ABSTRACT
The aim of this study was to compare scintigraphy, the standard method, and the (13)C-octanoic acid breath test (OBT) for measuring gastric emptying. Patients with functional dyspepsia (N = 21, 8 men and 13 women; ages, 40-75) underwent standardized dynamic scintigraphy and OBT. Scintigraphic images were obtained for 90 min and breath samples for 4 hr. The gastric half-emptying time for solids (T(1/2)) was calculated by two previously described mathematical models for the OBT samples: the nonlinear least-squares method and the geometrical method. T(1/2) was significantly longer measured by OBT than by scintigraphy (167 +/- 50 min for the nonlinear least-squares method (P < 0.05) and 185+/- 52 min for the geometrical method (P < 0.005) vs. 109 +/- 74 min for scintigraphy). No correlation appeared between T(1/2) measured by scintigraphy and T(1/2) measured by OBT (r = 0.26) for nonlinear least-squares method and (r = -0.13) for geometrical method). Furthermore, the correlation between the two mathematical models appeared to be low (r = 0.15). Although OBT is simple and safe, its correlation with scintigraphy appears to be weak. The usefulness of this test for measuring gastric emptying thus requires further validation.
Subject(s)
Breath Tests , Dyspepsia/physiopathology , Gastric Emptying/physiology , Stomach/diagnostic imaging , Adult , Aged , Caprylates , Carbon Dioxide/metabolism , Carbon Isotopes , Dyspepsia/diagnostic imaging , Dyspepsia/metabolism , Female , Humans , Male , Middle Aged , Models, Biological , Radionuclide Imaging , Reproducibility of ResultsABSTRACT
As double-stranded DNA is stretched to its B-form contour length, models of polymer elasticity can describe the dramatic increase in measured force. When the molecule is stretched beyond the contour length, it further shows a highly cooperative overstretching transition. We have developed a theoretical description for this transition by coupling the two-state model and the elasticity theory proposed earlier by others. Furthermore, we have extended this model to account for monovalent salt effects on elastic moduli during the transition. We find that this theoretical description is in very good agreement with recent measurements for the salt dependence of the overstretching transition, allowing us to gain insight into the mechanisms that govern the transition. In double-stranded DNA, the effective length per unit charge varies with salt in agreement with the Manning and Poisson-Boltzmann models for thin polyelectrolyte rods, whereas the other model parameters describing structural features have barely any salt dependence. The results thus suggest that the electrostatic component of force-induced overstretching is mediated mesoscopically via elasticity.
