Biomedical subjects

C Shu

Publications and source records attributed to C Shu.

At least 19 recordsLinked to original sources

PubMed2006

Prevalence of Toxoplasma infection in first-episode schizophrenia and comparison between Toxoplasma-seropositive and Toxoplasma-seronegative schizophrenia.

OBJECTIVE: To compare the prevalence of Toxoplasma infection between the first-episode schizophrenia and the controls and to compare the clinical features between the Toxoplasma-seronegative and Toxoplasma-seropositive patients with schizophrenia. METHOD: The rate of serum reactivity to Toxoplasma in 600 schizophrenia, 600 affective disorders, and 400 controls was investigated. The clinical symptoms of the schizophrenia patients were scored and compared. RESULTS: The rate of IgG antibody, not IgM in the schizophrenia patients, was higher than the control groups, and the odds ratio of schizophrenia associated with IgG antibody was 2.22-5.12. The affective disorders did not differ in the rate of IgG or IgM antibody from the normal or the physical disease control. The seropositive schizophrenia patients had higher scores on the positive subscale and three components of Positive and Negative Symptoms Scale than the seronegative patients. CONCLUSION: This study lent further weight to the hypothesis that exposure to Toxoplasma may be a risk factor for schizophrenia.

Adolescent↗

PubMed2005

Lattice Boltzmann interface capturing method for incompressible flows.

A lattice Boltzmann interface capturing method for incompressible flows is proposed in this paper. The interface is naturally captured by minimizing the free energy functional. It is easily implemented and does not require interface reconstruction as required by most of the traditional interface tracking methods such as the volume of fluid method. Moreover, the method does not require the isotropic property of the fourth order lattice tensor as do other lattice Boltzmann methods. Thus the D2Q5 (D2 means two dimensional, Q5 means five velocity model) discrete velocity model is applied in the method. The interface profile along the flat interface and coexistence curve can be given analytically. The proposed method is validated for some test cases, and compared to the volume of fluid and level set methods. Numerical results show that the present method performs very well and can generate very sharp interfaces.

Journal Article↗

PubMed2005

Chaotic micromixers using two-layer crossing channels to exhibit fast mixing at low Reynolds numbers.

We report two chaotic micromixers that exhibit fast mixing at low Reynolds numbers in this paper. Passive mixers usually use the channel geometry to stir the fluids, and many previously reported designs rely on inertial effects which are only available at moderate Re. In this paper, we propose two chaotic micromixers using two-layer crossing channels. Both numerical and experimental studies show that the mixers are very efficient for fluid manipulation at low Reynolds numbers, such as stretching and splitting, folding and recombination, through which chaotic advection can be generated and the mixing is significantly promoted. More importantly, the generation of chaotic advection does not rely on the fluid inertial forces, so the mixers work well at very low Re. The mixers are benchmarked against a three-dimensional serpentine mixer. Results show that the latter is inefficient at Re = 0.2, while the new design exhibits rapid mixing at Re = 0.2 and at Re of O(10(-2)). The new mixer design will benefit various microfluidic systems.

Journal Article↗

PubMed2004

Lattice kinetic scheme for the incompressible viscous thermal flows on arbitrary meshes.

A lattice kinetic scheme was developed for the incompressible viscous thermal flows on arbitrary meshes. The work was based on the lattice kinetic scheme proposed by Inamuro and the technique of Taylor series expansion- and least-square-based lattice Boltzmann method (TLLBM). Compared with the lattice Boltzmann method, the lattice kinetic scheme can save the computer memory since there is no need to store the density distributions. The implementation of the boundary condition is direct and just the same as the convectional Navier-Stokes solvers. By using the idea of TLLBM, the lattice kinetic scheme can be applied on arbitrary meshes, which makes this scheme suitable for practical applications. In order to validate this lattice kinetic scheme used on arbitrary meshes, numerical simulations of the natural convection in a square cavity and the natural convection in a concentric annulus between an outer square cylinder and an inner circular cylinder are carried out, and the results are compared very well with available data in the literature.

Journal Article↗

PubMed2003

Mode conversion and birefringence adjustment by focused-ion-beam etching for slanted rib waveguide walls.

We describe how focused-ion-beam (FIB) etching of slanted rib waveguide walls can be used to modify the differential group delay in a waveguide and introduce TE to TM mode conversion in a silicon-on-insulator rib waveguide. We achieved mode conversion by modifying the geometric cross section of a single-mode rib by FIB trimming. Waveguides with different lengths of 45 degrees slant angle rib waveguide walls were fabricated and characterized. We measured the differential group delays and the mode conversion achieved for waveguides with different lengths of a FIB-trimmed slanted rib wall.

Journal Article↗

PubMed2003

Simplified thermal lattice Boltzmann model for incompressible thermal flows.

Considering the fact that the compression work done by the pressure and the viscous heat dissipation can be neglected for the incompressible flow, and its relationship with the gradient term in the evolution equation for the temperature in the thermal energy distribution model, a simplified thermal energy distribution model is proposed. This thermal model does not have any gradient term and is much easier to be implemented. This model is validated by the numerical simulation of the natural convection in a square cavity at a wide range of Rayleigh numbers. Numerical experiments showed that the simplified thermal model can keep the same order of accuracy as the thermal energy distribution model, but it requires much less computational effort.

Journal Article↗

PubMed2003

Numerical simulation of natural convection in a concentric annulus between a square outer cylinder and a circular inner cylinder using the Taylor-series-expansion and least-squares-based lattice Boltzmann method.

In this paper, natural convective heat transfer in a horizontal concentric annulus between a square outer cylinder and a heated circular inner cylinder is numerically studied using the Taylor-series-expansion and least-squares-based lattice Boltzmann method (TLLBM). The TLLBM is used to extend the current thermal model to more practical applications. Since the TLLBM is basically a meshless approach and can be applied to any complex geometry, we can easily use it to solve the complex thermal problem accurately and effectively. The present method is validated by comparing its numerical results with available data in the literature, and very good agreement has been achieved.

Journal Article↗

PubMed2002

Taylor-series expansion and least-squares-based lattice Boltzmann method: Two-dimensional formulation and its applications.

An explicit lattice Boltzmann method (LBM) is developed in this paper to simulate flows in an arbitrary geometry. The method is based on the standard LBM, Taylor-series expansion, and the least-squares approach. The final formulation is an algebraic form and essentially has no limitation on the mesh structure and lattice model. Theoretical analysis for the one-dimensional (1D) case showed that the version of the LBM could recover the Navier-Stokes equations with second order accuracy. A generalized hydrodynamic analysis is conducted to study the wave-number dependence of shear viscosity for the method. Numerical simulations of the 2D lid-driven flow in a square cavity and a polar cavity flow as well as the "no flow" simulation in a square cavity have been carried out. Favorable results were obtained and compared well with available data in the literature, indicating that the present method has good prospects in practical applications.

Journal Article↗

PubMed2001

Enantiocontrolled synthesis of 2,3,6-trisubstituted piperidines using (eta(3)-dihydropyridinyl)molybdenum complexes as chiral scaffolds. Total synthesis of (-)-indolizidine 209B.

Enantiopure TpMo(CO)2(pyridinyl) complexes were prepared using an efficient and scalable enzymatic kinetic resolution of the precursor to the molybdenum complex. A single TpMo(CO)2(pyridinyl) complex can function as a chiral scaffold for the enantiocontrolled synthesis of either 2,3,6-cis- or 2,6-cis-3-trans-trisubstituted piperidines. The synthetic potential of this methodology was demonstrated by a total synthesis of (-)-indolizidine 209B.

Alkaloids↗

PubMed2001

Least-squares-based lattice Boltzmann method: a meshless approach for simulation of flows with complex geometry.

A version of lattice Boltzmann method (LBM) is presented in this work, which is derived from the standard LBM by using Taylor series expansion and optimized by the least squares method. The method is basically meshless, and can be applied to any complex geometry and nonuniform grids. It can also be applied to different lattice models. The proposed method explicitly updates the distribution functions at mesh points by an algebraic formulation, in which the relevant coefficients are precomputed from the coordinates of mesh points. We have successfully applied this method to simulate many two-dimensional incompressible viscous flows. The numerical results are very accurate, and the computational time needed is much less as compared with other existing methods. In this paper, we mainly show the method.

Journal Article↗

PubMed2001

Adjuvantation of epidermal powder immunization.

The skin is an immunologically active site and an attractive vaccination route. All current vaccines, however, are administered either orally, intramuscularly, or subcutaneously. We previously reported that epidermal powder immunization (EPI) with an extremely small dose of powdered influenza vaccine induces protective immunity in mice. In this study, we report that commonly used adjuvants can be used in EPI to further enhance the immune responses to an antigen. The IgG antibody response to diphtheria toxoid (DT) following EPI was augmented by 25- and 250-fold, when 1 microg DT was co-delivered with aluminum phosphate (alum) and a synthetic oligonucleotide containing CpG DNA motifs (CpG DNA), respectively. These antibodies had toxin-neutralization activity and were long lasting. Furthermore, EPI using an adjuvant selectively activated different subsets of T helper cells and gave either a Th1 or a Th2 type of immune response. Similar to needle injection into deeper tissues, EPI with alum adsorbed DT promoted a predominantly IgG1 subclass antibody response and elevated level of IL-4 secreting cells. These are indicative of Th2-type immunity. In contrast, co-delivery of CpG DNA adjuvant via EPI led to Th-1 type of response as characterized by the increased production of IgG2a antibodies and IFN-gamma secreting cells. This study indicated that EPI using appropriate adjuvants can produce an augmented antibody response and desirable cellular immune responses. EPI is a promising immunization method that may be used to administer a broad range of vaccines including vaccines with adjuvants.

Adjuvants, Immunologic↗

PubMed2001

[Study of in vitro cultured microencapsulated adrenal cortical tissues of rats].

In order to investigate the growth of in vitro cultured microencapsulated adrenal cortical tissues of rats, we produced the microcapsules by using sodium alginate, calcium chloride and poly-L-lysine, etc. The adrenal glands were taken out of 24 rats, half of the adrenal glands were microencapsulated (capsule group) while the other half were left free (noncapsule group). After 36 hours' in vitro culture, the concentrations of aldosterone and cortisol in culture solution were measured by radioimmunoassay. The two groups continued to be cultured for 24 and 36 hours with ACTH stimulation. The concentrations of aldosterone and cortisol at 24 and 36 hours were detected respectively. Parts of adrenal cortical tissues were observed under light microscope and electron microscope. The results showed that the concentrations of aldosterone and cortisol in the microencapsulated adrenal cortical tissues were significantly higher than those of noncapsule group (P < 0.01). In the capsule group, the concentration of cortisol after 36 hours' ACTH stimulation was significantly higher than that before ACTH stimulation (P < 0.01). After 24 and 36 hours' ACTH stimulation, the concentrations of aldosterone and cortisol were significantly higher in the capsule group than in the noncapsule group. In the noncapsule group, regardless of ACTH stimulation, no significant change was seen in the concentration of aldosterone and cortisol (P > 0.05). The cellular structure of adrenal tissues remained intact under light microscopic and electron microscopic observations, and the cells remained alive well. These data suggest that in vitro cultured cells of microencapsulated adrenal cortical tissues remain alive well. Microcapsule has not influenced the secretory function of adrenal tissues. Microencapsulated tissues have a good response to ACTH stimulation.

Adrenal Cortex↗

PubMed2001

Mechanism of intestinal absorption and renal reabsorption of an orally active ace inhibitor: uptake and transport of fosinopril in cell cultures.

The objective of this study was to delineate the transepithelial transport mechanisms of fosinopril in cultured cell lines expressing the intestinal and renal peptide transporters. Lineweaver-Burk, Dixon, and dose-response analyses revealed that GlySar uptake was competitively inhibited by fosinopril in both Caco-2 (K(i), 35.5 microM) and SKPT cells (K(i), 29.6 microM). Intracellular accumulations of fosinopril were 3 to 4 times higher from apical versus basolateral surfaces of the membrane, as was the apical-to-basal flux of the drug. The apical peptide transporter had a significantly greater affinity for fosinopril than did the basolateral peptide transporter in Caco-2 cells (K(m), 154 versus 458 microM, respectively; p < 0.001) and SKPT cells (K(m), 22 versus 104 microM, respectively; p < 0.001). Moreover, fosinopril uptake by the basolateral peptide transporter was less sensitive to changes in medium pH than the apical peptide transporter in both cell lines. Although Caco-2 cells are known to express PEPT1 protein (and not PEPT2), our immunoblot analyses provide definitive evidence that SKPT cells express PEPT2 protein (and not PEPT1). Taken as a whole, our findings demonstrate that fosinopril is transported intact by PEPT2 and PEPT1, with high-affinity and by a proton-coupled, saturable process. Our results also suggest that distinct peptide transporters exist at the basolateral and apical membranes and that they play an important role in modulating the intestinal absorption and renal reabsorption of peptides and peptide-like drugs.

Administration, Oral↗

PubMed2000

Fractional conductance quantization in metallic nanoconstrictions under electrochemical potential control

We study the electrical conductance of gold nanoconstrictions by controlling the electrochemical potential. At positive potentials, the conductance is quantized near integer multiples of G0(2e(2)/h) as shown by well-defined peaks in the conductance histogram. Below a certain potential, however, additional peaks near 0.5G(0) and 1. 5G(0) appear in the histogram. The fractional conductance steps are as stable and well defined as the integer steps. The experimental data are discussed in terms of electrochemical-potential-induced defect scattering and Fermi energy shift, but a complete theory of the phenomenon is yet to be developed.

Journal Article↗

PubMed2000

Indolinone derivatives inhibit constitutively activated KIT mutants and kill neoplastic mast cells.

Mastocytosis is a neoplastic disease caused at least in part by somatic mutations of the c-KIT proto-oncogene resulting in constitutive activation of its protein product, KIT, the receptor tyrosine kinase for stem cell factor. KIT stimulates mast cell proliferation and prevents apoptosis of neoplastic mast cells. To develop potential therapies for mastocytosis we used indolinones, small molecules that inhibit tyrosine kinases. Four indolinone derivatives (SU4984, SU6663, SU6577, and SU5614) inhibited wild-type KIT, but variably inhibited constitutively activated KIT mutants. SU4984, SU6577, and SU5614 were effective against KIT with juxtamembrane activating mutations, whereas only SU6577 could suppress KIT containing either juxtamembrane or kinase domain activating mutations. Furthermore, SU4984, SU6577, and SU5614 killed neoplastic mast cells expressing a juxtamembrane-mutated KIT, whereas SU4984 and SU6577 killed neoplastic mast cells expressing KIT bearing a kinase domain mutation. These data show a direct correlation between inhibition of constitutively activated KIT and the death of neoplastic mast cells, and point to specific tyrosine kinase inhibitors as a potential therapy aimed directly at a cause of mastocytosis.

Gene Expression Regulation↗

PubMed2000

An analysis of two polymorphic points of the 7th intron of human p53 gene.

OBJECTIVE: To detect polymorphic points of the 7th intron of human p53 oncogene. METHODS: Polymerase chain reaction (PCR) and double- strand DNA direct sequencing were used to analyse sequence alteration of p53 intron 7. One hundred and five cases of normal human peripheral blood samples with no genetic relation were investigated. RESULTS: There were two polymorphic points in the 7th intron of p53 gene. The first one was localized at 73 base pair (bp) to 3'-end of exon 7; the other one at 93. Three genotypes were found. Twenty-two cases were of type TG, 37 cases were of type CT, and the other 46 cases were of heterozygote. Because the first point was alteration of GGGCCC to GGGTCC or its heterozygote, it had a point alteration of enzyme Apa I. CONCLUSION: There are two polymorphic points in the 7th intron of human p53 gene, which may be of importance to identification of individual genetic relation and to judging of a case in forensic medicine.

Genes, p53↗

PubMed1999

Neutron activation analysis of fluoride release after treatment with a fluoride varnish in vitro.

OBJECTIVE: To use neutron activation analysis to study a new type of cariostatic material, fluoride varnish, in terms of its anti-caries mechanism and its release in vitro. MATERIALS AND METHODS: Twenty enamel specimens were measured for baseline fluoride content using neutron activation analysis. The enamel specimens were then fluoridated with 1.5% sodium fluoride varnish for 24 hours, and their enamel fluoride content was measured again with neutron activation analysis. RESULTS: The baseline fluoride content in the enamel specimens was 161.7 micrograms/g; after fluoridation, the fluoride content in the enamel specimens increased to 277.8 micrograms/g, or about 1.7 times. CONCLUSION: It is evident that this sodium fluoride varnish can significantly increase enamel fluoride content. The neutron activation analysis is a good method for fluoride measurement in vitro.

Cariostatic Agents↗

PubMed1999

[Effects of chloroquine on insulin sensitivity in insulin-resistant rats].

OBJECTIVE: To investigate the mechanism of chloroquine improving insulin sensitivity. METHODS: The changes in insulin sensitivity and the effects of chloroquine were observed in insulin-resistant (IR) rats induced by high-fat feeding. RESULTS: In IR rats, the glucose infusion rate (GIR) determined by euglycemic clamp and 2-deoxyglucose (DG) uptake in the skeletal muscle were lower than those in normal rats, but the activity of insulin degradation of liver (LIA), fasting plasma insulin (FINS) and plasma lipids were higher. In the high-fat fed rats with chloroquine administration, GIR and 2-DG uptake in the skeletal muscle were increased, and LIA, FINS and some plasma lipid indices were decreased compared with the IR rats. CONCLUSION: Chloroquine can improve the insulin sensitivity and hamper the onset and development of insulin resistance.

Animals↗