Pharmacokinetics, Safety Profile, and Tolerability of Tetramethylpyrazine Nitrone Tablets After Single and Multiple Ascending Doses in Healthy Chinese Volunteers.

BACKGROUND AND OBJECTIVES: Tetramethylpyrazine nitrone (TBN) is a novel tetramethylpyrazine derivative armed with a strong free radical scavenging nitrone moiety. This study aims to evaluate the pharmacokinetics, safety profile, and tolerability of TBN tablets after a single ascending dose (SAD) and multiple ascending doses (MAD) in healthy Chinese volunteers. METHODS: This phase I, single-center, open-label study was conducted in China. The SAD portion consisted of four cohorts with dose levels of 400-1800 mg. The MAD portion included three cohorts in which subjects received doses of 600-1800 mg twice daily for 7 days (13 consecutive doses). The third portion was a randomized, two-period, crossover design to assess the influence of food with a single dose of TBN tablets (1200 mg). The safety profile was evaluated by monitoring adverse events (AEs), vital signs, electrocardiograms, physical examinations, and laboratory test results. RESULTS: Fifty-two healthy subjects aged 18 to 45 years with a body mass index between 19.0 and 26.0 kg/m2 were enrolled. After a single dose of TBN, the median time to maximum plasma concentration (Tmax) was 2.48-3.24 h and the mean half-life (t1/2) was 1.28 to 2.10 h across all doses. In the MAD study, the median Tmax was 2.48 to 3.48 h. In the 400-1800 mg dose range, there was a tendency for less than proportional increases in the maximum plasma concentration (Cmax), the area under the concentration-time curve from 0 to time of last measurable concentration (AUC0-t), and the area under the concentration-time curve from 0 to infinity (AUC0-inf) in both single- and multiple-dose periods. A significantly higher TBN exposure was observed in females than males in both a single and multiple doses of the 600 mg and 1200 mg groups, with a geometric mean female-to-male ratio of 138.69-203.18%. Food decreased the Cmax and AUC0-t of TBN to 45.19% and 59.73%, respectively. Each dose group reached a steady state after 4 days. No drug accumulation was observed. Two subjects had drug-related AEs. A decreased neutrophil count and drug eruption in the SAD portion (1200 mg group) and an increased alanine aminotransferase level in the food effect group were found. All AEs were mild and tolerable (CTCAE grade 1) and resolved without any medical intervention. CONCLUSION: TBN tablets had a good safety profile and were well tolerated in healthy Chinese volunteers. Steady-state concentrations were reached after 4 consecutive days of oral administration. The results of this phase I study will provide guidance for the design of future TBN clinical studies. CHINESE CLINICAL TRIAL REGISTRY: ChiCTR1900022092.

Synthesis and Application of a Near-Infrared Light-Emitting Fluorescent Probe for Specific Imaging of Cancer Cells with High Sensitivity and Selectivity.

Background: The preclinical diagnosis of tumors is of great significance to cancer treatment. Near-infrared fluorescence imaging technology is promising for the in-situ detection of tumors with high sensitivity. Methods: Here, a fluorescent probe was synthesized on the basis of Au nanoclusters with near-infrared light emission and applied to fluorescent cancer cell labeling. Near-infrared methionine-N-Hydroxy succinimide Au nanoclusters (Met-NHs-AuNCs) were prepared successfully by one-pot synthesis using Au nanoclusters, methionine, and N-Hydroxy succinimide as frameworks, reductants, and stabilizers, respectively. The specific fluorescence imaging of tumor cells or tissues by fluorescent probe was studied on the basis of SYBYL Surflex-DOCK simulation model of LAT1 active site of overexpressed receptor on cancer cell surface. The results showed that Met-NHs-AuNCs interacted with the surface of LAT1, and C_Score scored the conformation of the probe and LAT1 as five. Results: Characterization and in vitro experiments were conducted to explore the Met-NHs-AuNCs targeted uptake of cancer cells. The prepared near-infrared fluorescent probe (Met-NHs-AuNCs) can specifically recognize the overexpression of L-type amino acid transporter 1 (LAT1) in cancer cells so that it can show red fluorescence in cancer cells. Meanwhile, normal cells (H9c2) have no fluorescence. Conclusion: The fluorescent probe demonstrates the power of targeting and imaging cancer cells.

A study of the correlation between stroke and gut microbiota over the last 20years: a bibliometric analysis.

Purpose: This study intends to uncover a more thorough knowledge structure, research hotspots, and future trends in the field by presenting an overview of the relationship between stroke and gut microbiota in the past two decades. Method: Studies on stroke and gut microbiota correlations published between 1st January 2002 and 31st December 2021 were retrieved from the Web of Science Core Collection and then visualized and scientometrically analyzed using CiteSpace V. Results: A total of 660 papers were included in the study, among which the United States, the United Kingdom, and Germany were the leading research centers. Cleveland Clinic, Southern Medical University, and Chinese Academy of Science were the top three institutions. The NATURE was the most frequently co-cited journal. STANLEY L HAZEN was the most published author, and Tang WHW was the most cited one. The co-occurrence analysis revealed eight clusters (i.e., brain-gut microbiota axis, fecal microbiome transplantation, gut microbiota, hypertension, TMAO, ischemic stroke, neuroinflammation, atopobiosis). "gut microbiota," "Escherichia coli," "cardiovascular disease," "risk," "disease," "ischemic stroke," "stroke," "metabolism," "inflammation," and "phosphatidylcholine" were the most recent keyword explosions. Conclusion: Findings suggest that in the next 10 years, the number of publications produced annually may increase significantly. Future research trends tend to concentrate on the mechanisms of stroke and gut microbiota, with the inflammation and immunological mechanisms, TMAO, and fecal transplantation as hotspots. And the relationship between these mechanisms and a particular cardiovascular illness may also be a future research trend.

Pharmacokinetics and bioequivalence study of montelukast sodium oral soluble film and chewable tablet in healthy Chinese volunteers: randomized trials under fasting and fed conditions.

Background: The oral soluble film (OSF) is a new drug delivery system. Whether montelukast sodium OSF has similar pharmacokinetic (PK) properties and bioequivalence to chewable tablet (CT) should be investigated. Methods: This study, conducted at Haikou People's Hospital, consisted of two trials: a randomized, open-label, single-dose, 3-sequence, 3-period crossover trial under fasting conditions and a randomized, open-label, single-dose, 2-sequence, 2-period crossover trial under fed conditions. Healthy volunteers were randomized 1:1:1 to receive single-dose oral montelukast sodium OSF without water, OSF, or CT with water in the fasting trial, and 1:1 to receive OSF or CT with water in the fed trial in each period, with a 7-day washout period. Randomization was performed according to random number tables generated using computer. Blood samples were collected over a 24-h period. Plasma drug concentrations were tested using high-performance liquid chromatography-tandem mass spectrometry. The primary PK parameters were maximum plasma drug concentration (Cmax), area under the plasma drug concentration-time curve (AUC) from t=0 to the last quantifiable concentration (AUC0-t), and AUC from t=0 to infinity (AUC0-∞). The other PK parameters included time to Cmax (Tmax), terminal elimination rate constant (λz), and half-life (t1/2). Safety was also assessed. Analysis of variance on log-transformed primary PK parameters was applied to analyze the bioequivalence between the OSF and CT. The bioequivalence margin was 80-125%. Results: From November 2018 to January 2019, 30 subjects were included in each trial. The PK parameters between OSF and CT were numerically similar. All 90% confidence intervals (CIs) of the geometric mean ratio (GMR) for the primary PK parameters fell within 80-125%, confirming the bioequivalence of montelukast sodium OSF and CT under fasting and fed conditions. In the fasting trial, 6 (20%) adverse events (AEs) were reported, including 3 (10%) cases after OSF administration without water and 3 (10%) after OSF administration with water, with no serious AEs. No AEs were recorded in the fed trial. Conclusions: Montelukast sodium OSF is bioequivalent to CT, with acceptable safety. The OSF is an alternative option of CT. Trial Registration: ClinicalTrials.gov identifiers: NCT05528198 (the fasting trial) and NCT05531994 (the fed trial).

YihE is a novel binding partner of Rho and regulates Rho-dependent transcription termination in the Cpx stress response.

The conjugative pilus expression (Cpx) stress response system can sense cell envelope stressors, such as misfolded proteins, and upregulate proteases to modify or degrade damaged proteins. YihE is a protein kinase implicated in the Cpx system, and Rho is a transcription termination factor in prokaryotes, but no functional connection between YihE and Rho has been reported. Here, we found that YihE can interact with Rho to form a binary complex with a stoichiometric ratio of 6:1 (Rho:YihE). A low resolution of Rho crystal structure in the presence of YihE was determined. YihE overexpression helped lessen the aberrant effects caused by Rho overexpression, including long cell morphology and other Rho-mediated phenotypes. Overall, YihE is a Rho binding partner that acts as a Rho antagonist in the Cpx stress. YihE binding to Rho would compete RNA from binding to Rho, thereby helping bacteria cope with stress through the regulation of Rho-dependent transcription termination.

A comprehensive system review of pharmacological effects and relative mechanisms of Ginsenoside Re: Recent advances and future perspectives.

BACKGROUND: Ginsenoside Re (Re) belongs to protopanaxatriol saponins and exists in Panax ginseng, Panax quinquefolium, Panax notoginseng, and other plants in the Araliaceae family. Re has recently become a research focus owing to its pharmacological activities and benefits to human bodies. PURPOSE: To summarize recent findings regarding the pharmacological effects and mechanisms of Re and highlight and predict the potential therapeutic effects and systematic mechanism of Re. METHODS: Recent studies (2011-2021) on the pharmacological effects and mechanisms of Re were retrieved from Web of Science, PubMed, Google Scholar, Scopus, and Embase up to December 2021 using relevant keywords. Network pharmacology and bioinformatics analysis were used to predict the therapeutic effects and mechanisms of Re against potential diseases. RESULTS: Re presented a wide range of therapeutic and biological activities, including neuroprotective, cardiovascular, antidepressant, antitumorigenic, and others effects. The related pharmacological mechanisms of Re include the regulation of cholinergic and antioxidant systems in the brain; the induction of tumor cell apoptosis; the inhibition of tau protein hyperphosphorylation and oxidative stress; the activation of p38MAPK, ERK1/2, and JNK signals; the improvement of lipid metabolism; and the reduction of endothelial cell dysfunction. CONCLUSION: This paper summarizes comprehensively the current research progress of Re and provides new research insights into the therapeutic effects and mechanisms of Re against potential diseases.

LC_Glucose-Inhibited Division Protein Is Required for Motility, Biofilm Formation, and Stress Response in Lysobacter capsici X2-3.

Glucose-inhibited division protein (GidA) plays a critical role in the growth, stress response, and virulence of bacteria. However, how gidA may affect plant growth-promoting bacteria (PGPB) is still not clear. Our study aimed to describe the regulatory function of the gidA gene in Lysobacter capsici, which produces a variety of lytic enzymes and novel antibiotics. Here, we generated an LC_GidA mutant, MT16, and an LC_GidA complemented strain, Com-16, by plasmid integration. The deletion of LC_GidA resulted in an attenuation of the bacterial growth rate, motility, and biofilm formation of L. capsici. Root colonization assays demonstrated that the LC_GidA mutant showed reduced colonization of wheat roots. In addition, disruption of LC_GidA showed a clear diminution of survival in the presence of high temperature, high salt, and different pH conditions. The downregulated expression of genes related to DNA replication, cell division, motility, and biofilm formation was further validated by real-time quantitative PCR (RT-qPCR). Together, understanding the regulatory function of GidA is helpful for improving the biocontrol of crop diseases and has strong potential for biological applications.

The effectiveness of Tai Chi for postpartum depression: A protocol for systematic review and meta-analysis.

BACKGROUND: As a specific type of depression, postpartum depression (PPD) causes an adverse hazard to the mother's physical and mental health. Considering the safety requirements for lactation and the expectation of the rapid response to treatment, the search for safe and effective alternative therapies has attracted wide attention. Tai Chi, a traditional Chinese exercise therapy, has been widely used to relieve the symptoms and complications of patients with PPD, which the clinical efficacy is questioned. We conduct a comprehensive systematic review and meta-analysis to find clinical medical evidence of Tai Chi in the treatment of PPD. METHODS: PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, China Science, and Technology Journal Database and Chinese Biomedical Literature Database will be searched from their inception of databases to September 30, 2021. Two reviewers will select articles, extract data, and assess the risk of bias independently. Any disagreement will be resolved by discussion with the third reviewer. Review Manager 5.3 software will be used for data synthesis. The Cochrane risk of bias assessment tool will be used to assess the risk of bias. RESULTS: This study will conduct a comprehensive literature search and provide a systematic synthesis of current published data to explore the effectiveness of Tai Chi for PPD. CONCLUSIONS: The findings of our study will provide updated evidence to determine whether Tai Chi is an effective intervention for patients with PPD, which will help clinicians make a better alternative treatment schedule of PPD patients and provide a reliable basis for health-related policymakers. STUDY REGISTRATION NUMBER: CRD42021276676.

Ciclopirox and bortezomib synergistically inhibits glioblastoma multiforme growth via simultaneously enhancing JNK/p38 MAPK and NF-κB signaling.

Ciclopirox (CPX) is an antifungal drug that has recently been reported to act as a potential anticancer drug. However, the effects and underlying molecular mechanisms of CPX on glioblastoma multiforme (GBM) remain unknown. Bortezomib (BTZ) is the first proteasome inhibitor-based anticancer drug approved to treat multiple myeloma and mantle cell lymphoma, as BTZ exhibits toxic effects on diverse tumor cells. Herein, we show that CPX displays strong anti-tumorigenic activity on GBM. Mechanistically, CPX inhibits GBM cellular migration and invasion by reducing N-Cadherin, MMP9 and Snail expression. Further analysis revealed that CPX suppresses the expression of several key subunits of mitochondrial enzyme complex, thus leading to the disruption of mitochondrial oxidative phosphorylation (OXPHOS) in GBM cells. In combination with BTZ, CPX promotes apoptosis in GBM cells through the induction of reactive oxygen species (ROS)-mediated c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) signaling. Moreover, CPX and BTZ synergistically activates nuclear factor kappa B (NF-κB) signaling and induces cellular senescence. Our findings suggest that a combination of CPX and BTZ may serve as a novel therapeutic strategy to enhance the anticancer activity of CPX against GBM.

Acupuncture Reduces the Risk of Dysphagia in Stroke Patients: A Propensity Score-Matched Cohort Study.

Background: Post-stroke dysphagia (PSD) affects the quality of life in stroke patients, impairs their rehabilitation ability, and causes other complications following stroke. Currently, there is currently some understanding of PSD risk factors, but its protective factors remain largely unknown. Objective: To analyze the effects of acupuncture (AP) on dysphagia in stroke patients and explore its potential as a preventive therapy. Methods: Patients with a diagnosis of stroke from 2010 to 2019 were selected and followed until 2020, utilizing factors such as age, gender, stroke location, stroke type, and baseline comorbidity. To compare the incidence of dysphagia, equal numbers of stroke patients treated with and without AP (n = 1,809) were matched by 1:1 propensity scoring. The Cox proportional hazards model and Kaplan-Meier method were used to assess the risk of dysphagia as an outcome measure. Results: The stroke patients treated with AP had a lower risk of dysphagia after adjusting for age, gender, stroke location, stroke type, and baseline comorbidity [adjusted hazard ratio (AHR) = 0.43, 95% confidence interval = 0.37-0.49] compared with those in the non-AP cohort. AP also decreased the risk of PSD among different gender groups. The risk ratios were AHR = 0.45 and AHR = 0.33 for males and females, respectively. AP also reduced the risk for PSD among different age groups. The risk ratios were AHR = 0.20, AHR = 0.37, AHR = 0.41, and AHR = 0.45 for the 18-39, 40-59, 60-79, and >80 years-old groups. Regarding stroke types (ischemic, hemorrhagic, and mixed type), patients treated with AP had a lower risk (AHR = 0.47, 0.28 and 0.17, respectively). With respect to stroke location, the risk of PSD in AP-treated patients was decreased regardless of location: brain stem (AHR = 0.41), diencephalon (AHR = 0.13), or multiple lesions (AHR = 0.40), the risk of PSD in AP-treated patients was decreased. For all baseline comorbidities, AP attenuated the risk of dysphagia. The cumulative incidence of dysphagia was remarkably lower in the AP group than in the non-AP group (log-rank test, P = 0.000). Limitations: First, this was a single-center clinical retrospective study. Second, we did not classify the severity of stroke and dysphagia. Third, all data were extracted manually. Lastly, the sample size was relatively small. Thus, future studies with larger sample sizes are warranted to verify our findings. Conclusion: Acupuncture treatment attenuates the risk of dysphagia in stroke patients. Future research should increase the sample size and elaborate further on the details of the AP protocol.

In situ growth of M-{001}TiO2/Ti photoelectrodes: synergetic dominant {001} facets and ratio-optimal surface junctions for the effective oxidation of environmental pollutants.

We report a novel {001}TiO2/Ti photoelectrode by directly constructing "mirror-like" TiO2 microspheres on a Ti foil substrate (M-{001}TiO2/Ti). It presents highly enhanced PEC oxidation capability of DMP wastewater, which is mainly attributed to the significant synergetic effects of high exposure of {001} facets and equivalent {001}/{101} facet junctions.

Artemisinin suppresses hepatocellular carcinoma cell growth, migration and invasion by targeting cellular bioenergetics and Hippo-YAP signaling.

The primary liver cancer (PLC) is one of the leading causes of cancer-related death worldwide. The predominant form of PLC is hepatocellular carcinoma (HCC), which accounts for about 85% of all PLC. Artemisinin (ART) was clinically used as anti-malarial agents. Recently, it was demonstrated to inhibit cell growth and migration in multiple cancer types. However, the molecular mechanism underlying these anti-cancer activity remains largely unknown. Herein, it is discovered that ART dramatically suppresses HCC cell growth in vitro through arresting cell cycle progression, and represses cell migration and invasion via regulating N-cadherin-Snail-E-cadherin axis. In addition, the disruption of cellular bioenergetics contributed to ART-caused cell growth, migration and invasion inhibition. Moreover, ART (100 mg/kg, intraperitoneally) substantially inhibits HCC xenograft growth in vivo. Importantly, Hippo-YAP signal transduction is remarkably inactivated in HCC cells upon ART administration. Collectively, these data reveal a novel mechanism of ART in regulating HCC cell growth, migration, and invasion, which indicates that ART could be considered as a potential drug for the treatment of HCC.

Cobalt-Catalyzed Diastereoselective Difluoroalkylation/Giese Addition Domino Reactions.

An efficient cobalt-catalyzed difluoroalkylation/Giese radical conjugate cyclization manifold with various alkyne-tethered cyclohexadienones and halogenated fluorinating reagents was accomplished under remarkable mild reaction conditions, thus providing an expedient route to valuable fluorinated chromens. The utility of this transformation was demonstrated by high site selectivity as well as chemo- and diastereoselectivity, broad substrate scope, excellent functional group tolerance, and facile late-stage modification.

Copper(I)-Catalyzed Oxydifluoroalkylation of Alkenes: A Route to Functionalization of Lactones.

An efficient copper(I)-catalyzed oxydifluoroalkylation of unsaturated carboxylic acids has been developed under mild reaction conditions. Various α-bromodifluoromethyl substituted heterocycles, esters, amides, and ketones were successfully employed as the CF2 source. This cost-effective copper(I) catalysis provides expedient access to high valued lactones with ample substrate scope, wide functional group tolerance, and up to 98% yield.

Phosphorylation of bacterial L9 and its functional implication in response to starvation stress.

The bacterial L9 (bL9) protein expressed and purified from Escherichia coli is stably phosphorylated. We mapped seven Ser/Thr phosphorylation sites, all of which but one are located at the carboxyl-terminal domain (CTD). When a histidine tag is fused to the C-terminus, bL9 is no longer phosphorylated. Phosphorylation of bL9 causes complete disordering of its CTD and helps cell survival under nutrient-limiting conditions. Previous structural studies of the ribosome have shown that bL9 exhibits two distinct conformations, one of which competes with binding of RelA to the 30s rRNA and prevents RelA activation. Taken together, we suggest that the flexibility of the bL9 CTD enabled by phosphorylation would remove the steric hindrance, serving as a previously unknown mechanism to regulate RelA function and help cell survival under starvation stress.

Characterization of C-terminal structure of MinC and its implication in evolution of bacterial cell division.

Proper cell division at the mid-site of Gram-negative bacteria reflects stringent regulation by the min system (MinC, MinD and MinE). Herein we report crystal structure of the C-terminal domain of MinC from Escherichia coli (EcMinCCTD). The MinCCTD beta helical domain is engaged in a tight homodimer, similar to Thermotoga maritima MinCCTD (TmMinCCTD). However, both EcMinCCTD and TmMinCCTD lack an α-helix (helix3) at their C-terminal tail, in comparison to Aquifex aerolicu MinCCTD (AaMinCCTD) which forms an extra interaction interface with MinD. To understand the role of this extra binding element in MinC/MinD interactions, we fused this helix (Aahelix3) to the C-terminus of EcMinC and examined its effect on cell morphology and cell growth. Our results revealed that Aahelix3 impaired normal cell division in vivo. Furthermore, results of a co-pelleting assay and binding free energy calculation suggested that Aahelix3 plays an essential role in AaMinCD complex formation, under the circumstance of lacking MinE in A. aerolicu. Combining these results with sequence analysis of MinC and MinD in different organisms, we propose an evolutionary relationship to rationalize different mechanisms in cell division positioning in various organisms.

C-H Alkylations of (Hetero)Arenes by Maleimides and Maleate Esters through Cobalt(III) Catalysis.

Efficient cobalt(III)-catalyzed (hetero)aryl and alkenyl C-H hydroarylations of maleimides and maleate esters have been achieved under remarkably mild reaction conditions. Thus, the versatile cobalt(III) catalyst [Cp*CoI2(CO)] showed excellent atom-and step-economy as well as high chemo- and site-selectivity providing expedient access to pharmacologically useful succinimides with wide functional group tolerance.

Carboxylate-Enhanced Rhodium(III)-Catalyzed Aryl C-H Alkylation with Conjugated Alkenes under Mild Conditions.

Rhodium(III)-catalyzed C-H bond functionalization for the synthesis of ß-aryl aldehydes and ketones from (hetero)aryl oximes, pyri(mi)dine, as well as pyrazoles and α,ß-unsaturated carbonyl compounds has been developed under exceedingly mild reaction conditions. Thus, the versatile rhodium(III) catalysis features high step- and atom-economy, oxidant-free reaction conditions, and broad substrate scope.

Benefits of mobile reporting systems in social home care: the case of seven Swedish municipalities.

OBJECTIVES: Mobile systems are widely adopted in healthcare services. Mobile reporting systems have been recently introduced for social home care by municipalities in Sweden. The study aims to assess the benefits of using these systems. METHODS: We followed an expert survey approach. Data were collected by means of telephone interviews with the experts in charge of managing and implementing the systems at the municipalities. In addition, several workshops were organized for assessing the economic value of the systems at one municipality. We performed thematic analysis and cost-benefit analysis of the data. RESULTS: The thematic analysis showed the three main benefits of using the mobile reporting systems in social home care: municipal benefits, care providers' benefits, and care recipients' benefits. The cost-benefit analysis indicated that the systems could bring substantial long-term economic value for municipalities. The results also revealed the difficulties encountered at the early stage of the deployment and implementation of the systems. CONCLUSIONS: The mobile systems yield benefits for all the actors, that is, municipalities, care recipients and care providers. These enhance the public-private coordination and cooperation in social home care in Sweden. The municipalities are called upon to address change management and technical challenges in the implementation.

[Application of chemometrics in composition-activity relationship research of traditional Chinese medicine].

Chemometrics is a new branch of chemistry which is widely applied to various fields of analytical chemistry. Chemometrics can use theories and methods of mathematics, statistics, computer science and other related disciplines to optimize the chemical measurement process and maximize access to acquire chemical information and other information on material systems by analyzing chemical measurement data. In recent years, traditional Chinese medicine has attracted widespread attention. In the research of traditional Chinese medicine, it has been a key problem that how to interpret the relationship between various chemical components and its efficacy, which seriously restricts the modernization of Chinese medicine. As chemometrics brings the multivariate analysis methods into the chemical research, it has been applied as an effective research tool in the composition-activity relationship research of Chinese medicine. This article reviews the applications of chemometrics methods in the composition-activity relationship research in recent years. The applications of multivariate statistical analysis methods (such as regression analysis, correlation analysis, principal component analysis, etc. ) and artificial neural network (such as back propagation artificial neural network, radical basis function neural network, support vector machine, etc. ) are summarized, including the brief fundamental principles, the research contents and the advantages and disadvantages. Finally, the existing main problems and prospects of its future researches are proposed.