Electric Impedance and Rectification of Fused Anion-Cation Membranes in Solution

At relatively high currents, fused anion-cation membranes give rise to rectifying and reactive effects. The rectification becomes less pronounced with increasing frequency. This effect results from changes in the concentration profiles of the ions during the positive and negative phases of the AC cycle. With reduction of the current, the voltage-current response becomes linear. The reactive effect can then be separated from the rectifying effect. The former effect can be attributed essentially to two factors: (a) the presence of transition regions of fixed charge and (b) the diffusion mechanism of the ions in an AC field. The first factor is largely frequency-independent and the second, frequency-dependent. A first approximation equivalent circuit is described. This circuit involves frequency-dependent elements.     

CHANGES IN HEPATIC STRUCTURE IN RATS PRODUCED BY BREATHING PURE OXYGEN

The livers of rats exposed to pure oxygen were examined electron microscopically to study toxic effects of oxygen in a metabolically sensitive organ. Pressures of 1/3 (258 mm Hg), 1 (760 mm Hg), and 3 (2280 mm Hg) atmospheres were used, with exposures up to 90 days with the lowest pressures. The first changes in the hepatocytes were loss of glycogen and enlargement of mitochondria with development of mitochondria with bizarre shapes which were seen after 3 days at 258 mm, 1 day at 760 mm, and 3 hours at 2280 mm. These changes were followed by formation of increased numbers of cristae, membranes surrounding mitochondria, autophagic vacuoles, and polyribosome clusters. After 2 weeks at 258 mm, which is the pressure of the atmosphere of space cabins, numerous mitochondrial myelin figures appeared but the mitochondrial enlargement had begun to regress. After 90 days at 258 mm, the liver cells appeared almost normal except that many pigment granules had accumulated in the pericanalicular zones. The changes were non-specific and seemed to parallel biochemical alterations recorded elsewhere. They are not considered the result of toxicity but rather of adaptation. These atmospheres, which are used in clinical medicine and in space travel, appear to have no permanent deleterious effects on the liver in rats under the conditions of this experiment.     

THE ROLE OF RESERVES IN LEAVES,BRANCHES, STEMS,AND ROOTS ON SHOOT GROWTH OF RED PINE

By defoliation, girdling, and various combinations of these before the growing season began, the role of foods in old needles, branches, main stems, and roots on shoot growth of 8-yr-old red pine (Pinus resinosa) trees was studied in northern Wisconsin. Defoliation and girdling, alone or in combination, reduced shoot growth but defoliation reduced shoot dry weight more than it reduced shoot elongation. Reductions in shoot growth due to treatment were in the following decreasing order: branch girdling + needle removal > girdling at stem base + needle removal > needle removal > branch girdling > base girdling. The old needles were the major source of food for shoot growth and accounted for four-fifths or more of all shoot growth. The combined reserves in the branches, main stem, and roots accounted for less than 15% of shoot growth. The contribution of reserves from tissues other than old leaves was in the following order: branches > main stem > roots. Defoliation weakened apical dominance relations. In defoliated trees, many secondary axes elongated more than the terminal leader, and secondary axes in lower whorls often grew more than those in upper ones. The data suggest an important role of nutritional factors in correlative growth inhibition.