Biomedical subjects

Yan Zhang

Publications and source records attributed to Yan Zhang.

At least 127 records · Page 7Linked to original sources

PubMed2006

Genome-wide analysis of the expression profile of Saccharomyces cerevisiae in response to treatment with the plant isoflavone, wighteone, as a potential antifungal agent.

The limitations of currently available antifungal agents and the rapid emergence of drug-resistant strains necessitate more efficient approaches to screening and developing novel antifungal drugs. The antifungal activity of the natural products of a series of plants was evaluated and wighteone, 5, 7, 4'-trihydroxy-6-(gamma,gamma-dimethylallyl)isoflavone showed excellent anti-yeast activity (MIC against Saccharomyces cerevisiae was 4 microg/ml). Transcriptome profiling of wighteone-treated S. cerevisiae indicated that wighteone is different from commonly used antifungal compounds in its mode of action.

Antifungal Agents↗

PubMed2006

Heterochromatin protein 1 deleted chromo domain decreases gene silencing of transgene in mouse.

The heterochromatin protein 1 (HP1) regulates epigenetic gene silencing by promoting and maintaining chromatin condensation. To decrease gene silencing, the chromo domain (CD) in the M31 (the main HP1 in mouse) was deleted by site-directed mutagenesis. Vector pcDNA3.1(+)/M31-DeltaCD, in which the M31-DeltaCD is driven by the CMV promoter, and vector pcDNA3.1(+)/P1A3-M31-DeltaCD, in which the M31-DeltaCD is driven by a goat ss-casein promoter were constructed. The former vector was transfected into a murine fibroblast cell line, which can express enhanced green fluorescent protein (EGFP). EGFP expression, which was determined by flow cytometric analysis, increased approximately 80% in the transfected cells. After injection of the latter vector into transgenic mouse mammary glands, which can express human clotting factor IX (hFIX), the hFIX expression level in the mouse milk increased approximately 40-60% and hFIX in one mouse milk was maintained at a high concentration for over 10 days.

Animals↗

PubMed2006

[Dual promoters enhance heterologous enzyme production from bacterial phage based recombinant Bacillus subtilis].

The effect of dual promoters on recombinant protein production from bacterial phage based Bacillus subtilis expression system was investigated. Alpha amylase (from Bacillus amyloliquefaciens) and penicillin acylase (from Bacillus megaterium) were selected as the indicating enzymes. Both the promoterless genes and the promoter-bearing genes were isolated through PCR amplification with properly designed primers, and were inserted into plasmid pSG703 that contains the lacZ-cat expression cartridge. The lysogenic B. subtilis (phi105 MU331) was transformed with the resultant recombinant plasmids, and the heterologous genes were thereby integrated into the chromosommal DNA of B. subtilis via homologous recombination. The transformants were designated as B. subtilis AMY1, B. subtilis AMY2, B. subtilis PA1, and B. subtilis PA2, respectively. In the recombinant B. subtilis strains, the inserted sequences were located down stream of a strong phage promoter that could be activated by thermal induction. In B. subtilis AMY1 and B. subtilis PA1, transcription of the heterologous genes was only initiated by the phage promoter after heat shock, whereas in B. subtilis AMY2 and B. subtilis PA2, transcription of the heterologous genes was initiated by dual promoters, the phage promoter and the native promoter. The application of dual promoters increased the productivity of both enzymes, with 133% enhancement for alpha-amylase production and 113% enhancement for penicillin acylase production.

Bacillus Phages↗

PubMed2006

Protease-modulated cellular uptake of quantum dots.

Quantum dots (QDs) are often cell-impermeable and require transporters to facilitate crossing over cell membranes. Here we present a simple and versatile method that utilizes enzymes, matrix metalloprotease 2 (MMP-2) and MMP-7, to modulate the cellular uptake of QDs. QD-peptide conjugates could be efficiently taken up into cells after the MMP treatment. This enzyme-modulated cellular uptake of QDs may be applied to other nanoparticles for biological imaging and selective drug delivery into tumor cells.

Cell Line, Tumor↗

PubMed2006

Copper catalyzing growth of single-walled carbon nanotubes on substrates.

Metallic copper, which is normally considered as a contaminant in the growth of single-walled carbon nanotubes (SWNTs), was found to be an efficient catalyst to grow SWNTs under suitable conditions. It showed very high catalytic activity for the growth of both random SWNT networks and horizontally aligned SWNT arrays. Especially, high-quality SWNT arrays were obtained when monodispersed copper nanoparticles were used. The catalytic behavior of copper for the growth of SWNTs was discussed. The weaker interaction between the copper and silica surfaces plays an important role in the growth of high-quality horizontally aligned SWNT arrays. This new synthesis process of SWNTs with a non-ferromagnetic catalyst brings more convenience to the study of magnetic properties of SWNTs and gives more insight in structure-controlled synthesis of SWNTs.

Journal Article↗

PubMed2006

Prevalence of metabolic syndrome and its relation to body composition in a Chinese rural population.

OBJECTIVE: To investigate the prevalence of metabolic syndrome (MetS) with three different working definitions in a rural Chinese population and to examine its relation to body composition. RESEARCH METHODS AND PROCEDURES: A total of 18,630 adults 25 to 64 years old (mean age, 45.8 years; 51.2% men) from 5686 families were enrolled from Anhui province of China during 2004 to 2005. Anthropometric measurement, body composition, blood pressure, plasma lipids, and fasting glucose and insulin and a questionnaire-based interview were obtained from each participant. Three different working definitions for MetS, including the U.S. National Cholesterol Education Program's Adult Treatment Panel III, a modified Adult Treatment Panel III that adopts the World Health Organization's criterion for central obesity in Asian populations, and one recently proposed by the International Diabetes Federation, were used in the study. RESULTS: According to the three definitions, the age-adjusted prevalence of MetS for adults 25 to 64 years old was 3.2%, 4.9%, and 3.9% in men and 7.2%, 11.5%, and 10.9% in women, respectively. MetS prevalence increases significantly with age in women, but not in men. Body fat percentage and BMI and waist circumference were significantly associated with each component of MetS, especially with triglyceride level, insulin resistance index, and number of MetS components (r = 0.28 to 0.49). DISCUSSION: The age-adjusted prevalence of MetS in our study population is lower than that reported in other urban Chinese populations. Significant gender differences in MetS prevalence were observed. The waist circumference is a good surrogate for abdominal fat percentage.

Abdominal Fat↗

PubMed2006

Immunization with autologous T cells enhances in vivo anti-tumor immune responses accompanied by up-regulation of GADD45beta.

Immunization with inactivated autoreactive T cells may induce idiotype anti-idiotypic reactions to deplete autoreactive T cells, which are involved in autoimmune diseases. However, it is unknown whether attenuated activated healthy autologous T-cell immunization could increase anti-tumor immune responses. To this end, C57Bl/6 mice were immunized with attenuated activated autologous T cells. The splenocytes from immunized mice showed a higher proliferative ability than that from naive mice. The special phenotype analysis showed that there were more CD8+ T cells and CD62L+ T cells in immunized mice after 24 h of culture with 10% fetal calf serum complete medium in vitro (P<0.01). These results demonstrated that this immunization may activate T cells in vivo. Furthermore, the splenocytes from immunized mice revealed resistance to activation-induced cell death (AICD) in vitro. To further study the relative genes that are responsible for the higher proliferation and resistance to AICD, the expression of Fas/Fas ligand (FasL) and GADD45b was measured by real-time PCR. The results indicated that GADD45beta transcription was higher in the splenocytes from immunized mice than that in the naive mice. In addition, the Fas expression showed a parallel higher, but FasL did not change obviously. To investigate the biologic functions induced by immunization in vivo, a tumor model was established by EL-4 tumor cell inoculation in C57/Bl mice. Mice receiving autologous T-cell immunization had significantly inhibited tumor growth in vivo (P<0.01). This study implicated that immunization with attenuated activated autologous T cells enhances anti-tumor immune responses that participate in tumor growth inhibition.

Animals↗

PubMed2006

Tube-immunoassay for rapid detection of carbaryl residues in agricultural products.

An antibody-based rapid, quantitative, and qualitative tube enzyme-linked immunosorbent assay (tube-ELISA) was developed and used to determine carbaryl (1-naphthyl methylcarbamate) residues in agricultural products (apple, Chinese cabbage, rice, and barley). The tube-ELISA is a competitive immunoassay in which the antibody is coated in the polystyrene tube, with a dynamic range between 0.7 and 46.3 microg kg(-1). Carbaryl was extracted from each agricultural sample by hand-shaking with methanol and examined for application to on-site analysis. After the liquid extraction, the sample extracts diluted with buffer were analyzed by rapid tube-ELISA directly. The overall test time was around 15-30 min, including sample preparation and assay performance. The results obtained from tube-ELISA correlated well with high-performance liquid chromatography (R2 > 0.9). The study shows that tube-ELISA is useful as a quality control tool and can be used to quantitatively detect carbaryl as well.

Carbaryl↗

PubMed2006

Unintentional injuries among primary and middle school students in Maanshan City, eastern China.

AIM: To describe the rates and patterns of unintentional injuries among primary and middle school students in China. METHODS: A cross-sectional survey was conducted in Maanshan City of the Anhui Province in eastern China. All students attending six primary and four middle schools, selected randomly, were asked to report unintentional injuries occurring in the 12-mo period before the survey. The occurrence of unintentional injuries that resulted in medical attendance was summarized by study grade, sex, month and external causes. RESULTS: The annual event-based injury rate per 100 students was higher among boys (21.7) than girls (17.6). Only 1.9% of the episodes resulted in hospitalization, and 17.8% resulted in missing school. The most frequent injuries were falls (38.2%) and transportation-related injuries (19.6%). The risk of injury was lower in middle schools than primary schools. Distribution by month of occurrence showed two peaks in boys during spring and autumn, but no clear peak was observed in girls. CONCLUSION: The descriptive epidemiology of unintentional injuries among students in China provides useful information on the distributions in person, place and time, which in turn provide hints for the further exploration of possible risk factors that are important in planning strategies for future prevention.

Accidents↗

PubMed2006

The brain targeting efficiency following nasally applied MPEG-PLA nanoparticles in rats.

The aim of this study was to encapsulate nimodipine (NM) within methoxy poly(ethylene glycol)-poly(lactic acid) (MPEG-PLA) nanoparticles and to investigate its brain targeting efficiency following intranasal administration. NM-loaded nanoparticles, prepared through an emulsion/solvent evaporation technique, were characterized in terms of size, zeta potential, NM loading and in vitro release. The nanoparticles were administered intranasally to rats, and the concentrations of NM in blood, cerebrospinal fluid (CSF) and brain tissues were monitored. The contribution of the olfactory pathway to the uptake of NM in the brain was determined by calculating the brain/plasma concentration ratios and "brain drug direct transport percentage (DTP)" following intranasal administration of the nanoparticles and the solution formulation. The results showed that MPEG-PLA nanoparticles had a mean particle size of 76.5 +/- 7.4 nm, a negative surface charge and a 5.2% NM loading. In vitro release was moderate under sink conditions. The intranasal administration of nanoparticles resulted in a low but constant NM level in plasma. The ratio of AUC values of the nanoparticles to the solution was 1.56 in CSF. The olfactory bulb/plasma and CSF/plasma concentration ratios were significantly higher (P < 0.05) after application of nanoparticles than those of the nasal solution, except the ratio in olfactory bulb at 5 min. Furthermore, nasally administered nanoparticles yielded 1.6-3.3-fold greater DTP values in CSF, olfactory bulb and other brain tissues compared to nasal solution. Thus, MPEG-PLA nanoparticles demonstrated its potential on improving the efficacy of the direct nose-brain transport for drugs.

Administration, Intranasal↗

PubMed2006

Comparing transfection efficiency and safety for antisense oligodeoxyribonucleotide between phospholipids-based microbubbles and liposomes.

OBJECTIVE: To compare transfection efficiency and safety for antisense oligodeoxynucleotides (AS-ODNs) between two type of phospholipids-based vectors. METHODS: An AS-ODNs sequence HA824 combined with luciferase reporter plasmid was used. Under low intensity ultrasound (US), a breast cancer cell line SK-BR-3 was exposed to different concentration of microbubbles and liposomes. Transfection efficiency was detected by fluorescence microscopy. Cell viability was verified by propidium iodide assay. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the inhibitory effect of HA824 on HER-2 expression at mRNA level. Atomic force microscopy (AFM) scanning techniques was employed to observe the change of membrane pore size. RESULTS: AS-ODNs transfection efficiency showed an increasing tend with microbubble concentration, but not with liposome concentration. Maximum transfection efficiency with minimum cell viability was achieved under 2% microbubble concentration. Too strong sonoporation activity would enlarge membrane pores significantly and cause low cell viability. CONCLUSION: US-mediated AS-ODNs transfection enhanced by phospholipids-based microbubbles represents an effective and safe avenue.

Cell Line, Tumor↗

PubMed2006

Salvianolic acid B improves motor function after cerebral ischemia in rats.

In a previous short-term study, salvianolic acid B was reported to have a protective effect on cerebral ischemia. Here, we investigated whether salvianolic acid B improves the recovery of motor function after cerebral ischemia in a 14-day investigation. Cerebral ischemia was induced by middle cerebral artery occlusion in rats. Motor function was evaluated with beam-walking performance. Neural cell injury in both the sensorimotor cortex and CA1 of the hippocampus ipsilateral to ischemia was studied by Nissl stain with methylene blue. The integrity of cerebral microvessels was monitored by immunoglobulin extravasations. Neurogenesis in the subgranular zone in the dentate gyrus of the hippocampus was detected with 5'-bromo-2'-deoxyuridine incorporation. Animals receiving salvianolic acid B at a dose of 10 mg/kg had a more rapid recovery of beam-walking performance than vehicle-treated ischemia animals, and the improvement became significant at 10 and 14 days after ischemia (P<0.05). Treatment with salvianolic acid B at a dose of 10 mg/kg also significantly prevented neural cell loss in CA1 of the hippocampus. Neural cells in the sensorimotor cortex were also preserved in animals that received salvianolic acid B at a high dose of 10 mg/kg. Salvianolic acid B (10 mg/kg) also improved the integrity of microvessels after ischemia. We observed a slight increase in 5'-bromo-2'-deoxyuridine-positive cells in the subgranular zone of the hippocampus in the animals treated with salvianolic acid B at a dose of 10 mg/kg. These data indicate that salvianolic acid B could improve the recovery of motor function after cerebral ischemia in rats.

Animals↗

PubMed2006

Cross-reactivity among shrimp, crab and scallops in a patient with a seafood allergy.

Shrimp is known to be the most common causative agent in seafood allergy. Patients with shrimp allergy often exhibit allergic symptoms to a variety of seafoods such as crabs and clams. We experienced a 14-year-old girl with shrimp allergy who developed oral swelling and pain accompanied with an uncomfortable feeling after ingestion of scallops followed by intensive exercise. Laboratory investigation showed that she had serum immunoglobulin (Ig)E molecules reacting with several kinds of crustaceans and mollusks, including shrimp, crab and scallops. Immunoblotting revealed that her serum IgE reacted with the 38 kDa bands for shrimp, crab and scallops, suggesting that tropomyosin was the major allergen. Dot-blot inhibition analysis showed a cross-reactivity among shrimp, crab and scallops. We conclude that the cross-reactivity of IgE in this patient resulted from the high homology of tropomyosins.

Adolescent↗

PubMed2006

Infectious keratitis related to orthokeratology.

PURPOSE: To report 28 cases of infectious keratitis related to orthokeratology lens overnight wear in China. METHODS: From March 2000 to August 2001, 28 cases of infectious keratitis related to overnight orthokeratology lens wear were diagnosed in Beijing Institute of Ophthalmology. These were retrospectively reviewed with regard to the pathogens isolated, duration of wear, the time since onset of symptoms, and age. Cultures of corneal scrapes for bacteria, fungus and Acanthamoeba were performed in all of the 28 cases. RESULTS: All cases were students, including 10 males and 18 females, average age was 16 years (range 10-21 years). The duration of orthokeratology overnight wearing was from 2 weeks to 2 years. Uncorrected visual acuity (UCVA) on initial examination in our institute was from 20/200 to light perception. Of 28 isolates, 24 were culture positive (including 11 bacteria, 11 Acanthamoeba and two fungi), and four were culture negative. In two of the four culture negative cases, Acanthamoeba cysts were detected in the corneal stroma with the confocal microscope. Acanthamoeba and Pseudomonas aeruginosa accounted for 75% (21 of 28) of the cases of infectious keratitis. CONCLUSION: Infectious keratitis is a severe complication associated with overnight orthokeratology lens wear. Ophthalmologists should pay more attention to this complication in practice.

Acanthamoeba Keratitis↗

PubMed2006

Fluoride down-regulates the expression of matrix metalloproteinase-20 in human fetal tooth ameloblast-lineage cells in vitro.

Fluoride is associated with a decrease in the incidence of dental caries, but excessive fluoride intake during tooth enamel formation can result in enamel fluorosis. Fluorosed enamel has increased porosity, which has been related to a delay in the removal of amelogenin proteins as the enamel matures. This delay in protein removal suggests that fluoride may affect either the amount or the activity of enamel matrix proteinases. In this study, we investigated the role of fluoride in the synthesis and secretion of matrix metalloproteinase-20 (MMP-20), the proteinase primarily responsible for the initial hydrolysis of amelogenin during the secretory stage of enamel formation. Cultured human fetus tooth organ ameloblast-lineage cells were exposed to 10 microM fluoride and analyzed for synthesis of MMP-20. Immunoblotting showed that 10 microM NaF down-regulated the synthesis of MMP-20 by 21% compared with control cells, but did not alter the amount of amelogenin or kalikrein-4 (KLK-4) synthesized by the cells. Real-time polymerase chain reaction (PCR) showed that 10 microM NaF down-regulated MMP-20 mRNA expression to 28% of the levels found in the non-treated cells. These in vitro results suggest that fluoride can alter the expression of MMP-20 by ameloblasts, resulting in a disturbance of the balance between MMP-20 and its substrate that may contribute to the retention of amelogenins in the formation of fluorosed enamel.

Ameloblasts↗

PubMed2006

Differentiation of human ameloblast-lineage cells in vitro.

Previous studies have shown that ameloblast-like cells can be selectively cultured from the enamel organ in a serum-free medium with low calcium concentrations. The purpose of this study was to further characterize this culture system to identify differentiated ameloblast-lineage cells. Tooth organs from 19-24-wk-old fetal cadavers were either frozen and cryosectioned for immunostaining, or digested in collagenase/dispase for cell culture. The cells were grown in keratinocyte media supplemented with 0.05 mM calcium, and characterized by morphology and immunofluorescence. Epithelial clones with two distinct morphologies, including smaller cobblestone-shaped cells and larger (5-15 times in size) rounded cells, began to form between day 8 and day 12 after culture. The cobblestone-shaped cells continued to proliferate in culture, while the larger cells proliferated slowly or not at all. These larger cells formed filopodia, usually had two or more nuclei and a radiating cytoplasm at the cell margin, and were more abundant with increasing time in culture. Both cell types stained for cytokeratin 14, and the larger cells appeared more differentiated, showing stronger staining for amelogenin and ameloblastin. Immunofluorescence of the tooth bud sections showed staining for these matrix proteins as ameloblasts differentiated from the inner enamel epithelium. These results show the successful culture of differentiating ameloblast-lineage cells, and lay a foundation for use of these cells to further understand ameloblast biology with application to tooth enamel tissue engineering.

Ameloblasts↗

PubMed2006

Adenovirus-mediated expression of both antisense ODC and AdoMetDC inhibited colorectal cancer cell growth in vitro.

AIM: To construct a recombinant adenovirus that can simultaneously express both antisense ornithine decarboxylase (ODC) and adenosylmethionine decarboxylase ( AdoMetDC ) and detect its inhibitory effect on the intracellular polyamine pool and colorectal cancer cell growth. METHODS: A 205-bp cDNA of AdoMetDC was reverse-inserted into recombinant pAdTrack-ODCas vectors and recombined with pAdEasy-1 vectors in AdEasy-1 cells. Positive clones were selected and transfected into the packaging cell HEK293 after they were linearized by PacI. Green fluorescent protein expression was used to monitor the process of adenovirus packaging. The ODC and AdoMetDC protein levels were identified by western blotting, and intracellular polyamine content was detected by reverse-phase high performance liquid chromatography. A viable cell count was used to determine the growth of HT-29 cells with or without exogenous polyamine. RESULTS: Sequencing confirmed that AdoMetDC cDNA was successfully ligated into the pAdTrack-ODCas vector. GFP expression in 293 cells during virus packing and amplification was observed by fluorescence microscopy. Western blotting demonstrated that both ODC and AdoMetDC were downregulated by Ad-ODC-AdoMetDCas, and consequently 3 kinds of polyamine (putrescine, spermidine and spermine) were reduced to very low levels. HT-29 cell growth was significantly inhibited as compared with control conditions, and growth arrest was not reversed by exogenous putrescine. CONCLUSION: The successfully constructed recombinant adenovirus, Ad-ODC-AdoMetDCas, blocked polyamine synthesis and has therapeutic potential for treating colorectal cancer in vitro.

Adenosylmethionine Decarboxylase↗

PubMed2006

Antitumor effect of antisense ornithine decarboxylase adenovirus on human lung cancer cells.

Ornithine decarboxylase (ODC), the first enzyme of polyamine biosynthesis, was found to increase in cancer cells, especially lung cancer cells. Some chemotherapeutic agents aimed at decreasing ODC gene expression showed inhibitory effects on cancer cells. In this study, we examined the effects of adenoviral transduced antisense ODC on lung cancer cells. An adenovirus carrying antisense ODC (rAd-ODC/Ex3as) was used to infect lung cancer cell line A-549. The 3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay was used to analyze the effect on cell growth. Expression of ODC and concentration of polyamines in cells were determined by Western blot analysis and high performance liquid chromatography. Terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling was used to analyze cell apoptosis. The expression of ODC in A-549 cells was reduced to 54%, and that of three polyamines was also decreased through the rAd-ODC/Ex3as treatment. Consequently, cell growth was substantially inhibited and terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling showed that rAd-ODC/Ex3as could lead to cell apoptosis, with apoptosis index of 46%. This study suggests that rAd-ODC/Ex3as has an antitumor effect on the human lung cancer cells.

Adenoviridae↗