Ultratrace voltammetric determination of DNA-bound platinum in patients after administration of oxaliplatin.

Oxaliplatin, a novel diaminocyclohexane-platinum complex, is used for the treatment of metastatic colorectal cancer. The amount of DNA-adduct formation of this drug in white blood cells of patients is determined after isolation of the DNA by density gradient centrifugation and a four-step solid phase extraction procedure. DNA is quantified by UV spectrometry, and platinum is determined after mineralization of the DNA sample by adsorptive stripping voltammetry (formazone method). It is possible to determine Pt-nucleotide ratios in clinical samples down to five Pt atoms in 10(8) nucleotides, and the dynamic range of the method covers three orders of magnitude. An absolute amount of 25 microg of DNA is sufficient for such measurements. With the method described, the time-dependent formation of oxaliplatin DNA adducts can be monitored in clinical studies, which may help us to understand inter-individual differences in the responses of patients to oxaliplatin-based therapy.

Recent advances in modelling the effects of roll motion on the human operator.

An experiment is presented in which the effects of roll motions on human operator performance were investigated. The motion cues considered were the result of commanded vehicle motion and vehicle disturbances. An optimal control pilot-vehicle model was used in the design of the experiment and to predict system performance prior to executing the experiment. The model predictions and experimental results are compared. Of the model predictions, 78% are within 1 S.D. of the means of the experimental results. The high correlation between model predictions and system performance indicate the usefulness of the predictive model for experimental design and for prediction of pilot performance influenced by motion cues.

Effect of labyrinthectomy on the dynamic vestibulo-ocular counterrol reflex in the rhesus monkey.

Timeline records of eyeball counterrotation to constant speed rotations about the line of sight were examined in the Rhesus monkey via a linear transformer measurement system using a contact lens. Normal monkeys exhibited a decrease in the amplitude ratio of eye-to-chair motion and an increasing phase lag between eye and chair as the frequency of the motion platform increased. Bilateral labyrinthectomy or prolonged dosage with streptomycin was found to nearly abolish the counterroll reflex. Unilateral damage to the vestibular system resulted in a decrease in the amplitude ratio of the eye-to-chair motion by approximately 50% 1 month after surgery.

Motion effects on the human operator in a roll axis tracking task.

To better understand the effects of motion on tracking performance, a simulator, capable of being controlled in a static as well as motion mode, was developed. Using this simulator, 12 volunteers, separated into groups of four, attempted to track a wing angle target displayy. The target was driven with band-limited (0.5 rad/s) Gaussian noise so that a roll angle of 120 degrees was equivalent to 1 S.D. Different control dynamics (plants) were used for each group of volunteers. For manual control of plants of the form2, the experimental results indicate that large amplitude roll motion information reduces task learning time and cuases a significant improvement in tracking performance. For control of simpler plants, of the form K/S, no improvement due to the presence of the motion environment was observed.