Biomedical subjects

Chunxia Zhang

Publications and source records attributed to Chunxia Zhang.

4 recordsLinked to original sources

PubMed2006

Chemical turbulence and line defects induced by gradient effects in a three-dimensional reaction-diffusion system.

We report experimental observations of chemical turbulence and line defects in a three-dimensional (3-D) Belousov-Zhabotinsky (BZ) reaction-diffusion system. Transitions from spiral waves to 3-D chemical turbulence to line defects are observed. These transitions are caused by concentration gradients across the third dimension in the 3-D reaction medium, indicating the observed line defects have a 3-D structure. The line defects come out of the 3-D turbulent state, and become smooth with the increase of the control parameter. Simulation with the two-variable Oregonator model in the 3-D system reproduces similar line defects.

Catalysis↗

PubMed2005

Spontaneous scroll ring creation and scroll instability in oscillatory medium with gradients.

Scroll waves in a quasi-three-dimensional reaction-diffusion medium with a gradient in the third dimension are studied by numerical simulations using the Fitzhugh-Nagumo model. Under a simple initial condition with only one straight filament, we show a spontaneous creation of twisted scroll rings surrounding the initial filament when the control parameter is increased across a threshold. We find that due to the presence of the gradient, the difference of oscillation frequencies in the third dimension is the underlying cause of the phenomenon. Further increase of the control parameter will lead to the spiral breakups, as a result of the interaction of filaments. Observations in the experiments conducted in the same type of medium with the Belousov-Zhabotinsiky reaction qualitatively agree with our simulation results.

Journal Article↗

PubMed2003

Transition from spiral waves to defect-mediated turbulence induced by gradient effects in a reaction-diffusion system.

The transition from spiral waves to defect-mediated turbulence was studied in a spatial open reactor using Belousov-Zhabotinsky reaction. The experimental results show a new mechanism of the transition from spirals to spatiotemporal chaos, in which the gradient effects in the three-dimensional system are essential. The transition scenario consists of two stages: first, the effects of gradients in the third dimension cause a splitting of the spiral tip and a deletion of certain wave segments, generating new wave sources; second, the waves sent by the new wave sources undergo a backfire instability, and the back waves are laterally unstable. As a result, defects are automatically generated and fill all over the system. The result of numerical simulation using the FitzHugh-Nagumo model essentially agrees with the experimental observation.

Journal Article↗

PubMed2002

[Effect of methylmercuric chloride on apoptosis and c-fos expression of brain glial cells].

In order to explore the injury of brain development caused by methylmercuric chloride(MMC) and the relationship between the injury and c-fos expression, the damaging effects of MMC on the morphology of cultured brain glial cells derived from neonatal Wistar rat were studied by microscope and electronic microscope, and the effect of MMC on the c-fos expression of glial cells were studied by immunocytochemical method. The results showed that the characteristics of apoptosis, such as condensed cytoplasm, marginal nuclear chromatin and pyknotic nuclei were found after cultured glial cells was exposed to MMC. The expressed c-Fos protein began to increase in the nuclei of cultured glial cells at 0.5 h after MMC was added to DMEM medium for 10 min and increased markedly with time prolonged. The percentage of Fos-positive nuclei reached a peak at 2 h and declined gradually from 4 to 6 h. The percentage of Fos-positive glial nuclei in the group exposed to 0.32 mmol/L MMC was significantly higher than those in other groups, which were exposed to 0.00125, 0.005 and 0.02 mmol/L MMC respectively (P < 0.01) at 2 h after MMC was added. It is concluded that MMC can induce the expression of c-fos and the apoptosis of glial cells in vitro. The findings suggested that the apoptosis might be mediated by c-fos expression.

Animals↗