Glucose deprivation depolarizes plasma membrane of cultured astrocytes and collapses transmembrane potassium and glutamate gradients.

Primary cultures of astrocytes were used to investigate the effects of glucose deprivation on plasma membrane potential, on the respiration and on the energy status of these cells. Plasma membrane potential, as monitored with a cyanine dye, 3,3'-diethylthiadicarbocyanine, hyperpolarized by about 100% when glucose was added to substrate-deprived cells. The effect of glucose was prevented by iodoacetate or ouabain. In the absence of glucose, cellular adenosine triphosphate/adenosine diphosphate ratio was extensively reduced and pyruvate was unable either to restore energy status or to hyperpolarize the plasma membrane of astrocytes, although it was the preferential substrate for mitochondria within the cells. Glucose deprivation and inhibition of glycolysis or respiration in the presence of glucose caused dramatic decrease in transmembrane potassium ion and L-glutamate gradients. The gradients were not restored in the presence of pyruvate. Thus, aerobic glycolysis, rather than oxidation of pyruvate, is required to maintain maximal plasma membrane potential, adenosine triphosphate/adenosine diphosphate ratios as well as K+ and L-glutamate gradients. This evidence, together with the unresponsiveness of astrocyte respiration to ouabain, indicates a functional dissociation between energy dissipation at the plasma membrane and mitochondrial synthesis of adenosine triphosphate. The results are discussed with regard to the vulnerability of glia at low levels of blood glucose and the contribution of glial dysfunction to development of hypoglycaemic encephalopathy.

The use of LOTUS 1-2-3 in statistics.

This paper describes a convenient way of performing statistical tests in biology. The recent development of powerful spreadsheet programs for microcomputers has made it possible to easily apply various statistical significance tests on biological data. Presently the following tests have been implemented in the LOTUS 1-2-3 framework: Student's t-test, chi-square test, analysis of variance (single classification random ANOVA), Student-Neumann-Kuels test, correlation analysis and analysis of linear regression (single and multilevel design). The most important advantages gained by using 1-2-3 instead of the commercial statistical software packages are the simplicity of entering data, the possibility of asking "what-if?" questions, the simple, but useful graphical presentation of data and the ease of actual building of the tests.