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Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 73 records · Page 4Linked to original sources
PubMed2004

Fibre reinforced composite dental bridge. Part II: Numerical investigation.

Motivated by the clinical success and limitations on experimental investigation of the fibre-reinforced composite dental bridge, this paper aims at providing a numerical investigation into the bridge structure. The finite element (FE) model adopted here is constructed from computer tomography images of a physical bridge specimen. The stress and strain distributions in the bridge structure especially in the bonding interfaces are analyzed in detail. The peak stresses and their variations with the different bridge designs are evaluated. Due to the lower bond strengths of adhesives and the high stress concentration in the pontic-abutment interface, the likelihood of failure in the interface is predicted by finite element analysis. The validity of the numerical results is established by a good agreement between the FE prediction and the tests in the load-deflection responses, the structural stiffness as well as the failure location of the composite dental bridge.

Composite Resins↗
PubMed2004

Expression of Smad2 and Smad4 in mouse uterus during the oestrous cycle and early pregnancy.

SMAD2 and SMAD4 are intracellular transducers of TGF-beta superfamily. In situ hybridization and semi-quantitative RT-PCR were employed to determine the temporal and spatial expression of Smad2 and Smad4 mRNA in mouse uterus during the oestrous cycle and early pregnancy. Smad2 mRNA was predominantly present in the luminal and glandular epithelium at dioestrus and prooestrus, while Smad4 expression was at a steady level in the luminal and glandular epithelium throughout the oestrous cycle. During pre-implantation period, Smad2 hybridization signals were accumulated in the luminal and glandular epithelium at a basal level; Smad4 mRNA appeared in the epithelium with a little variation in hybridization signal intensity. After implantation, on day 5 of pregnancy, Smad2 signals were localized to the subluminal stroma surrounding the implanting blastocyst, and Smad4 mRNA were accumulated in the decidua near the luminal epithelium. Both Smads were present in the decidua on days 6-7 with a switch from the mesometrial pole to the antimesometrial pole. RT-PCR results showed that both Smad2 and Smad4 mRNA levels were rising during peri-implantatation. The results suggest that Smad2 and Smad4 might be involved in the cycling changes of mouse uterus during the oestrous cycle and embryo implantation.

Animals↗
PubMed2004

Soyfood consumption and risk of glycosuria: a cross-sectional study within the Shanghai Women's Health Study.

OBJECTIVE: To assess the association between soyfood intake and risk of glycosuria. DESIGN AND METHODS: A cross-sectional study was conducted among participants of the Shanghai Women's Health Study, a population-based cohort study of women aged 40-70 y. Information on usual intake of soyfoods was obtained at baseline survey through an in-person interview using a validated food-frequency questionnaire. Included in this study were 39,385 cohort members screened for diabetes at the baseline survey and free of previously diagnosed diabetes, cardiovascular diseases, kidney diseases, and cancer. There were 323 women who tested positive for urine glucose. Odds ratios (ORs) and 95% confidence intervals (CIs) were employed to measure the association between soyfood intake and glycosuria using unconditional logistic regression. SETTING: Urban communities of Shanghai, China. RESULTS: Overall, soyfood intake was not related to the risk of glycosuria. Among postmenopausal women, however, intake of tofu and other soy products was inversely associated with risk of glycosuria after adjustment for potential confounders. The ORs across quintiles of intake were 1.0, 0.75 (95% CI=0.47-1.20), 0.79 (95% CI=0.51-1.25), 0.53 (95% CI=0.32-0.88), and 0.51 (95% CI=0.26-0.98; P for trend=0.05). Further analyses showed that the inverse association was primarily confined to postmenopausal women with a body mass index (BMI) of <25 kg/m2. The adjusted OR comparing the extreme quintiles was 0.36 (95% CI=0.13-0.97; P for trend=0.004). CONCLUSIONS: Soyfoods may play a role in the development of glycosuria, an important indicator of diabetes, among postmenopausal women with a low BMI.

Adult↗
PubMed2004

Body fat distribution and risk of diabetes among Chinese women.

OBJECTIVE: To assess the relationship between measures of central and overall obesity and risk of diabetes. DESIGN: Nested case-control study. SETTING: Shanghai, China. PARTICIPANTS: A total of 57 130 women were screened for diabetes at enrollment for the Shanghai Women's Health Study (SWHS), a population-based cohort study of Chinese women aged 40-70 y. In this study, 345 women diagnosed with diabetes and 2760 age-matched controls (eight controls per case), randomly selected from women who tested negative for urine glucose, were included. RESULTS: Risk of diabetes increased significantly with increasing levels of obesity, particularly with measures of central obesity. Compared to those in the lowest quartile, women in the highest quartile of body mass index (BMI) (>/=26.57) and waist to hip ratio (WHR) (>/=0.855) had a 2.57-fold (95% CI 1.75-3.77) and a 6.05-fold (95% CI 4.05-9.04) increased risk of diabetes, respectively. The risk of diabetes was elevated with increasing WHR at all levels of BMI, while the positive association between BMI and diabetes was observed primarily among women with a low WHR. However, test for multiplicative interaction was not statistically significant. CONCLUSIONS: Our data indicated that central obesity is a stronger risk factor for diabetes than overall obesity, suggesting that WHR may be a better indicator of risk of diabetes than BMI among Chinese women.

Adult↗
PubMed2004

Anthropometric predictors of coronary heart disease in Chinese women.

OBJECTIVE: To evaluate the associations of body size and fat distribution with incidence of coronary heart disease (CHD) in Chinese women. DESIGN: Population-based, prospective cohort study. SUBJECTS: A total of 67 334 women aged 40-70 y, who had no prior history of CHD, stroke, and cancer at study recruitment. MEASUREMENTS: Weight, standing and sitting heights, circumferences of waist and hip, and ratios of the anthropometric measurements. OUTCOME: incidence of CHD (non-fatal myocardial infarction (MI) or fatal CHD). RESULTS: After a mean follow-up of 2.5 y (168 164 person-years), there were 70 incident cases of CHD (49 non-fatal MIs and 21 CHD deaths). Body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-standing height ratio (WHtR), waist-to-sitting height ratio (WsHtR), and conicity index were all positively associated with the risk of CHD. With the exception of WHR, all other anthropometric indexes only predicted the risk of CHD among women </=55 y of age at enrollment. The relative risks (RRs) between extreme tertiles of BMI were 9.0 (95% CI, 2.0-41.5; P for trend=0.002) for younger women vs 1.3 (0.6-3.0; P for trend=0.83) for older women. Similarly, the RRs for WC, WHtR, WsHtR, and conicity index were 6.1 (1.8-21.4) vs 1.9 (0.6-5.4), 9.4 (2.6-33.8) vs 1.2 (0.5-3.1), 15.2 (3.3-69.1) vs 1.0 (0.4-2.5), and 7.8 (2.2-28.0) vs 0.9 (0.4-2.3) for the young and elderly, respectively. In contrast, the RR for WHR was 3.2 (1.1-9.1) for the young and 2.9 (1.0-8.4) for the elderly. CONCLUSIONS: WHR was positively associated with the risk of CHD in both younger and older women, while other anthropometrics, including BMI, were related to CHD risk primarily among younger women.

Adult↗
PubMed2004

Effects of high intensity focused ultrasound on vascular endothelial growth factor in melanoma bearing mice.

This study was to investigate the effects of high intensity focused ultrasound on vascular endothelial growth factor. A B16 melanoma model was adopted in our study. Melanoma bearing mice were randomly divided into two groups: HIFU group and surgery group. While the control group was only injected with isovolumetric normal saline solution and treated as the surgery group. We detected VEGF both in tissues and sera through immunohistochemical method and ELISA respectively. Tissues were sampled pre- and at the 3rd day post-operation in HIFU group and blood samples were taken pre- and at the 1st, 3rd, and 7th day post-operation in all the groups. As a result, in the tissues, VEGF was expressed in 80% melanomas, but none was detected in the targeted area after HIFU treatment. In the sera, there was a decreasing tendency of serum-VEGF concentrations in group HIFU and surgery after operation, while that in the control group increased after operation. The levels in the HIFU group on day 1, 3, and 7 postoperatively were all lower than that in the surgery group respectively (79.16 pg/ml vs 91.59 pg/ml; 33.64 pg/ml vs 49.39 pg/ml; 30.37 pg/ml vs 46.68 pg/ml), but there wasn't any significant difference (P > 0.05). So HIFU can destroy VEGF in the targeted area and maybe have less of an effect on serum-VEGF than surgery.

Animals↗
PubMed2004

Locomotor activity and behavior of mutant mice deleted for gastrin gene expression.

The current studies were initiated to investigate the role of brain-gut peptide, gastrin, on locomotor activity and anxiety-like behavior. Young, male mutant mice, lacking gastrin gene expression (GAS-KO mice), were used in the experiments. The locomotor activity of GAS-KO vs wild type (WT) mice was compared by open field test. The anxiety-like behavior was examined using elevated plus maze. The time and entries to the open arms of the elevated plus maze were used as an indicator for the anxiety-like behavior and the data were analyzed using Hindsight program. On the open field test, locomotor activity of GAS-KO mice was similar to that of the WT mice for the first 10 min of the test, but decreased significantly after that. Anxiety-like behavior was more evident in the GAS-KO vs WT mice in the elevated plus maze experiments. The number of entries to and time spent on the open arms of plus-maze were significantly reduced for the GAS-KO vs WT mice suggesting an increased anxiety-like behavior of GAS-KO mice. Our studies suggest that normal circulating levels of gastrins may play a direct or indirect role in the regulation of locomotor activity and anxiety-like behavior.

Animals↗
PubMed2003

The C-terminal module of Chi1 from Aeromonas caviae CB101 has a function in substrate binding and hydrolysis.

The chitinase gene chi1 of Aeromonas caviae CB101 encodes an 865-amino-acid protein (with signal peptide) composed of four domains named from the N-terminal as an all-beta-sheet domain ChiN, a triosephosphate isomerase (TIM) catalytic domain, a function-unknown A region, and a putative chitin-binding domain (ChBD) composed of two repeated sequences. The N-terminal 563-amino-acid segment of Chi1 (Chi1DeltaADeltaChBD) shares 74% identity with ChiA of Serratia marcescens. By the homology modeling method, the three-dimensional (3D) structure of Chi1DeltaADeltaChBD was constructed. It fit the structure of ChiA very well. To understand fully the function of the C-terminal module of Chi1 (from 564 to 865 amino acids), two different C-terminal truncates, Chi1DeltaChBD and Chi1DeltaADeltaChBD, were constructed, based on polymerase chain reaction (PCR). Comparison studies of the substrate binding, hydrolysis capacity, and specificity among Chi1 and its two truncates showed that the C-terminal putative ChBD contributed to the insoluble substrate-protein binding and hydrolysis; the A region did not have any function in the insoluble substrate-protein binding, but it did have a role in the chitin hydrolysis: Deletion of the A region caused the enzyme to lose 30-40% of its activity toward amorphous colloidal chitin and soluble chitin, and around 50% toward p-nitrophenyl (pNP)-chitobiose pNP-chitotriose, and its activity toward low-molecular-weight chitooligomers (GlcNAc)3-6 also dropped, as shown by analysis of its digestion processes. This is the first clear demonstration that a domain or segment without a function in insoluble substrate-chitinase binding has a role in the digestion of a broad range of chitin substrates, including low-molecular-weight chitin oligomers. The reaction mode of Chi1 is also described and discussed.

Aeromonas↗
PubMed2003

Identification of a collagen-like protein gene from white spot syndrome virus.

The most unique feature of white spot syndrome virus (WSSV) is the presence of a collagen-like protein (termed as WSSV-CLP). In this report, the N-terminal fragment of WSSV-CLP (CLPn) was expressed as a fusion protein with glutathione S-transferase (GST) in Escherichia coli and purified. Specific antibody was then raised against the purified fusion protein (GST-CLPn). Temporal analysis showed that the WSSV collagen gene was an early viral gene. Immunogold localization using specific antibody revealed that the gold particles, under a transmission electron microscope, were presented along the outer envelope of WSSV virions. This experiment suggested that the collagen gene encoded an envelope protein of WSSV. Using immuno-affinity chromatography, the WSSV-CLP was purified from crudely purified WSSV virions. The WSSV-CLP was N-glycosylated, as indicated by the increased migration in SDS-PAGE after treatment with N-linked glycosidase F.

Animals↗
PubMed2003

Genomic characterization of Rim2/Hipa elements reveals a CACTA-like transposon superfamily with unique features in the rice genome.

The availability of huge amounts of rice genome sequence now permits large-scale analysis of the structure and molecular characteristics of the previously identified transposase-encoding Rim2 (also called Hipa) element, which is transcriptionally activated by infection with the fungal pathogen Magnaporthe grisea and by treatment with the corresponding fungal elicitor. Based on genomic cloning and data mining from 230 Mb of rice genome sequence, 347 Rim2 elements, with an average size of 5.8 kb, were identified. This indicates that an estimated total of 600-700 Rim2 elements are present in the whole genome. Rim2 insertions occur non-randomly on the chromosomes, as visualized by fluorescence in situ hybridization. The elements harbor 16-bp terminal inverted repeats with the core sequence CACTG, 16-bp sub-terminal repeats, internal variable regions, 3-bp target sequence duplications in the flanking regions, and genes coding for Rim2 proteins (the putative transposase) and hydroxyproline-rich glycoproteins. High levels of insertion into genic regions are observed for members of this family, and the transposition history of the family can be deduced from the high level of shared sequences and analysis of repeat target sites of the elements. Phylogenetic analysis indicates that the putative RIM2 proteins fall into a subgroup distinct from the TNP2-like subgroup of transposases. Southern hybridization with genomic DNA from monocotyledonous and dicotyledonous plants demonstrates that the RIM2-coding sequence is unique to the Oryza genome. Our results demonstrate that the Rim2 elements from rice belong to a distinct superfamily of CACTA-like elements with evolutionary diversity.

Amino Acid Sequence↗
PubMed2003

Coherent acousto-optic mode coupling in dispersion-compensating fiber by two acoustic gratings with orthogonal vibration directions.

The acousto-optic mode coupling from core to LP11(cl) mode of a dispersion-compensating fiber excited by two acoustic waves with orthogonal perturbations is studied by use of a novel composite piezoelectric transducer. Highly polarization-dependent mode-selective spectra are observed that are due to coherent acousto-optic coupling between the core and various constituent cladding modes. Potential applications for implementing an all-fiber wavelength-tunable polarization analyzer are also discussed.

Journal Article↗
PubMed2003

Fasting differentially regulates expression of agouti-related peptide, pro-opiomelanocortin, prepro-orexin, and vasoactive intestinal polypeptide mRNAs in the hypothalamus of Japanese quail.

Research in mammals has established the existence of a neuronal network that lies within the hypothalamus and that regulates energy homeostasis. However, it is unknown whether this system has been evolutionarily conserved. The objective of the present study was therefore to examine the influence of the agouti-related peptide (AGRP), pro-opiomelanocortin (POMC), prepro-orexin, and vasoactive intestinal polypeptide (VIP) genes on energy balance in birds by quantifying the effect of a 24-h fast on their expression in the hypothalamus of the Japanese quail. In situ hybridization revealed strong signals for AGRP and POMC mRNAs in the infundibular nucleus (IN), for prepro-orexin in the lateral hypothalamic area (LHy) and periventricular hypothalamic nucleus, and for VIP in the LHy. POMC mRNA was co-localized with alpha-melanocyte-stimulating hormone-like immunoreactivity in individual IN neurons. Compared with the ad-libitum-fed state, a 24-h fast resulted in a 2.2-fold increased expression of AGRP mRNA in the IN. However, fasting did not induce changes in POMC, prepro-orexin, or VIP mRNAs. The results suggest an involvement of the central melanocortin system in the regulation of energy balance in birds, as in mammals. In contrast, orexins in birds may be primarily involved in the control of physiological functions other than energy homeostasis.

Agouti-Related Protein↗
PubMed2003

DNA delivery from an intravascular stent with a denatured collagen-polylactic-polyglycolic acid-controlled release coating: mechanisms of enhanced transfection.

We previously demonstrated that DNA-polylactic-polyglycolic acid (PLGA)-coated stents can deliver genes to the arterial wall with reporter expression involving 1% of neointimal cells. The present study investigated a novel formulation utilizing denatured collagen in DNA-stent coatings; denatured collagen was hypothesized to enhance gene transfer due to adhesion molecule interactions and actin-related mechanisms. Arterial smooth muscle cells (SMCs) cultivated on denatured collagen had significantly greater plasmid DNA (beta-galactosidase) transfection than SMC grown on native collagen (18.3+/-1.2 vs 1.0+/-0.1%, P<0.001). The denatured-collagen effect was completely blocked with anti-alpha(v)beta(3) integrin antibody. SMCs cultivated on native collagen supplemented with tenascin-C (TN-C), a protein recognized by alpha(v)beta(3) integrins, showed a 33-fold increase in transfection compared to control (P<0.001); this effect was also blocked with anti-alpha(v)beta(3) antibody. We observed that cells grown on denatured collagen had marked F-actin-enriched stress fibers and intense perinuclear G actin, compared to those grown on native collagen, which demonstrated F-actin-enriched focal adhesions without perinuclear G-actin localization. Cytochalasin-D, an F actin depolymerizing agent, caused significantly increased SMC transfection in cells cultivated on native collagen compared to control cells (18.0+/-1.8 vs 3.02+/-0.9%, P<0.001) further supporting the view that actin-related cytoskeletal changes influence transfection. A denatured-collagen-PLGA composite vascular stent coating similarly resulted in increased plasmid DNA green fluorescent protein (GFP) expression compared to controls (P<0.001) in SMC cultures; the increased transfection was blocked by anti-alpha(v)beta(3) antibody. Pig coronary studies comparing denatured-collagen-PLGA-coated stents containing plasmid DNA (encoding GFP) to coated stents without DNA demonstrated 10.8% of neointimal cells transfected; this level of expression was almost an order of magnitude greater than previously reported with a DNA delivery stent. It is concluded that denatured collagen incorporated into plasmid DNA-stent coating formulations may increase the level of gene expression in vitro and in vivo because of integrin-related mechanisms and associated changes in the arterial smooth muscle cell actin cytoskeleton.

Actins↗
PubMed2003

The inhibitory effect of VitD3 on proliferation of keratinocyte cell line HACAT is mediated by down-regulation of CXCR2 expression.

Psoriasis is a disease characterized by inflammation and increased population of hyperproliferative keratinocytes. It is well known that chemokines and chemokine receptors, such as interleukin-8 and its receptors (CXCR1 and CXCR2), play important roles in the pathogenesis of psoriasis. So far, examination of CXCR2 expression in psoriatic lesional keratinocytes by FACS calibur has not been reported and whether VitD3 inhibits psoriatic lesional keratinocyte proliferation through down-regulation of CXCR2 expression has not been elucidated. In the present study, CXCR2 expression in psoriatic lesional keratinocytes and HACAT treated with VitD3 was detected by flow cytometry. The proliferative capacity of HACAT treated with VitD3 was assayed by MTT assay. The results showed that CXCR2 expression in psoriatic lesional keratinocytes was higher than that in normal human keratinocytes. At the correct concentration VitD3 could inhibit human keratinocyte proliferation and down-regulate CXCR2 expression in HACAT. The data demonstrate that the inhibitory effect of VitD3 on keratinocyte proliferation might be mediated by down-regulation of CXCR2 expression.

Administration, Topical↗
PubMed2003

Oral administration of type II collagen suppresses pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis.

The objective of this study was to investigate the effect of the oral administration of type II collagen (CII) on pro-inflammatory mediator production by synoviocytes in rats with adjuvant arthritis (AA). Sprague-Dawley rats were fed with bovine CII either before immunization with Complete Freund's adjuvant (CFA) or after initiation of arthritis. Hind paw secondary swelling was measured and synoviocytes were harvested. Sera from portal vein of oral tolerized rats were collected and in vitro synoviocytes culture or synoviocytes-Peyer's Patches (PP) cells coculture system were developed. Interleukin (IL)-1 activity was measured by a mouse thymocyte activation assayed by MTT dye reduction and tumour necrosis factor (TNF) activity was measured by an L929 cytotoxicity bioassay. Nitric oxide (NO) and malondialdehyde (MDA) levels were measured by biochemical methods. We found that feeding with CII (5, 50 and 500 micro g/kg) for 7 days before immunization significantly suppressed hind paw secondary swelling measured at day 16, 20, 24 and 28 (all P < 0.01) and pro-inflammatory mediator (IL-1, TNF, NO and MDA) production by synoviocytes (all P < 0.01) in rats with AA. Feeding with CII (5, 50 and 500 micro g/kg) for 7 days after initiation of arthritis had a similar effect. CII (1, 10, 100 micro g/ml) had no effect on IL-1 and TNF production by synoviocytes in vitro, but CII 10 micro g/ml suppressed IL-1 and TNF production by synoviocytes-PP cells coculture system (P < 0.01), which was antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). Portal serum (1 : 10) from oral tolerized rats suppressed IL-1 and TNF production by synoviocytes (P < 0.01), which was also antagonized by anti-TGF-beta antibody (10 micro g/ml) (P < 0.01). We conclude that oral administration of CII had prophylactic and therapeutic effects on AA and over-production of IL-1, TNF, NO and MDA by synoviocytes was suppressed. Bystander active suppression may be the main mechanism of oral CII in the suppression of synoviocyte function.

Administration, Oral↗
PubMed2003

New aspects in pathogenesis of konzo: neural cell damage directly caused by linamarin contained in cassava (Manihot esculenta Crantz).

Epidemic spastic paraparesis (konzo) found in tropical and subtropical countries is known to be caused by long-term intake of cassava (Manihot esculenta Crantz), which contains a cyanoglucoside linamarin (alpha-hydroxyisobutyronitrile-beta-d-glucopyranoside). It has been reported that linamarin is enzymatically converted to cyanide by bacteria in the intestine, and this is absorbed into the blood and then damages neural cells. However, unmetabolized linamarin was found in the urine after oral administration of cassava; thus, we hypothesized that konzo could be caused by direct toxicity of the unmetabolized linamarin that was transferred to the brain and could be transported into neural cells via a glucose transporter. In the present study it was confirmed that linamarin directly damaged neural culture pheochromocytoma cell (PC) 12 cells; 0.10 mm-linamarin caused cell death at 13.31 (SD 2.07) %, which was significantly different from that of control group (3.18 (SD 0.92) %, P=0.0004). Additional 10 microM-cytochalasin B, an inhibitor of a glucose transporter, prevented cell death: the percentage of dead cells significantly decreased to 6.06 (SD 1.98), P=0.0088). Furthermore, glucose also prevented cell death. These present results strongly suggest that linamarin competes with cytochalasin B and glucose for binding to a glucose transporter and enters into cells via glucose transporter.

Animals↗