Variation characteristics of microorganisms at different soil depths of typical forests in southwest China.

Microbial biomass and community structure play a significant role in soil carbon cycling. There is a large amount of organic carbon in the subsoil, but most studies on soil microbial community have focused on the surface soil. The changes and influencing mechanisms of microbial community in subsoil are unclear. We analyzed soil microbial biomass and community structure at different soil depths (0-20, 20-40, 40-60, 60-80, and 80-100 cm) in three typical forests in southwest China, Xishuangbanna tropical rain forest, Ailao Mountain subtropical broad-leaved forest, and Lijiang temperate coniferous forest, by using phospholipid fatty acid technology, to explore their variation characteristics and influencing factors in different forests and soil depths. The results showed that contents of soil organic carbon and total nitrogen decreased gradually, microbial biomass declined significantly. The ratio of Gram-positive bacteria to Gram-negative bacteria (G+:G-) reduced gradually, while the ratio of fungi to bacteria (F:B) increased with the increasing soil depth. Microbial community turned from G--dominated which adapted to eutrophic environment into G+-dominated which adapted to oligotrophic environment. The three forest types differed little in soil microbial biomass, but different significantly in microbial community structure. Ailao Mountain subtropical broad-leaved forest and Lijiang temperate coniferous forest had much higher F:B at 0-20 cm than Xishuangbanna tropical rain forest, while significantly higher G+:G- at 0-100 cm in Xishuangbanna tropical rain forest was observed. Results of the redundancy analysis showed that the contents of soil organic carbon and total nitrogen were the main factors determining microbial biomass, with combined explanation of 78.3%. Results of the stepwise regression analysis showed that C:N was the most important driving factor on F:B and G+:G-. The change in microbial community structure and the decrease in biomass along soil profile might strongly affect the dynamics of soil organic carbon in southwest China forests.

C(76)Cl(34): high chlorination of the inherent chiral fullerene with a helical configuration.

As the smallest chiral fullerene in conformity with the Isolated Pentagon Rule (IPR), D(2)-symmetric C(76) has been chlorinated with iodine monochloride to form C(76)Cl(34), a highly chlorinated derivative. Its structure with the chiral cage enwrapped by a helical chlorine pattern has been established using single-crystal X-ray diffraction analysis. The high chlorination and its implication for constructing novel chiral fullerene-based materials are discussed.

Diagnosis and treatment of postoperative intestinal perforation in infants and young children with congenital heart disease: A report of three cases.

The aim of the present study was to analyze risk factors of intestinal perforation following surgery for the treatment of congenital heart disease in infants and young children, and to summarize experiences of diagnosis and treatment. A total of 3,270 children, who underwent congenital heart disease surgery under extracorporeal circulation from January 2010 to July 2015, were retrospectively analyzed. Among these children, three (0.09%) developed postoperative intestinal perforation. Primary diseases were Tetralogy of Fallot (two cases) and ventricular septal defect combined with atrial septal defect (one case). The age range of the children was 6-11 months and the weight range was 7.3-8.6 kg. Furthermore, these children underwent radical surgery under general anesthesia and extracorporeal circulation in low temperatures. Abdominal symptoms appeared 4-10 days after surgery, and included poor appetite, abdominal distension, intermittent vomiting, high fever, refractory irritability, crying and shortness of breath. One case was confirmed by routine abdominal puncture and the remaining two were confirmed by the detection of free gas under the diaphragm, as revealed by abdominal X-ray. Following the diagnosis of intestinal perforation, emergency intestinal fistula surgery was performed. At 3-5 days post-surgery, the patients underwent treatment by fasting and intravenously administered parenteral nutrition. Diet was increased following recovery of bowel function. All patients recovered following active treatment and 3-4 months following hospital discharge, the fistula was successfully closed. In conclusion, a concerted effort should be made to identify intestinal perforation in infants and young children with postoperative congenital heart disease during emergency surgery. Early diagnosis and treatment may significantly improve prognosis and reduce mortality.

Chlorination for efficient identification of polycyclic aromatic hydrocarbons by liquid chromatography-mass spectrometry.

Utilizing liquid chromatography-mass spectrometry (LC-MS) for identification of polycyclic aromatic hydrocarbons (PAHs) has long been underrated, as the sensitivity for determination of PAHs directly by MS is very poor. In the present work a chlorination method for high-sensitive determination of PAHs by LC-MS is discussed. This method includes two steps: (1) chlorination of PAHs by the BMC method; (2) determination of the chlorinated PAHs by LC-MS. Interfaced by atmospheric pressure chemical ionization in negative ion mode, five representative perchlorinated PAHs producing from the languidly detectable parent PAHs (naphthalene C(10)H(8), acenaphthene C(12)H(10), phenanthrene C(14)H(10), pyrene C(16)H(10) and fluoranthene C(16)H(10)) have been LC-MS characterized in high sensitivity with determination limits in 10(-9)g/mL level. In addition, molecular compositions and polycyclic carbon-frameworks of unknown PAHs can be identified according to the isotopic pattern of the chloro-derivatives ions in the corresponding mass spectra. Our experiments demonstrate that the proposed chlorination-involving LC-MS method is efficient for the PAHs analysis, for example, in soot and soil samples.

The novel inhibitory effect of Pangdahai on fatty acid synthase.

Recently, animal fatty acid synthase (FASN) is reported as a potential therapeutic target for obesity and cancer. Considerable interest has been developed in searching for novel inhibitors of this enzyme. An extract from Pangdahai has been found to inhibit FASN in both reversible and irreversible manners, with an IC(50) of 3.5 microg/ml and an apparent inactivation rate constant of k(obs) of 2.2 x 10(-3)/min. The kinetic study showed that the Pangdahai extract inhibited the overall FASN reaction uncompetitively with acetyl-CoA, but it presented in a mixed manner both with NADPH and with malonyl-CoA. Its major reacting site on this enzyme, as compared between two IC(50) values, is not in the beta-ketoacyl reduction domain. A weight reducing experiment in rats showed that the extract significantly reduced the adipose and food intake, but in view of statistics (P < 0.05), a correlation between the reductions in the adipose and in the food consumption and the inhibition of hepatic FASN could not be established. Three known flavonoid compounds were isolated from the extract and the structure-activity relationship was discussed.