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Ling Zhang

Publications and source records attributed to Ling Zhang.

At least 91 records · Page 5Linked to original sources
PubMed2005

Solubility of disulfide-bonded proteins in the cytoplasm of Escherichia coli and its "oxidizing" mutant.

AIM: To study the influence of redox environment of Escherichia coli (E. coli) cytoplasm on disulfide bond formation of recombinant proteins. METHODS: Bovine fibroblast growth factor (BbFGF) was selected as a model of simple proteins with a single disulfide bond and free cysteines. Anti-HBsAg single-chain Fv (HBscFv), an artificial multidomain protein, was selected as the model molecule of complex protein with 2 disulfide bonds. A BbFGF-producing plasmid, pJN-BbFGF, and a HBscFv producing-plasmid, pQE-HBscFv, were constructed and transformed into E. coli strains BL21(DE3) and M15(pREP4) respectively. At the same time, both plasmids were transformed into a reductase-deficient host strain, E. coli Origami(DE3). The 4 recombinant E. coli strains were cultured and the target proteins were purified. Solubility and bioactivity of recombinant BbFGF and HBscFv produced in different host strains were analyzed and compared respectively. RESULTS: All recombinant E. coli strains could efficiently produce target proteins. The level of BbFGF in BL21(DE3) was 15-23% of the total protein, and was 5-10% in Origami (DE3). In addition, 65% of the BbFGF produced in BL21(DE3) formed into inclusion body in the cytoplasm, and all the target proteins became soluble in Origami(DE3). The bioactivity of BbFGF purified from Origami(DE3) was higher than its counterpart from BL21(DE3). The ED(50) of BbFGF from Origami(DE3) and BL21(DE3) was 1.6 microg/L and 2.2 microg/L, respectively. Both HBscFv formed into inclusion body in the cytoplasm of M15(pQE-HBscFv) or Origami(pQE-HBscFv). But the supernatant of Origami(pQE-HBscFv) lysate displayed weak bioactivity and its counterpart from M15(pQE-HBscFv) did not display any bioactivity. The soluble HBscFv in Origami(pQE-HBscFv) was purified to be 1-2 mg/L and its affinity constant was determined to be 2.62 x 10(7) mol/L. The yield of native HBscFv refolded from inclusion body in M15(pQE-HBscFv) was 30-35 mg/L and the affinity constant was 1.98 x 10(7) mol/L. There was no significant difference between the bioactivity of HBscFvs refolded from the inclusion bodies produced in different host strains. CONCLUSION: Modification of the redox environment of E. coli cytoplasm can significantly improve the folding of recombinant disulfide-bonded proteins produced in it.

Animals↗
PubMed2005

Global gene expression profile of Yersinia pestis induced by streptomycin.

Plague, caused by Yersinia pestis, is one of the most dangerous diseases that impressed a horror onto human consciousness that persists to this day. Cases of plague can be normally controlled by timely antibiotic administration. Streptomycin is the first-line antibiotic for plague treatment. In this study, a DNA microarray was used to investigate the changes in the gene expression profile of Y. pestis upon exposure to streptomycin. A total of 345 genes were identified to be differentially regulated, 144 of which were up-regulated, and 201 down-regulated. Streptomycin-induced transcriptional changes occurred in genes responsible for heat shock response, drug/analogue sensitivity, biosynthesis of the branched-chain amino acids, chemotaxis and mobility and broad regulatory functions. A wide set of genes involved in energy metabolism, biosynthesis of small macromolecules, synthesis and modification of macromolecules and degradation of small and macro molecules were among those down-regulated. The results reveal general changes in gene expression that are consistent with known mechanisms of action of streptomycin and many new genes that are likely to play important roles in the response to streptomycin treatment, providing useful candidates for investigating the specific mechanisms of streptomycin action.

Animals↗
PubMed2005

DNA microarray analysis of the heat- and cold-shock stimulons in Yersinia pestis.

DNA microarray was used as a tool to define the heat- and cold-shock stimulons in Yersinia pestis. Heat shock dramatically enhanced the transcription of genes encoding major heat-shock proteins (MHSPs) that are important for cell survival against the heat. Many other genes were also greatly up-regulated, but their roles in heat-shock response need to be elucidated. Meanwhile, heat shock retarded most of the metabolic processes, i.e. RNA transcription, protein translation, aerobic respiration, energy metabolism, small molecule metabolism, peptidoglycan biosynthesis, sulfate uptake and cysteine biosynthesis. In response to cold shock, Y. pestis has evolved complex adaptive mechanisms by elevating the transcription of a specific set of genes whose protein products are designed to prevent or eliminate cold-induced DNA or RNA structuring, to remodel cell membrane components for maintenance of normal functions, to elevate the energy generation for ensuring ATP-dependent responses during cold adaptation and to synthesize or transport compatible solutes such as cryoprotectants, and at the same time, by repressing the mRNA level of certain genes whose protein products are not needed for bacterial growth at low temperatures, such as the MHSPs. These results provide a set of new candidate genes for hypothesis-based investigations of their roles in stress response, host adaptation and pathogenicity of this deadly pathogen.

Biological Transport↗
PubMed2005

Assembly of plasmid DNA into liposomes after condensation by cationic lipid in anionic detergent solution.

A novel strategy to prepare negatively charged and small DNA-containing liposomes after condensation of plasmid DNA by a cationic lipid in deoxycholate micelle environment is described. The average diameter of resulting complexes was 62 +/- 8 nm. DNA-containing liposomes were then prepared by dialysis. The shape of the resulting liposomes was spherical. The average diameter and the surface charge of the liposomes were 86 +/- 6 nm and -24 +/- 3 mV, respectively. The plasmid DNA inside liposomes remained in a supercoiled form after incubation with DNase.

Cations↗
PubMed2005

Simvastatin regulates myocardial cytokine expression and improves ventricular remodeling in rats after acute myocardial infarction.

PURPOSE: Studies have showed that inflammatory cytokines were involved in the process of left ventricular (LV) remodeling after acute myocardial infarction (AMI), anti-inflammation treatment ameliorated LV remodeling and improved cardiac performance. Hydroxymethylglutary coenzyme A reductase inhibition (statins) could affect the expression of inflammatory cytokines. We hypothesized that statins have beneficial effects on early LV remodeling and cardiac performance in rats with AMI by modulating the production of inflammatory cytokines. METHODS: Rats with AMI were treated with placebo or simvastatin (gastric gavage) for 4 weeks. The pro-inflammatory cytokines: tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and the anti-inflammatory cytokine: IL-10 excreted by cardiac myocytes was examined. Echocardiography, hemodynamics and collagen type I production were measured to evaluate LV remodeling and cardiac function. RESULTS: The mRNA expression and protein production of TNF-alpha, IL-1beta, IL-6 and IL-10 in AMI group were significantly elevated compared with sham rats. Simvastatin markedly attenuated the production of TNF-alpha, IL-1beta, IL-6 and increased IL-10 levels in the noninfarcted and infarcted regions, reduced collagen deposition in the noninfarcted myocardium and improved left ventricular function. However simvastatin did not alter plasma lipids. CONCLUSIONS: Simvastatin ameliorates early LV remodeling and improve cardiac function after AMI. Simultaneously, it decreased pro-inflammatory and increased anti-inflammatory cytokines, which suggests, but does not prove, a causal relationship independent of plasma lipid-lowering effects.

Animals↗
PubMed2005

Effects of free fatty acids on plasma resistin and insulin resistance in awake rats.

Resistin has been postulated to play a role in obesity-related insulin resistance. To explore this possibility, we have investigated effects of acute euglycemic (5.2+/-0.1 mmol/L) hyperinsulinemia (96+/-8 microU/mL) with and without concurrent infusion of lipid plus heparin (to raise or lower plasma free fatty acid [FFA] levels) on glucose turnover and plasma resistin levels in alert rats. Plasma FFA concentrations increased during lipid/heparin (L/H) infusion (from 0.82 to 2.86 mmol/L, P<.001) and decreased (from 0.83 to 0.21 mmol/L, P<.001) in controls who were infused with insulin but not with L/H. L/H infusion reduced insulin suppression of endogenous glucose production by approximately 90% (from 28.9 to 3.1 mg. kg-1 . min-1, P<.001) and insulin-stimulated glucose uptake (glucose rate of disappearance) by 78% (from 30.8% to 6.9%, P<.001). Plasma resistin levels increased by 46% (from 39.9 to 58.4 microg/L, P<.05) during L/H infusion and did not change in controls (39.7 vs 39.3 microg/L). Plasma ghrelin levels decreased by 41% (from 892 to 584 ng/L, P<.05) in response to hyperinsulinemia, whereas concurrent L/H infusion had no additional effect on ghrelin levels (584+/-67 vs 548+/-82 ng/L). In summary, we found that FFA induced hepatic insulin resistance, and to a lesser extent, peripheral insulin resistance was associated with elevated plasma resistin levels. We conclude that FFA-induced release of resistin may contribute to the development of FFA-induced insulin resistance in rats.

Animals↗
PubMed2005

Molecular dynamics of a food carcinogen-DNA adduct in a replicative DNA polymerase suggest hindered nucleotide incorporation and extension.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant of the carcinogenic heterocyclic aromatic amines in the human diet, and the major mutagenic effect of dietary PhIP is G-->T transversions. The major PhIP-derived DNA adduct is to C8 of guanine. We have investigated this adduct in a PhIP-induced mutational hotspot 5'-GGGA-3' of the Apc tumor suppressor gene, frequently mutated in mammalian colon tumors. We have carried out a molecular dynamics study to elucidate on a structural level nucleotide incorporation and extension opposite this major adduct during replication. The PhIP adduct was modeled into the ternary complex closed conformation of DNA polymerase RB69, at incorporation and extension positions, with normal cytosine or mismatched partner adenine. RB69 polymerase is a member of the B family as are most replicative eukaryotic DNA polymerases such as DNA polymerase alpha. These systems were subjected to molecular dynamics simulations with AMBER. Our results show that the adduct can reside on the major groove side of the modified DNA template opposite an incoming dCTP or dATP. In the case of the normal partner, disturbance to the active site is observed at the incorporation step, but there is less perturbance in the extension simulation. In the case of the mismatched partner, a less disturbed active site is observed during the incorporation step, but extension appears to be more difficult. Disturbances include adverse impacts on Watson-Crick hydrogen bonding in the nascent base pair, on the distance between the alpha-phosphate of the incoming dNTP and the primer terminus 3'-OH, and on critical protein interactions with the dNTP. However, in all of these cases, a near reaction ready distance (within 3.5 angstroms) between the 3'-terminal oxygen of the primer and the Palpha of the incoming nucleotide triphosphate is sampled occasionally (0.4-23.5% of the time). Thus, error-free bypass or the induction of a G-->T transversion mutation could occur at times and contribute to an extent to the mutagenic effect of PhIP. Polymerase stalling would be the more common outcome and in vivo could lead to switch to an error-prone bypass polymerase.

Amino Acids↗
PubMed2005

Therapeutic effects of hydroxysafflor yellow A on focal cerebral ischemic injury in rats and its primary mechanisms.

The therapeutic effects of hydroxysafflor yellow A (HSYA), extracted from Carthamus tinctorius. L, on focal cerebral ischemic injury in rats and its related mechanisms have been investigated. Focal cerebral ischemia in rats were made by inserting a monofilament suture into internal carotid artery to block the origin of the middle cerebral artery and administrated by HSYA via sublingular vein injection in doses of 1.5, 3.0, 6.0 mg kg(-1) at 30 min after the onset of ischemia, in comparison with the potency of nimodipine at a dose of 0.2 mg kg(-1). Then, 24 h later, the evaluation for neurological deficit scores of the rats were recorded and postmortem infarct areas determined by quantitative image analysis. At the end of the experiment, blood samples were taken to determine plasma 6-Keto-PGF1alpha/TXB2 by radioimmunoassays and blood rheological parameters. The effects exerted by HSYA on thrombosis formation by artery vein by-pass method and ADP-induced platelet aggregation in vivo and in vitro were investigated, respectively. The results indicated that more than 30% of the area of ischemic cerebrum was observed in the ischemic model group. HSYA dose-dependently improved the neurological deficit scores and reduced the cerebral infarct area, and HSYA bore a similarity in potency of the therapeutic effects on focal cerebral ischemia to nimodipine. The inhibition rates of thrombosis formation by HSYA at the designated doses were 20.3%, 43.6% and 54.2%, respectively, compared with saline-treated group. Inhibitory activities of HSYA were observed on ADP-induced platelets aggregation in a dose-dependent manner, and the maximum inhibitory aggregation rate of HSYA was 41.8%. HSYA provided a suppressive effect on production of TXA2 without significant effect on plasma PGI2 concentrations. Blood rheological parameters were markedly improved by HSYA, such as whole blood viscosity (from 21.71 +/- 4.77 to 11.61 +/- 0.90 mPa.s), plasma viscosity (from 2.73 +/- 0.53 to 1.42 +/- 0.07 mPa.s), deformability (from 0.66 +/- 0.26 to 0.77 +/- 0.33) and aggregation of erythrocyte (from 3.24 +/- 0.41 to 2.57 +/- 0.30), but no significant effect of HSYA on homatocrit was found (from 51.38 +/- 4.68% to 49.91 +/- 2.32%). HSYA appears to be a good potential agent to treat focal cerebral ischemia, and the underlying mechanisms exerted by HSYA might be involved in its inhibitory effects on thrombosis formation and platelet aggregation as well as its beneficial action on regulation of PGI2/TXA2 and blood rheological changes in rats.

Animals↗
PubMed2005

Enhanced antitumor effect of the combination of tumstatin gene therapy and gemcitabine in murine models.

Targeting tumor endothelium is an important strategy for cancer therapy. We evaluated the effectiveness of gene therapy, that is, intramuscular delivery of plasmid DNA encoding tumstatin (pSecTag2B-tum), combined with gemcitabine administration in vitro and in vivo, using colon carcinoma (CT26) and Lewis lung carcinoma (LLC) murine models. The in vitro growth-inhibitory and proapoptotic effects of gemcitabine and/or tumstatin on human umbilical vein endothelial cells (HUVECs) and mouse endothelial cells (SVEC4-10), respectively, were assessed. in vitro, conditioned medium from pSecTag2B-tum-transfected COS cells inhibited the growth of endothelial cells but not of CT26 or LLC cells, whereas gemcitabine inhibited the growth of both endothelial cells and CT26 and LLC cells. Mice bearing subcutaneously established CT26 or LLC tumors received pSecTag2B-tum alone or in combination with gemcitabine to assess tumor growth inhibition. in vivo, combined treatment with pSecTag2B-tum and gemcitabine significantly decreased tumor growth through increased inhibition of tumor angiogenesis and increased tumor cell apoptosis compared with either agent alone. Enhanced antiproliferative and proapoptotic activity of the combination therapy on tumor-associated endothelial cells was calculated to be significant. This study suggests that combined treatment by the intramuscular delivery of plasmid DNA encoding tumstatin and gemcitabine augments tumor growth inhibition by suppressing angiogenesis and enhancing apoptosis in murine models. A combination of these agents could be used in future studies and translated into the clinical setting.

Angiogenesis Inhibitors↗
PubMed2005

Automatic detection of three-dimensional vascular tree centerlines and bifurcations in high-resolution magnetic resonance angiography.

OBJECTIVES: We sought to develop a simple and robust algorithm capable of automatically detecting centerlines and bifurcations of a three-dimensional (3D) vascular bed. MATERIALS AND METHODS: After necessary preprocessing, an appropriate cost function is computed for all vessel voxels and Dijkstra's minimum-cost-path algorithm is implemented. By back tracing all the minimum-cost paths, centerlines and bifurcation are detected. The detected paths are then split into segments between adjacent nodes (bifurcations or vessel end-points) and smoothed by curve fitting. RESULTS: Application of the algorithm to both simulated 3D vessels and 3D magnetic resonance angiography (MRA) images of an actual intracranial arterial tree produced well-centered vessel skeletons. Quantitative assessment of the algorithm was performed. For the simulated data, the root mean square error for centerline detection is about half a voxel. For the human intracranial MRA data, the sensitivity, positive predictive value (PPV), and accuracy of bifurcation detection were calculated for different cost functions. The best case gave a sensitivity of 91.4%, a PPV of 91.4%, and an RMS error of 1.7 voxels. CONCLUSIONS: To the extent that imperfections are eliminated from the segmented image, the algorithm is effective and robust in automatic and accurate detection of centerlines and bifurcations. The cost function and algorithm used are demonstrated to be an improvement over similar algorithms in the literature.

Algorithms↗
PubMed2005

Pseudogene accumulation might promote the adaptive microevolution of Yersinia pestis.

Plague is a natural focus-based disease, and for better understanding of this disease it is crucial to determine the molecular mechanisms of its pathogen, Yersinia pestis, for adapting to different foci. Gene inactivation, loss and acquisition are the main mechanisms that contribute to a pathogen's fitness. Determination of the whole-genome sequences of three Y. pestis strains, CO92, KIM and 91001, provided a good opportunity to probe into its genome in minute detail. Many genetic variations were found between the three strains. The present work focused on adaptive microevolutionary analysis of Y. pestis from different natural plague foci in China based on pseudogene profiles. Twenty-four mutations that led to inactivation in the corresponding genes were analysed, and a PCR-based screening method was employed to investigate the distribution of these mutations among Y. pestis isolates from different foci and also among seven strains of Yersinia pseudotuberculosis. It was found that Y. pestis isolates from the same focus had identical mutation profiles, and 260 isolates of Y. pestis were divided into eight genotypes, while Y. pseudotuberculosis harboured wild-type alleles for all the mutations. The isolates of three known biovars were grouped into distinct branches in the phylogenetic tree, which supports the proposition that biovars mediaevalis and orientalis directly arose from biovar antiqua individually. The constructed phylogenetic tree suggests that the isolates from focus B should be the oldest lineage of Y. pestis in China except for isolates from foci L and M, which might be a special lineage of Y. pestis and originated differently to the others.

Adaptation, Physiological↗
PubMed2005

Anterior cingulate cortex contributes to the descending facilitatory modulation of pain via dorsal reticular nucleus.

Supraspinal centres biphasically modulate spinal nociceptive transmission, including descending inhibition and facilitation. Recent studies have revealed that descending facilitatory modulation is a key mechanism underlying induction and maintenance of neuropathic and inflammatory pain. The anterior cingulate cortex (ACC) is not only involved in the transmission of pain sensation but also plays a role in processing pain-related emotion. The ACC also widely connects with relevant regions of the descending modulation system. Here we used electrophysiological and behavioural techniques to study the possible pathways behind the modulation of spinal nociceptive transmission from the ACC. C-fibre-evoked field potentials in the spinal dorsal horn were produced by electrical stimulation of the sciatic nerve at an intensity high enough to excite C fibres, and paw withdrawal latencies (PWLs) to noxious heating were recorded. The results showed that high-frequency tetanic electrical stimulation of the ACC both unilaterally enhanced the C-fibre-evoked field potentials in the spinal dorsal horn and bilaterally shortened PWLs, indicating a facilitation of spinal nociception. A similar effect was observed after microinjection of N-methyl-d-aspartic acid (NMDA; 10 nm, 1 microL) or homocysteic acid (HCA; 0.1 m, 1 microL) into the ACC. When the dorsal reticular nucleus (DRt) was electrolytically lesioned, ACC-induced facilitation of spinal nociception was blocked. These results imply that: (i) activation of the ACC may facilitate spinal nociception; (ii) NMDA receptors in the ACC may be involved in descending facilitation; and (iii) the DRt plays a crucial role in mediating ACC-induced facilitation of spinal nociception.

Animals↗
PubMed2005

Mass screening of prostate cancer in a Chinese population: the relationship between pathological features of prostate cancer and serum prostate specific antigen.

AIM: To investigate the pathological features of the prostate biopsy through mass screening for prostate cancer in a Chinese cohort and their association with serum prostate specific antigen (PSA). METHODS: A total of 12027 Chinese men in Changchun were screened for prostate cancer by means of the serum total prostate specific antigen tPSA test (by Elisa assay). Transrectal ultrasound-guided systematic six-sextant biopsies were performed on those whose serum tPSA value was > 4.0 ng/mL and those who had obstructive symptoms (despite their tPSA value) and were subject to subsequent pathological analysis with the aid of the statistic software SPSS 10.0 (SPSS. Inc., Chicago. USA). RESULTS: Of the 12027 cases, 158 (including 137 patients whose serum tPSA values were 4.0 ng/mL and 21 patients [serum tPSA < 4.0 ng/mL] who had obstructive symptoms) undertook prostate biopsy. Of the 158 biopsies, 41 cases of prostatic carcinoma were found (25.9 %, 41/158). The moderately differentiated carcinoma and poorly differentiated carcinoma accounted for 61% and 34%, respectively. A significant linear positive correlation between the serum tPSA and the Gleason scores in the 41 cases of prostatic carcinoma (r = 0.312, P < 0.01) was established. A significant linear positive correlation between the serum tPSA value of the 41 prostatic carcinoma and the positive counts of carcinoma in sextant biopsies was established (r = 0.406, P < 0.01), indicating a significant linear relationship between serum tPSA and the size of tumor. CONCLUSION: This study was the first to conduct mass screening for prostate cancer by testing for serum tPSA values and the first to investigate the pathological features of prostate cancer in a cohort of Chinese men. Our results reveal that the moderately differentiated carcinoma is the most common type of prostate cancer. This study also has shown that the serum tPSA value in prostate cancer is associated with the Gleason score and the size of tumor.

Biopsy↗
PubMed2005

Measurement of serum zinc improves prostate cancer detection efficiency in patients with PSA levels between 4 ng/mL and 10 ng/mL.

AIM: To investigate whether the measurement of serum zinc may improve the detection of prostate cancer (PCa) in men who had total prostate-specific antigen (PSA) levels higher than 4.1 ng/mL. METHODS: A mass screening for PCa of 3940 men over 50 years old was undertaken using total serum PSA. Of the 190 men (4.8%) with elevated PSA, 143 (3.6%) underwent a transrectal ultrasonography (TRUS)-guided biopsy of the prostate, and 42 men (1% of total and 29.3% of men undergoing biopsy) were found to have cancer. The areas under the receiver operating characteristic curves (ROC-AUC) were used to compare the diagnostic power of cancer detection by means of serum zinc, and free PSA/total PSA ratio (f/t). RESULTS: The men with levels of serum zinc that ranged from 40 ng/mL-60 ng/mL, had an age-adjusted odds ratios(OR) of 5.0. A cutoff value of 100 microg/mL for serum zinc concentration provided a sensitivity of 90.5% and a specificity of 32.7% in elevated PSA range, and a sensitivity of 93.3% and specificity of 27.1% in gray zone, respectively. In the gray zone ranges of 4.1 ng/mL-10.0 ng/mL, the ROC-AUC for zinc was 73.0% higher than 62.7% of f/t PSA ratio and 56.7% of total PSA. CONCLUSION: PCa displays a lower serum zinc concentration. The measurement of zinc levels improves PCa detection in the gray zone compared with the f/t PSA ratio and total PSA.

Area Under Curve↗
PubMed2005

Improved accuracy and consistency in T1 measurement of flowing blood by using inversion recovery GE-EPI.

Problems associated with techniques currently used to measure the T1 of flowing blood are evaluated and a method to improve the consistency and repeatability of measurements is presented. Similar to some currently used techniques, the pulse sequence employs a nonselective adiabatic inversion pulse followed by a series of ECG-gated gradient echo EPI (echo planar imaging) images to obtain images where the blood (fluid) signal exhibits a T1-dependent inversion recovery signal from which the spin lattice relaxation constant (T1) of the flowing fluid can be measured. The new method combines curve fitting with a measure of the curve null point to acquire more accurate and consistent T1 values. Simulation and experimental results show that this combined fitting-nulling method is more stable and consistent in measuring the T1 of flowing fluid. The feasibility of temperature measurement of a flowing fluid based on the temperature dependence of the T1 of water protons is shown in this paper. ECG gating is used to reduce the effects of cyclic intensity changes for measurement of T1 in pulsatile flowing blood.

Blood Flow Velocity↗
PubMed2005

Studies on functionalization of poly(epsilon-caprolactone) by a cholesteryl moiety.

Biodegradable polymers/oligomers based on epsilon-caprolactone (CL) were end-functionalized by a cholesteryl moiety. The functionalized polymers/oligomers, Chol-(CL)n, were synthesized through ring-opening polymerization initiated by cholesterol with a hydroxyl group. The chemical structure of end-functionalized polymers/oligomers was confirmed by FT-IR and 1H-NMR. The molecular weight of the functionalized polymer/oligomer increases with decreasing feed ratio of the initiator cholesterol to the monomer CL. Incorporation of the cholesteryl moiety to the polymer chain results in liquid crystallinity for the resultant oligomers when their molecular chains are not very long. The enzymatic degradation of the functionalized polymers/oligomers was investigated. The microsphere drug-delivery system of a functionalized oligomer was fabricated and its drug release properties were evaluated. The cell-culture experiment indicates the incorporation of cholesteryl moiety to the polymer chain results in improved cell proliferation.

3T3 Cells↗
PubMed2005

Genetic variations in the pgm locus among natural isolates of Yersinia pestis.

A PCR-based screening method was used to study the genetic variations of the pgm locus among natural isolates of Yersinia pestis from China. Our results indicate that genetic variations in the pgm locus are well correlated with biovars of Y. pestis and plague foci, suggesting that the pgm locus plays a role in Y. pestis adaptation to its environment. The gene encoding two-component regulatory system sensor kinase became a pseudogene in all strains of biovar Orientalis due to a thymidine deletion, while it is intact in all the strains of the other biovars. Only strains from Foci H and L are the same as Yersinia pseudotuberculosis in that they have an intact transmembrane helix in the sensor kinase protein, which is lost in all the other strains because of the 18 bp in-frame deletion. The IS100 element that flanks the 39 terminus of the pgm locus was inserted into the chromosome during the within-species microevolution of Y. pestis, which is absent in strains from Foci G, H and L and also in Y. pseudotuberculosis. This fact indicates that the strains from these three foci are of an older lineage of Chinese Y. pestis. It is this IS100 element's absence that maintained high stability of the pgm locus in the Y. pestis strains from these three foci. The IS285 element insertion in the pigmentation segment and the IS100 element insertion in the downstream flanking region of the pgm locus are only present in strains from Foci H and L. The flanking region outside the 59 terminus of the upstream IS100 element is identical in the strains from these two foci, which is different in the other strains. All of these unique characteristics suggest that they are of a special lineage of Chinese Y. pestis.

Alleles↗