ray.

The article focuses on the concepts of impedance, which is defined as the ratio of a voltage to a current, and mutual impedance, and their relation to issues dealing with the study of biological tissues. It talks about the construction of the impedance concept around a series circuit model and its relationship to equivalent capacitance. Some methods of measuring the vectorial value of impedance representation and an example showing the measurement of impedance in biological tissues are discussed.