Nitrate content and nitrate reductase activity in Rumex obtusifolius L. : I. Differences in organs and diurnal changes.

With Rumex obtusifolius L., the influence of some environmental conditions on nitrate uptake and reduction were investigated. Nitrate concentrations of plant material were determined by HPLC, the activity of nitrate reductase by an "in vivo" test.

Some characteristics of the purinergic nervous system in normal and sensitized airway smooth muscle.

Supramaximal electrical field stimulation was employed to produce biphasic response in segments of cervical and thoracic tracheas and in first generation of bronchi isolated from guinea pigs. This response consists of contraction (as measured by maximal active tension, ATmax) followed by relaxation (as measured by maximal active relaxation, ARmax). First, the effect of electrical stimulation was studied in relation to frequency and duration of impulse.