Localization and quantification of the cytoskeleton-associated protein adducin in the kidneys of normal and Milan hypertensive rats

 Hypertension and kidney dysfunction in sodium transport observed in the Milan hypertensive strain (MHS) of rats are genetically associated with point mutations of adducin, an actin- and spectrin-binding protein of the membrane cytoskeleton. Polymorphism in the adducin locus has been reported to occur also in cases of human primary hypertension. In this study we show by immunostaining that adducin is localized along the basolateral epithelial membrane surface of the entire proximal and distal tubule with no detectable differences between MHS rats and the normotensive control strain (MNS). However, the total amount of adducin in kidney homogenates is reduced by about 45% in MHS rats as determined by quantitative immunoblotting. In erythrocyte membranes of MHS rats, adducin is reduced approximately 10%. The reduction of renal adducin in MHS rats is mainly caused by a reduction of the adducin pool that is loosely associated with kidney membranes and can be released by the non-ionic detergent, Triton X-100. The Triton-resistant, tightly membrane-bound pool of renal adducin differed by approximately 10% between MHS and MNS rats. Since several ion transporters have been shown to be tethered to the membrane cytoskeleton, we suppose that the reduction of the dynamic, loosely bound pool of adducin in MHS rats might interfere with the normal turnover and incorporation of yet unknown transporters involved in kidney sodium transport. However, the Na⁺,K⁺-ATPase appears to be not involved, as indicated by normal distribution and amounts of NA⁺,K⁺-ATPase in the kidney of MHS rats revealed by immunostaining and immunoblotting. Accepted: 23 June 1997     

The electric generator in the photosynthesis of green plants. II. Kinetic correlation between protolytic reactions and redox reactions

In a preceding paper (Junge, W. and Ausländer, W. (1974) Biochim. Biophys. Acta 333, 59–70), we attributed the four protolytic reactions at the outer and the inner side of the functional membrane of photosynthesis to the protolytic properties of the redox components, water, plastoquinone and the terminal acceptor. The experimental evidence presented was conclusive except for one argument. The rate of the protolytic reactions as detected by the dye cresol red after a short flash of light was considerably slower than the rate of the corresponding redox reactions.In this communication it is demonstrated that the rate of proton uptake from the outer phase of the functional membrane is slowed down by a diffusion barrier for protons which shields the redox reaction sites at the outer side of the membrane against the outer aqueous phase. This barrier can be lowered by sand grinding the chloroplasts, by digitonin treatment and by uncoupling agents. At the extreme the barrier can be practically eliminated to yield rates of proton uptake matching the rates of the corresponding redox reactions. This gives conclusive evidence that the electrochemical potential difference which light induces across the functional membrane of photosynthesis is generated by a vectorial electron-hydrogen transport system as postulated by Mitchell (e.g. (1966) Biol. Rev. 41, 445–502).     

Daphnia swimming behavior during vertical migration

We observed the individual swimming behavior of a clone of Daphniahyalina swiniming freely inside a mesocosm-scale plankton tower.Changes in light intensity and the presence or absence of fishsmell induced vertical migration through     

Functions of Soil for Society and the Environment

Six key environmental, social and economic functions of soil are described, as well as the reversible and irreversible threats, caused by their uses. Sustainable use of soil is defined by the temporal and/or spatial (local or regional) harmonisation in the uses of the 6 functions, excluding or minimising irreversible ones, which is not a scientific but a political task.