Exposure of biological preparations to radiofrequency electromagnetic fields under low gravity.

There is interest as to whether the electromagnetic fields used in mobile radiotelephony might affect biological processes. Other weak fields such as gravity intervene in a number of physical and biological processes. Under appropriate in vitro conditions, the macroscopic self-organization of microtubules, a major cellular component, is triggered by gravity. We wished to investigate whether self-organization might also be affected by radiotelephone electromagnetic fields. Detecting a possible effect requires removing the obscuring effects triggered by gravity. A simple manner of doing this is by rotating the sample about the horizontal. However, if the external field does not also rotate with the sample, its possible effect might also be averaged down by rotation. Here, we describe an apparatus in which both the sample and an applied radiofrequency electromagnetic field (1.8 GHz) are stationary with respect to one another while undergoing horizontal rotation. The electromagnetic field profile within the apparatus has been measured and the apparatus tested by reproducing the in vitro behavior of microtubule preparations under conditions of weightlessness. Specific adsorption rates of electromagnetic energy within a sample are measured from the initial temperature rise the incident field causes. The apparatus can be readily adapted to expose samples to various other external fields and factors under conditions of weightlessness.

Sucrose cycling in heterotrophic plant cell metabolism: first step towards an experimental model.

Sucrose is the cornerstone of higher plant metabolism. Produced by photosynthesis, sucrose is the main substrate for respiration and biosynthesis. The emerging idea is that sucrose may act as regulator of its own metabolism, characterized in particular by a permanent process of degradation and formation. This sucrose turnover may control several important physiological functions. Of particular concern is an energy dependent cycle involving the hexokinase. This report presents an experimental approach to define quantitatively physiological states of suspension-cultured plant cells wih reference to their sucrose content and respiration rate. Sucrose depletion of normal cells incubated in a medium devoid of sugar is measured in vivo using 13C and respiration is simultaneously recorded. Results obtained with sucrose-storing cells and Arabidopsis thaliana show that respiration rate is closely linked to the available sucrose. Sucrose-depleted cells offer a stable model to study the bioenergetics of the process.