In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the re...In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.展开更多
Aim In order to improve the solubility of azithromycin, the objectives of the present study were to screen an appropriate salt for azithromycin by comparing acute hepatic and renal toxicities in animals, and study the...Aim In order to improve the solubility of azithromycin, the objectives of the present study were to screen an appropriate salt for azithromycin by comparing acute hepatic and renal toxicities in animals, and study the pharmacokinetics of final chosen azithromycin salt. Methods Various salts of azithromycin, such as glutamate, citrate, hydrochloride, sulphate, dihydrogen phosphate, lactobionate, tartrate, and aspartate were given intravenously to Sprague Dawley rats at a dose of 10 mg once daily for 14 consecutive days via tail vein. The acute hepatic and renal indicators were measured before and after administration. A pharmacokinetic study was performed on 12 healthy human volunteers. The subjects were equally divided into two groups by a randomized crossover design. Azithromycin glutamate injection was administered by intravenous infusion or intramuscular injection at a single dose of 500 mg, respectively. Azithromycin concentrations in plasma were determined by microbial inhibition zone assay, and the pharmacokinetic parameters were calculated using a practical pharmacokinetic software 3P87 program. Results Azithromycin glutamate was least toxic to the liver and kidney of the rats, thus being selected as a final salt for parenteral preparation of azithromycin. Pharmacokinetic results showed that the area under the plasma concentration-time curves （AUC0-120h） were 21.47 ± 1.57 h·μg·mL^-1 for intravenous infusion, and 19.36 ± 2.44 h·μg·mL^-1 for intramuscular injection. The absolute bioavailability of intramuscular injection was 92.59%. Conclusion Azithromycin glutamate is suitable for the future clinical application, and its pharmacokinetics is characterized in human volunteers in the present study.展开更多
Models for diseases spreading are not just limited to SIS or SIR. For instance, for the spreading of AIDS/HIV, the susceptible individuals can be classified into different cases according to their immunity, and simila...Models for diseases spreading are not just limited to SIS or SIR. For instance, for the spreading of AIDS/HIV, the susceptible individuals can be classified into different cases according to their immunity, and similarly, the infected individuals can be sorted into different classes according to their infectivity. Moreover, some diseases may develop through several stages. Many authors have shown that the individuals＇ relation can be viewed as a complex network. So in this paper, in order to better explain the dynamical behavior of epidemics, we consider different epidemic models on complex networks, and obtain the epidemic threshold for each ease. Finally, we present numerical simulations for each case to verify our results.展开更多
AIM:To characterise the viral kinetics of enterovirus 71 (EV71).METHODS:In this study,human rhabdomyosarcoma (RD) cells were infected with EV71 at different multiplicity of infection (MOI).After infection,the cytopath...AIM:To characterise the viral kinetics of enterovirus 71 (EV71).METHODS:In this study,human rhabdomyosarcoma (RD) cells were infected with EV71 at different multiplicity of infection (MOI).After infection,the cytopathic effect (CPE) was monitored and recorded using a phase contrast microscope associated with a CCD camera at different time points post viral infection (0,6,12,24 h post infection).Cell growth and viability were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in both EV71 infected and mock infected cells at each time point.EV71 replication kinet-ics in RD cells was determined by measuring the total intracellular viral RNA with real-time reverse-transcription polymerase chain reaction (qRT-PCR).Also,the intracellular and extracellular virion RNA was isolated and quantified at different time points to analyze the viral package and secretion.The expression of viral protein was determined by analyze the levels of viral structure protein VP1 with Western blotting.RESULTS:EV71 infection induced a significant CPE as early as 6 h post infection (p.i.) in both RD cells infected with high ratio of virus (MOI 10) and low ratio of virus (MOI 1).In EV71 infected cells,the cell growth was inhibited and the number of viable cells was rapidly decreased in the later phase of infection.EV71 virions were uncoated immediately after entry.The intracellular viral RNA began to increase at as early as 3 h p.i.and the exponential increase was found between 3 h to 6 h p.i.in both infected groups.For viral structure protein synthesis,results from western-blot showed that intracellular viral protein VP1 could not be detected until 6 h p.i.in the cells infected at either MOI 1 or MOI 10;and reached the peak at 9 h p.i.in the cells infected with EV71 at both MOI 1 and MOI 10.Simultaneously,the viral package and secretion were also actively processed as the virus underwent rapid replication.The viral package kinetics was comparable for both MOI 1 and MOI 10 infected groups.It was observed that at 3 h p.i,the intracellular virions obviously decreased,thereafter,the intracellular virions began to increase and enter into the exponential phase until 12 h p.i.The total amounts of intracellular virons were decreased from 12 to 24 h p.i.Consistent with this result,the increase of virus secretion occurred during 6 to 12 h p.i.CONCLUSION:The viral kinetics of EV71 were established by analyzing viral replication,package and secretion in RD cells.展开更多
In the past 15 years, we have seen few therapeutic advances for patients with pancreatic cancer, which is the fourth leading cause of cancer-related death in the United States. Currently, only about 6% of patients wit...In the past 15 years, we have seen few therapeutic advances for patients with pancreatic cancer, which is the fourth leading cause of cancer-related death in the United States. Currently, only about 6% of patients with advanced disease respond to standard gemcitabine therapy, and median survival is only about 6 mo. Moreover, phase Ⅲ trials have shown that adding various cytotoxic and targeted chemotherapeutic agents to gemcitabine has failed to improve overall survival, except in cases in which gemcitabine combined with erlotinib show minimal survival benefi t. Several metaanalyses have shown that the combination of gemcitabine with either a platinum analog or capecitabine may lead to clinically relevant survival prolongation, especially for patients with good performance status. Meanwhile, many studies have focused on the pharmacokinetic modulation of gemcitabine by fi xed-dose administration, and metabolic or transport enzymes related to the response and toxicity of gemcitabine. Strikingly, a phase Ⅲ trial in 2010 showed that, in comparison to gemcitabine alone, the FOLFIRINOX regimen in patients with advanced disease and good performance status, produced better median overall survival, median progression-free survival, and objective response rates. This regimen also resulted in greater, albeit manageable toxicity.展开更多
The Pharmacokinetics informations of aminoglycosides, their monograph and clinical Pharmacokinetics parameters are reported in this review. The Aminoglycosides are highly polarity and in reserve for serious infections...The Pharmacokinetics informations of aminoglycosides, their monograph and clinical Pharmacokinetics parameters are reported in this review. The Aminoglycosides are highly polarity and in reserve for serious infections caused by aerobic gram negative bacteria and some gram positive bacteria but their toxicity are major limitations in clinical use.展开更多
Coxsackievirus A16(CVA16),together with enterovirus type 71(EV71),is responsible for most cases of hand,foot and mouth disease(HFMD) worldwide.Recent findings suggest that the recombination between CVA16 and EV71,and ...Coxsackievirus A16(CVA16),together with enterovirus type 71(EV71),is responsible for most cases of hand,foot and mouth disease(HFMD) worldwide.Recent findings suggest that the recombination between CVA16 and EV71,and the co-circulation of these two viruses may have contributed to the increase of HFMD cases in China over the past few years.It is therefore important to further understand the virology,epidemiology,virus-host interactions and host pathogenesis of CVA16.In this study,we describe the viral kinetics of CVA16 in human rhabdomyosarcoma(RD) cells by analyzing the cytopathic effect(CPE),viral RNA replication,viral protein expression,viral RNA package and viral particle secretion in RD cells.We show that CVA16 appears to first attach,uncoat and enter into the host cell after adsorption for 1 h.Later on,CVA16 undergoes rapid replication from 3 to 6 h at MOI 1 and until 9 h at MOI 0.1.At MOI 0.1,CVA16 initiates a secondary infection as the virions were secreted before 9 h p.i.CPE was observed after 12 h p.i.,and viral antigen was first detected at 6 h p.i.at MOI 1 and at 9 h p.i.at MOI 0.1.Thus,our study provides important information for further investigation of CVA16 in order to better understand and ultimately control infections with this virus.展开更多
文摘In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.
文摘Aim In order to improve the solubility of azithromycin, the objectives of the present study were to screen an appropriate salt for azithromycin by comparing acute hepatic and renal toxicities in animals, and study the pharmacokinetics of final chosen azithromycin salt. Methods Various salts of azithromycin, such as glutamate, citrate, hydrochloride, sulphate, dihydrogen phosphate, lactobionate, tartrate, and aspartate were given intravenously to Sprague Dawley rats at a dose of 10 mg once daily for 14 consecutive days via tail vein. The acute hepatic and renal indicators were measured before and after administration. A pharmacokinetic study was performed on 12 healthy human volunteers. The subjects were equally divided into two groups by a randomized crossover design. Azithromycin glutamate injection was administered by intravenous infusion or intramuscular injection at a single dose of 500 mg, respectively. Azithromycin concentrations in plasma were determined by microbial inhibition zone assay, and the pharmacokinetic parameters were calculated using a practical pharmacokinetic software 3P87 program. Results Azithromycin glutamate was least toxic to the liver and kidney of the rats, thus being selected as a final salt for parenteral preparation of azithromycin. Pharmacokinetic results showed that the area under the plasma concentration-time curves （AUC0-120h） were 21.47 ± 1.57 h·μg·mL^-1 for intravenous infusion, and 19.36 ± 2.44 h·μg·mL^-1 for intramuscular injection. The absolute bioavailability of intramuscular injection was 92.59%. Conclusion Azithromycin glutamate is suitable for the future clinical application, and its pharmacokinetics is characterized in human volunteers in the present study.
基金Supported by the Foundation of Anhui Education Bureau under Grant No.KJ2007A003the Natural Science Foundation of Anhui,China under Grant No.070416225+2 种基金a Grant from the Health,Welfare and Food Bureau of the Hong Kong SAR GovernmentNSFC under Grant No.10672146supported by Shanghai Leading Academic Discipline Project,Project Number:S30104
文摘Models for diseases spreading are not just limited to SIS or SIR. For instance, for the spreading of AIDS/HIV, the susceptible individuals can be classified into different cases according to their immunity, and similarly, the infected individuals can be sorted into different classes according to their infectivity. Moreover, some diseases may develop through several stages. Many authors have shown that the individuals＇ relation can be viewed as a complex network. So in this paper, in order to better explain the dynamical behavior of epidemics, we consider different epidemic models on complex networks, and obtain the epidemic threshold for each ease. Finally, we present numerical simulations for each case to verify our results.
基金Supported by Research Grant Council (RGC,CUHK4428/06M)a commissioned grant of the Research Fund for Control of Infectious Diseases (CU-09-02-02)Food and Health Bureau,the Government of Hong Kong Special Administration Region (HKSAR)
文摘AIM:To characterise the viral kinetics of enterovirus 71 (EV71).METHODS:In this study,human rhabdomyosarcoma (RD) cells were infected with EV71 at different multiplicity of infection (MOI).After infection,the cytopathic effect (CPE) was monitored and recorded using a phase contrast microscope associated with a CCD camera at different time points post viral infection (0,6,12,24 h post infection).Cell growth and viability were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in both EV71 infected and mock infected cells at each time point.EV71 replication kinet-ics in RD cells was determined by measuring the total intracellular viral RNA with real-time reverse-transcription polymerase chain reaction (qRT-PCR).Also,the intracellular and extracellular virion RNA was isolated and quantified at different time points to analyze the viral package and secretion.The expression of viral protein was determined by analyze the levels of viral structure protein VP1 with Western blotting.RESULTS:EV71 infection induced a significant CPE as early as 6 h post infection (p.i.) in both RD cells infected with high ratio of virus (MOI 10) and low ratio of virus (MOI 1).In EV71 infected cells,the cell growth was inhibited and the number of viable cells was rapidly decreased in the later phase of infection.EV71 virions were uncoated immediately after entry.The intracellular viral RNA began to increase at as early as 3 h p.i.and the exponential increase was found between 3 h to 6 h p.i.in both infected groups.For viral structure protein synthesis,results from western-blot showed that intracellular viral protein VP1 could not be detected until 6 h p.i.in the cells infected at either MOI 1 or MOI 10;and reached the peak at 9 h p.i.in the cells infected with EV71 at both MOI 1 and MOI 10.Simultaneously,the viral package and secretion were also actively processed as the virus underwent rapid replication.The viral package kinetics was comparable for both MOI 1 and MOI 10 infected groups.It was observed that at 3 h p.i,the intracellular virions obviously decreased,thereafter,the intracellular virions began to increase and enter into the exponential phase until 12 h p.i.The total amounts of intracellular virons were decreased from 12 to 24 h p.i.Consistent with this result,the increase of virus secretion occurred during 6 to 12 h p.i.CONCLUSION:The viral kinetics of EV71 were established by analyzing viral replication,package and secretion in RD cells.
文摘In the past 15 years, we have seen few therapeutic advances for patients with pancreatic cancer, which is the fourth leading cause of cancer-related death in the United States. Currently, only about 6% of patients with advanced disease respond to standard gemcitabine therapy, and median survival is only about 6 mo. Moreover, phase Ⅲ trials have shown that adding various cytotoxic and targeted chemotherapeutic agents to gemcitabine has failed to improve overall survival, except in cases in which gemcitabine combined with erlotinib show minimal survival benefi t. Several metaanalyses have shown that the combination of gemcitabine with either a platinum analog or capecitabine may lead to clinically relevant survival prolongation, especially for patients with good performance status. Meanwhile, many studies have focused on the pharmacokinetic modulation of gemcitabine by fi xed-dose administration, and metabolic or transport enzymes related to the response and toxicity of gemcitabine. Strikingly, a phase Ⅲ trial in 2010 showed that, in comparison to gemcitabine alone, the FOLFIRINOX regimen in patients with advanced disease and good performance status, produced better median overall survival, median progression-free survival, and objective response rates. This regimen also resulted in greater, albeit manageable toxicity.
文摘The Pharmacokinetics informations of aminoglycosides, their monograph and clinical Pharmacokinetics parameters are reported in this review. The Aminoglycosides are highly polarity and in reserve for serious infections caused by aerobic gram negative bacteria and some gram positive bacteria but their toxicity are major limitations in clinical use.
基金Partly supported by the National Natural Science Foundation of China (No. 20872048)
文摘Coxsackievirus A16(CVA16),together with enterovirus type 71(EV71),is responsible for most cases of hand,foot and mouth disease(HFMD) worldwide.Recent findings suggest that the recombination between CVA16 and EV71,and the co-circulation of these two viruses may have contributed to the increase of HFMD cases in China over the past few years.It is therefore important to further understand the virology,epidemiology,virus-host interactions and host pathogenesis of CVA16.In this study,we describe the viral kinetics of CVA16 in human rhabdomyosarcoma(RD) cells by analyzing the cytopathic effect(CPE),viral RNA replication,viral protein expression,viral RNA package and viral particle secretion in RD cells.We show that CVA16 appears to first attach,uncoat and enter into the host cell after adsorption for 1 h.Later on,CVA16 undergoes rapid replication from 3 to 6 h at MOI 1 and until 9 h at MOI 0.1.At MOI 0.1,CVA16 initiates a secondary infection as the virions were secreted before 9 h p.i.CPE was observed after 12 h p.i.,and viral antigen was first detected at 6 h p.i.at MOI 1 and at 9 h p.i.at MOI 0.1.Thus,our study provides important information for further investigation of CVA16 in order to better understand and ultimately control infections with this virus.
