Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 55 records · Page 3Linked to original sources

PubMed2006

[Detection of plasma urokinase-type plasminogen activator and its receptor in acute or chronic hepatitis B patients and its clinical significance.].

BACKGROUND: To study the expression of plasma uPA and uPAR in Acute or Chronic Hepatitis B patients, to investigate changes of blood fibrinolytic system in Hepatitis B and its clinical significance. METHODS: The level of detected plasma urokinase-type plasminogen activator (uPA) and urokinase-type plasminogen activator receptor (uPAR) were measured by Enzyme Linked Immuno Sorbent Assay (ELISA). RESULTS: The levels of plasma uPA and uPAR were significantly higher in patients with Acute or Chronic Hepatitis B than that of control group (P less than 0.05, P less than 0.01), and also higher in serious group than that of non-serious group of Chronic Hepatitis B patients (P less than 0.05), and also higher in chronic group than in acute group (P less than 0.05). The level of plasma uPAR was significantly higher in patients with serious jaundice than that of non-serious jaundice group (P less than 0.01). The levels of uPA and uPAR are significantly higher in acute period than that in recover period of Acute Hepatitis B patients, but the levels in recover period is also higher than that in control group. The level of plasma uPAR have positive correlation with prothrombin (PT), international normalized ratio (INR) and total bilirubin (P less than 0.01). CONCLUSION: The level of plasma UPA nad UPAR were enhanced in Acute or Chronic Hepatitis B patients was related with the degree of inflammation, was also related with high expression of serious damage of liver cell. It may be one of important cause to imbalance between coagulation and fibrinolytic in hepatitis.

Hepatitis B↗

PubMed2005

Infrared-active vibrational modes of single-walled carbon nanotubes.

The IR-active vibrational modes of single-walled carbon nanotubes have been observed by optical transmission through thin films of bundled nanotubes. Because IR-active chemical functional groups, e.g., -COOH, -OH, might be attached to the tube walls and contribute additional spectral features, we have also studied the effects of chemical purification and long-term high-temperature vacuum annealing on the IR spectrum. Through comparison with theory, we are able to assign much of the sharp structure observed in our IR spectra.

Journal Article↗

PubMed2005

Serological identification and bioinformatics analysis of immunogenic antigens in multiple myeloma.

Identifying appropriate tumor antigens is critical to the development of successful specific cancer immunotherapy. Serological analysis of tumor antigens by a recombinant cDNA expression library (SEREX) allows the systematic cloning of tumor antigens recognized by the spontaneous autoantibody repertoire of cancer patients. We applied SEREX to the cDNA expression library of cell line HMy2, which led to the isolation of six known characterized genes and 12 novel genes. Known genes, including ring finger protein 167, KLF10, TPT1, p02 protein, cDNA FLJ46859 fis, and DNMT1, were related to the development of different tumors. Bioinformatics was performed to predict 12 novel MMSA (multiple myeloma special antigen) genes. The prediction of tumor antigens provides potential targets for the immunotherapy of patients with multiple myeloma (MM) and help in the understanding of carcinogenesis. Crude lysate ELISA methodology indicated that the optical density value of MMSA-3 and MMSA-7 were significantly higher in MM patients than in healthy donors. Furthermore, SYBR Green real-time PCR showed that MMSA-1 presented with a high number of copy messages in MM. In summary, the antigens identified in this study may be potential candidates for diagnosis and targets for immunotherapy in MM.

Antigens, Neoplasm↗

PubMed2005

Immune challenge differentially affects transcript abundance of three antimicrobial peptides in hemocytes from the moth Pseudoplusia includens.

Inducible expression of antimicrobial peptides and other humoral immune factors by the insect fat body is well documented. Hemocytes comprise the second essential arm of the insect immune system but it is unclear whether antimicrobial peptide genes are expressed by all or only some types of hemocytes. Here we report the cloning of cecropin A (Pi-cecA), lebocin (Pi-leb) and lysozyme (Pi-lys) homologs from the moth Pseudoplusia includens. Relative-quantitative real-time PCR (rq-rtPCR) indicated that transcript abundance for each antimicrobial gene increased in fat body and hemocytes following immune challenge with the Gram-negative bacterium Escherichia coli. Relative transcript abundance of Pi-cecA was much higher in fat body than hemocytes. In contrast, transcript levels of Pi-leb were three-fold lower in hemocytes than fat body while transcript levels of Pi-lys were three-fold higher. Estimates for the overall contribution of the fat body and hemocytes to antimicrobial peptide expression suggested that hemocytes contribute significantly to Pi-lys transcript levels in larvae but produce much smaller amounts of Pi-cecA and Pi-leb compared to the fat body. Each antimicrobial peptide was also inducibly expressed in hemocytes following challenge with the Gram-positive bacterium Micrococcus luteus or when hemocytes formed capsules around chromatography beads. Analysis of hemocyte types indicated that granulocytes and plasmatocytes expressed all three antimicrobial peptides, whereas spherule cells and oenocytoids expressed only lysozyme. Transcriptional profiles of these antimicrobial genes were similar in granulocytes and plasmatocytes in vivo but were very different in vitro.

Amino Acid Sequence↗

PubMed2005

Atomic-scale imaging of wall-by-wall breakdown and concurrent transport measurements in multiwall carbon nanotubes.

We report the atomic-scale imaging with concurrent transport measurements of the breakdown of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezomanipulator. We found unexpectedly three distinct breakdown sequences: namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic.

Journal Article↗

PubMed2005

Quantitative trait loci for partial resistance to crown rust, Puccinia coronata, in cultivated oat, Avena sativa L.

To facilitate the detection of quantitative trait loci (QTLs) for partial resistance to oat crown rust, Puccinia coronata f. sp. avenae Eriks., a genetic map was generated in a population of 158 F(6)-derived oat recombinant inbred lines from a cross of a partial resistance line MN841801-1 by a susceptible cultivar selection 'Noble-2'. The map, developed using 230 marker loci, mostly restriction fragment length polymorphism and amplified fragment length polymorphism markers, spanned 1,509 cM (Haldane) arranged into 30 linkage groups of 2-18 markers each. Four consistently detected major QTLs for partial rust resistance, Prq1a, Prq1b, Prq2, and Prq7, and three minor QTLs, Prq3, Prq5, and Prq6, were found in tests involving three field and two greenhouse environments. In addition, two major QTLs for flowering time, Ftq1 and Ftq7, and five weaker QTLs, Ftq2, Ftq3, Ftq4, Ftq5, and Ftq6, were revealed. Overlapping of the map segments of Ftq1 and Prq1 and of Ftq7 and Prq7 suggested either linkage between the flowering time QTLs and resistance QTLs or a pleiotropic effect of the Ftq QTLs on rust resistance. Relatively low heritability estimates (0.30) obtained for partial resistance to crown rust in the field indicate a potential value for marker-assisted selection.

Avena↗

PubMed2005

The genome of the social amoeba Dictyostelium discoideum.

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

ATP-Binding Cassette Transporters↗

PubMed2005

Regulation of parathyroid hormone-related peptide by estradiol: effect on tumor growth and metastasis in vitro and in vivo.

We evaluated the capacity of estradiol (E(2)) to regulate PTHrP production, cell growth, tumor growth, and metastasis to the skeleton in breast cancer. In estrogen receptor (ER)-negative human breast cancer cells, MDA-MB-231, and cells transfected with full-length cDNA encoding ER (S-30), E(2) caused a marked decrease in cell growth and PTHrP production, effects that were abrogated by anti-E(2) tamoxifen. E(2) also inhibited PTHrP promoter activity in S-30 cells. For in vivo studies, MDA-MB-231 and S-30 cells were inoculated into the mammary fat pad of female BALB/c nu.nu mice. Animals receiving S-30 cells developed tumors of significantly smaller volume compared with MDA-MB-231 tumor-bearing animals. This change in tumor volume was reversed when S-30 cells were inoculated into ovariectomized (OVX) hosts. Inoculation of MDA-MB-231 cells into the left ventricle resulted in the development of lesions in femora and tibia as determined by x-ray analysis. In contrast, these lesions were significantly smaller in volume and number in animals inoculated with S-30, and this lower incidence was reversed in OVX animals. Bone histological analysis showed that the tumor volume to tissue volume ratio was comparable with that seen by x-ray. Immunohistochemical analysis showed that PTHrP production was inhibited in S-30 group and restored to levels comparable to that seen in MDA-MB-231 tumor-bearing animals when S-30 cells were inoculated in OVX animals. Collectively these studies show that E(2) production is inversely correlated with PTHrP production and that the growth-promoting effect of PTHrP has a direct impact on tumor growth at both nonskeletal and skeletal sites.

Animals↗

PubMed2005

Effect of load and temperature on in vitro degradation of poly(glycolide-co-L-lactide) multifilament braids.

The effects of load and temperature on in vitro degradation behaviors of poly(glycolide-co-L-lactide) 90/10 multifilament braids were investigated in phosphate buffer solution at pH 7.4. The property changes of the braids with time were monitored by tensile test, gel permeation chromatography analysis, and scanning electron microscopy. The interrelationships between material properties, time and experimental conditions were explored. The results showed that the polymer braids gradually lost their strength and molecular weight with the increasing in vitro time. While the load levels applied had no effect on the materials, raising temperatures significantly accelerated the degradation. It was found that for a given tensile breaking strength retention (BSR), the dependence of degradation time on temperature could be illustrated by an Arrhenius-type equation, from which the activation energy could be derived. Further analysis indicated that there are well-defined relationships between molecular weight, BSR and breaking strain retention, and these relationships can be illustrated mathematically. Finally, the surface morphology of the fiber showed visible change during the degradation process.

Absorbable Implants↗

PubMed2005

Beta cell function and response to treatment in Nigerians with Type 2 diabetes mellitus.

There are scant data from African populations on the association between beta-cell function and response to treatment with oral hypoglycaemic agents in Type 2 diabetes mellitus (T2DM). Fasting plasma C-peptide (FCP) and glucagon-stimulated C-peptide (GSCP) levels were measured in 116 Nigerians with T2DM at a university teaching hospital. After 9 months of follow-up and treatment, they were categorized into three groups based on response to treatment: (A) good control but not on maximum sulphonylurea (SU) therapy, (B) inadequate control but not on maximum SU therapy and (C) on maximum SU therapy+/-insulin or biguanide. Logistic regression models were used to investigate how well C-peptide levels predicted the subjects belonging to Group C who are likely to require insulin. The mean FCP and mean GSCP levels of Group C were significantly lower than in the other groups (p=0.024; p= <0.001 respectively). A GSCP cut-off value of < or =1.3 ng/mL predicted membership of Group C with 85% sensitivity and 89% specificity while a cut-off of < or =1.8 ng/mL was associated with 91% sensitivity and 66% specificity. In resource-poor settings where inadequate treatment are common, estimation of GSCP may be useful in predicting treatment response and should be weighed against the cost of inadequate therapy with higher morbidity and mortality.

Blood Glucose↗

PubMed2005

Psychological symptoms and nonfatal unintentional injuries among Chinese adolescents: a prospective study.

PURPOSE: To describe patterns of nonfatal unintentional injuries and investigate the association of psychological symptoms with injury risk among adolescents in Guangxi, China. METHODS: Adolescents were selected from middle and high school students in Baise City, Guangxi, China. Psychological symptoms at baseline were measured using SCL-90-R and nonfatal unintentional injuries that occurred among participants were recorded using a standardized injury surveillance questionnaire. Annual injury rates per 100 adolescents by adolescents' demographic and family characteristics were calculated. Student's t-test and the Chi-square test were used to test differences in mean raw scores of SCL-90-R subscales and injury rates. Relative risks and odds ratios of injury with 95% confidence intervals were calculated in univariate analyses and multivariate logistic models. RESULTS: A total of 1474 middle and high school students finished the study. Of them, 442 reported nonfatal unintentional injuries during the study period, resulting in an annual injury rate of 30.3 per 100 adolescents. Boys had a significantly higher injury rate than girls (32.6% vs. 27.4%). Injury rate decreased as the adolescents' age increased. Compared with adolescents who were not injured, the injured adolescents had higher average raw scores of all subscales of SCL-90-R, with an exception of the subscale for hostility. All SCL-90-R subscales factors, except those for hostility and phobia, were associated with injury risk. After confounding effects of age, gender, and ethnicity were controlled using logistic regression models, SCL-90-R subscales for somatization (OR = 2.00, 95% CI 1.52-2.63), obsessive-compulsiveness (OR = 2.10, 95% CI 1.71-2.58), interpersonal-sensitivity (OR = 1.66, 95% CI 1.34-2.06), depression (OR = 2.00, 95% CI 1.59-2.51), anxiety (OR = 2.08, 95% CI 1.62-2.66), and psychoticism (OR = 1.60, 95% CI 1.26-2.03) were significantly associated with an elevated injury risk. CONCLUSION: Psychological symptoms are associated with an elevated risk of nonfatal unintentional injury among middle and high school students. Mental health services, such as psychological counseling, may help reduce the risk of nonfatal unintentional injuries among Chinese adolescents.

Accidents↗

PubMed2005

Pravastatin modulates early diabetic nephropathy in an experimental model of diabetic renal disease.

BACKGROUND: Development of diabetes causes early functional (endothelial dysfunction) and morphological abnormalities in the kidney. If left untreated, these will ultimately progress to renal failure. Apart from strategies aimed at maintaining very tight glycemic control, attention has turned to the development of adjuvant therapy to maintain endothelial function in these patients. The agents receiving the most critical appraisal due to their endothelial protective effects are the 3-hydrox 3-methylglutaryl (HMG)-Co-enzyme A (CoA) reductase inhibitors. The aim of the study was to investigate: (1) the early alterations in the renal diabetic injury; and (2) to examine the protective role of Pravastatin in this end-organ diabetic model. MATERIALS AND METHODS: Sprague Dawley rats (n = 21) were randomized into three groups: (1) control; (2) diabetic; and (3) diabetic treated with Pravastatin. Diabetic nephropathy was investigated with serum biochemical parameters (urea, creatinine), functional parameters (total urinary protein loss, glomerular filtration rate, renal cortical blood flow), and structural assessment (hemotoxylin and eosin staining). RESULTS: We demonstrated impairment in functional, biochemical, and structural parameters in the diabetic nephropathy group, which was diminished by treatment with Pravastatin. This was attributed to an up-regulation in endothelial constitutive nitric oxide synthase (ecNOS) expression in the treated diabetic group. CONCLUSIONS: We have shown that Pravastatin, in an experimental model of early diabetes nephropathy preserves microvascular endothelial function in the presence of hyperglycemia, thus inhibiting the early stage of diabetic microangiopathy.

Animals↗

PubMed2005

A genome-wide scan for quantitative trait loci linked to obesity phenotypes among West Africans.

OBJECTIVE: To identify quantitative trait loci (QTL) for three obesity phenotypes: body mass index (BMI), fat mass (FM) and percent body fat (PBF) in West Africans with type 2 diabetes (T2DM). DESIGN: An affected sibling pair (ASP) design, in which both siblings had T2DM. Obesity was analyzed as a quantitative trait using a variance components approach. SUBJECTS: Sib-pairs affected with T2DM from the Africa America Diabetes Mellitus (AADM) study, comprising 321 sibling pairs and 36 half-sibling pairs. MEASUREMENTS: Weight was measured on an electronic scale to the nearest 0.1 kg, and height was measured with a stadiometer to the nearest 0.1 cm. Body composition was estimated using bioelectric impedance analysis (BIA). Genotyping was carried out at the Center for Inherited Disease Research (CIDR) with a panel of 390 trinucleotide and tetranucleotide repeats. RESULTS: The obesity-related phenotype showing the strongest linkage evidence was PBF on chromosome 2 (LOD 3.30 at 72.6 cM, marker D2S739). Suggestive linkage to FM was found on chromosomes 2 (LOD 2.56 at 80.4 cM) and 5 (LOD 2.25 at 98 cM, marker D5S1725). The highest LOD score for BMI was 1.68 (chromosome 4, 113.8 cM). The areas of linkage for the three phenotypes showed some clustering as all three phenotypes were linked to the same regions of 2p13 and 5q14, and our study replicated linkage evidence for several regions previously reported in other studies. CONCLUSION: We obtained evidence for several QTLs on chromosome 2, 4 and 5 to three obesity phenotypes. This study provides data on the genetics of obesity in populations that are currently under represented in the global effort directed at understanding the pathophysiology of excess adiposity in free living individuals.

Adipose Tissue↗

PubMed2005

Differential gene expression in hematopoietic progenitors from paroxysmal nocturnal hemoglobinuria patients reveals an apoptosis/immune response in 'normal' phenotype cells.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder characterized clinically by intravascular hemolysis, venous thrombosis, and bone marrow failure. Despite elucidation of the biochemical and molecular defects in PNH, the pathophysiology of clonal expansion of glycosylphosphatidylinositol-anchored protein (GPI-AP)-deficient cells remains unexplained. In pursuit of evidence of differences between GPI-AP-normal and -deficient CD34 cells, we determined gene expression profiles of isolated marrow CD34 cells of each phenotype from PNH patients and healthy donors, using DNA microarrays. Pooled and individual patient samples revealed consistent gene expression patterns relative to normal controls. GPI-AP-normal cells from PNH patients showed upregulation of genes involved in apoptosis and the immune response. Conversely, genes associated with antiapoptotic function and hematopoietic cell proliferation and differentiation were downregulated in these cells. In contrast, the PNH clone of GPI-AP-deficient cells appeared more similar to CD34 cells of healthy individuals. Gene chip data were confirmed by other methods. Similar gene expression patterns were present in PNH that was predominantly hemolytic as in PNH associated with aplastic anemia. Our results implicate an environmental influence on hematopoietic cell proliferation, in which the PNH clone evades immune attack and destruction, while normal cells suffer a stress response followed by programmed cell death.

Antigens, CD34↗

PubMed2005

Boar taint is related to endocrine and anatomical changes at puberty but not to aggressive behaviour in entire male pigs.

This study aimed to describe the association between incidence of boar taint and pubertal changes in gonadal hormones, size of reproductive organs and aggressive behaviour in entire male pigs. In total, 111 entire male pigs were included in the study. Sampling was performed first at 90 kg live weight (LW) and, then, at 115 kg LW. Variables measured were skatole and androstenone levels in plasma and fat, testosterone and oestrone sulphate in plasma, free oestrone in fat, weight of testes and length of bulbourethral glands. Aggressive interactions between pigs were registered when a limited amount of feed was provided to the pigs prior to routine feeding. The number of initiated interactions (attacks) and the difference between number of initiated and received interactions (relative attacks) were calculated for each pig. Multivariate analysis revealed that gonadal hormones and reproductive organ size influenced prevalence of boar taint, accounting for 30% of the variation in skatole levels in fat and for 37% of the variation in androstenone levels in fat. These relations were independent of aggression levels in entire male pigs. Skatole levels were influenced by the levels of oestrone sulphate in plasma and free oestrone in fat, but not levels of plasma testosterone. Pigs with testes weight below 565 g and a bulbourethral gland length <90 mm did not produce high amounts of skatole; therefore, these values can be used as a threshold level to detect pig carcasses with low skatole levels. High androstenone levels could not be predicted by measuring reproductive organ sizes. More research is required to develop a rapid and accurate method for the analysis of carcasses of entire male pigs.

Adipose Tissue↗

PubMed2005

Biodesulfurization using Pseudomonas delafieldii in magnetic polyvinyl alcohol beads.

AIMS: To immobilize Pseudomonas delafieldii R-8 cells in magnetic polyvinyl alcohol (PVA) beads for biodesulfurization. METHODS AND RESULTS: Magnetic PVA beads were prepared by a freezing-thawing technique under liquid nitrogen. The beads have distinct super-paramagnetic properties and their saturation magnetization is 8.02 emu g(-1). The desulfurization rate of the immobilized cells could reach 40.2 mmol kg(-1) h(-1). Desulfurization patterns of dibenzothiophene in model oil with the immobilized and free cells were represented by the Michaelis-Menten equation. The Michaelis constant for both immobilized and free cells was 1.3 mmol l(-1). CONCLUSIONS: The cells immobilized in magnetic PVA beads could be stably stored and be repeatedly used over 12 times for biodesulfurization. The immobilized cells could be easily separated by magnetic field. SIGNIFICANCE AND IMPACT OF THE STUDY: Magnetic PVA beads are easy to prepare. The immobilization process in the paper is to increase the efficiency of cells and to decrease the cost of operations.

Bacterial Adhesion↗

PubMed2005

Effect of detached/re-suspended solids from sewer sediment on the sewage phase bacterial activity.

This study was conducted to make an assessment of the effects of the detached/re-suspended solids on the bacterial activity in the sewage phase of a gravity sewer. A physical sewer-model was used to simulate two extreme conditions: sewage flow without the presence of sewer sediment, and filtered sewage flow with the sediment. The first scenario was to evaluate the effect of the settling of solids on the bacterial activity, while the second scenario was to examine the effect of purely re-suspended or detached solids. The water media were aerated to obtain an initial DO level at about 6 mg/L, and the bacterial activity was monitored at a regular time interval during each operation. Two bacterial cell staining techniques, one using 4', 6-diamidino-2-phenyl indole (DAPI), and another using 5-cyano 2, 3-ditoyl tetrazolium chloride (CTC), were employed to measure the amount of total and respiring bacteria, respectively. Both the DAPI and CTC counts decreased with time in the first case, while that increased with time in the second case. The bacterial activity in a sewer phase was observed to be contributed by smaller sized particles. Also, the solids originated from the sewer sediment through re-suspension or detachment demonstrated a higher bacterial activity than the solids originally present in the sewage.

Bacteria↗

PubMed2004

Genetic basis of barley caryopsis dormancy and seedling desiccation tolerance at the germination stage.

The genomic regions controlling caryopsis dormancy and seedling desiccation tolerance were identified using 152 F4 lines derived from a cross between Mona, a Swedish cultivar, and an Israeli xeric wild barley Hordeum spontaneum genotype collected at Wadi Qilt, Israel. Dormancy, the inability of a viable seed to germinate, and desiccation tolerance, the ability of the desiccated seedlings to revive after rehydration, were characterized by fitting the germination and revival data with growth curves, using three parameters: minimum, maximum, and slope of germination or revival rate derived by the least square method. The genetic map was constructed with 85 genetic markers (SSRs, AFLPs, STSs, and Dhn genes) using the MULTIPOINT: -mapping algorithm. Quantitative trait loci (QTLs) mapping was conducted with the MULTIQTL: package. Ten genomic regions were detected that affected the target traits, seven of which affected both dormancy and desiccation tolerance traits. Both the wild barley genotype and the Swedish cultivar contributed the favorite alleles for caryopsis dormancy, whereas seedling desiccation tolerance was attributed to alleles descending from the cultivar. The results indicate that some barley dormancy genes are lost during domestication and that dormancy QTLs are associated with abiotic stress tolerance.

Chromosome Mapping↗