Biomedical subjects
Publications and source records attributed to Ke Li.
[reaction: see text] Titration of porphyrin-fullerene rotaxanes with DABCO or 4,4'-bipyridine led to photo- and redoxactive catenanic architectures, which upon photoexcitation undergo a sequence of short-range energy and electron transfer events to give a long-lived charge-separated radical-pair state.
A series of Sauvage-type rotaxanes containing [60]fullerene and tetraarylporphyrin moieties has been synthesized by a convergent route. Photoinduced energy-transfer and electron-transfer reactions in these rotaxanes yield long-lived change-separated states, in agreement with the large distance between the fullerene and porphyrin chromophores.
Following a detailed study, a reversed-phase high performance liquid chromatographic method (HPLC) has been developed and validated for analysis of three bioactive alkaloids, matrine, sophoridine and oxymatrine, in Sophora flavescens Ait. HPLC separation of the alkaloids was performed on a Kromasil C(18) column and detected by ultraviolet absorbance at 208 nm. The column temperature was maintained at 40 degrees C. A mobile phase composed of 0.01 mol/L KH(2)PO(4) buffer-methanol-triethylamine in the ratios 94:6:0.01 (v/v) was found to be the most suitable for this separation at a fl ow-rate of 1.0 mL/min and enabled the baseline separation of the three analytes free from interferences with isocratic elution. The analysis time was 24 min per injection. The calibration was linear in the range of 0.2-120.0 micro g/mL for matrine, 0.2-115.2 micro g/mL for sophoridine and 0.2-110.4 micro g/mL for oxymatrine, respectively. For assaying Sophora Flavescens Ait. samples, the relative standard deviations were 2.0% for matrine, 2.8% for sophoridine and 1.8% for oxymatrine analysis. The average recoveries of matrine, sophoridine and oxymatrine were 93.9, 95.3 and 93.5% for the Sophora flavescens Ait. samples, respectively. The method has been successfully applied to the simultaneous determination of matrine, sophoridine and oxymatrine in Sophora Flavescens Ait. samples collected in different habitats.
Nucleotide triphosphate alpha-(4-azidophenyl)-1,N6-etheno-dATP 3 and its monophosphate 3m were synthesized by condensation of 2-halo-2-(4-azidophenyl)acetaldehyes with dATP and dAMP, respectively. Structure analysis shows that the azidophenyl side chain is attached to the alpha-position of the etheno ring (i.e., the carbon attached to N1 of the purine), and conformation calculations show minima in the etheno-phenyl bond rotation at 50 and 130 degrees where the bulk of the phenyl ring projects out from the plane of the etheno group. Like DNA Pol inhibitor 2-(4-azidophenacyl)thio-2'-deoxyadenosine 5'-triphosphate 1, nucleotide 3 is a template-competitive DNA polymerase inhibitor (TCPI), with a competitive Ki for Pol I KF of 3.41 microM, but has only weak activity as an HIV RT inhibitor relative to the template-competitive reverse transcriptase inhibitor 2-(4-azidophenacyl)thio-1,N6-etheno-2'-deoxyadenosine 5'-triphosphate 2. Additionally, 3 photoinactivates KF in a time-dependent manner, confirming the kinetic data that 3 binds to the free form of KF. The TCPI activity of 3 provides evidence for an extended side chain conformational preference in the combined substrate polymerase inhibitors.
Previous studies showed that sodium ferulate, the effective component of Chinese herb, can inhibit platelet aggregation and decrease serum lipid. However, it is still unknown if sodium ferulate could prevent atherosclerogenesis. The experiments were designed to study its effects and mechanisms on atherosclerogenesis. Blood samples and thoracic aortas obtained from Japanese rabbits fed by high-lipid or high-lipid plus sodium ferulate forage were analyzed and compared. Simultaneously, vascular endothelial cells were cultured and treated by hyperlipidemic serum solely or plus sodium ferulate. Cellular ultrastructure, nitric oxide (NO) production, and cytokines expressions were studied and compared. In vivo experiment, aorta atherosclerotic plaque area of sodium ferulate-treated rabbits was much smaller than that of high-lipid-fed rabbits and serum triglyceride was correlated positively with the plaque area in both groups. In vitro, endothelial cells incubated with hyperlipidemic serum exhibited pronounced ultrastructural abnormalities, transforming growth factor beta1 expression and NO release were significantly decreased, while basic fibroblast growth factor expression was increased. Interestingly, the treatment group results clearly demonstrated that sodium ferulate was effective to protect cells from detrimental effects of hyperlipidemic serum and to help maintain normal NO and cytokines expressions. We concluded that sodium ferulate could inhibit rabbit aorta atherosclerogenesis, possibly through decreasing the serum lipid concentration and preventing vascular endothelial cells from the injury of hyperlipidemic serum.
Tissue expression of C3 is an unexpected regulator of the alloimmune response in mouse kidney transplantation. It is unclear, however, whether a direct or an indirect action of complement on the host immune response is involved. Also unknown is which of the complement effector products, cleaved C3, cleaved C5, or C5b-9, is responsible. Proximal tubular epithelial cells (PTEC) not only constitute a major target of the alloimmune response but also produce substantial amounts of C3. This study investigated the property of mouse PTEC to stimulate alloreactive T cells in a complement-dependent manner. The proliferative and cytokine responses of primed alloreactive T cells were measured after exposure to donor-specific PTEC that had been pretreated with normal mouse serum, heat-inactivated mouse serum, or complement- deficient (C3, C5, or C6) mouse sera to differentially deposit complement components. PTEC were able to stimulate alloreactive T cells in an antigen-specific manner. Complement activation leading to the deposition of cleaved C3 on PTEC enhanced the alloreactive T cell response. This complement-mediated stimulation of the T cell response was dependent on C3 but not on C5 or C6. The primary influence of tissue-bound complement was on CD4(+) T cells. Moreover, the effect of complement on alloreactive T cells was B7 dependent, shown by inhibition studies with CTLA4-Ig. These results suggest that donor epithelium-bound C3 can upregulate the alloimmune response. It is postulated that surface-bound C3 interacts with complement receptors on alloreactive T cells or on antigen presenting cells to increase allo-immune stimulation.
Recombinant DNA technologies enable the direct isolation and expression of novel genes from biotopes containing complex consortia of uncultured microorganisms. In this study, genomic libraries were constructed from microbial DNA isolated from insect intestinal tracts from the orders Isoptera (termites) and Lepidoptera (moths). Using a targeted functional assay, these environmental DNA libraries were screened for genes that encode proteins with xylanase activity. Several novel xylanase enzymes with unusual primary sequences and novel domains of unknown function were discovered. Phylogenetic analysis demonstrated remarkable distance between the sequences of these enzymes and other known xylanases. Biochemical analysis confirmed that these enzymes are true xylanases, which catalyze the hydrolysis of a variety of substituted beta-1,4-linked xylose oligomeric and polymeric substrates and produce unique hydrolysis products. From detailed polyacrylamide carbohydrate electrophoresis analysis of substrate cleavage patterns, the xylan polymer binding sites of these enzymes are proposed.
OBJECTIVE: To screen and identify the protein interacting with HBV antigen in hepatocytes. Then investigate the biological functions of hepatitis B virus antigen in the pathogenesis of hepatitis B and seek effective methods to prevent and treat it. METHODS: The yeast two-hybrid system-3 technique was used to construct HBV PreS2, HBeAg, HBcAg, HBxAg bait plasmids. The bait plasmids transformed the yeast AH109 and expressed themselves in it. After being identified by SDS-PAGE and Western blot, the AH109 yeast was mated with yeast Y187 containing liver cDNA library plasmid in 2 x YPDA medium to form diploid yeast and was then plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-alpha-gal for screening. Plasmids of blue colonies were extracted and transformed into Escherichia coli, then analyzed by DNA sequencing and bioinformatics. To further prove the interaction between HBV antigen and metallothionein, translation was performed by using reticulocyte lysate and coimmunoprecipitation was displayed in vitro. RESULTS: Genes coding for HBV antigen binding protein were successfully cloned and metallothionein was found in that protein. The interaction between HBeAg, HBcAg and HBxAg and metallothionein were further proved by coimmunoprecipitation in vitro. CONCLUSION: The interaction between HBV antigen and metallothionein indicates that metallothionein may participate in the pathogenesis of hepatitis B
OBJECTIVE: To evaluate the efficacy of L-carnitine on asthenospermia with epididymal knob. METHODS: Thirty-five patients aged 25-39 years with asthenospermia with epididymal knob were received at our clinic of andrology from May 2003 to July 2004, and given oral L-carnitine 2 g/d for 3 months. The sperm parameters of the patients were analyzed by computer-assisted sperm analysis system before and after L-carnitine treatment. RESULTS: Of the 32 patients who accomplished the 3-month L-carnitine therapy, only 4 remained unimproved in sperm parameters, while the other 28 were significantly improved in sperm concentration, forward sperm motility, total sperm motility, straight line velocity, curvilinear velocity and average path velocity. Four of the patients wives were pregnant and one patient fathered a child. CONCLUSION: Oral L-carnitine therapy is efficacious for asthenospermia with epididymal knob.
BACKGROUND: Budd-Chiari syndrome (BCS) is an uncommon disorder caused by the obstruction of hepatic venous outflow and/or the inferior vena cava. Major therapeutic approaches include operation and radiological intervention. This study was conducted to investigate the treatment of severe BCS. METHODS: The clinical data of 147 patients with severe BCS who had been treated at our hospital from November 1994 to December 2003 were retrospectively analyzed. RESULTS: One hundred twenty-one patients with BCS underwent surgery, including mesocaval C type shunt with artificial graft (82 patients), splenojugular shunt (37), mesojugular shunt (2), percutaneous transhepatic recanalization and dilatation and/or stent placement of the main hepatic vein (MHV) (12), and combined percutaneous transhepatic angioplasty (PTA) and stent placement of the inferior vena cava and mesocaval shunt (14). Follow-up for 6-108 months showed excellent results in 102 patients (69.4%), good results in 40 (27.2%), and 5 deaths. CONCLUSION: Good results could be obtained in most of patients with BCS after different surgical treatments according to the pathological changes of the IVC and MHV.
BACKGROUND: Portal hypertension is a common disease. The surgical therapy of this disease focuses on the resultant upper digestive tract bleeding, which can imperil patients' life directly. This study was to evaluate the effect of triplex operation (mesocaval C shunt with artificial graft, ligation of the coronary vein and splenic artery) on portal hypertension and its associated upper digestive tract bleeding. METHODS: A retrospective study was made on clinical data of 140 patients undergoing triplex operation, who had suffered from portal hypertension and upper digestive tract bleeding. RESULTS: Postoperative portal pressure was 25-43 cmH2O(preoperative portal pressure 27-45 cmH2O) with the average reduction of 10 cmH2O. One patient (0.7%) died of cerebrovascular disease. Five patients (3.5%) suffered from mild hepatic encephalopathy, which was ameliorated through conservative treatment. Lymphatic fistula occurred in 3 patients (2.1%) who recovered without treatment 5, 10 days and 3 months after operation respectively. One hundred patients were followed up for 1 month to 6 years without recurrent hemorrhage or hepatic encephalopathy. Hypersplenism and ascites disappeared in 70 patients (70%) and 80 patients (80%) respectively. A significant reduction of ascites was seen in 12 patients(12%). The artificial vessels remained unblocking detected by B type ultrasonography and Doppler sonography in 95 patients(95%). CONCLUSION: Triplex operation is suitable for patients with the following portal hypertensions: portal hypertension caused by simple occlusion of the hepatic vein (a pathological type of Budd-Chiari syndrome); thrombosis of the portal vein or prehepatic portal hypertension because of cavernous transformation; intrahepatic portal hypertension with rebleeding after splenectomy or non-operation, and those patients with liver function in grade A or B according to the Child-Pugh classification.
A simple and reliable high performance liquid chromatographic (HPLC) method has been developed and validated for the analysis of malondialdehyde (MDA) in human seminal plasma. After human seminal plasma was hydrolyzed, MDA, one of the hydrolysis products, reacted with thiobarbituric acid (TBA) to form MDA (TBA)2, a red-colored adduct with a maximum absorbance at 532 nm. HPLC separation of the adduct in human seminal plasma was performed on a Lichrospher C18 column. A mobile phase composed of 0.025 mol/L KH2PO4 (pH 6.2)-methanol in 58:42 (v/v) was found to be the most suitable ratio for this separation at a flow rate of 1.0 mL/min and enabled the baseline separation of the adduct with isocratic elution. Under the chromatographic conditions described, the MDA-TBA adduct had a retention time of approximately 4 min, and good separation and detectability of MDA in human seminal plasma samples were obtained. The method proved to be linear in the range of MDA from 0.10 micromol/L to 2.50 micromol/L. The relative standard deviations of MDA analysis within- and between-assay were 3.1% (n = 7) and 3.8% (n = 5), respectively. The average recoveries were 90.0% -98.8% for the human seminal plasma samples. The method has been successfully applied to the study of male infertility induced by overproduction of lipid peroxidation in male reproductive system. Exception of obstructive azoospermic group, MDA concentrations of seminal plasma in control group made very significant difference from those in other infertile groups (P < 0.01).
Zeeman split takes place for the hyperfine level structure of neutral atoms where magnetic field exists. In addition, being excited by right circularly polarized light and left circularly polarized light, atoms obey different transition rules. So, the absorption peak between the hyperfine Zeeman level shifts with respect to the absorption peak without magnetic field. Accordingly, the authors demonstrated a kind of simple and flexible method to stabilize the frequency of diode laser. The linewidth of diode laser was reduced to less than 1 MHz using this method. Through analyzing the experiment results, the authors found that when the sum of both shifts of the hyperfine level of atoms excited by right circularly polarized light and left circularly polarized light was equal to the FWHM (Full Width at Half Maximum) of the saturated absorption peak, the laser frequency was stabilized best.
OBJECTIVE: To explore genetic polymorphisms CCR5 of HIV coreceptor and CCR2 in Chinese Yi Ethnic group in Sichuan. METHODS: Genomic DNA samples were obtained from 119 healthy individuals and 88 HIV-1 infected individuals of Chinese Yi Ethnic group in Sichuan. Polymerase chain reaction (PCR), cloning and gene sequencing techniques were employed to identify the genotype of CCR5Delta32; PCR-restriction fragment length polymorphism (RFLP) and gene sequencing were employed to identify the CCR2-64I alleles. RESULTS: At CCR5 locus, 2 heterozygotes (CCR5-wt/Delta32) and none homozygote (CCR5-Delta32/Delta32) were observed in 119 healthy individuals, allelic frequency of CCR5-Delta32 was 0.84%; No mutant was found in 88 HIV-1 infected individuals. At CCR2 locus, 26 heterozygotes (CCR2-64V/64I) and two homozygotes (CCR2-64I/64I) were observed in healthy individuals but the allelic frequency CCR2-64I was 12.61%. Among infected individuals, 12 heterozygotes (CCR2-64V/64I) and 7 homozygotes (CCR2-64I/64I) were observed and the allelic frequency CCR2-64I was 13.27%. Statistical analysis revealed that the differences of both loci between healthy and infected individuals were insignificant. Both loci were consistent with the Hardy-Weinberg equilibrium in the two different groups. CONCLUSION: The polymorphism of CCR5Delta32 and CCR2-64I alleles from Chinese Yi Ethnic group was detected which was of significance for the evaluation of genetic resistance to HIV-1 infection in Chinese population.
A validated high-performance liquid chromatography method is described for the determination of scutellarin in rat plasma using a liquid-liquid extraction and ultraviolet (UV) absorbance detection. The separation used a Diamonsil ODS column (250 mm x 4.6mm i.d., 5 microm particle size) with an isocratic mobile phase consisting of methanol-acetonitrile-50mM dihydrogen ammonium phosphate buffer (22:15:63 (v/v/v), adjusted to pH 2.5 with 1M phosphoric acid). The ultraviolet detector operated at 335 nm. Plasma samples were extracted with ethyl acetate after acidification. The extraction recovery of scutellarin ranged from 68.1 to 80.5%. High selectivity and a low quantitation limit (0.050 microg/ml) were achieved. The linear range was 0.050-12.5 microg/ml, correlation coefficient r=0.9981. The method has a good reproducibility, R.S.D. values were below 7.9% for within-day and between-day precision. The method is simple, rapid, and applicable to preliminary pharmacokinetic studies of scutellarin in rats.
Erythroid progenitor cell expansion depends upon co-signaling by Epo receptor (EpoR) and Kit, but underlying mechanisms are incompletely understood. To quantitatively analyze EpoR contributions to co-signaling, phosphotyrosine (Tyr(P)) mutants were expressed as human epidermal growth factor (hEGF) receptor-mEpoR EE chimeras at matched and physiological levels in FDCW2 hematopoietic progenitor cells and were assayed for proliferative activities in the absence or presence of endogenous Kit stimulation. Two Tyr(P)-null (but Jak2-coupled) EpoR forms each retained <or=25% of the wild-type activity, whereas the add-back of single Tyr(P) sites in the EpoR forms EE-T-Y343 (Stat5 binding site), EE-Y479 (p85/phosphatidylinositol 3-kinase binding site), or EE-Y464 (Src kinase binding site) significantly enhanced activities (to 100, 95, and 50% of EE-WT (wild type) levels, respectively). EE-Y343&Y401 and EEF343&F401 double add-back and deletion constructs were also prepared and were shown to possess 90 and <or=50% of wild-type activity. In contrast, efficient Kit co-signaling activity was retained only by EE-T-Y343 and EE-Y343&Y401 EpoR forms. EE-T-Y343 together with EE-T-Y343F and EE-WT EpoR forms were also analyzed in embryonic stem cell-derived erythroid G1E-2 cells with highly comparable outcomes, including the ability of EE-T-Y343 (but not EE-T-Y-343F) to synergize with Kit. Despite specific connection of EE-T-Y343 to Stat5, the contributions of Kit to EpoR-dependent proliferation did not involve Kit effects on Stat5 activation (but was limited by the mutation of Kit Tyr(P)-567 and Tyr(P)-569 Src kinase recruitment sites). Instead, co-signaling appears to depend upon the downstream integration of Kit signals with the targets of an EpoR/Jak2/Y343/Stat 5 response axis.
Signals provided by the erythropoieitin receptor (EpoR) are required for erythroid development beyond the erythroid colony-forming unit (CFU-e) stage and are propagated via the EpoR-tethered Janus kinase, JAK2. JAK2 functions, in part, to phosphorylate 8 conserved EpoR phosphotyrosine (PY) sites for the binding of a diverse set of signaling factors. However, recent studies in transgenic and knock-in mice have demonstrated substantial bioactivity for PY-null EpoR forms. Presently, the activities of a PY-null EpoR-HM form in primary progenitor cells from knock-in mice were further assessed using optimized Epo dose-dependent proliferation, survival, and differentiation assays. As compared with the wild-type (wt)-EpoR, EpoR-HM activity was compromised several-fold in each context when Epo was limited to physiologic concentrations. Possible compensatory increases in serum growth factor levels also were investigated, and as assayed using embryonic stem (ES) cell-derived erythroid G1E2 cells, activities in serum from EpoR-HM mice were substantially elevated. In addition, when challenged with phenylhydrazine-induced anemia, EpoR-HM mice failed to respond with efficient splenic stress erythropoiesis. Thus, the function of this JAK2-coupled but minimal PY-null EpoR-HM form appears to be attenuated in several contexts and to be assisted in vivo by compensatory mechanisms. Roles normally played by EpoR PY sites and distal domains therefore should receive continued attention.
A simple and sensitive reversed-phase high performance liquid chromatographic method (HPLC) has been developed and validated for the routine analysis of diltiazem in human plasma and the study of the pharmacokinetics of the drug in the human body. Diltiazem and diazepa (internal standard) were extracted with a mixed organic solution of hexane, chloroform and isopropanol (60:40:5, v/v/v), and then HPLC separation of the drugs was performed on an Spherisorb C(18) column and detected by ultraviolet absorbance at 239 nm. The use of methanol-water solution (containing 2.8 mm triethylamine, 80:20, v/v) as the mobile phase at a fl ow-rate of 1.2 mL/min enables the baseline separation of the drugs free from interferences with isocratic elution. The method was linear in the clinical range 0-300 ng/mL and the lower limit of detection of diltiazem in plasma was 3 ng/mL. The range of percentage of relative standard deviation (%RSD) was from 3.5 to 6.8% for within-day analyses and from 6.2 to 8.4% for between-day analyses, respectively. The extraction recoveries of diltiazem from spiked human plasma (n = 5) at three concentrations were 91.4-104.0%. The method has been used to determine diltiazem in human plasma samples from eight volunteers who had taken diltiazem hydrochloride slow release tables and the data obtained was fitted with a program on computer to study the pharmacokinetics. The results showed that the peak level in plasma approximately averaged 118.5 +/- 14.3 ng/mL at 3.1 +/- 0.4 h, and the areas under the drug concentration curves (AUC) was 793.1 +/- 83.1 ng.h/mL.