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Biomedical subjects

Pei Sun

Publications and source records attributed to Pei Sun.

7 recordsLinked to original sources
PubMed2006

[Study on the selection of crude drugs of rhubarb dispensing granule].

OBJECTIVE: To research and choose the best crude drugs of Rhubarb dispensing granule. METHODS: According to standard method from the eighth edition of China pharmacopoeia, determined and compared the contents of TLC, water, total ash, acid insoluble ash, extractives, total anthraquinones, rhein, emodin and chrysophanol of Rhubarb in diffrent producing areas and species. RESULTS: The Contents of Rheum palmatum from Rhubarb GAP base in Ganzhi state were higher than others and the drug yield was large. CONCLUSION: This species are chosen to be the crude drugs for Rhubarb dispensing granule. The preliminary study provides the scientific grounds for next study about establishment of quality criteria.

Anthraquinones↗
PubMed2005

Contrast adaptation and representation in human early visual cortex.

The human visual system can distinguish variations in image contrast over a much larger range than measurements of the static relationship between contrast and response in visual cortex would suggest. This discrepancy may be explained if adaptation serves to re-center contrast response functions around the ambient contrast, yet experiments on humans have yet to report such an effect. By using event-related fMRI and a data-driven analysis approach, we found that contrast response functions in V1, V2, and V3 shift to approximately center on the adapting contrast. Furthermore, we discovered that, unlike earlier areas, human V4 (hV4) responds positively to contrast changes, whether increments or decrements, suggesting that hV4 does not faithfully represent contrast, but instead responds to salient changes. These findings suggest that the visual system discounts slow uninformative changes in contrast with adaptation, yet remains exquisitely sensitive to changes that may signal important events in the environment.

Adaptation, Physiological↗
PubMed2005

A comparative Langmuir-Blodgett study on a set of covalently linked porphyrin-based amphiphiles: a detailed atomic force microscopic study.

A set of covalently linked phenyl-amidophenyl-substituted porphyrin amphiphiles with n-C15H31 tails have been synthesized and completely characterized. These amphiphiles form good Langmuir-Blodgett (LB) films at the air/water interface. Mean molecular areas for the series were measured from the isotherms and found to increase as the number of aliphatic chains increased from one to four. No influence of the subphase pH was observed on the isotherms. LB films can be transferred successfully onto different solid surfaces. The LB films were characterized using tapping mode atomic force microscopy (AFM). Bis-, tris-, and tetra-substituted porphyrins were found to be fairly good film-forming amphiphiles, whereas irregular aggregates were seen in the case of the monosubstituted porphyrin amphiphile. Multilayers were also formed with tetra-substituted amphiphiles on mica. Detailed AFM studies of tetra-substituted amphiphiles have been carried out to investigate the effect of preparation procedure and solid substrates on film formation and transfer. The absorption and fluorescence spectra for the amphiphiles in solution and LB films deposited onto mica and glass were recorded, which demonstrated the successful transfer of LB films onto the substrates and provided more information about the arrangement of porphyrin molecules within the LB films. For comparison, self-assembled monolayers (SAMs) and the cast thin films of the amphiphiles were prepared and characterized.

Journal Article↗
PubMed2005

Biocomposite films synthesized at a fluid/fluid interface.

In the synthesis of mesostructured particles and films, the cooperative self-organization of amphiphilic molecules in the presence of reactive species is a key factor in the reaction mechanism. This paper presents a method for preparing structured collagen films synthesized at fluid/fluid interfaces. This work is an extension of previous efforts in our group to synthesize structured silica films in a reaction system confined at the interface between two immiscible fluid phases, providing an additional level of control over the structural evolution that occurs during reaction. Synthesis at a liquid/liquid interface was shown to provide excellent control over the mesostructure of the final product, avoiding a major problem encountered in many film synthesis techniques in which the reaction occurs at a liquid/solid interface: namely, the undesired effect of the solid surface on the film structure. The focus of this paper is the synthesis of structured composite films containing amphiphilic phospholipids and collagen. These films provide a way to pattern cell growth on biocompatible surfaces and a model system for studying the self-assembly mechanism of lipids and collagen. Self-assembled monolayers and bilayers composed of phosphatidylethanolamine (PE) lipids and collagen were investigated to determine how regularly patterned films can be prepared in a manner that preserves the bioactive properties of the collagen. Mixtures of PEs and acid-soluble collagen were spread on an aqueous subphase in a Langmuir trough. Surface pressure-area compression isotherms for the composite lipid/collagen monolayers provide information about interactions between these components. Langmuir-Blodgett (LB) techniques were utilized to transfer the composite films onto freshly cleaved mica. The mica-supported films were characterized by atomic force microscopy. The lipid/collagen ratio in the composite films was found to be the most important factor in determining how the collagen is assembled and distributed. The temperature and pH of the aqueous subphase, the process for spreading collagen on the subphase, the deposition speed, and the deposition pressure are factors that can be used to selectively control the film patterning. For most of these experimental factors, the range over which a highly structured uniform film can be fabricated over significant length scales is generally very narrow. Based on the experimental results and understanding of the fundamental interactions involved, a mechanism for the co-self-assembly of phospholipids and collagen is suggested. The adhesion and growth of Chinese hamster ovary (CHO) cells on the patterned film surfaces demonstrates the biocompatibility of these composite films.

Animals↗
PubMed2004

Population characteristics of traffic accident-related deaths in Japan and Ireland, 1950-2000.

To compare epidemiological characteristics of traffic accidents in Japan and Ireland, we analyzed mortality and the negative effect on life expectancy between 1950 and 2000 and generated a multivariate model. The characteristics were similar in the two countries: The time trends showed an increase in mortality followed by a decrease. The mortality rates were about 13 and 5/100,000 for males and females, respectively, in 2000. Correlation coefficients for sex were over 0.9. Age distribution obeyed the natural logarithm regularity. The negative effect on life expectancy was about 0.34 year for males, and 0.13 year for females. The economic level was positively associated with mortality, whereas "number of vehicles owned" was associated negatively. In conclusion, we can take advantage of the broad consistencies in these two countries when we draw up an intervention strategy. Any preventive strategy should be directed to the young, particularly males.

Accidents, Traffic↗
PubMed2002

Wavefront aberrations in eyes of emmetropic and moderately myopic school children and young adults.

Wavefront aberrations were measured using a psychophysical ray-tracing technique in both eyes of 316 emmetropic and moderately myopic school children and young adults. Myopic subjects were found to have greater mean root mean square (RMS) value of wavefront aberrations than emmetropic subjects. Emmetropic adults had the smallest mean RMS, which remained smaller than the values for myopic adults and children and for emmetropic children both when second order Zernike aberrations (astigmatism) and third order Zernike aberrations were removed. Twenty percent of myopic adults had RMS values greater than values for all of the emmetropic adults, with significantly greater values for Zernike aberrations from second to seventh orders. High amounts of wavefront aberrations, which degrade the retinal image, may play a role in the development of myopia.

Adolescent↗