Universal measuring site for the determination of tissue-impedance variations in relation to blood perfusion]

In view of the importance of impedance plethysmography requirements are formulated for a modern impedance measuring device basing on a long experience with this method of measurement. The principle mode of action of the measuring equipment and the pneumatics with the timing element are described. A number of recordings is shown to illustrate the universality of the measuring equipment.     

Protists have divergent effects on bacterial diversity along a productivity gradient

Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators.     

Inhibitors of reverse serotonin uptake and of specific imipramine binding in human blood plasma

Human blood plasma contains low-molecular substances that inhibit in a dose-dependent manner both high-affinity specific binding of imipramine and reverse serotonin uptake by platelets. Incubation of human blood plasma with alumina was made use of to extract and study these imipramine-like inhibitors. The extract obtained from human blood plasma inhibited imipramine binding and reverse uptake of serotonin with median inhibitory concentrations of 0.18 +/- 0.1 and 0.36 +/- 0.15 mg/ml, respectively. After gel chromatography on Biogel P-2 the elution profile of the extract showed 2 major peaks of reverse serotonin uptake and imipramine binding inhibition and 3 additional peaks of reverse serotonin uptake inhibition, which did not have any considerable effect on imipramine specific binding. It is assumed that endogenous inhibitors of imipramine binding and reverse serotonin uptake are involved in the development of affective disorders.     

Spinal control of afferent temperature information in the cat

The effect of picrotoxin (at sub-convulsant doses, i.v.) on the background and invoked spike activity of cat dorsal horn internerons was investigated while thermal and mechanical influences were at work on the skin receptor areas. It was found that information on skin temperature is modulated at the presynaptic level and largely mediated by competitive interaction between large and small diameter fibers.Institute of Physiology, Academy of Sciences of the Kazakh SSR, Alma Ata. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 773–779, November–December, 1986.