Reconstitution of highly purified saxitoxin-sensitive Na+-channels into planar lipid bilayers.

Highly purified Na+-channels isolated from rat brain have been reconstituted into virtually solvent-free planar lipid bilayer membranes. Two different types of electrically excitable channels were detected in the absence of any neurotoxins. The activity of both channels was blocked by saxitoxin. The first channel type is highly selective for Na+ over K+ (approximately 10:1), it shows a bursting behavior, a conductance of 25 pS in Na+-Ringer and undergoes continuous opening and closing events for periods of minutes within a defined range of negative membranes voltages. The second channel type has a conductance of 150 pS and a lower selectivity for Na+ and K+ (2.2:1); only a few opening and closing events are observed with this channel after one voltage jump. The latter type of channel is also found with highly purified Na+-channel from Electrophorus electricus electroplax. A qualitative analysis of the physicochemical and pharmacological properties of the high conductance channel has been carried out. Channel properties are affected not only by saxitoxin but also by a scorpion (Centruroides suffusus suffusus) toxin and a sea anemone (Anemonia sulcata) toxin both known to be selective for the Na+-channel. The spontaneous transformation of the large conductance channel type into the small one has been considered; the two channel types may represent the expression of activity of different conformational states of the same protein.     

The puzzle of hydrodynamic information processing: how are complex water motions analyzed by the lateral line?

We studied the discharges of neurons in the ascending lateral line pathway in response to the complex water motions generated by a moving object. The wave stimulus generated by the object was monitored with a hot-wire anemometer and with a custom-built particle imaging system. Responses of central lateral line neurons differ from those of primary afferent fibers in aspects like temporal discharge patterns and directional sensitivity. The data are consistent with the hypothesis that central lateral line neurons integrate input from many afferents innervating neuromasts distributed across large portions of the body surface.     

Phenylalanyl-tRNA synthetase from E. coli: synergistic coupling between the sites for binding of L-phenylalanine and ATP

Binding of small ligands to the sites binding L-phenylalanine and ATP was measured by fluorescence titration technique. It is found that complex formation is not independent under conditions when both types of ligands are present in solution. The coupling is expressed as a synergistic binding rendering higher stabilities for complexes with ligand couples than expected on basis of separate binding of each ligand. In contrast, the substrate couple L-phenylalanine — ATP does not exhibit synergistic binding.     

Die Beeinflussung der Wundheilung bei Säugetieren durch histostatische und morphogenetische Substanzen

Ohne Zusammenfassung     

The effects of pentachlorophenol, phenol and other pollutants on the liver of carp (Cyprinus carpio L.)

Liver tissue of carp was kept in roller tubes and the basal and epinephrine-induced release of glucose after 6 or 24 hr incubation were measured. The amount of liver glycogen after incubation was also determined. The liver was taken from carp treated in vivo with pollutants, mainly PCP or phenol, or was exposed to these pollutants in vitro. Treatment of carp in vivo with 10-10(4) micrograms/l phenol reduced the basal and the epinephrine-induced release of glucose from the liver. Treatment with low doses increased the glycogen content of the liver slightly, treatment with higher doses reduced the amount. Treatment of carp with low doses of several pollutants decreased mainly the basal glucose release from the liver and reduced the glycogen content. In vitro incubation of the liver with PCP or phenol for 3 days reduced at first the basal release and later the epinephrine-stimulated release of glucose from the liver. After a few days the glycogen content of liver exposed to pollutants was more strongly reduced than that of controls. The phosphorylase activity was slightly increased in liver tissue by the pollutants.