Dual Tracer Experiments Research Articles

The role of the low density lipoprotein receptor in transport and metabolism of LDL through the wall of normal rabbit aortain vivo. estimation of model parameters from optimally designed dual-tracer experiments

The role of the low density lipoprotein receptor in transport and metabolism of LDL through the wall of normal rabbit aortain vivo. estimation of model parameters from optimally designed dual-tracer experiments

The in vivo kinetics of 111In‐ and 51Cr‐labelled platelets: a comparative study using both stored and fresh platelets

The in vivo kinetics of simultaneously injected 51Cr- and 111In-labelled platelets was investigated in 20 healthy male volunteers. The studies were carried out using both fresh platelets and platelets stored for 5 d at 22 degrees C; the disappearance of platelet-bound radioactivity was measured on whole blood samples as well as platelet pellets. Compared to 111In, the labelling efficiency was notably lower for 51Cr, and a higher amount of 51Cr was bound to contaminating red cells. As regards the fresh platelets, only small dissimilarities were observed in the in vivo kinetics obtained with the two labels. 51Cr yielded a slightly higher platelet recovery and longer T1/2 than 111In, when whole blood samples were used for calculations; no differences were seen when using platelet pellets. When stored platelets were studied, 51Cr gave significantly longer T1/2 and mean life-span (MLS) than did 111In. This difference was present for all mathematical models used for the calculation of MLS, and when whole blood samples as well as platelet pellets were employed. It was demonstrated that the estimation of MLS was also highly dependent upon techniques of blood sampling and curve fitting. Calculation, in which the initial data points were excluded, gave consistently longer MLS (P less than 0.0001), as compared to when all data points were included. Furthermore, when all survival studies were grouped together, calculations using platelet pellets gave a significantly (P less than 0.001) shorter platelet MLS than calculations using whole blood samples. It is concluded that both 51Cr and 111In are acceptable as radiolabels for both fresh and stored platelets. However, it appears that the viability of stored platelets may be influenced by the choice of label, and caution must be taken when these isotopes are used together in dual tracer experiments. Also, our results show that a meticulously standardized processing of blood samples and experimental data is required to enable interlaboratory comparisons of the results.

The influence of car speed on dispersion of exhaust gases

Results of seven dual tracer experiments (SF 6 and CBrF 3) show that the vertical diffusion of exhaust gases tends to be larger from cars driving with high speed than from cars driving with lower speed. The experiments were carried out over a flat snow covered plain and the tracer gases were emitted from two moving cars. The vertical tracer distributions were determined at 10, 30 and 70 m from the road using 5–10 m masts. Gaussian distributions were found to fit the vertical profiles of tracer concentrations. The results encourage further use of dual tracer experiments to study dispersion effects of the interaction of car wakes with the atmospheric surface layer. When the atmospheric wind was perpendicular to the road (five experiments), the vertical dispersion parameter for tracer material ( σ z ) was linearly dependent on an estimated scale of the wake in each experiment. The coefficients of linearity varied with the state of the atmospheric surface layer as indicated by wind measurements and stability classification. The empirical results are applicable only when the scales of turbulence in the atmospheric surface layer are smaller than the scale of the wake. Houses and trees located close to the road will influence the dispersion of the automobile exhaust and the conditions for interaction are changed.

Photosynthesis of amino acids

Methods have been developed for performing dual tracer experiments with 15N and 14C on the photosynthesis and biosynthesis of amino acids in Chlorella pyrenoidosa. These methods involved the development of apparatus for maintaining algae in a condition of steady-state photosynthesis, including amino acid synthesis, and of adding tracers in a stepwise fashion so that specific activity of the tracer is maintained at a constant level without alteration of other environmental factors. This method has been applied, and the kinetics of the labeling of several primary amino acids with 14C and 15N have been studied. The results indicate that the reductive amination to form glutamic acid is the primary route for incorporation of 15N in this organism during photosynthesis of amino acids. Certain relationships between the site of the photosynthesis of carbon skeletons of primary amino acids and the site of 15N incorporation have been proposed and discussed.