Effects of light on ultradian rhythms in the lateral leaflets of<Emphasis Type="Italic">Desmodium gyrans</Emphasis>

Rhythmic up-down movements were studied in the lateral leaflets ofDesmodium gyrans (L.F.) DC. These were recorded with a video-computer system, whereby the digital video signals from a CCD camera were processed with special software. Under control conditions (24°C and 0.1 nM cm^-2 s^-1 of stable, dim light), the average period of lateral leaflet movement was 3.5 min. In the presence of light stimuli (for 2 min), those leaflets always moved toward the light, regardless of where it was applied to any axial part of the pulvinus. The strongest effect was manifested by a reduced amplitude of movement and, thus, a shortened period, which could be up to ~43% less under moderate light intensity (5 nM cm^-2 s^-2). Oscillations regained their original regularity over ~10 cycles after the light stimulus was removed. In addition, these oscillations temporarily disappeared after long exposure (~10 min) under moderate light, or when the leaflets were quickly exposed to a higher intensity (~12 nM cm^-2s^-1). Therefore, we have now demonstrated that light can affect physiological parameters that are involved in the control of oscillations.     

Determination of iodide using flow injection with acidic potassium permanganate chemiluminescence detection.

A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r2 = 0.9955) with relative standard deviations (n = 4) in the range 1.0-3.5%. The detection limit (3sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(II), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO4(2-), PO4(3-), NO3-, NO2-, F- and SO3(2-)) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005 - 0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed.     

Ultrasonographic contrast-agent imaging of sub-millimeter vessel structures with spatial compounding: in vitro analyses.

In clinical diagnostics, ultrasonographic contrast-agent imaging gives access to medical parameters such as perfusion and vascularization. In addition to the artifacts that are typical for ultrasonic imaging, e.g., speckle noise and depth-dependent sensitivity and resolution, contrast-agent imaging shows more pronounced depth dependence and may suffer from shadowing artifacts that arise from high attenuation of the ultrasound waves by the contrast agent at high concentrations. By imaging an object from different viewing angles in one 2D image plane and summing the images obtained (spatial compounding), image quality can be increased and artifacts can be suppressed. In the present study, we combined both techniques to overcome the limitations of contrast-agent imaging. We used a commercially available ultrasound scanner and a custom-made high-precision mechanical system to rotate the ultrasound transducer fully around the object under investigation. Using this set-up, ultrasound data were acquired in reflection mode to generate a 360 degrees compound scan of a flow-mimicking phantom supplied with contrast agent.