Biomedical subjects

Rui Yan

Publications and source records attributed to Rui Yan.

5 recordsLinked to original sources

PubMed2005

[Directed differentiation embryonic stem cells into the chondrocyte].

Cartilage is a tough, elastic, and fibrous connective tissue, composed of chondrocyte and extracellular matrix (ECM) structural entity. Because of the poor self-regeneration capabilities of chondrocytes, cell transplantation is necessanry once the cartilage is damaged. Traditionally autologous chondrocytes implantation is applied at the damage site, which has many problems such as the losing of its primary characteristics. A well-defined and efficient protocol to direct the differentiation of embryonic stem cells into the chondrocyte will provide a novel choice for cartilage repair. This article reviews some major progresses in this field.

Animals↗

PubMed2004

Image construction methods for phased array magnetic resonance imaging.

PURPOSE: To study image construction in phased array magnetic resonance imaging (MRI) systems from a statistical signal processing point of view. MATERIALS AND METHODS: Three new approaches for image combination with multiple coils are proposed: 1) one based on the singular value decomposition of the measurement matrix, which is asymptotically optimal in the signal-to-noise ratio sense; 2) one based on a maximum-likelihood formulation, incorporating a priori information on the coil sensitivities in a Bayesian manner; and 3) one based on a least-squares formulation, which incorporates a smoothness constraint on the coil sensitivities. RESULTS: Numerical examples using synthetic and real data are presented to illustrate the performance of these new approaches. Results on the synthetic data show improvement in signal-to-error ratio, while results on the real data (a 4.7 T four-coil image of a cat spinal cord) show that the proposed methods can improve the SNR in the final image by up to 3 dB in the regions of interest compared to conventional sum-of-squares processing. CONCLUSION: It is demonstrated that phased array MRI reconstruction performance can be improved by the use of more elaborate statistical signal processing algorithms.

Algorithms↗

PubMed2004

[Changes of mitochondrial genes expressed in the brain tissue of rat in stroke-like episodes rats].

OBJECTIVE: Stroke is a complex disorder caused by a combination of genetic and environmental factors. Epidemiological studies have provided evidence of genetic influence on the development of human stroke. However, genetic changes which contribute to the development of stroke are not well known. This study was designed to gain a deep insight into that aspect. METHODS: Using cold-stimuli plus high-salt intake as environmental risk factors, the authors established a hypertension model in rats, which produced a complication of stroke. Then, they used the suppression subtractive hybridization(SSH) technique to identify the differential genes that specifically expressed in total cerebrum tissue of the rats in stroke group. A comparison was made between two populations, namely the control group and stroke group. RESULTS: By the use of SSH approach, a total of 576 clones were generated in this study from two subtractive libraries, among them 456 clones were usable and were analyzed. Genes for metabolism transcripts in stroke group were shown to be up-regulated (P<0.01). Mitochondrial transcripts were observed in a high rate of 26.5%. CONCLUSION: The findings suggested that mitochondrial genes should induce an increased sensitivity to stroke through the changes of gene expressions. Mitochondrial genes probably play important roles in the causes and effects of stroke.

Animals↗

PubMed2003

SNR-optimality of sum-of-squares reconstruction for phased-array magnetic resonance imaging.

We consider the commonly used "Sum-of-Squares" (SoS) reconstruction method for phased-array magnetic resonance imaging with unknown coil sensitivities. We show that the signal-to-noise ratio (SNR) in the image produced by SoS is asymptotically (as the input SNR--> infinity ) equal to that of maximum-ratio combining, which is the best unbiased reconstruction method when the coil sensitivities are known. Finally, we discuss the implications of this result.

Computer Simulation↗

PubMed2003

[Change of expression of cell/organs defense genes in brain tissue of rats with stroke-like episodes induced by complex environmental factors].

OBJECTIVE: To investigate the effect of environmental risk factors on the development of stroke. METHODS: With the use of cold-stimuli plus high-salt intake as environmental risk factors, a hypertension model with the complication of stroke was established in rats, then, a new technique, suppression subtractive hybridization (SSH), was used to identify the differential genes which specifically expressed in total cerebrum tissue of rat in each group. Comparison was made between control group and stroke group. RESULTS: By the application of SSH, a total of 576 clones were generated in this study from two subtractive libraries, among them 456 clones were usable and were analyzed. Genes for cell/organs defense were down-regulated in stroke group and metabolism transcripts were shown to be up-regulated (P<0.01). CONCLUSION: Cell/organs defense genes may play important roles in the development of stroke. The above findings suggested that environmental risk factors could genetically alter individual sensitivity to stroke.

Animals↗