Oriented immobilization of bacterial photosynthetic membrane.

We have examined a method for oriented immobilization of photosynthetic membrane fragments on a solid surface by specific avidin-biotin interaction. Photosynthetic membrane fragments from the purple non-sulphur photosynthetic bacterium Rhodopseudomonas viridis, of which the H-subunit of the photosynthetic reaction centre was biotinylated, was immobilized on an avidin-adsorbed plate. Orientation of the immobilized membrane on the plastic plate was checked by an antisera binding assay that could react to the respective sides of the membrane: the H-subunit side was selectively adsorbed on the plate. Light-induced potential and current responses could be measured when the membrane immobilized on the SnO2-coated glass plate was dried and sandwiched with a counter electrode of Hg. The electrical response in the immobilized membrane was much improved in comparison with the control (membranes were simply adsorbed on the plate), supporting the idea that the membranes have an orientation on solid surfaces.

Estimation of the energy of cytoplasmic movements by magnetometry: effects of temperature and intracellular concentration of ATP.

Ferrimagnetic particles (gamma-Fe2O3) were spontaneously phagocytized by pulmonary macrophages obtained from the lungs of hamsters. By the magnetometric method proposed earlier, changes in the energy of the movements of the intracellular structures and also that of the apparent viscosity of the cytoplasm were estimated. The changes were created by lowering the incubation temperature or by decreasing the intracellular concentration of ATP. While the low temperature decreased the energy and increased the apparent viscosity, the low concentration of ATP decreased the energy but had little effects on the apparent viscosity. Estimation of the these parameters was based on the model previously proposed.

Magnetometric estimation of organelle motion in hamster lung macrophages in vitro: the effects of temperature.

Pulmonary macrophages, containing ingested ferrimagnetic particles, were studied in vitro. Magnetic particles (Fe3O4) suspended in saline were repeatedly instilled intratracheally into the lungs of Syrian golden hamsters. Later the animals were sacrificed and pulmonary macrophages were harvested by repeated lung lavage. After monolayer cultures were established, the particles previously phagocytized by the macrophages were magnetized and aligned by applying an external field. After the external field was removed, the particles produced a remanent magnetic field which gradually decreased due to random misalignment of the particles (relaxation). When relaxation was measured at various incubation temperatures, we found that relaxation slowed as the temperature decreased; we believe that this reflects decreased organelle motion. These results provide direct evidence that relaxation measured previously in intact animals is related to intracellular movements. Magnetometry can be used to quantitate the motion of cell organelles and thus the influence of altered cytoplasmic rheology and cytoskeletal activity.

Directional change of ciliary beat effected with Mg2+ in Paramecium.

Two types of Triton X-100 extracted model of Paramecium caudatum were prepared and effects of the ionic compositions of the reactivating medium on the swimming behaviour of the extracted models were examined. Type I, prepared by the method of Naitoh and Keneko, did not change swimming direction depending on the concentrations of Mg2+ and K+ in the reactivating medium. Type II, prepared by a different method, however, reversed the swimming direction depending on the concentrations of Mg2+ and K+ in the reactivating medium, even when the concentration of Ca2+ was kept at an extremely low level (below 10-8M). Decreasing the concentration of Mb2+ induced the type II model to swim backwards. Intracellular injection of EDTA into a live paramecium cell induced reversal of the direction of ciliary beat. The concentration of Mg2+ at which the reversal of swimming direction occurred varied with the concentration of adenosine triphosphate (ATP) in a manner which suggested that the concentration of free ATP4- might be the critical determinant of swimming direction.