Biomedical subjects

Xiaoheng Liu

Publications and source records attributed to Xiaoheng Liu.

11 recordsLinked to original sources

PubMed2006

Self-assembled nanodisks with targetlike multirings aggregated at the air-water interface.

In this communication, we report the self-assembly of zirconia by mixing its precursor with another solution containing surfactant as well as gelatin. The resulting zirconia product consists of many disks with a range of diameter from approximately 100 nm to approximately 2 mum. These disks can be assembled inside aqueous systems. Meanwhile the disks rise gradually and eventually form a visible film at the air-water interface. Remarkably, the structure of zirconia disks templated by surfactant has been found to be targetlike multirings with a d spacing of approximately 3.3 nm. We propose that a successful multirings self-assembly depends on two different template-functions from the same surfactant, excellent tenacity of the zirconia layers and the strong ability of the gelatin to stabilize and disperse the disks.

Journal Article↗

PubMed2006

[Experimental study on the migration of vascular endothelial cells stimulated by IL-8].

To investigate the influence of different concentrations of IL-8 on the migration of vascular endothelial cells and find out the best IL-8 concentration, the transwell chamber motility assay and the scrape motility assay were applied to observe the migration of vascular endothelial cells induced by IL-8. The results demonstrated that the migration of vascular endothelial cells was increased significantly under different IL-8 concentrations, while the best effect occurred when IL-8 concentration was 100 ng/ml.

Cell Movement↗

PubMed2005

[Coupling between adherent leukocytes and blood flow].

A theoretical model was developed to simulate the coupling between the adhered leukocyte and blood flow. Methods of computational fluid dynamics (CFD) were introduced to analyze the distributions of the shear stress and the pressure on the cell surface. Meanwhile, the hemodynamical parameters were measured with laser Doppler velocimetry. The results showed that the deformation index of the leukocyte was increased with initial contact angle and Reynolds number. The blood flow induced the redistributions of the shear stress and pressure on the surface of the cell, but the maximum shear stress was on the top point of the cell. It suggests that the non-uniform distribution of shear stress on the cell surface may play a particular role in the change of cell shape and functions.

Blood Circulation↗

PubMed2004

Deformation mechanism of leukocyte adhering to vascular surface under steady shear flow.

The adhesion of leukocytes to vascular surface is an important biomedical problem and has drawn extensive attention. In this study, we propose a compound drop model to simulate a leukocyte with a nucleus adhering to the surface of blood vessel under steady shear flow. A two-dimensional computational fluid dynamics (CFD) is conducted to determine the local distribution of pressure on the surface of the adherent model cell. By introducing the parameter of deformation index (DI), we investigate the deformation of the leukocyte and its nucleus under controlled conditions. Our numerical results show that: (i) the leukocyte is capable of deformation under external exposed flow field. The deformation index increases with initial contact angle and Reynolds number of external exposed flow. (ii) The nucleus deforms with the cell, and the deformation index of the leukocyte is greater than that of the nucleus. The leukocyte is more deformable while the nucleus is more capable of resisting external shear flow. (iii) The leukocyte and the nucleus are not able to deform infinitely with the increase of Reynolds number because the deformation index reaches a maximum. (iv) Pressure distribution confirms that there exists a region downstream of the cell, which produces high pressure to retard continuous deformation and provide a positive lift force on the cell. Meanwhile, we have measured the deformation of human leukocytes exposed to shear flow by using a flow chamber system. We found that the numerical results are well consistent with those of experiment. We conclude that the nucleus with high viscosity plays a particular role in leukocyte deformation.

Cell Adhesion↗

PubMed2004

[The research progress in ligament tissue engineering].

Ligament injury always has an unsatisfied outcome because of the poor blood supply and scar tissue formation. This may result in severe joint dysfunction. Tissue engineering, as a most prospective field, may provide an effective approach for the treatment of ligament injury. This paper has reviewed some recently published articles focusing on the sources of seed cells in ligament tissue engineering, application of growth factors, screening of scaffold materials with specific mechanical and biodegradable properties, and interaction between cells and scaffold materials. At present, what should be extensively studied are scaffolds with specific mechanical and biodegradable properties, and bioreactors providing three-dimensional culture microenvironment mimic in vivo.

Animals↗

PubMed2004

[A system for testing alternating frequency properties of body fluid and tissues].

The electric properties of biotic tissues are of importance to our understanding biotic substances even life. But the measurement taken in this aspect is different from the measurement of ordinary materials, we need a special testing instrument for living substances. In order to understand the alternating frequency properties of body fluid and tissues in detail, we have developed an electricity characteristic testing system, which is more proper for testing living substances. This system adopts advanced measuring method and expert circuit. As the measure and the control core, the single chip processor is used. This system has wide frequency range and wide impedance testing range, much more adapted objects, and it is dependable, more precise and intelligent. The application of this system in practical testing has obtained optimal results.

Body Composition↗

PubMed2003

Effects of laminar shear stress on IL-8 mRNA expression in endothelial cells.

In order to demonstrate that IL-8 mRNA expression in endothelial cells is not only regulated by chemical factors, but also by mechanical factors, in this article, after pretreating cultured human umbilical vein endothelial cells (HUVECs) with shear stress for different time, we employed both RT-PCR to assay IL-8 mRNA expression and immunocytochemical staining to detect NF-kappaB activation in HUVECs. We found that: (i) IL-8 mRNA expressed little in HUVECs untreated or pretreated with low laminar shear stress for 0.5 hour; IL-8 mRNA expression was increased when HUVECs were pretreated with low laminar shear stress for 1 hour, and increased further when pretreated for 2 hours; (ii) the immunoreactivity of NF-kappaB p65 in the nuclei of HUVECs untreated or pretreated with low laminar shear stress for 0.5 hour was negative, while it became weak positive in the nuclei of HUVECs pretreated with shear stress for 1 hour and positive in the nuclei of HUVECs pretreated for 2 hours. The results imply that low laminar shear stress was capable of inducing IL-8 gene expression and activating NF-kappaB, which were both time-dependent. The induction of IL-8 gene expression by laminar shear stress is probably due to the activation of NF-kappaB. We suggest that IL-8 mRNA expression in endothelial cells induced by low shear stress may play a key role in the pathogenesis and development of both inflammation and arterioatherosclerosis.

Cell Culture Techniques↗

PubMed2003

[A biomechanical model for simulating the deformation of a leukocyte adhered to the surface of a blood vessel under steady shear flow].

The adhesion of leukocytes to substrate is an important biomedical engineering problem and has drawn extensive research. In this study, we have proposed a compound drop model to simulate a leukocyte with a nucleus adhered to the surface of a blood vessel under steady shear flow. A two-dimensional computational fluid dynamics (CFD) is conducted to determine the local distribution of pressure on the surface of the adherent model cell. By introducing the parameter of deformation index (DI), we have investigated the deformation of the model cell and it's nucleus under controlled conditions. Our numerical results show that: (1) the model cell is capable of deformation with the increase of initial contact angle, capillary number, and Reynolds number, and that the cytoplasm is more deformable while the nucleus is more capable of resisting external imposed shear flow; (2) the model cell is not able to deform infinitely with the increase of external shear flow because the deformation index reaches a maximum; (3) pressure distribution confirms that there exists a region downstream of the cell, which produces high pressure to retard continuous deformation and provide a positive lift force on the cell. Our results of nucleus deformation may help to develop a better understanding of how leukocytes transduce external mechanical signal like shear stress into nucleus.

Biomechanical Phenomena↗

PubMed2003

[Changes in the VASP expression feature of endothelial cells under steady laminar flow].

To investigate the effects of physiological shear stress on the vasodilator-stimulated phosphoprotein (VASP) location and expression changes associated with actin remodeling, we isolated and cultured human umbilical endothelial cells(HUVECs) with trypsin digestion. A parallel-plated flow chamber device was used to create laminar shear stress in vitro. The distributions of VASP and microfilaments in cells were observed by double staining with Alexa488 and rhodamine-phalloidin. Changes of VASP expression and phosphorylation were analyzed quantitatively with Western blot before and after exposure to shear flow for different times. We found that, under a shear stress of 10 dyn/cm2, HUVECs were elongated and oriented gradually to the flow direction. Microfilaments were recruited and oriented also to the flow direction with thicker VASP, specially targeted to their extremities. Western blotting data showed a rapid phosphorylation of VASP, and an increase of total VASP expression which peaked at 2 h (2 folds), then recovered until 8 h, followed by a slow increase again. These results suggest that VASP is a potential component which participates in the regulation of cell actin remodelling induced by shear flow.

Cell Adhesion Molecules↗

PubMed2002

[Simulation of the deformation of the endothelial cell under a shear flow].

The coupling between the endothelium and blood flow is an important biomedical problem and has drawn extensive research. Endothelial cells are known to adapt their shapes and functions in response to applied shear flow. Shear Stress being regarded as a primary triggering signal for cellular remodeling, it is important to understand the interaction mechanism between applied shear flow and endothelial cells. In present study we have established a theoretical model to simulate the coupling between the deformation of an endothelial cell and applied shear flow. A two dimensional computational fluid dynamic (CFD) is conducted to determine the local distributions of mechanical stress and pressure on cell surface. Our results show that: (1) the deformation of endothelial cell changes with alpha (corresponding to the shear stress imposed on cell surface by flow fluid). When alpha is greater than 0.021, the cell deformability increases greatly; (2) the distributions of stress and pressure on cell surface are not uniform, but the maximal shear stress and displacement are always at the top point of the cell. Meanwhile, we have measured the deformation of cultured human aortic endothelial cells (HAECs) exposed to shear flow by using a flow chamber. We found that the numerical results are well consistent with those of experiment. These results suggest that the non-uniformity distributions of mechanical stress and pressure on cell surface may play a particular role in the mechanism of cell activation and in the regulation of endothelial cells functions (modification of cytoskeleton, distributions of adhesion molecules, etc.). The present study offers a framework to facilitate the development of a comprehensive dynamic model for endothelial cells.

Aorta↗

PubMed2002

[Effects of shear stress and lysophosphatidylcholine on adhesion molecules expression of endothelial cells].

Extensive monocyte recruitment is an early phenomenon associated with the development of atherosclerotic lesion. Although the molecular mechanisms are not completely understood, monocyte recruitment into these early lesions may involve changes in endothelial adhesion for monocyte, in which adhesion molecules expressed by endothelial cell play an active role. In vivo, the function of endothelial cells is not only affected by the chemical factors, but also by the mechanical factors. The purpose of this article was to investigate the induction of adhesion molecules expression by synergistic effects of Lysophosphatidylcholine (Lyso-PC) and shear stress in cultured human umbilical vein endothelial cells (HUVEC). The surface expression of ICAM-1, VCAM-1 and E-selectin on HUVEC induced by Lyso-PC(30 micrograms/ml) and shear stress(2.23, 4.20 dyne/cm2) were analyzed using flow cytometry. The results showed that: Compared with what were simultaneously exposed to shear stress and Lyso-PC, activating the cells with Lyso-PC prior to shear stress, or pre-conditioning the cells exposed shear stress prior to Lyso-PC incubation, a significantly higher expression of ICAM-1 and VCAM-1(P < 0.05) was resulted. HUVEC were exposed to shear stress and Lyso-PC at the same time or treated with each agonist alone, E-selectin expression was not significantly different from the control group. However, a sequential action of the two stimuli significantly increased E-selectin expression(P < 0.05). We concluded that: a sequential action of the shear stress and Lyso-PC induced an even greater expression of ICAM-1 and VCAM-1, thus it could be understood that the flows-hear stress in combination with endothelial activated by chemical factors may increase the ability of endothelial cells to recruit leukocytes even under the mechanical environment unfavorable for cell adhesion.

Cell Adhesion Molecules↗