Inaccuracies in quantitative radionuclide renal imaging due to patient position or diverging collimation.

Radionuclide renal studies with quantitative measurements in patients confined to intensive care units usually require the use of a 10-inch field-of-view mobile gamma camera and a diverging collimator to image both kidneys simultaneously. The patient must frequently be in the lateral decubitus position so imaging can be performed in the posterior projection. Due to spatial distortion caused by the diverging collimator, variations in detector angulation and kidney depth produce different detection efficiencies for each kidney. Counts in regions of interest over the kidneys were compared as a function of detector angulation and patient position (prone and lateral decubitus). Substantial variations were observed comparing the diverging collimator data to 15-inch field-of view parallel hole acquisitions. Significant variation can also be obtained with parallel hole collimators when the patient's position is changed.

Olfactory responses of a specialist and a generalist grasshopper to volatiles ofArtemisia ludoviciana nutt. (Asteraceae).

Hypochlora alba is a specialist grasshopper that lives and feeds almost exclusively onArtemisia ludoviciana, a plant that produces large amounts of allelochemics including a variety of monoterpenes. This plant is not a host for generalist grasshoppers such asMelanoplus sanguinipes. The role of olfaction in the grasshopper-plant relationship was investigated by comparing electroantennograms (EAGs) of males and females of both species generated by solvent-extracted volatiles from plant leaves and by major individual components. Volatiles ofA. ludoviciana were identified by gas chromatography-mass spectrometry. The major components were 1,8-cineole, camphor, camphene, and borneol, while minor identified compounds were α- and ß-pinene, α-thujene, myrcene,p-cymene, Artemisia ketone, α-thujone, and bornyl acetate. The EAGs (mV) ofH. alba males to a range of concentrations of individual volatiles or the total plant extract were nearly double those of conspecific females or both sexes ofM. sanguinipes. However, both sexes ofM. sanguinipes were more sensitive than either sex ofH, alba to geraniol, a monoterpene that commonly occurs in many plant species but is absent or is present in only trace amounts inA. ludoviciana. The increased sensitivity ofH. alba males to the odor components of their host plant appears to be related to the greater number of certain olfactory chemoreceptors on male versus female antennae. The significance of this phenomenon is discussed.