The statistical power of k-mer based aggregative statistics for alignment-free detection of horizontal gene transfer.

Alignment-based database search and sequence comparison are commonly used to detect horizontal gene transfer (HGT). However, with the rapid increase of sequencing depth, hundreds of thousands of contigs are routinely assembled from metagenomics studies, which challenges alignment-based HGT analysis by overwhelming the known reference sequences. Detecting HGT by k-mer statistics thus becomes an attractive alternative. These alignment-free statistics have been demonstrated in high performance and efficiency in whole-genome and transcriptome comparisons. To adapt k-mer statistics for HGT detection, we developed two aggregative statistics T s u m S and T s u m * , which subsample metagenome contigs by their representative regions, and summarize the regional D 2 S and D 2 * metrics by their upper bounds. We systematically studied the aggregative statistics' power at different k-mer size using simulations. Our analysis showed that, in general, the power of T s u m S and T s u m * increases with sequencing coverage, and reaches a maximum power >80% at k = 6, with 5% Type-I error and the coverage ratio >0.2x. The statistical power of T s u m S and T s u m * was evaluated with realistic simulations of HGT mechanism, sequencing depth, read length, and base error. We expect these statistics to be useful distance metrics for identifying HGT in metagenomic studies.

Pharmacokinetics of natural borneol after oral administration in mice brain and its effect on excitation ratio.

Previous studies have indicated that borneol has double side effects on the central nervous system (CNS), but the mechanism is unknown. The aim of this study was to clarify the relationship between excitation ratio [contents of excitatory amino acids (AAs) versus that of inhibitory] and the content of natural borneol after a single oral dose. Mice were administered a 1.2 g/kg dose of natural borneol (containing 98% D: -borneol) by oral ingestion. Brain samples were collected before administration and at 0.083, 0.167, 0.25, 0.333, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 4 and 5 h after administration. The brain concentration of natural borneol and contents of AA neurotransmitters in mice brain were determined by GC-MS and HPLC-FLU, respectively. After per oral application, natural borneol was absorbed rapidly into the brain and could be determined 5 min after dosing. The maximal brain concentration (86.52 µg/g) was reached after 1 h post-dosing. Natural borneol could affect the contents of AA neurotransmitters in mice brain: L: -aspartic acid increased significantly from 0.083 to 1 h after administration, L: -glutamic acid increased significantly at 0.333 h and decreased from 1.5 to 5 h, gamma-amino-N-butyric acid increased significantly from 0.167 to 5 h, whereas glycine was not affected. The excitation ratio is the contents of excitatory AAs versus that of inhibitory AAs, which reflects the excitatory or inhibitory state of the body. The excitation ratio elevated transitorily and then declined 0.5 h post-dosing; there were significant differences between 1.5-5 h post-dose compared with pre-dose. The present study indicated that natural borneol could affect the contents of AA neurotransmitters, and the change in excitatory ratio led to borneol's double side effects on the CNS.

In vitro characterization of borneol metabolites by GC-MS upon incubation with rat liver microsomes.

The metabolism of borneol is studied by the analysis of incubations of in vitro-prepared rat liver microsomes. A sensitive gas chromatography (GC)-mass spectrometry (MS) method is developed for the identification of borneol and its metabolites. Four novel metabolites, which have not previously been reported, are isolated and confirmed by comparison of the GC-MS method. The biotransformation pathway of borneol in rat liver microsomes is proposed based on the in vitro results.

Pharmacokinetics of dihydroartemisinin in Artekin tablets for single and repeated dosing in Chinese healthy volunteers.

Aim. To study the pharmacokinetics of dihydroartemisinin (DHA) in Artekin (compound dihydroartemisinin) tablets in Chinese healthy volunteers. Methods. Eighteen healthy volunteers (9 males, 9 females) received Artekin tablets for oral administration. The plasma samples of DHA were analysed by liquid-liquid extraction and determined by HPLC/ESI/MS. Results. The plasma DHA concentration-time curves of single dose and repeated doses of DHA were fitted to a two-compartment open model. The mean pharmacokinetic parameters of DHA in a single dose were: t(1/2(beta))=1.245 +/- 0.495 h, C(max)=243.6 +/- 56.15 microg/l, AUC(0 --> infinity)=450 +/- 69 h x microg/l, V(d)=5.75 +/- 2.2 l/kg and Cl=3.245 +/- 0.38 l/h/kg, while in repeated doses they were: t(1/2(beta))=1.085 +/- 0.298 h, AUC(0 --> infinity)=444.35 +/- 80.43 h x ng/ml, V(d)=4.62 +/- 1.128 ml/kg, Cl=3.0125 +/- 0.875 ml/h/kg, respectively. Conclusion. The study showed that DHA in Artekin was rapidly absorbed, distributed and eliminated in the healthy subjects. The pharmacokinetic properties of DHA in Artekin were not affected by gender in a single dose. While in repeated doses accumulation of DHA did not appear after repeated doses.

Determination of CQP propionic acid in rat plasma and study of pharmacokinetics of CQP propionic acid in rats by liquid chromatography.

A sensitive method for the determination of CQP propionic acid in rat plasma was developed and validated after solid-phase extraction. Chromatographic separation was achieved on a reversed-phase Alltima C18 column with the mobile phase of methanol-0.15% (v/v) phosphoric acid solution (pH 2.5) and step gradient elution resulted in a total run time of about 20min. The analytes were detected by using UV detector at 345nm. A good linear relationship was obtained in the concentration range of 50-12,800ng/mL (r=0.9998). The intra-day RSDs and the inter-day RSDs at the concentration of 200, 800, 6400 and 12,800ng/mL were less than 7.0% and 11.0%, respectively. The intra-day accuracy ranged from 96.3 to 106.5% and the inter-day accuracy ranged from 98.6 to 113.4%, respectively. Average extraction recoveries ranged from 83.6 to 94.3% in plasma at the concentrations of 200, 800, 6400 and 12,800ng/mL. This method was successfully applied to the pharmacokinetic studies on rats.

[Pharmacokinetics of Chuanxinlian tablet in healthy Chinese volunteers].

OBJECTIVE: To study pharmacokinetics of debydroandrographolide, that is a main active component in Chuanxinlian tablet, in healthy Chinese volunteers. METHODS: Eight volunteers were chosen for a single dose of two Chuanxinlian tablet drug concentrations in plasma were measured by HPLC-MS method and the pharmacokinetic parameters were calculated by PK Solution 2.0 software. RESULTS: t(1/2) ka, t(1/2) alpha, t/(1/2) beta, Cmax, tmax and AUCO-t were (0.51 +/- 0.28) h, (0.60 +/- 0.33) h, (3.62 +/- 1.16) h, (147.30 +/- 53.29) microg x L(-1), (1.50 +/- 0.21) h, and (256.63 +/- 64.18) microg x h x L(-1), respectively. CONCLUSION: Dehydroandrographolide has rapid absorption and long elimination rate after oral administration. The results can provide an evidence for the safety and efficiency of Chuanxinlian tablet in clinical application.