Biomedical subjects

Ya Ping Li

Publications and source records attributed to Ya Ping Li.

7 recordsLinked to original sources

PubMed2006

Coupling effects on energy transduction in coupled polymer chains with perturbation of noise.

Noise-assistant transduction was investigated in coupled polymer chains where one subsystem was exposed to environment noise. It was found that coupling could transfer oscillation from one subsystem disturbed by noise to the other not disturbed by noise and play a role of a noise filtering for the other. Then, a sort of coupling-induced synchronization was investigated as a function of noise intensity and coupling strength. In particular, we calculated the minimum coupling strength to reach synchronization and pointed out that noise dominated at small coupling strength, otherwise, coupling dominated.

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PubMed2006

Critical threshold of noise-induced energy transduction in molecular machinery system.

Responses of energy transduction of molecular machinery to random perturbation were investigated at the conditions where the system stayed near the bifurcation point. It was found that noise-induced oscillation (NIO) could occur. But how far from bifurcation point could one get the admissible region of NIO? We proposed and demonstrated numerically that there existed a critical threshold of NIO for each fixed noise intensity. Furthermore, it was found that noise intensity was a key factor for the determination of critical threshold. Finally, the detailed bifurcation diagram depending on noise intensity was replotted.

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PubMed2004

Controlling of explicit internal signal stochastic resonance by external signal.

Explicit internal signal stochastic resonance (EISSR) is investigated in a model of energy transduction of molecular machinery when noise is added to the region of oscillation in the presence of external signal (ES). It is found that EISSR could be controlled, i.e., enhanced or suppressed by adjusting frequency (omega(e)) and amplitude (A) of ES, and that there exits an optimal frequency for ES, which makes EISSR strength reach the maximum. Meanwhile, a critical amplitude (A(c)) is found, which is a threshold of occurrence of EISSR. Finally, the difference and similarity between EISSR and IISSR (implicit internal signal stochastic resonance) are discussed.

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PubMed2004

Internal stochastic resonance under two-parameter modulation in intercellular calcium ion oscillations.

Internal stochastic resonance (ISR) in a model of intercellular calcium ion oscillations is investigated under the modulation of two parameters, viz., degree of extracellular stimulation (beta) and leak rate (k(f)). ISR can occur when either beta or k(f) is subjected to a noise. Internal stochastic biresonance (ISBR) can occur when noise is added to the two parameters simultaneously. The distance to the bifurcation point is found to be able to enhance or suppress the ISBR, and to affect the number of peaks of ISR.

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PubMed2004

Internal stochastic resonance in two coupled liquid membrane oscillators.

Internal stochastic resonance (ISR) is investigated in two coupled liquid membrane oscillators when only one oscillator is subjected to environmental noise in the absence of an external signal. Comparing the responses of both subsystems, it is found that enhancement or suppression of ISR for each oscillator depends on the coupling strength, that synchronization of the two oscillators can occur only at strong coupling strength, and that ISR without tuning can also occur under certain conditions in the above-mentioned models.

Journal Article↗

PubMed2004

[Gene delivery system based on low molecular weight polyethylenimine and its transfection activity in the skin tissue].

Low molecular weight polyethylenimine (LMW-PEI) was linked to an expressing plasmid contains a green fluorescence protein (GFP) reporter gene and effective gene transfer was observed in CM7221 cell line tested. We examined the relationship among the molecular weight, structure of PEI and their transfection activity and cytotoxicity on CM7221 cell line. We also examined the position and continuance time of the GFP reporter gene expressed in the skin tissue of mouse. Results showed that LMW-PEI/DNA complexes led to high levels of expression in the CM7221 cell line (about 55%). However, with the increasing of PEI molecular weight, the transfection activity of PEI was decreasing. There was an increasing cytotoxicity with the larger PEI molecules. Further research showed that LMW-PEI induced a significant and long-lasting (7 days) expression of the GFP reporter gene in the hair vesicle, sweat, gland, sebaceous gland in the mouse skin tissues. The LMW-PEI described here is a new, highly efficient and non-cytotoxic vector. It would be a useful non-viral vector for gene delivery technology, particular useful as simple skin-specific vehicles of therapeutic genes.

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PubMed2002

Apoptosis induced by box jellyfish (Chiropsalmus quadrigatus) toxin in glioma and vascular endothelial cell lines.

This study was made to investigate whether Chiropsalmus Quadrigatus toxins (CqTX), which isolated from box jellyfish C. Quadrigatus venom, could induce apoptosis in human U251 and rat C6 malignant glioma cells and transformed vascular endothelial ECV 304 cell lines. Cell viability was estimated by MTT assay. Apoptosis was evaluated using TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labeling (TUNEL) method and DNA gel electrophoresis. Furthermore, the expression of p53 protein was examined immunohistochemically in the U251 cells. After the CqTX treatment, the growth of all cell lines was inhibited, the fragmented DNA was observed and some cells became TUNEL positive. The expression of p53 protein was increased in the tested U251 cells. The results suggested that CqTX induced apoptosis in these cell lines. The promotion of the p53 expression might be one mechanism of apoptosis induced by CqTX in the glioma cells.

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