[Spatial interpolation model of soil organic carbon density considering land-use and spatial heterogeneity.] / 综合土地利用及空间异质性的土壤有机碳空间插值模型.

Soil organic carbon pool is an important component of terrestrial carbon pool. Soil organic carbon pool and its dynamic change have important influence on carbon cycle in terrestrial ecosystem. Soil organic carbon density (SOCD) is an important parameter of soil carbon storage, and it is also an important index to evaluate farmland soil quality. Accurate prediction of regional organic carbon density spatial distribution is of great significance to the development of precision agriculture. A total of 242 farmland soil samples collected from the Jianghan Plain were used to explore the effects of land use types on the spatial distribution of SOCD in plain areas. Moreover, in the presence of spatial heterogeneity and spatial outliers of SOCD, three Kriging approaches combining land use types were used for the spatial prediction of SOCD. They were dummy variable regression Kriging (DV_RK), mean centering ordinary Kriging (MC_OK1) and median centering ordinary Kriging (MC_OK2). Results showed that the difference of land use types between paddy field and irrigable land was one of the reasons for the spatial heterogeneity of SOCD in the study area, resulting in spatial non-stationary characteristics of SOCD and lowering the performance of OK. DV_RK, MC_OK1 and MC_OK2, however, eliminating the impacts of SOCD spatialheterogeneity caused by land use types while modeling, enhancing the model stability. Therefore, the prediction accuracy of these three models was higher than that of ordinary Kriging (OK). Moreover, MC_OK2 outperformed the others in terms of model reliability, prediction accuracy and the ability to explain the total variance of SOCD. In summary, as an easily accessed auxiliary variable, land use type could effectively decrease the effects of spatial heterogeneity and spatial outliers on SOCD spatial interpolation model, improving the prediction performance and reducing the model uncertainty. SOCD map with higher quality could also be achieved to help reveal the spatial characteristics of SOCD for guiding the agricultural production.

[Establishment of coronary heart disease models of Qi-deficiency and blood-stasis syndrome in rats].

To establish Qi-deficiency and blood-stasis syndrome type coronary heart disease models by fatigue running exercise and high ligation of left anterior descending coronary artery (LAD), male Wistar rats were selected and randomly divided into sham operation group (JSS), coronary ligation group (DZ), fatigue running exercise+coronary ligation group (PZ). Coronary ligation alone was done in DZ group; while the rats in PZ group had running exercise in on the animal treadmill system for 2 weeks to establish fatigue models, and then coronary ligation was done based on the models. The exhausted running was maintained for 28 days at the frequency of 1 time/2 days after operation. Twenty-eight to thirty-one days after the operation, all the rats were observed for macroscopic physical signs, and ultrasonic echocardiography indexes and breathing extent of the rats were collected to evaluate the main symptoms of rats with Qi-deficiency and blood-stasis syndrome type coronary heart disease; related indexes of open field test, exhaustive running time, and colorimetric analysis data on images of plantar were collected to evaluate the accompanied symptoms; colorimetric analysis data on lingual surface was collected to evaluate the tongue characteristics; pulse distension data was collected to evaluate the pulse condition, and meanwhile, blood rheology and coagulation function were also detected. From the 28th day postoperatively, the main symptoms, accompanied symptoms, tongue characteristics and pulse conditions of rats in PZ group conformed to the symptoms of coronary heart disease and Qi-deficiency and blood-stasis syndrome. Combined with related pathological results, the study revealed that Qi-deficiency and blood-stasis syndrome type coronary heart disease models could be successfully established by fatigue running exercise and high ligation of left anterior descending coronary artery for the rats.

Distribution of superantigenic toxin genes in Staphylococcus aureus isolates from milk samples of bovine subclinical mastitis cases in two major diary production regions of China.

To evaluate the distribution of most known staphylococcal superantigen (SAg) genes in Staphylococcus aureus isolated from bovine mastitis cases, a genetic analysis of 15 SAg genes and genotypes was performed in a total of 283 S. aureus isolates collected from milk samples of cows with subclinical mastitis in two major diary production regions of China. Almost 65% of the isolates possessed at least one toxin gene. The most frequently found genes were sea (36.0%) followed by sei (31.8%), seg (31.4%) and selm (26.9%). The genes see, selk, or selo were not found in any of the isolates tested. Overall, 28 SAg genotypes were observed, among which the genotypes sea-seg-sei-selm, seg-sei-selm-seln, and sea-sed-selj predominated at the rate of 8.8%, 7.4%, and 6.7%, respectively. Marked geographical variations were noticed in the distribution of individual SAg genes and genotypes among S. aureus isolates from the two different regions. The relationship between toxin genotypes and toxin genes encoding profiles of mobile genetic elements (MGEs) was analyzed, revealing that majority of SAg genes were present in certain MGEs, which were in accordance with current knowledge about MGEs carrying those genes. However, some gene combinations suggest the possibility of the existence of variants or new types of MGEs.

Characterization of antimicrobial resistance among Escherichia coli isolates from chickens in China between 2001 and 2006.

Escherichia coli is a common commensal bacterium and is regarded as a good indicator organism for antimicrobial resistance for a wide range of bacteria in the community and on farms. Antimicrobial resistance of E. coli isolated from chickens from 49 farms in China between 2001 and 2006 was studied. A total of 536 E. coli isolates were collected, and minimal inhibitory concentrations (MICs) of eight antimicrobials were determined by the broth microdilution method. Isolates exhibited high levels of resistance to ampicillin (80.2%), doxycycline (75.0%) and enrofloxacin (67.5%). Relatively lower resistance rates to cephalothin (32.8%), cefazolin (17.0%) and amikacin (6.5%) were observed. Strains were comparatively susceptible to colistin (MIC(50) = 1 microg mL(-1)). A marked increase in isolates with elevated MICs for florfenicol was observed over the study period. Therefore, five resistance genes leading to the dissemination of phenicol resistance in the isolates (n = 113) with florfenicol MICs > or = 32 microg mL(-1) were analyzed. The gene floR was the most prevalent resistance gene and was detected in 92% of the 113 isolates, followed by the cmlA (53%), catA1 (23%) and catA2 (10%) genes. catA3 was not detected in these isolates. Eight isolates with florfenicol MICs = 32 microg mL(-1) and one with MIC = 64 microg mL(-1) were negative for the floR gene.