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Gross ammonification (GA) and gross nitrification (GN) are key regulators of the bioavailability of nitrogen (N) in terrestrial ecosystems. In arid and semi-arid grassland ecosystems, the impacts of precipitation change on in situ GA and GN and their seasonal variations are understudied. A manipulative experiment with five precipitation levels (−60%, −30%, unchanged ambient precipitation as control, +30%, +60% of ambient precipitation) was set up in May 2012. After a 2-year equilibration period, the 15N pool dilution technique was applied to determine GA and GN rates in surface soil (0–5 cm) within 8 sampling dates ranging from the onset to the end of the growing season. Pronounced temporal variability of GA and GN rates were observed with the highest GA and GN rates in the mid-growing season (August) and the lowest in the post-growing season (October). GA rates during the growing season were primarily controlled by precipitation and soil water availability, while this effect diminished at the onset and end of the growing season when the temperature dropped. In contrast, GN was predominately controlled by ammonium (NH4+) production through GA. In the peak-growing season, the +60% precipitation treatment enhanced GA and GN rates by up to 4-fold, while the −30% precipitation treatment marginally suppressed GA and GN rates. The −60% precipitation treatment suppressed GA and GN rates to below detection limits across the entire study period, suggesting that extreme and persistent droughts greatly inhibited N turnover in the surface soil, thereby forcing plants to mobilize and access nutrients from deeper soil layers. Our findings provide a season-specific mechanistic insight into precipitation impacts on topsoil gross N turnover and suggest that the N cycling represented in ecosystem models needs to consider a mechanism that allows a strong suppression of microbial functions under extreme droughts.

This study was designed to investigate whether hepatic arterial pressure and portal pressure have an effect on liver stiffness during the development of liver fibrosis. Liver fibrosis was induced in 50 healthy New Zealand white rabbits. Laparotomy was performed to measure liver stiffness, and the portal vein and hepatic artery were successively ligated to repeat the measurements. A significant difference was observed among liver stiffness values measured at different time points (F = 22.82, p < 0.001). Differences between original liver stiffness and liver stiffness measured after portal ligation were positively correlated with portal pressure (r = 0.801, p < 0.001). In animals with grade 4 liver fibrosis, the increase in liver stiffness caused by pressure was greater than that caused by extracellular matrix accumulation (p = 0.002). In conclusion, hepatic arterial pressure and portal pressure have a significant effect on liver stiffness during the development of liver fibrosis.

Rationale and Objectives Our goal was to evaluate the role of contrast-enhanced gray-scale transrectal ultrasound (CETRUS)-guided prostate biopsy in patients with elevated serum prostate-specific antigen (PSA) levels. Materials and Methods A total of 115 men (mean age, 70 years; range, 47−85) with serum PSA levels of greater than 4.0 ng/ml were assessed using gray-scale transrectal ultrasound (TRUS), power Doppler ultrasound (PDU), and CETRUS. Subsequently, these patients underwent systematic sextant transrectal biopsy and additional biopsies for positive sites on gray-scale TRUS, PDU, and CETRUS. The cancer detection rates of the three techniques were compared. Results Cancer was detected in 63 of the 115 patients (55%). CETRUS was positive in 50 patients, 35 of whom (70%) had prostate cancer; CETRUS had a higher sensitivity, specificity, and accuracy of 65% (41/63), 83% (43/52), and 73% (84/115), respectively. CETRUS could have saved a significant number of patients from undergoing unnecessary biopsies, compared to TRUS and PDU. However, no significant correlation was found between the Gleason score and CETRUS grade. Conclusions The use of CETRUS in detecting prostate cancer might reduce the number of unnecessary needle biopsies of the prostate in patients with abnormally high serum PSA levels and increase the detection rate of clinically significant prostate cancer.