Impact of tillage erosion on water erosion in a hilly landscape.

Little has been known of the interaction between tillage erosion and water erosion, while the two erosion processes was independently studied. Can tillage-induced soil redistribution lead to exaggerated (or retarded) runoff flow and sediment concentrations in steeply sloping fields? A series of simulated tillage and artificial rainfall events were applied to rectangular runoff plots (2m×8m) with a slope of 15° to examine the impacts of tillage erosion intensities on water erosion in the Yangtze Three Gorges Reservoir Area, China. Mean flow velocity, effective/critical shear stress, and soil erodibility factor K were calculated to analyze the differences in hydrodynamic characteristics induced by tillage. Our experimental results suggest that mean runoff rates were 2.26, 1.19, and 0.65Lmin(-1) and that mean soil detachment rates were 1.53, 1.01, and 0.61gm(-2)min(-1) during the 70-min simulated rainfall events for 52-, 31-, and 10-year tillage, respectively. A significant difference (P<0.05) in cumulative detachment amounts was found among different tillage intensities. Compared with the soil flux of 0kgm(-1), cumulative detachment amounts for the soil fluxes of 9.86 and 24.72kgm(-1) increased by 40.02% and 100.94%, respectively, during the 30-min rainfall event. The results imply that soil and water losses tended to increase with increasing tillage intensity. A significant difference in mean flow velocity occurred near the upper and lower slope boundaries of the field, while significant differences (P<0.05) in runoff depth and effective shear stress were observed among different slope positions. Soil erodibility factor K for the soil fluxes of 9.86 and 24.72kgm(-1) were 2.40 and 5.11 times higher, respectively, than that for the soil flux of 0kgm(-1). As tillage intensity increased, critical shear stress trended to gradually decrease for all soil fluxes. Our results indicate that tillage erosion increases soil erodibility and delivers the soil for water erosion in sloping fields, accelerating water erosion.

Evaluation of 99mTc-peptide-ZHER2:342 Affibody® molecule for in vivo molecular imaging.

OBJECTIVE: The aim of this study was to develop an improved method for labelling ZHER2:342 with Technetium-99m ((99m)Tc) using Gly-(d) Ala-Gly-Gly as a chelator and to evaluate the feasibility of its use for visualization of HER2 expression in vivo. METHODS: The Affibody® molecule ZHER2:342 was synthesized by Fmoc/tBu solid phase synthesis. The chelator, Gly-(d) Ala-Gly-Gly, was introduced by manual synthesis as the N-terminal extensions of ZHER2:342. ZHER2:342 was labelled with (99m)Tc. The labelling efficiency, radiochemical purity and in vitro stability of the labelled molecular probe were analysed by reversed-phase high performance liquid chromatography. Biodistribution and molecular imaging using (99m)Tc-peptide-ZHER2:342 were performed. RESULTS: The molecular probe was successfully synthesized and labelled with (99m)Tc with the labelling efficiency of 98.10 ± 1.73% (n=5). The radiolabelled molecular probe remained highly stable in vitro. The molecular imaging showed high uptake in HER2-expressing SKOV-3 xenografts, whereas the MDA-MB-231 xenografts with low HER2 expression were not clearly imaged at any time after the injection of (99m)Tc-peptide-ZHER2:342. The predominant clearance pathway for (99m)Tc-peptide-ZHER2:342 was through the kidneys. Conculsion: (99m)Tc-peptide-ZHER2:342 using Gly-(d) Ala-Gly-Gly as a chelator is a promising tracer agent with favourable biodistribution and imaging properties that may be developed as a radiopharmaceutical for the detection of HER2-positive malignant tumours. ADVANCES IN KNOWLEDGE: The (99m)Tc-peptide-ZHER2:342 molecular probe is a promising tracer agent, and the results in this study provide a foundation for future development of protocols for earlier visual detection of cancer in the clinical setting.

Value of QT dispersion in evaluating spatial dispersion of ventricular repolarization during acute myocardial ischemia.

OBJECTIVES: To study the value of epicardial QT interval dispersion in predicting ischemia-induced heterogeneity of ventricular repolarization. ANIMALS AND METHODS: Ischemia was produced by total occlusion of the obtuse branch of the circumflex coronary artery in seven open-chest sheep. A 64-channel electrocardiogram (ECG) was acquired from the epicardium before and after coronary artery occlusion. Wavelet transformation was used to determine the characteristic points of the epicardial ECGs, and to measure the QT interval and activation-recovery interval (ARI) and their dispersions. RESULTS: The average QT interval and ARI from the epicardial ECG were not changed by acute myocardial ischemia (P=0.07 and P=0.13, respectively). QT dispersion remained unchanged during ischemia (P=0.17), whereas ARI dispersion was significantly increased by acute ischemia (59.9+/-24.0 ms versus 126.3+/-32.1 ms, P<0.001). CONCLUSIONS: These findings indicate that epicardial QT dispersion is less sensitive than ARI dispersion in estimating repolarization heterogeneity induced by acute myocardial ischemia.

Determinants of BDNF-induced hippocampal synaptic plasticity: role of the Trk B receptor and the kinetics of neurotrophin delivery.

The neurotrophins are a class of signaling molecules known for their growth and survival-promoting activities during neuronal development. Recent studies suggest that the neurotrophins, including brain-derived neurotrophic factor (BDNF), can also dramatically influence synaptic transmission in the adult hippocampus. The experiments described in this paper indicate that ability of BDNF to potentiate synaptic transmission in the hippocampus relies on functional Trk B receptors. Moreover, the rate at which BDNF is applied to hippocampal synapses is also a potent determinant of whether synaptic potentiation will result. Hippocampal slices perfused with BDNF at a very slow flow rate (e.g., < or = 25 ml/hr) did not show synaptic potentiation. Increasing the rate of BDNF application resulted in synaptic potentiation in which the magnitude and onset kinetics of the potentiation were determined by the rate of BDNF delivery. Immunocytochemical analysis of BDNF detected with confocal microscopy confirmed these electrophysiological observations, indicating that the penetration of BDNF into hippocampal slices is influenced dramatically by the perfusion rate.