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J Cao

Publications and source records attributed to J Cao.

360 records · Page 20Linked to original sources
PubMedDate not supplied

Development of a side-view chamber for studying cell-surface adhesion under flow conditions.

Observing microscopic specimens is often useful in studies of cellular interaction with a vascular wall. We have developed an in vitro side-view flow chamber that permits observations from the side of the cell's contact with various adhesive surfaces under dynamic flow conditions. This side-view flow chamber consists of two precision rectangular glass tubes called microslides. A smaller microslide is inserted into a larger one to create a flow channel with a flat surface on which either cultured vascular endothelium can be grown or purified adhesion molecules can be coated. Two optical prisms with a 45 degrees chromium-coated surface are used along the flow channel to generate light illumination and observation pathways. The side-view images of cell-substrate contact can be obtained using a light microscope. This design allows us not only to measure the effects of flow on cell-surface adhesion strength, but also to have close observation of cell deformation and adhesive contact to various surfaces in shear flow. In addition, this chamber can readily serve for a conventional top-view flow channel, similar to the parallel-plate flow chambers used in many areas. The development of such a side-view flow chamber can be beneficial to various in vitro applications in cellular studies that require an edge view, especially for various cell interactions with cultured vascular endothelium or surfaces containing single-type adhesive molecules under flow conditions.

Animals↗
PubMedDate not supplied

Ring opening cross-metathesis on solid support: a combinatorial library synthesis of highly functionalized cyclopentanes.

Ruthenium catalyzed ring opening cross-metathesis of resin-bound bicyclic alkenes with terminal aryl olefins was utilized for the construction of a combinatorial library containing highly functionalized cyclopentane derivatives. The technology described herein represents a convergent method for the diastereospecific synthesis of unique cyclopentane molecular scaffolds useful for exploratory medicinal chemistry.

Chemistry, Organic↗
PubMedDate not supplied

RUS skeletal maturity of children in Beijing.

BACKGROUND: RUS (radius-ulna-short bones) maturity of children has been estimated in two provinces in China, but not in the capital. In order to obtain a clearer picture of skeletal maturity in China, it is indispensable to include children from Beijing in the study. AIM: The aims of this study were three-fold: (1) to establish RUS skeletal maturity of children in Beijing, (2) to compare RUS skeletal maturity in Beijing with the Tanner-Whitehouse 3 (TW3) standard and the Tokyo standard, and (3) to examine regional variation in skeletal maturity in China. METHODS: Hand and wrist radiographs of 631 boys and 642 girls, aged 6-18, were obtained in Beijing in 1997, and their RUS skeletal maturity was estimated using the TW3 method. RESULTS: RUS maturity of the Beijing children was very similar to the TW3 standard until the age of 10 years in the girls, and the age of 12 years in the boys. The girls attained full maturity at 15 years of age, matching the TW3 and Tokyo standards, while the boys reached full maturity at the age of 16 years, as in Tokyo boys, but 1 year earlier than the TW3 standards. Beijing children showed progressively more rapid bone maturation than the Harbin and Changsha children, and attained full maturation 1 year earlier, in both girls and boys. CONCLUSION: The RUS maturity of the Beijing children was comparable with that of Tokyo children, except for the boys between 11 and 13 years. Variability of the RUS maturation among the Chinese children was greater than that found among the TW3, Tokyo and Beijing children.

Adolescent↗
PubMedDate not supplied

Particle motion within in vitro models of stenosed internal carotid and left anterior descending coronary arteries.

Asymmetric 75% and 95% area reduction, transparent Sylgard stenotic models were operated under internal carotid artery (ICA) [Womersley parameter, alpha=5.36, Re(mean) =213 and 180, respectively, and Re(peak)=734 and 410, respectively] and left anterior descending coronary artery (LAD) flow wave forms (alpha=2.65, Re(mean)=59 and 57, respectively, and Re(peak)= 137 and 94, respectively) to evaluate the effect of these conditions on particle residence times downstream of the stenoses. Amberlite particles (1.05 g/cm3, 400 microm) were added to the fluid to simulate platelets and their motion through the stenotic region and were traced using a laser light sheet flow visualization method with pseudo-color display. Two-dimensional (2D) particle motions were recorded and particle washout in the stenotic throat and downstream section were computed for all cases. All four model cases demonstrated jetting through the stenosis which followed an arching pattern around a large separation zone downstream. Considerable mixing was observed within these vortex regions during high flow phases. Particle washout profiles showed no clear trend between the degrees of stenosis although particles downstream of the stenoses tended to remain longer for LAD conditions. The critical washout cycle (1% of particles remaining downstream of the stenosis), however, was longer for the 95% stenoses cases under each flow condition due to the larger protected region immediately downstream and maximal for the LAD 95% case. Results of this study suggest that particle residence times downstream of 75% and 95% stenoses (approximately 3-6 s for ICA and approximately 8-10 s for LAD) exceed the minimum time for platelet adhesion (approximately 1 s) for at least 1% of cells and, thus, may be sufficient to initiate thrombus formation under resting conditions.

Biomedical Engineering↗
PubMedDate not supplied

Mechanics of leukocyte deformation and adhesion to endothelium in shear flow.

The mechanics of leukocyte [white blood cell (WBC)] deformation and adhesion to endothelial cells (EC) in shear flow has been investigated. Experimental data on transient WBC-EC adhesion were obtained from in vivo measurements. Microscopic images of WBC-EC contact during incipient WBC rolling revealed that for a given wall shear stress, the contact area increases with time as new bonds are formed at the leading edge, and then decreases with time as the trailing edge of the WBC membrane peels away from the EC. A two-dimensional model (2D) was developed consisting of an elastic ring adhered to a surface under fluid stresses. This ring represents an actin-rich WBC cortical layer and contains an incompressible fluid as the cell interior. All molecular bonds are modeled as elastic springs distributed in the WBC-EC contact region. Variations of the proportionality between wall shear stress (tau(w)) in the vicinity of the WBC and the resulting drag force (F(s)), i.e., F(s)/tau(w), reveal its decrease with WBC deformation and increasing vessel channel height (2D). The computations also find that the peeling zone between adherent WBC and EC may account for less than 5% of the total contact interface. Computational studies describe the WBC-EC adhesion and the extent of WBC deformation during the adhesive process.

Animals↗
PubMedDate not supplied

Cytokines in stress.

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Animals↗
PubMedDate not supplied

Modeling the fate of benzo[a]pyrene in the wastewater-irrigated areas of Tianjin with a fugacity model.

A Level III fugacity model was applied to characterize the transfer processes and environmental fate of benzo[a]pyrene in wastewater-irrigated areas of Tianjin, China. The physical-chemical properties and transfer parameters of benzo[a]pyrene were used in the model and the concentration distribution of benzo[a]pyrene in sediment, soil, water, air, fish, and crop compartments, as well as transfer fluxes across the compartments, were then derived under steady-state assumptions. The calculated results were compared with monitoring data for air, soil, water, and sediment collected from the literature. The results indicate that there was generally good agreement and the differences were within an order of magnitude for air, soil, and sediment. The concentration of benzo[a]pyrene in the ambient air in the area was very low with a majority present sorbed to aerosol. In the water compartment, approximately 70% of benzo[a]pyrene dissolved in water phase. Relatively high concentrations of the compound were found in the soil and sediment, with the soil serving as the dominant sink in the area. Benzo[a]pyrene, with a slow metabolic rate, was found to accumulate in fish in the area.

Aerosols↗
PubMedDate not supplied

A comparison of the fragment constant and molecular connectivity indices models for normalized sorption coefficient estimation.

Fragment constant and molecular connectivity indices models were developed based on the measured normalized sorption coefficient values of 592 chemicals. The two models were compared for precision in terms of their adjusted coefficients of determination and their mean residuals. Model robustness was evaluated and compared using jackknifed mean residuals derived from class-by-class deletion. Results indicated that a relatively greater precision could be achieved using the fragment constant approach compared with the molecular connectivity indices model. The adjusted coefficients of determination of the two models were 0.965 and 0.765 and the mean residuals were 0.366 and 0.440, respectively. Although there were a relatively small number of independent variables involved, the robustness of the molecular connectivity indices model was greater than that of the fragment constant method as far as extrapolation among chemical classes is concerned.

Adsorption↗
PubMedDate not supplied

Deletion of genetic material from a poly(ADP-ribose) polymerase-like gene on chromosome 13 occurs frequently in patients with monoclonal gammopathies.

Recently, by using a probe for the nuclear DNA repair enzyme poly(ADP-ribose) polymerase gene, a pseudogene was found on the long arm of chromosome 13. RFLP analysis demonstrates the presence of a common "A" allele and a rare "B" allele, which has a deletion of approximately 200 bp. This deletion occurs more frequently in blacks than in whites in the United States. In two B-cell malignancies, Burkitt's and follicular lymphomas, there is a marked increased frequency of the expression of the B allele. Thus, we have analyzed the frequency of this allele in another B-cell malignancy, multiple myeloma (MM), which is also more frequently observed in blacks. We studied 97 patients with MM (41 black and 56 white patients) and 30 patients with the related disorder monoclonal gammopathy of undetermined significance (MGUS; 13 black and 17 white patients). The results demonstrate that the overall frequency of B allele expression (37%) is higher than in a noncancer control population (23%; P < 0.01). This difference is mainly due to the much higher frequency of B expression in black patients (52 versus 35% in black controls; P < 0.01), whereas there is no significant difference in white patients (18 versus 14% in white controls). Overall, B allelic frequency is similar in patients with MM and MGUS. Matched germline and tumor DNA show identical patterns of expression of these alleles. These results suggest germline B allelic expression predisposes one to MM and MGUS.

Alleles↗